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Home My WebLink AboutAPA1179• • • • • • • • • Biological Services Program FWS/OBS-80/08 June 1980 Gravel Removal Studies in Arctic And Subarctic Floodplains in Alaska NORTHERN INTERIOR Interagency Energy-Environment Research and Development Program OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY and SOUTHERN INTERIOR ~ Fish and Wildlife Service U.S. Department of the Interior The Biological Services Program was established within the U.S. Fish and Wildlife Service to supply scientific information and methodologies on key environmental issues that impact fish and wildlife resources and their supporting ecosystems. Projects have been initiated in the following areas: coal extraction and conversion; power plants; mineral development; water resource analysis, including stream alterations and western water allocation; coastal ecosystems and Outer Continental Shelf devetopment; Natior.~al Wetland Inventory; habitat classification and evaluation; inventory and data manage- ment systems; and information management. The Biological Services Program consists of the Office of Biological Services in Washington, D.C., which is responsible for overall planning and management; National Teams, which provide the Program's central scien- tific and technical expertise and arrange for development of information and technology by contracting with States, universities, consulting firms, and others; Regional Teams, which provide local expertise and are an important link between the National Teams and the problems at 'the operating level; and staff at certain Fish and Wildlife Service research facilities, who conduct in-house research studies. FWS/OBS-80/08 June 1980 GRAVEL REMOVAL STUDIES IN ARCTIC AND SUBARCTIC FLOODPLAINS IN ALASKA Technical Report by Woodward-Clyde Consultants 4791 Business Park Blvd., Suite 1, Anchorage, Alaska 99503 Contract Number F\"IS= 14~ 16=0008 .. 970 Norval Netsch, FWS Project Officer Water Resources Analysis Project Biological Services Program U.S. Fish and Wildlife Service 1011 E. Tudor Drive Anchorage, AK 99503 This study was funded in part by the Interagency Energy-Environment Research and Development Program Office of Research and Development U.S. Environmental Protection Agency Performed for the Water Resources Analysis Project Office of Biological Services U.S. Department of the Interior Washington, DC 20240 DISCLAIMER The opinions, findings, conclusions, or recommendations expressed in this report are those of the authors and do not reflect the views of the Office of Biological Services, Fish and Wild- life Service or the Office of Research and Development, u.s. Environmental Protection Agency. EXECUTIVE SUMMARY A 5-year gravel removal study was initiated in mid-1975 to evaluate the effects of gravel removal from arctic and subarctic floodplains in Alaska. The primary purpose of the project was to provide information that wi II assist resource managers in minimizing detrimental environmental effects resulting from floodplain gravel mining. To achieve this objective 25 ma- terial sites were studied by a team of scientists and engineers. Two major products of the project are a Technical Report which synthesizes and eval- uates the data collected at the sites, and a Guide! ines Manu~ I that aids the user in developing plans and operating material sites to minimize envi- ronmental effects. Data from the 25 study sites were collected and analyzed by the follow- ing six disciplines: • River Hydrology and Hydraulics • Aquatic Biology • Terrestrial Ecology • Water Qua I i ty • Aesthetics • Geotechnical Engineering Data Analysis compared the Physical Site Characteristics (drainage basin size, channel width, channel configuration, channel slope, and stream ori- gin! and the Gravel Removal Area Characteristics !type of gravel removal method, location of gravel removal, and age of the gravel removal site! with the measured effects of mining activities. iii The general conclusion reached was that proper site select'ion and project design facilitate gravel mining with minimal effects on the habi- tats and fauna of floodplains. The key to the successful mitigation of· potential detrimental effects is to carefully match the material site design and operation !site lbcation, configuration, profile, schedule, and rehabi 1- itationl with the Physical Site Characteristics of the selected floodplain. VARIABLES INFLUENCING MINING EFFECTS Physical Site Characteristics Among the Physical Site Characteristics, channel configuration was the most important. Potential floodplain change is least for a braided river and greatest for a straight river. Size of channel is an important factor, with the least change to be expected in a large system and the greatest in a smal I system (assuming equally-sized material sites!. Combining these two variables (channel configuration and size!, gravel removal operations can be expected to have the least effect on large braided rivers and the greatest effect on smal I straight rivers. Other influencing Physical Site Characteristics, which are related to configuration and size, are the availability and size of unvegetated gravel bars, floodplain width, and the distance that can be maintained between the mining site and the active channel. For example, in a smal I straight river system the floodplain is narrow and gravel bars are neither plentiful nor large. Thus, to extract gravel, either a significant length of active flood- plain or the adjacent inactive floodplain and terrace must be disturbed. In the latter case the narrowness of the floodplain forces the operation to closely encroach upon the active channel. In large river systems these problems can be less significant because gravel bars are larger and, if the inactive floodplain or terrace are used, the wider floodplain allows mainten- ance of a broader undisturbed buffer zone between the material site and active floodplain. iv J 0 = J :J Gravel Removal Area Characteristic.s AI I of the Gravel Removal Area Characteristics were found to signifi- cantly influence the effects of gravel mining. The location of the material site relative to the active channel is considered to be the most important factor. Whether a material site is scraped or pit-excavated is important, but often pits are located away from an active channel, avoiding the types of changes tha~ can be associated with scraping in active floodplains. The major effects of pit sites located in inactive floodplains and terraces are the loss of vegetated habitat, the possibility for the occur- rence of fish entrapment, a change in the appearance of the floodplain, and long-term delay in the re-establishment of predisturbance conditions. Where pit sites are srtuated close to active channels, particularly on the inside bends. in meandering systems, the possibi I ity exists for diversion of the channel through the pit, eventually forming a channel cutoff in the meander. This highlights the importance of providing a buffer between the material site and the active channel. Where pit sites are of suitable size, of suffi- cient depth, and have contoured perimeters, they can increase local habitat diversity and provide conditions suitable for fish and various species of terrestrial fauna. Scraped material sites in active floodplains have minimal effects on the floodplain environment when only exposed gravel bars are excavated above the water level, and when slope and contours are maintained !resem- bling those of natural barsl. Removal of vegetated areas or banks, which results in decreased lateral stability of active channels oral lows water to spread over a large area, is not desirable. Decreased water depth·and veloc- ity increases sedimentation rates, alters water temperature, and alters dissolved oxygen levels. These changes in aquatic habitat usually affect the local distribution and community structure of benthos and fish. The effects of scraping in vegetated areas of inactive floodplains and terraces can be similar to those described for pits. However, long-term changes typically are minimal because the lack of standing water in the v closed site wi I I faci I itate re-establishment of pre-mining vegetation con- ditions. If material sites are located and operated to prevent or greatly mini- mize effects on channel hydraulics, and to utilize only exposed gravel bars, the probabi I ity of major localized changes to a floodplain generally is greatly reduced. Where exposed gravel bars are not available or are inadequate, a tradeoff decision between sites must be made that weighs the potential effects of aquatic disturbances against terrestrial disturbarices. In these cases, minimization of hydraulic change to active channels should be important in the decision major hydraulic changes can have a greater long-term effect on terrestrial systems than the control led disturbances associated with a site located in a vegetated inactive floodplain or ter- race. RECOMMENDED FUTURE B,TUD IES During the present study a number of subject areas were identified that should be investigated. I. Evaluation of gravel mining from coastal and upland sources; and, preparation of guidelines for users of these sources. These alternatives to sources have not been studied. 2. Evaluation of the effects of multiple sites on one river system. Such an investigation should be aimed at determining the critical, spatial, and temporal relationships of multiple sites. Gravel replen1shment rate predictions should be an integral part of this inve~tigation. 3. Several floodplain gravel removal sites should be investigated before, during, and after mining to assess the adequacy of the Guide I ines Manu a I. 4. Several topJcs of the Guidelines Manual should be studied in detai.l to assess their adequacy, (f.e., buffers, pit design, and active channel dredging). vi ) J This report was submitted in fulfillment of Contract Number 14-16- 0008-970 by Woodward-Clyde Consultants, Anchorage, Alaska, under sponsor- ship of the Office of Biological Services, U.S. Fish and Wildlife Service. Work was completed as of June 1980. vii EXECUTIVE SUMMARY LIST OF FIGURES LIST OF TABLES ACKNOWLEDGMENTS TABLE OF CONTENTS INTRODUCTION, E. H. Follmann BACKGROUND PHILOSOPHY PROJECT DESCRIPTION REFERENCES . . • . APPROACH AND METHODOLOGY, E. H. Follmann SITE SELECTION .•.••. DATA REVIEW •••..... FIELD STUDY OF SELECTED MATERIAL SITES DATA BASE TECHNICAL REPORT GUIDELINES MANUAL REFERENCES . ~ DESCRIPTION OF STUDY RIVERS, L. L. Moulton, Ed. SEWARD PENINSULA NORTH SLOPE NORTHERN INTERIOR SOUTHERN INTERIOR REFERENCES EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS, L. A. Rundquist I NTRODUCT I ON • . • . • . . METHODS OF DATA COLLECTION METHODS OF DATA ANALYSIS HYDROLOGY HYDRAULICS QUANTIFICATION OF CHANGES RESULTS AND DISCUSSION ••.• CHANNEL CONFIGURATION AND PROCESS HYDRAULICS SEDIMENTATION ICE CHARACTERISTICS HYDROLOGY . . . . SUMMARY AND CONCLUSIONS CHANNEL CONFIGURATION AND PROCESS HYDRAULICS •... SEDIMENTATION ICE CHARACTERISTICS HYDROLOGY RECOMMENDATIONS REFERENCES • • • • viii iii xi i xix xxi i 5 7 9 II II 17 17 29 30 31 33 35 35 42 51 58 66 67 67 70 71 71 72 74 81 81 99 115 122 127 134 134 135 135 136 136 136 138 ) ) ) J EFFECTS OF GRAVEL REMOVAL ON AQUATIC BIOTA, L. L. Moulton . . . . . . . . . . . . . . I NTRODUCT I ON • • • • • • • • • • • • • • • • • • METHODS OF DATA COLLECTION •••••••••••••• METHODS OF DATA ANALYSIS • • • • • • • • • • ••• RESULTS AN~ DISCUSSION • • • • • • • • •••• MAJOR GRAVEL REMOVAL HABITAT ALTERATION EFFECTS OF HABITAT ALTERATION ON FISH POPULATIONS • EFFECTS OF HABITAT ALTERATION ON AQUATIC MACROINVERTEBRATES ••••••••••••••••• SUMMARY AND CONCLUSIONS ••••••••••••••• EFFECTS OF GRAVEL SCRAPING ON RIVERINE HABITATS EFFECTS OF INUNDATED PIT FORMATION ON THE ASSOCIATED RIVER BIOTA • • • • • • • • • • • • • • • RECOMMENDATIONS ••••••• REFERENCES • • • • • • • • • • • • • • • • • • • • • • • • EFFECTS OF GRAVEL REMOVAL ON TERRESTRIAL BIOTA, M. R •. Joyce . . . . . . . . . . . . . . . . . . I NTRODUCT I ON • • • • • • • • • • METHODS OF DATA COLLECTION • • • • • • • • • ••• METHODS OF DATA ANALYSIS ••••• RESULTS AND DISCUSSION • • • • • • • ••••••• VEGETATIVE COMMUNITIES uF STUDY AREA FLOODPLAINS •••• VEGETATIVE COMMUNITY CHANGES AT GRAVEL REMOVAL 5 I TES • • • • • • • • • • • • • • • • • • • • "' • FACTORS AFFECTING VEGETATIVE RECOVERY RATE •••• FAUNAL COMMUNITY CHANGES AT GRAVEL REMOVAL SITES •••• FACTORS AFFECTING RECOVERY RATE OF FAUNAL COMMUNITIES PERMANENTLY PONDED S!TES •••••••••••• SIMILARITIES OF RESPONSE BETWEEN BIOTA AND STUDY SITE PARAMETERS • • • • • • • ••• SUMMARY AND CONCLUSIONS • • • • • • • • • • • • • • ••• VEGETATIVE REMOVAL •••• MINING DEPTH AND LOCATION •••• OVERBURDEN • • • • • • • • • • • PERMANENTLY PONDED HABITATS •••• RECOMMENDATIONS •••••••• REFERENCES • • • • • • • • • EFFECTS OF GRAVEL REMOVAL ON WATER QUALITY, L. L. Moulton . . . . . . . . . . . . . . I NTRODUCT I ON • • • • • • • • • • • • • • • • • • RESULTS AN~ DISCUSSION ••••••••••••• POST-MINING EFFECTS OF GRAVEL REMOVAL OPERATIONS SUMMARY AND CONCLUSIONS ••••••••••••• REFERENCES • • • • • • • • • • • • • • • • • • • • • ix 141 141 144 145 148 148 167 198 209 209 211 213 214 215 215 218 220 222 222 225 241 248 253 254 259 268 268 268 269 269 270 271 273 273 276 276 284 285 EFFECTS OF GRAVEL REMOVAL ON AESTHETICS, D. K. Hardinger . . . . . ......•. INTRODUCTION • • • • • • • •••••••••• SCENIC QUALITY • • • • • ••••• VISUAL SENSITIVITY ••••• DEGREE OF VISIBILITY • • • • • • ••••• APPROACH • • • • • • • • • • • • • • • • • • • • THE VISUAL RESOURCES OF THE STUDY REGIONS • SEWARD PENINSULA • • • • • ••••••• NORTH SLOPE • • • • • • • • • , NORTHERN INTERIOR •• , • • •• , • SOUTHERN INTERIOR •••••• EFFECTS OF GRAVEL REMOVAL ON VISUAL RESOURCES SEWARD PENINSULA • • • • • • • ••• NORTH SLOPE • , • • NORTHERN INTERIOR ••••••• SOUTHERN INTERIOR •••• SUMMARY • • • • • • • • • • , GEOTECHNICAL ENGINEERING CONSIDERATIONS OF GRAVEL REMOVAL, H. P. Thomas and R. G. Tart, Jr ..... INTRODUCTION ••••••••••• , •• APPROACH • • • • • • • • • • • • • • • • • • • • • • SITE SELECTION AND INVESTIGATION ••••• PRELIMINARY SITE SELECTION •••••••••••• SITE INVESTIGATION ••• , ••••••••• FINAL SITE SELECTION •••• MINING PLAN PREPARATION ••••• SITE PREPARATION • • • • • •••••••••• ACCESS OVERBURDEN REMOVAL , CHANNEL DIVERSION SETTLING PONDS •••••• SITE OPERATION ••••••••• EXCAVATION ••••• , •••••• TRANSPORTATION AND STOCKPILING •••• , • PROCESSING •••• , • • • • • • • •••• SITE REHABILITATION • • • • • • • • • • • ••• REFERENCES • • • • • • • • • • • • • • • • • • • INTERDISCIPLINARY OVERVIEW OF GRAVEL REMOVAL, E. H. Follmann . . . . . . . ... INTRODUCTION •••••••• PHYSICAL SITE CHARACTERISTICS •••• CHANNEL CONFIGURATION •••••••• DRAINAGE BASIN SIZE <CHANNEL WIDTH! •••• CHANNEL SLOPE AND STREAM ORIGIN GRAVEL REMOVAL AREA CHARACTERISTICS TYPE OF GRAVEL REMOVAL LOCATION OF GRAVEL REMOVAL DIKES AND STOCKPILES X 287 287 289 289 290 291 292 292 295 297 300 304 304 305 306 306 308 311 311 314 315 315 317 318 319 321 321 324 324 325 326 326 327 328 329 330 331 331 333 333 348 350 354 354 363 376 SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS SUMMARY . • . • • • • • • RECOMMENDATIONS • • ••• RECOMMENDED FUTURE STUDIES APPENDICES A. SCIENTIFIC NAMES B. GLOSSARY xi 379 379 382 384 385 395 Number 3 4 5 6 7 8 9 10 II i2 13 14 15 16 17 LIST OF FIGURES Location of the 25 gravel removal study sites in Alaska Typical Seward Peninsula terrain Arctic Coastal Plain wetlands Northern portion of the Arctic Foothi I Is • Typical view of the White Hi I Is section of the Arctic Foothi I Is ••.• M. F. Koyukuk River val ley looking upstream Typical terrain of the Kokrine-Hodzana Highlands Typical terrain in the Yukon-Tanana Upland Section Glaciofluvial deposits in Dry Creek floodplain Typical view of Alaska Range section .• Aer~al photograph showing the two gravel remova I I ocat ions at S i nuk River considered separately in the hydrology/hydraulics analysis Aerial photograph of Washington Creek showing the upper and lower gravel removal areas • Aerial photograph of Oregon Creek showing the upper and lower gravel removal areas • Aerial photograph of Aufeis Creek showing upper and lower gravel removal areas •• Aerial photograph of Middle Fork Koyukuk River- Upstream showing upper and lower gravel removal areas Schematic diagram of the plan view and cross section of a typical braided river •••. Maximum depths and corresponding top widths of undisturbed major, side, and high-water chan- nels at four braided study sites ••••.•• xi i 13 37 43 44 44 52 53 59 60 61 75 77 78 79 80 83 84 ' ' ) Number 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Schematic diagram of the plan view and cross section of a typical split channel river •• Maximum depths and corresponding top widths of undisturbed major, side, and high-water channels at four split channel study sites Schematic diagram of the plan view and two cross sections of a typical meandering river Maximum depths and corresponding top widths of undisturbed major, side, and high-water channels at 15 study sites with meandering, sinuous, and straight configurations ...•• Schematic diagram of the plan view and cross section of a typical sinuous river Schematic diagram of the plan view and cross section of a typical straight river Schematic diagram of an alluvial fan Comparative aerial photography of the Nome River showing change in channel configuration resulting from gravel removal activities Aerial photograph of the Ugnuravik River pit site showing the insufficient buffer zone Aerial photograph of the Tanana River-Upstream site with substantial buffer zone separating the pit from the active side channel •••• Aeria.l photograph of the Prospect Creek pit showing wide buffer zone separating the pit from the active channel ••.••• Schematic diagram i I lustrating definitions of channel geometric and hyraulic variables. Average hydraulic geometry of river channels expressed by relations of width, depth, and veloc- ity to discharge at two locations along a river (modified from Leopold, Wolman, and Mi I ler 1964) • Schematic diagram showing change in water surface slope in response to a change in water discharge • • • ...••••.• xi i i 85 86 87 88 90 90 91 96 98 100 101 102 104 105 Number 32 33 34 35 36 37 38 39 40 41 42 43 Schematic diagram i I lustrating the effects of a flow obstruction on the local hydraulics Comparative aerial photography of the Penny River showing change in hydraulic character- istics resulting from gravel removal activities Schematic diagram i I lustrating an example of a change in local water surface slope result- ing from an in-channel gravel removal operation Schematic diagram showing degradation process Upstream view of thermal and fluvial erosion in the access road at Ugnuravik River, acting as a long-term sediment source to the river View of erosion of a diversion dam which acts as a long-term sediment source to Skeetercake Creek. Dunes in foreground are atypical of the undisturbed river •••••••••• Large area of aufeis at the upper gravel removal area at Washington Creek as it appeared in ear I y June • • . • • Aerial photographs of Washington Creek !top! and Aufeis Creek (bottom! showing material site loca- tions and approximate channel locations before the disturbance Si I tat ion resulting from extensive aufeis field at Oregon Creek mined study area, 20 June 1977 ••••.•..••••.. Removal of bank cover at Oregon Creek as observed on 24 June 1977 •••••• Removal of bank cover at Skeetercake Creek as observed on 18 June 1977 .••• Washington Creek upstream and mined area on 9 September 1977 showing reduction of instream cover due to gravel removal operation (flow level [0. I I m3 /sec] = 20 percent of mean annual flow!. Other habitat alterations include increased braiding, si I tat ion, and intergravel f I ow • . • • • • . . • • • • • • · • · • • • · • xiv 107 113 114 116 123 123 125 i33 149 152 153 154 ) Number 44 45 46 47 48 49 50 51 52 .J 53 54 Reduction of instream cover as provided by boulders at Sagavanirktok River, 3 August 1978 !flow level, 60m 3 /sec,= 155% of estimated mean annual flowl. • • . . • • • • • • • Increased braiding at Sagavanirktok River study site caused by mining mid-channel gravel bars and a vegetated island in the active channel !mining operation conducted during the winter of 1974-19751 •••••••••••••••• Response of cross-sectional wetted perimeters to percentage of mean annual flow and percent- age of cross sections comprised of selected depth intervals at mean annual flow at three gravel removal study sites ••••••. Low velocity backwaters formed by gravel removal at Dietrich River-Downstream ! 13 July 19781 and Middle Fork Koyukuk River-Upstream ( 18 July 19781, note extensive si It deposition in both cases Creation of low velocity side channels and inundated pit following gravel extraction Sequence of aerial photographs showing effects of overmining the inside of a meander bend at Middle Fbrk Koyukuk River-Upstream. Immedi- ately following mining !bl there was an increase in backwater areas. The next year !cl the meander was partially cut off, creating a vari- ety of low velocity habitats •....••• Temperature and dissolved oxygen profiles at four deep gravel pit study sites ••••. Ponded area at Kuparuk River study site where three seine hauls captured 61 Arctic grayling and 2 slimy sculpin, 9 August 1978 !pool I in Table 211 •••••••••••.••••• Ponded area at Middle Fork Koyukuk-Upstream study site where one seine haul captured 28 Arctic gray I ing, 3 round whitefish and 3 slimy sculpin, 18 July 1978 !pool 2 in Table 21 l • Potential migration blockages, aufeis fields at Washington Creek and Oregon Creek, June 1977 Region where Aufeis Creek went subsurface creating migration blockage due to lack of surface flow •••••.•••••.••• XV 155 157 158 159 160 163 165 179 179 182 183 Number 55 56 57 58 59 60 61 62 63 64 65 Prospect Creek study site -sha I I ow pond habitat supporting Arctic gray I ing, chinook salmon juven- iles, round whitefi~h, northern pike, burbot, and slimy sculpin, 12 August 1978 .••. West Fork Tolovana River study site-deep pond with extensive shallows providing northern pike and Arctic grayling habitat, 29 July 1978 Tanana River-Upstream upper pit showing exten- sive vegetation beds, 18 August 1978. Note difference in the extent of vegetative develop- ment in this 13-year old pit as compared to the 2 and 3-year old pits in Figures 55 and 56 ••• Potential overwintering area at Willow Creek. This spring-fed tributary, open throughout the winter, had previously entered Penny River at a deep pool •••••.•••.•••• Creation of a potential overwintering area at West Fork Tolovana River downstream from pit . Densities of selected aquatic macroinvertebrates at Aufeis Creek study areas during 1977 sampling trips Penny River undisturbed floodplain showing typical North Slope and Seward Peninsula floodplain charac- teristics of sinuous channel bordered with dense shrub thickets with incised outside meander bank, and narrow gravel point bar on inside meander West Fork Tolovana River showing typical South- ern and Northern Interior medium river flood- plain characteristics with shrub thickets and white spruce-paper birch stands along the riparian zone West Fork Tolovana River showing permanently flooded pit excavated adjacent to the active floodplain with a downstream connection A view of Oregon Creek looking downstream through the mined area showing site conditions that remain 13 years after gravel removal Penny River mined area looking upstream. Note the flooded conditions within the disturbed area, and the overburden pi I es in the center of the site •••••••••••••••• xvi 188 188 190 192 196 206 224 224 226 229 230 ) Number 66 67 68 69 70 71 72 73 74 75 76 77 Close-up view of an overburden pile in River mined area. Note the development ous and woody vegetation during the I I following gravel removal .•••.•• the Penny of herbace- years Washington Creek mined area showing vegetative recovery only present on the overburden pile 13 years after gravel removal .•••• Woody revegetation occurring through develop- ment of adventitious stems . Distribution of woody slash debris and other organics over the ground on the edge of the gravel removal area at Aufeis Creek .•.. View of the upper pit at Tanana River-Upstream showing diversity of shoreline configuration and development of woody and herbaceous vegeta- tion 13 years after gravel removal ..•• View of the Ivishak River floodplain looking downstream showing typical braided channel characteristics with extensive gravel bars and isolated, vegetated islands .•...•• View of both undisturbed !background! and mined (foreground! reaches of the Shaviovik River. Note that gravel removal maintained natural point bar contours and shapes and did not disturb riparian,vegetative zones Compacted surface gravels in an access road leading to the Dietrich River-Downstream site Inorganic overburden pi led on the edge of the Oregon Creek site which supported no vegetation 13 years after gravel removal •••.•••.• Close-up of dense and diverse vegetative devel- opment in an area of surface broadcast of woody slash and organics. Note the willow adventi- tious stem development ••.•.•. Distant view of a large ~ilt depositional area at the Sagavanirktok River study site • A silt depositional area of the Kavik River supporting a wei !-developed pioneer vegetative community • . ••.•.•.•....•••• xvi i 234 234 235 236 237 239 240 244 244 246 247 247 Number 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 Close-up of a concentration of willow seedlings at the shoreline of the Jim River ponded area Vegetated organic mats that were washed down- stream and grounded during high water on Toolik River floodplain gravel bars .••.••.•• Tanana River-Upstream showing shoreline diver- sity and vegetative development in the upper pit Undisturbed buffer along the original stream channel at Aufeis Creek !downstream disturbed area onlyl • • • • • • • • • . • • ••. Gravel fi II ramp used to protect the incised bank at the Sagavanirktok River study site • Thermal and hydraulic erosion of permafrost induced by multiple passes of a tracked vehicle across an unprotected incised floodplain bank and adjacent tundra . . . • • . . • • • • Armored bank protecting the West Fork Tolovana River pit from a channel diversion into the mined site •.••••••••••• Typical Seward Peninsula landform at Penny River • Typical view of an Arctic Coastal Plain floodplain • Dietrich River val ley Lower Middle Fork Koyukuk River val ley McManus Creek val ley Phelan Creek valley • Gravel ramp at Shaviovik River site providing access over a permafrost river bank ..••• Thermal erosion near Ugnuravik River resulting from compaction and destruction of the vegeta- tive mat overlying ice-rich permafrost soi Is Configurations of study rivers •.•. xvi i i 248 249 256 264 266 267 267 293 295 298 298 301 302 322 323 335 Number 2 3 4 5 6 7 0 8 9 10 '> 'J II 12 ~ 13 14 J 15 LIST OF TABLES Major Variable Matrix ••••••••••••••• Methods Used for Measuring Water Quality Parameters with the Number of Replicates Taken per Study Area •• Aquatic Biology Sampling Methods Used at Each Study Site. Size and Quanfity Values of the 25 Study Sites Quantification Ratings of Change in Channel Configuration Characteristics Resulting from the Gravel Removal Operation at Each of the 25 Sites ••••••••••• Values of Exponents for Hydraulic Geometry Power Relations Quantification of Change in Hydraulic Variables Resulting from the Gravel Removal Operation at Each of the 25 Sites ••••• Quantification Ratings of Change in Sedimentation Characteristics Resulting from the Gravel Removal Operation at Each of the 25 Sites •••••••• Quantification Ratings of Change in Aufeis Potential that Resulted from the Gravel Removal Operation at Each of the 25 Sites • • • • • • • • • • • ••••••• 15 21 24 36 93 106 109 119 126 Mean Annual Flow Estimates at Each of the 25 Study Sites. 129 Calculated Discharges in m3 ts Corresponding to Selected Recurrence Intervals for Each of the 25 Study Sites • 130 Quantification Ratings of Change in Quantity of lntergravel Flow Resulting from the Gravel Removal Operation at Each of the 25 Sites • 131 Major Habitat Alterations Observed at Sites Mined by Scraping • • • • 150 Percent of Pit Area Composed of Selected Depth Intervals. 164 Effects of Cumulative Habitat Alterations on Fish Populations in the Mined Area of Study Sites Mined by Scraping •••••••••••••••••••• xix 168 Number 16 17 Estimated Densities and Biomass of Arctic Char and Slimy Sculpin at Washington Creek Study Site Based on Repeated Electroshocking of Blocked Sections of Stream 21-23 June 1977 • . .•.•..•••.•. Estimated Densities and Biomass of Arctic Char and Arctic Grayling at Kavik River St~dy Site Based on Repeated Electroshocking of Blocked Sections of Stream, 1976 18 Comparison of Fish Densities in Mined and Undisturbed Areas as Determined by Electroshocking Blocked Sections of Stream at Kavik River Study Site, 1976 19 Catch of Arctic Grayling per Angler Hour at Kavik River Study Areas During Summer 1976 Sampling Trips 20 Change in Catch per Effort and Percent Composition of Indicator Species at Selected Study Sites ••• • . 21 Summary of Catch from Ponded Water Areas Isolated from Active Channels at Two Study Sites •••..••.•• 22 Mean Fork Lengths of Coho Salmon Caught by Minnow Trap at the Penny River Study Site During 1977 •.•• 23 Differences of Coho Salmon Mean Fork Length Between Sample Areas and Associated Significance Levels, Penny River Study Site During 1977. • • . • . . • • • • ••• 24 Physical Conditions at Pits Visited During Winter 25 Response of Aquatic Riffle Macroinvertebrate Taxa to Habitat Alterations Observed at Selected Study Sites 26 Changes in Aquatic Macroinvertebrate Densities at Sites Exhibiting Type I and 2 Substrate Alterations • 27 Densities of Aquatic Macroinvertebrates Collected at Inundated Pit Sites, 1976-1978 ••... 28 Quantitative Changes in Selected Terrestrial Biological Parameters at Gravel Removal Study Sites .•.••.• 29 Location, Response Time, and Community Characteristics of Vegetative Recovery at Selected Study Sites .••... 30 Quantification of Change in Selected Hydrology Parameters 31 Which Were Impeding Vegetative Recovery at Study Sites Qualitative Evaluation of Habitat Quality and Fauna Use at Permanently Ponded Gravel Removal Sites XX 172 174 175 { ' 176 177 !' " 181 186 187 !93 f " 199 203 208 223 232 243 255 ) ) ) J ) ) Number 32 33 34 35 36 37 38 39 Bird Observations by Habitat Type Within the Control and Disturbed Areas at Tanana River-Upstream 3-7 June, 1978. Numbers Indicate Minimum Individuals Known to Occur in Each Habitat Type ...••••••••..•••. Bird Observations by Habitat Type Within the Control and Disturbed Stations at West Fork Tolovana River 9-1 I June, 1978. Numbers Indicate Total Individuals Known to Occur 257 in Each Habitat Type • . • • • . • . . . . . . . • . 258 Two Way Coincidence Table Displaying a Hierarchial Clus- tering of Similar Sites and Similar Biotic Parameters • 260 Selected Alaska Water Quality Standards .• Water Quality Parameters Measured at Gravel Removal Sites Which Exceeded Alaska Water Quality Standards . Changes in Turbidity and Suspended Solids Between Sample Areas at Selected Study Sites ••..• Relative Change of Water Quality Parameters Between Up- stream and Downstream Samp I e Areas at Se I ected S\tudy S i t es • . • . • • . • . • • • • • • · • Average Measured Values of Selected Water Quality Param- eters at Study Sites with Inundated Pits .••• 274 275 278 281 283 40 Interdisciplinary Rating of Cumu!ative Effect of Scraping, 41 A-I A-2 A-3 A-4 A-5 Using Various Jnd!ces of Change on Study Sites Visited from 1976 to 1978 • • . . . . . • • . . . • . . • . . . 338 Interdisciplinary Rating of Effects of Pits on Associated Floodplains at Selected Study Sites Visited from 1976 to 1978 Using Various Indices of Change • Vegetation Identified in the Text • Mammals Identified in the Text Birds Identified in the Text Fish Species Reported and Caught or Observed in Major Geographical Areas Represented by the Twenty-Five S i t es • • . • • . . . . . . • • • . . . . . • • Aquatic Macroinvertebrates Caught at Study Sites During i976-1978 Field Sampling ....... . xxi 359 386 387 388 390 392 ACKNOWLEDGMENTS Woodward-Clyde Consultants appreciates the contributions of a number of scientists and engineers. Dr. A. 0. Ott, now with the Alaska State Pipet ine Coordinator's Office, conceived the aquatic' biology field program and was responsible for much of its implementation. He also served as a principal investigator on the study for one and one half years of the field phase. Brent Drage, now with R & M Consultants, was responsible for early imple- mentation of the hydrology field program. Other scientists whose contributions have benefited the study are, James A. Glaspel I of the Alaska Department of Fish and Game; Michael A. Scott of the U. S. Bureau of land Management; and Dr. Keshavan Nair, Dr. Ulrich Luscher and Robert Pitt of Woodward-Clyde Consultants. A number. of Woodward-Clyde personnel assisted in the field at various times, including Donald 0. McKay (now with the U. S. Fish and Wildlife Service), Kenneth E. Tarbox, Jonathan Isaacs, and Jerry P. Borstad. Thanks are also due to Alyeska Pipeline Service 9ompany and the Alaska Department of Transportation for use of their photographs of some mining sites and the use of their mining plans. We are also grateful to Susan Ogle for graphics production and Marnie Isaacs for editorial review. And finally, we are deeply indebted to Jean Borstad and Jayne Voorhis for report production. xxi i / ' ) ) ) J ) J J J J The U.S. Fish and Wildlife Service Project Officer appreciates the tech- nical and administrative assistance provided by Summer Dole throughout the project and to Dr. Norman Benson for technical advice during the data col lec- tion and analysis phases. We thank the following individuals who reviewed and commented on some portions or alI of the report in draft form: Bob Bowker, Hank Hosking, Ronald Ki~nuner, Jim Lewis, Lou Pamplin, John Stout and Jerald Stroeble, alI with the U. S. Fish and Wildlife Service, various stations; ~ Gabriel and Earl Boone with the Bureau of Land Management, Anchorage, Alaska; Joe Childers and Bob Madison with U. S. Geological Survey, Anchorage, Alaska; Dr. Alvin Ott with the State Pipe I ine Coordinators Office, Fairbanks, Alaska; Bruce Barrett and Carl Yanagawa with the Alaska Department of Fish and Game, Anchorage, Alaska; Brien Winkley, U. S. Army Corps of Engineers, Vicksburg, Mississippi; and W. P. Metz and A. W. Schwarz with ARCO Oil and Gas Company, Anchorage, Alaska. xxiii ) ) ) ) ) ) ) ) INTRODUCTION a E. H. Follmann This Technical Report and the accompanying Gravel Removal Guidelines Manual for Arctic and Subarctic Floodplains (Guidelines Manual l present data analyses and conclusions resulting from a 5-year study of 25 floodplain material sites in arctic and subarctic Alaska, and provide guidelines to insure minimal environmental degradation when siting, operating, and closing floodplain material sites. This study, its results and conclusions, and these reports directly relate only to floodplains, although several aspects may also be applicable in nonfloodplain locations. BACKGROUND A commo~ denominator in alI resource and industrial development is the need for granular material; gravel is used worldwide for construction projects and transportation routes. In t~e arctic and subarctic, however, the presence of permafrost creates special construction problems that place additional demands on the supply of gravel. Even slight alterations in the permafrost thermal regime caused by surface disturbances can cause thawing, thermokarst formation, subsidence, and erosional problems. Maintenance of the thermal regime is essen~ial when building or operating in permafrost areas, but especially in regions characterized by fine grained soi Is with high water content. These latter areas are highly susceptible to subsidence when surface disturbance alters a E. H. Fol lmann is presently associated with the Institute of Arctic Biology of the University of Alaska. the thermal regime. In these cases, the thawed ground becomes a morass in which vehicle passage can be impossible and maintenance of structural sta- b i I i ty of fac iIi ties becomes d iff i cuI t. The current major solution for eliminating or greatly reducing perma- frost thaw is to use gravel as either pads for structures or as roadways. Although these demands exist elsewhere, the thickness of gravel required in permafrost areas is far greater than in nonpermafrost areas. The gravel pad in permafrost areas replaces the insulative function of the vegetative mat that was removed or compressed by the gravel fi I I. Since the insulative quality of the vegetative mat is greater than that of an equivalent thick- ness of gravel, a gravel pad must be considerably thicker to maintain an equivalent thermal regime. Under these circumstances the most important considerations for determining pad or road thickness are: climatic factors, soi I surface temperatures, permafrost temperatures, and subgrade soi I proper- ties (McPhail et al. 1975l. The objective is to establish the freeze front in or slightly below the fill (McPhail et al. 1975). Where this is accom- plished, potential thaw problems can be greatly diminished. Arctic and subarctic regions have been the focus of attention during the past several decades because of the wealth of natural resources known or thought to occur in these regions. The discovery of oi I and gas on Naval Petroleum Reserve No. 4 (now the National Petroleum Reserve-Alaska) in the 1940's, at Prudhoe Bay in 1968, and in northern Canada has stimulated this interest and expanded it to include metal lie minerals and coal. Expan- sion of exploration activities can be expected to continue. As resource development in remote arctic and subarctic areas becomes more economically feasible the region's resources wil I be utilized to meet society's energy and material needs. These future projects wi I I require increased quantities of gravel to faci I itate construction and to provide stable substrates for various permanent and temporary faci I ities. For ex- ample, the gravel requirement for the Trans-Alaska Pipe! ine System was about 49 mi II ion cubic meters (m 3 J (Michael Baker, Inc. 1977). Smaller projects requiring gravel, such as exploratory wei I dri I I pads and associated camps, 2 ) ) ) ) ) ) 3 typically use up to 75,000 m • If, however, airstrips and roads are associ- ated with these sites, quantities can increase to several hundred thousand cubic meters. Based on experience constructing the Yukon River to Prudhoe Bay Haul Road (Haul Roadl, approximately 31,000 m3 of gravel are required per kilometer of road construction, and maintenance requirements average about 700m3 per kilometer (kml per year for about the first 5 years (Aison personal communication!. Alyeska Pipeline Service Company requested about 3 1.5 mil lion m of gravel for maintenance of their project over a 5 year period. The figures presented above for the large pipe! ine projects repre- sent gravel needs from both upland and floodplain sites. About half of the gravel used on the oi I pipe! ine was from floodplains. Alluvial deposits found in broad floodplains offer one of the prime sources of gravel in northern areas. Individual material sites vary consider- ably in size, as indicated by the range of those considered for study in 3 this project: 7,738 to 631,000 m of material removed. Several different sites may be necessary to supply material meeting the required project specifications because one site may not contain alI types of material needed. For example, not all potential sites wi II have material suitable for topping. Also, since road and pipeline construction projects need materials throughout their lengths, one site or a series of sites in one area wi I I not satisfy the demands of these projects. A haul distance of 6.5 km or less has been estimated to be economically efficient for construction in Alaska, and haul distances of 13 to 16 km or less are planned for mainten- ance of the Trans-Alaska Pipeline System (Aison personal communication!. Therefore, material sites for these types of projects necessarily must be located at regular intervals due to economic considerations. To protect an environment from unacceptable disturbance, the elements comprising the environment must be known, the various elements of the pro- posed activity must be known, and the effects of the activity on the environ- mental elements separately and as a whole must be known. Where this infor- ma~ion is avai !able, guide! ines to conduct the proposed activity with a minimum of environmental perturbation can be developed. Where information on one or more of these elements is lacking or is only partly understood, any 3 guidelines that are developed are based on estimates and assumptions whose validity is dependent on the experience and predictive powers of those developing the guidelines. The latter condition is the rule in most cases where environmental impacts are concerned. Impacts from resource exploration and development have not been studied as much as is necessary to make intel- 1 igent decisions regarding environmental impacts. This lack of research is particularly true in arctic and subarctic regions. The remoteness of the area and the high cost of conducting research have not facilitated an ade- quate description of the environmental elements. Studies of the environ- mental effects of development have been similarly hindered. Extensive literature review revealed that the specific impacts of gravel removal had seldom been studied and, therefore, were poorly under- stood. Description of impact had been attempted in only a few cases !Bul I and Scott 1974, Federal Water Pollution Control Administration 1968, Forshage and Carter 1973, Sheridan 19671; and these studies dealt specif- ical iy with only one aspect, e.g., fisheries. LaBelle ( 1973) reviewed gravel and sand availability in the Barrow area of the National Petroleum Reserve- Alaska and made recommendations oh gravel extraction and evaluations of potential environmental impact. Northern Engineering Services Company Limited and Aquatic Environments Limited ( 19751 evaluated the material sites associated with the Trans-Alaska Pipeline System with reference to aquatic habitat. In addition, several reports identified problems associated with gravel extraction as one of many sources of environmental perturbations that could be expected from new and continued exploration and development in the north !Bliss and Peterson 1973, Klein 1973, Weeden and Klein 1971, West 19761. None of these latter reports presented results of any material site studies. There have been few studies on the environmental effects resulting from construction of the Trans-Alaska Pipeline System. The Joint State/ Federal Fish and Wildlife Advisory Team (JFWATI prepared a report on survei 1- lance experience with gravel mining recommendations (Burger and Swenson 19771. The JFWAT also produced a series of reports dealing with experiences on the pipe I ine, including environmental effects studies. However, the major 4 c c c c c c c c c ) ) responsibility of the majority of JFWAT staff was environmental surveil lance of construction, not research on environmental effects. Weeden and Klein ! 1971:481 l stated: "As with so many other problems of tundra management, the design of criteria for mining operations in gravel lags far behind present need because detailed knowledge of fish populations where they are, when they migrate, where they spawn, their vulnerabi I ity to added si It loadings of river waters, etc. --is lacking". By early 1975, the state of knowledge had not progressed or expanded gr~atly. This fact, coupled with the dependence on gravel for arctic and subarctic construc- tion, stimulated the U.S. Fish and Wildlife Service to initiate a project to investigate the effects of gravel removal on floodplain systems. The project objective was to provide a comprehensive information review and data synthesis to form the basis for future mining of river and floodplain gravels. The purpose of the project is to provide an information base that wi I I assist resource managers to formulate recommendations concerning oper- ations that wil I minimize detrimental environmental effects of grave! re- moval from arctic and subarctic streams. PHILOSOPHY Little is known about the natural changes which occur in riverine systems in arctic and subarctic regions. Therefore, determining the effects of resource exploitation in these regions is often difficult because of the interplay of natural changes and man-induced disturbances. The basis for this study was the assumption that gravel removal operations in a floodplain cause change, the magnitude of change depending primarily on the floodplain characteristics, the location of the site, and the method of gravel extrac- tion. Since almost alI riverine systems in arctic and subarctic regions have evolved to the present through natural change and without man-induced dis- turbances, alI changes due to gravel removal identified in this study were considered undesirable •. To maintain a river system in its natural or near- natural state was considered the essence of guidelines development and provided the best conceptual base from which to minimize environmental degradation. However, it is recognized that there may be situations where 5 resource managers may wish to exercise other options. Any site character- istics or methods that facilitated rapid recovery to predisturbance con- ditions were considered for implementation as guide! ines. The presupposition that alI changes due to graVel removal are undesir- able does not, by necessity, cause the data analyses and recommendations to be impractical. It is a foregone conclusion that changes wi II occur when gravel is removed from a floodplain. To note that changes from the natural state were less at one site than another suggests that the former site was operated more consistently with characteristics of the system than the latter, thereby reducing the magnitude of change. The floodplain and gravel removal characteristics at sites that produced these minor changes formed the primary basis for development of constructive guide! ines to minimize change. Conversely, the floodplain and gravel removal character- istics at sites with major changes supported development of guidelines primarily of a precautionary nature. The analyses in succeeding chapters treat the changes that were meas- ured at individual study sites. There are sites, for example, where species diversity increased as a result of site disturbance. In some contexts, this increased diversity would be considered a beneficial effect of gravel removal. However, in the context of this project, this effect initially was evaluated equal to one which caused an equivalent decrease in species diver- sity because it reflected a change from the natu-rally evolved condition. This project treats all changes consistently and objectively as a change from the natural, and special interest perspectives are neither recommended nor encouraged. However, it is recognized that a resource man- ager in certain circumstances may be greatly influenced by the need to consider a site from a multiple or optimal use standpoint. For example, subsequent to gravel removal a deeply dug site might be considered as a water source in areas where winter supplies of water are minimal. Several study sites were deep pits that contained water throughout the year. For- mation of a pit represents a major change from the natural situation and the site wi II not revert back to a natural situation for many years, if at all. 6 c c c 0 c c c c c c c -, _/ \ J In the context of this project, pits represent a major divergence from the natural. However, when considered from the standpoint of multiple use or habitat diversification, a resource manager may elect to recommend or ap- prove a permit for this form of gravel removal. In these situations the resource manager wi I I be able to predict the results of such an operation by review of the following sections in this report. PROJECT DESCRIPTION A 5-year gravel removal study was initiated in mid-1975 to evaluate the effects of gravel removal from arctic and subarctic streams in Alaska. The primary purpose of the project was to provide an information base that wi II assist resource managers in formulating recommendations for minimizing detrimental environmental effects of removing gravel from arctic and sub- arctic streams. To achieve this the following objectives were met: • A comprehensive literature review and synthesis was conducted to evaluate known and conjectured effects of gravel removal and other "\ v similar disturbances on floodplain environments. • Physical, chemical, and biological characteristics of seven sites inhabited by fish after gravel removal were evaluated in moderate ) detai I on a short-term basis. • Physical, chemical, and biological characteristics of 18 sites that reflected various removal methods, stream types, and times since completion of operations were determined in gross detai I and on a short-term basis. • Relationships between parameters related to gravel removal operations, geomorphic characteristics of streams, water quality, and biota were evaluated. The study of three sites prior to, during, and immediately after gravel removal was an original project objective that was eliminated due to a lack of suitable sites meeting project schedules. 7 A thorough and broad-spectrum evaluation of the impacts gravel removal can have in floodplains requires assessment from a number of disciplines. To look at only one element could lead to conclusions and recommendations that might cause major changes to a riverine system on a long-term basis. Therefore, the approach taken in this study included analyses in the follow- ing six disciplines: • River Hydrology and Hydraulics • Aquatic Biology • Terrestrial Ecology • Water Quality • Aesthetics • Geotechnical Engineering This approach not only allowed analysis by individual discipline, but per- mitted consideration of the interdiscipline trade-offs inherent in evalu- ations of disturbances to natural environments. For example, gravel mining techniques that would avoid effects on aquatic biota could require removal of important floodplain habitat used by terrestrial fauna or be impractical from geotechnical considerations. These disciplines were selected for the study because they were be- c c c c lieved to cover the various impacts that were known or surmized to be associ-() ated with gravel removal. Due to a paucity of background information, it was not possible to be assured that alI significant impacts were addressed by these disciplines. Although the main' purpose of this gravel removal study was to provide an information base for recommendations to be made by resource managers, another important contribution is to provide a base for subsequent long- term studies. For example, a problem needing extensive study is the effect of removing gravel from many sites in one river system, as occurs along highways and pipelines when they paral lei floodplains for routing or geo- technical reasons. This problem is not treated in the present study and, in fact, was consciously avoided when sites were selected. 8 c c c ) ) REFERENCES Bliss, L. C., and E. B. Peterson. 1973. The ecological impact of northern petroleum development. Fifth International Congress. Arctic Oi I and Gas: Problems and Possibi I ities. Le Havre. 26 pp. Bull, B., and K. M. Scott. 1974. Impact of mining gravel from urban stream beds in the southwestern United States. Geology 2(4!:171-174. Burger, C., and L. Swenson. 1977. Environmental Survei I lance of Gravel Re- moval on the Trans-Alaska Pipeline System with Recommendations for Future Gravel Mining. Joint State/Federal Fish and Wildlife Adivsory Team Special Report No. 13. Anchorage, Alaska. 35 pp. Federal Water Pollution Control Administration. 1968. Sand and Gravel Waste Evaluation Study, South Platte River Basin, Colorado. Forschage, A., and N. E. Carter. 1973. Effects of Gravel Dredging on the Brazos River. Texas Parks and Wildlife Department, Inland Fisheries Research. Klein, D. R. 1973. The impact of oi I development in the northern environ- ment. Proceedings lnterpetroleum Congress 3:109-121. Rome, Italy. LaBelle, J. C. 1973. Fi II Materials and Aggregate Near Barrow Naval Petro- leum Reserve No. 4, Alaska. The Arctic Institute of North America for the Office of Naval Petroleum and Oi I Shale Reserves. Washington, D. C. 146 pp. McPhai I, J. F., W. B. McMullen, and A. W. Murfitt. 1975. Design and con- struction of roads on muskeg in arctic and sub-arctic regions. Six- teenth Annual Muskeg Research Conference. Montreal, Quebec, Canada. 51 pp. Michael Baker, Inc. 1977. Accounting of sale/free use permit materials. Prepared for Alyeska Pipeline Service Company. Anchorage, Alaska. Northern Engineering Services Company, Ltd. and Aquatic Environments, Ltd. 1975. Reconnaissance of the Alyeska Pipeline-Material Source Borrow Methods and an Evaluation of These Methods with Respect to Aquatic Habitats. Canadian Arctic Gas Study, Ltd. Calgary, Alberta, Canada. Sheridan, W. L. 1967. Effects of Gravel Removal on a Salmon Spawning Stream. U. S. Department of Agriculture, Forest Service. 26 pp. 9 Weeden, R. B., and D. R. Klein. 1971. Wildlife and oi 1: a survey of cri- tical issues in Alaska. The Polar Record 15!91:479-494. West, G. C. 1976. Environmental problems associated with arctic develop- ment especially in Alaska. Environ. Conserv. 3!3):218-224. 10 c c c c c c c c c c J ) ) ) SITE SELECTION APPROACH AND METHODOLOGY E. H. Fo1lmanna The site selection process began in July 1975 and initial work in- volved contacting various agencies and groups to locate potential study sites. Among those contacted, the main sources of information were the Bureau of Land Management, the Alaska Pipeline Office, the Alaska Division of Lands, and the State Pipeline Coordinator's Office. In addition, the Alaska Department of Highways~(now Alaska Department of Transportation and Public Faci litiesl provided a considerable amount of information. A total of 575 potential sites were identified and subdivided into three areas north of Latitude 66° --the North Slope, the Yukon River Basin, and the Seward Peninsula --to obtain representative sites throughout arctic and subarctic Alaska. Later in the project the Yukon River Basin sites were separated into Northern Interior and Southern Interior sites. Following identification of these sites, field reconnaissance was initiated to assess the suitability of the sites for the study and to characterize those sites considered potential candidates for the study. Sixty-four sites remained as candidates following field reconnaissance. To augment the drainage and material site descriptions developed in the field for the 64 sites, additional information on gravel removal activi- ties and watershed characteristics was obtained from various agencies, a E. H. Fol lmann is presently associated with the Institute of Arctic Biology of the University of Alaska. II topographic maps, and other data sources. Based on more complete site des- criptions, preliminary variables were established with which to compare and select sites. Site comparisons were restricted to sites within the same region to insure adequate representation of the North Slope, the Northern Interior, Southern Interior, and the Seward Peninsula. Six sites were selected to represent the Seward Peninsula, eight for the North Slope, six for the Northern Interior, and five for the Southern Interior !Figure ll. The sites were categorized by the presence or absence of fish on the basis of field observation and reliable background information. The sites that were known to contain fish after gravel removal were compared to determine which should receive additional study. AI I sites were previously mined. As stated earlier, sites could not be identified which would allow studies !within project schedules! before, during, and after grave! removal operations. AI I sites were named in ac- cordance with the U.S. Board of Geographic Names. However, two sites oc- curred on unnamed streams and were assigned project names of Skeetercake Creek !unnamed tributary to the Toolik River! and Aufeis Creek !unnamed tributary to the Kuparuk River!. When two study sites occurred on the same river, they were designated upstream and downstream respective to their locations. Major Variable Matrix Following site selection the preliminary variables used to compare sites were reviewed to determine which should be considered major variables. Initially, nine major variables identified as either site characteristics or mining characteristics were selected to describe each of the 25 sites !Woodward-Clyde Consultants 1976!. These parameters were chosen because they were thought to be important from the standpoint of assessing gravel removal effects, they best described the sites, and they allowed selection of sites which exhibited the greatest variety of variables. The variety was especially important because it insured that sites were different, thus 12 c c c c c c 0 c c e ~tis I Leavitt I KAVIK • I) . ) Figure I. Location of the 25 gravel removal study sites in Alaska. 13 permitting assessment of the effects of various gravel removal procedures on sites with different physical and biological characteristics. The major variables were again reviewed following the field inves- tigation, when detailed site characteristics were available to determine which were sti I I suitable for comparing the 25 material sites. The seven variables selected for the final Major Variables Matrix included: • Drainage basin size, • Channel.width, • Channel configuration, • Channel slope, • Str~am origin, • Type of gravel removal, and • Location of gravel removal. These parameters were categorized as either Physical Site Characteristics or Gravel Removal Area Characteristics. Each of the sites was characterized according to these v~riables !Table ll. Definitions of these variables are included in the Glossary. Physical Site Characteristics. Drainage basin size and channel width are significant because the impact of gravel removal could differ depending on the amount of disturbance in proportion to the size of stream and flood- plain. Also, systems having greater discharge and bed load movement could be expected to regenerate a material site more rapidly than a system with smaller discharge and less bed load movement assuming the amount of mining disturbance is proportionate in the two streams. Categories used were smal I, medium, and large based on the drainage area above the site and smal I, medium, and large based on the channel top width within the study reach at mean annual flow. Although from a hydrological standpoint categorization only according to drainage basin area would have been sufficient, we con- sidered it important to include channel width because width is a tangible measurement that can be observed at a site location. 14 c c c c e 0 0 c c Study Site SEWARD PENINSULA Gold Run Creek Sinuk River Washington Creek Oregon Creek Penny River Nome River NORTH SLOPE Ugnuravik River Aufeis Creek Kuparuk River Skeetercake Creek Sagavanirktok River Ivishak River Shaviovik River Kavik River NORTHERN INTERIOR Dietrich River-US Dietrich River-DS M.F. Koyukuk River-US M.F. Koyukuk River·DS Jim River Prospect Creek SOUTHERN INTERIOR W.F. Tolovana River McManus Creek Tanana River·DS Tanana River·US Phelan Creek Drainage basin size X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Channel width X X X X X X X X X X X X X X X X X X u Table 1. Major Variable Matrix Physical site characteristics X X X X X X Channel configuration X X X X X X X X X X X X X X X X X X X X X Channel slope X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Stream origin X X X X X X X X X X X )( )( X ~he Kavik River was mined during two separate periods: 1968 ·1969 and 1973 ·1974. Type of gravel removal X X X X X X X X X X X X X X X X X X X X X X X X X X X X X In channel X X X X X X X X X X X X X X X X X X X X X X X X Gravel removal area characteristics Location of gravel removal Adjoining Separatedfrom channel active channel X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Years since gravel removal 11 10 13 13 11 20± 7 5 9 11' 3 3 5 7&3a 2 3 4 2 2 2 3 16 4 13 3 Channel configurations vary from straight mountain streams to braided rivers. Factors associated with various types of streams such as bed load movement, bank erosion, and water fluctuation were considered important. Configurations included in this st~dy were braided, split, meandering, sinuous, and straight. Channel slope, along with other variables, is a major factor governing water velocity, discharge, and sediment transport. Therefore, streams with slopes-categorized as mild, moderate, and steep were included. Stream origin was considered because it governs aspects of stream hydrology. Stream origin also influences the amount of bed load material avai I able for transport, thereby indicating the regenerative capacity of a stream, and the avai labi I ity of suspended sediment that could deposit in a gravel removal area. Categories used were mountain, foothi I I, coastal plain, and glacial. Other factors such as stream bed material, bank vegetation, and water- shed characteristics are important, but were not considered as major vari- ables. To a large extent these factors are accounted for by the major vari- ables and the physiographic provinces occurring within the regions. Gravel Removal Area Characteristics. Two major types of gravel removal operations used in floodplain areas are pits and scrapes, distinguished primarily by depth of excavation and permanent inundation by water after site closure. During site visits it was apparent that pits were either connected or not connected to an active stream channel. Because magnitude of change to a system could be greatly influenced by this factor, pits were characterized as either connected or not connected. Location of gravel removal sites within a floodplain influences the degree of impact and the regenerative potential of a site. Therefore, dis- tinctions were made between sites located in a channel, adjoining a channel, and separated from a channel. 16 c c c 0 c 0 c c \ J ) To determine the impact of gravel removal over time and the regenera- tive capacity of various types of streams, it was necessary to observe sites that were active during different years. Information was not available for sites associated with construction activity early in this century, but was for sites ranging back to the late 1950's. Specific descriptions of the regional characteristics, physical site characteristics, and characteristics of the gravel removal operation at the 25 study sites occur in a subsequent section. DATA REVIEW Available information regarding the effects of gravel removal and other similar disturbances in floodplains was reviewed. Information was solicited from many Federal and most State agencies, from various Canadian groups, and from I iterature sources. Due to a minimum of information on the effects of gravel removal, particularly in arctic and subarctic re- gions, some of the processes involved had to be discussed from a theoretical standpoint. The results of this work were included in a Preliminary Report prepared in 1976 (Woodward-Clyde Consultants 1976!. This report should be referred to if a review of available literature is desired. FIELD STUDY OF SELECTED MATERIAL SITES Preparation for the field program began in Spring 1976 and the last site was visited in March 1979. Site visits were split over three summers with 7 sites studied in 1976, 10 sites in 1977, and 8 sites in 1978. In addition, seven sites were visited during the winters of 1977-1978 and 1978-1979 to determine the presence or absence of fish, to record water quality parameters, and to describe the occurrence of icing conditions. During the 1976 field program field teams representing River Hydrology and Hydraulics, Aquatic Biology, and Terrestrial Ecology worked each site 17 simultaneously. The Aquatic Biology team also collected water quality data. Simultaneous effort of field teams was considered advantageous during the first field season to insure coordination of work where necessary. In ad- dition, simultaneous work permitted on-site discussion of methodology changes by alI disciplines, thus further insuring coordination and co- operation. During subsequent field seasons, some of the sites were visited by individual field teams, but alI teams visited the sites during the same summer. These individual visits allowed each team to visit sites during peak events for parameters associated with their discipline. Data and sample collection areas were flagged to facilitate collection of data at the same sites during subsequent visits by either the same or different teams. In addition, the hydrology and hydraulics and terrestrial teams placed semi- permanent posts at each site from which to initiate surveys for future studies. The following section includes a review of the field and laboratory programs conducted during the field effort. Programs are described only for River Hydrology and Hydraulics, Water Quality, Aquatic Biology, and Terrestrial Ecology because these were the only disciplines for which data were specifically collected. Geotechnical Engineering and Aesthetics rei ied completely on field information collected by other groups. River Hydrology and Hydraulics Introduction. Emphasis of the field program was on describing local fluvial geomorphic processes, obtaining evidence of past flood histories, measuring river hydraulic parameters, investigating sediment transport properties of the channels, describing river processes, and investigating specific effects of gravel removal on these factors. Photographs were taken for documentation of significant features. Hydraulic and hydrological data collection were coordinated with the water quality, aquatic biology, and terrestrial ecology studies. Hydrological and geomorphological literature pertaining to each site and its drainage basin, e.g., hydrological records, surficial geology, 18 c c ( (' e 0 0 c c c ) ' J and aerial photographic interpretations were also used in the analysis of each site. Geology and Geomorphology. Using topographic maps, stereo aerial photo- graphy, and surficial geology maps, a brief analysis of each drainage basin was made to evaluate the geomorphology of the river val ley, the river ter- races, and the present and past regime of the river. The morphological fea- tures pertaining to the general area around the material site were verified in the field. Hydrology. The U.S. Geological Survey Water Resources Records were reviewed for flow measurements within a study site's drainage basin. Where flow measurements were representative, various key discharges with the respective stages were estimated and documented. In the field, evidences of floods were investigated. Where sufficient data could be obtained at the study site or near vicinity, a stage-discharge relationship and flood frequency analysis were included in the data package. For the rivers that had no past flow records, the hydrology was synthesized using a regional flow analysis !Lamke 19791. Hydraulics. Hydraulic parameters for each river channel and floodplain were measured in the field. At each study site cross sections were surveyed upstream from, within, and downstream from the area of gravel removal !in conjunction with the aquatic ecology program! to measure the following hydraulic parameters: width, depth, and area. AI I cross section locations were documented and elevations referenced to temporary benchmarks. The longitudinal slope of the water surface and, where possible, the bed were surveyed. AI I surveys used standard surveying techniques. The discharge at the time of the survey was measured using standard techniques !Buchanan and Somers 1969!. Materials and Sediment. Representative samples of the river's flood- plain surface material were obtained upstream and downstream from the gravel removal area using the photographic-grid method !Kel lerhals 1971!. These were considered to be representative of the channel bed material. The size 19 distribution was determined by the frequency-by-number method. In addition, the underlying material was measured using hydraulic sieves and the size distribution determined by percentage-by-weight. The river bank materials were described at cross section locations based on a subjective evaluation and photographed for documentation. Ma- terial gradation samples of river bank· materials were not obtained. Channel Processes~ The fluvial morphology at each site was assessed using comparative aerial photography. In the field, fluvial morphological features were verified and documented in more detai I, e.g., gravel bar types, bed formations, scour holes, and sediment deposition. Degradation and/or aggradation upstream from, and downstream from the gravel removal site were investigated. River Ice. In the field, evidences of ice processes !breakup jams, ice scour, gouging, and aufeisl were documented to he!p evaluate the ro!e of ice on the river morphology. Water Quality Water quality parameters measured were temperature !°CJ, dissolved oxygen lppml, conductivity !micromhos/cm2 J, turbidity (JTUJ, suspended sol ids lmg/~J, oxidation-reduction potential !MVJ, and pH !Table 21. Water quality measurements were taken at the aquatic macroinvertebrate sample sites. Usually the measurements were taken along a transect across the river or pit with the number of replicates wit~in a site adjusted to the size of the water body. The measurements were normally within 30 em of the water surface, although depth profiles were taken in pits. Aquatic Biology Introduction. Field emphasis was placed on aquatic invertebrates, changes in fish distribution in relation to the gravel mined area, and potential fish spawning and rearing habitat during the ice-free period. 20 c c c c 0 0 c c c c ' ._; Table 2. Methods Used for Measuring Water Quality Parameters with the Number of Replicates Taken per Study Area Parameter Dissolved oxygen Temperature Conductivity Turbidity Suspended sol ids Oxidation-reduction potential pH Method of determination YSI Model 57 DO meter YSI Model 57 DO meter Hach Model 2510 conductivity meter Hach Model 2100A turbidimeter Mi I lipore fi Iter procedure I 5 llm f i I t er l Delta Scientific 1212-P2 ORP meter Delta Scientific 1212 pH meter Hach pH kit 21 Rep I i cates per study area 3 -15 3 -15 3 -15 2 -II - 3 2 - 5 - 5 Additional visits were conducted to specific sites if potential over- wintering habitat or suspected spawning areas were present within the mined area. Study sites were categorized into two groups. Eighteen sites were visited once during the open water season. Seven sites with known fish uti I ization in the mined area were subject to additional field study. These seven sites were visited on three separate -occasions during open water conditions of I calendar year. In addition, seven pit sites where winter utilization by fish was suspected were visited to document overwintering. The 18 sites subject to a less intensive field program were visited only once. Selection of Sample Areas. Three sample areas were selected at alI sites: upstream, within the mined area, and downstream. Selection of up- stream and downstream sample areas was based on simi !arity to the aquatic and terrestrial characteristics exhibited in the mined area prior to gravel removal. Selection of sample areas was made so that substrate, depth, width, velocity, and pool:riffle ratio were similar at the upstream and downstream locations. The upstream area was typically located at least 400 m above the mined area and the downstream area was between 400 and 800 m below the mined area. Selection of the 400 m criteria was based on the assumption that the hydrological effect of gravel removal would be minimal that far up- stream. Selection of a downstream area between 400 and 800 m below the mined area was based on the probability that changes occurred in this area either during or immediately after gravel removal. At sites with more than one mined area, additional sample areas were selected to assess effects. Similar selection criteria were used. Selection of Sample Gear. Fish and aquatic macroinvertebrate sampling gear were selected relative to the types of habitat present. Features such 22 c c c c e c 0 c c c as width, depth, stream velocity, shore! ine configuration, stream bank vegetation, obstructions~ channel substrate, and presence of pits affected the gear selection process. Sample gear used at each study site is listed in Table 3. Sample Program. Information recorded in the field included stream name, sample location and description, description of the disturbed area, and the date, time, and existing weather conditions. Visual surveys were conducted within sampling areas to describe habitat and to record the pres- ence of fish. Sample Collection, Disposition, and Analysis. A variety of seines with square mesh !3.2 mml, 6 to 10m long and 1.8 m deep, were used. Seines were extended across the stream from bank to bank and pulled downstream in narrow streams. In larger streams and pits the quarter-haul technique was used. Experimental, multifilament gi I I nets 15 x 1.8 m, with panels of 12.7, 25.4, 38. I, 50.8, and 76.2 mm square mesh, were anchor-set in pits, and, in one case, in the deep, slow-moving section of a large river. A backpack shocker, one of the least selective of alI active fishing methods, was used in appropriate watercourses. Stream width permitting, a preselected length of stream was blocked with seines and the enclosed area shocked repeatedly unti I fish were no longer captured or observed. The area of the shocked section was usually measured to allow for density estimation. Minnow traps selective for juvenile and smal I adult fishes were used to sample aquatic habitats. Traps were located in pools, riffles, and pits and were baited with salmon eggs. Traps were usually fished from 12 to 24 hours. A dip net was used at one site to capture juvenile fishes for identi- fication. Visual surveys were made at each site to record distribution and unusual events or critical habitats, such as spawning areas. 23 c Table 3. Aquatic Biology Sampling Methods Used at Each Study Site c Macro invertebrate samp I i ng gear Fish samp I i ng gear Surber Ponar Minnow Gi II Electro-Hook & Set Study site sampler grab trap Seine net shocker I ine I ine c Seward Peninsula Gold Run Creek + + Sinuk River + + + + c Washington Creek + + + Oregon Creek + + + + Penny River + + + + Nome River + + + North Slope c Ugnuravik River + + + + Aufeis Creek + + + + f<uparuk River + + + + Skeetercake Creek + +· + Sagavanirktok River + + + + + Ivishak River + + + + 0 Shaviovik River + + + + Kavik River + + + + + Northern Interior Dietrich River-US + + + + + 0 Dietrich River-DS + + + M.F. Koyukuk River-US + + + M.F. Koyukuk River-DS + + + + Jim River + + + + + Prospect Creek + + + + Southern Interior c W.F. Tolovana River + + + + + + McManus Creek + + + + Tanana River-DS + + + Tanana River-US + + + + + Phelan Creek + + + c e 24 c c Captured fishes were identified, measured (fork length!, weighed, and released except when preserved for reference. Data collected were used to determine species composition, size distribution, and relative abundance; estimates of density were made. These evaluations were compared within and between gravel removal sites. Macroinvertebrates. A 30-cm square Surber sampler was used to collect macroinvertebrates in riffle areas. Sampling areas were stratified by depth, bottom type, current velocity, and other variables that may have been corre- lated with benthic distribution. At most study areas three sampling sites were selected and five replicate samples were collected at each sampling site. Two sampling sites were selected in a few cases where there were multiple mined areas or where the river was not directly affected by gravel removal, e.g., a pit site away from the stream channel, with five replicates taken per site. A Ponar grab was used to collect macroinvertebrates in pits. Single grabs were taken at several stations spaced to cover the main depth regions within the pits. Ponar grab samples were cleaned, separated !the slurry passed through a U.S. Standard No. 30 sieve!, and placed in labeled con- tainers. Samples col lected.with the Surber sampler were placed directly into labeled containers. AI I sample containers were fi I led with 70 percent al- cohol to preserve specimens for later examination. Samples were picked and sorted in the laboratory. Organisms were sorted into major categories and placed into labeled vials containing 70 percent alcohol. Identification was to the lowest practical taxonomic level. Data from quantitative samples were used to obtain total and individual taxon density. Data on standing crop and number of taxa were evaluated; comparisons were made within and between sample sites. Pit Sampling Program. Four pits were visited during March 1978 to assess the potential for fish entrapment and overwintering. During the 25 following summer these pits, plus three additional ones, were visited to assess if fish were present. The pits were then revisited during the 1978-79 winter to assess if fish remained in the pit after freezeup or moved into the river. If fish remained in the pit, subsequent visits were made to determine if fish could survive the winter. Sampling was conducted with a variety of gear types including minnow traps, set lines, gi I I nets, hook and I ine, and observation. In addition, an underwater television system was used for survei I lance under the ice at two pits. Dissolved oxygen and temperature were measured when water was present. Ice thickness, presence or c c:· c· absence of flowing or open water, or both, and formation of aufeis by over-C• flow were recorded. Terrestrial Ecology Introduction. The terrestrial field program identified habitats af- fected by gravel removal operations and assessed the impact of habitat modification on associated wi ldi ife. Qualitative and quantitative surveys were conducted during a 3-day field effort to characterize the plant com- munities and seral stages present on disturbed and undisturbed areas. Wild- 1 ife uti I ization of these habitats also was evaluated. The undisturbed sites encompassed seral stages likely to develop with time on the disturbed site, and were believed to be most representative of the disturbed areas prior to gravel removal. The program was expanded to 5 days at one representative study site (regional representative sitel in each of five geographical areas: Arctic Coastal Plain !North Slopel, Arctic Foothi I Is !North Slopel, Seward Penin- sula, Northern Interior, and Southern Interior. The increased time at these study sites allowed for additional sampling efforts using the same sampling procedures. Soi Is. Soi I sampling was conducted within each habitat on disturbed and undisturbed sites to evaluate the growing conditions and the potential for revegetation. Within each habitat or definable soil unit, the character of the upper horizon, depth of organic layer, surface drainage, and domi- 26 e c c e c e c ) J nant vegetation were recorded. Approximately 15 subsamples were collected with a sol I auger-tube sampler from the ground-cover rooting zone (approxi- mately the upper 20 cml. These subsamples were combined to form one compos- ite sample for each sol I unit. Composite samples were air dried and ana- lyzed for pH, percent organic matter, and percent nitrogen, phosphorus, and potassium. A particle size distribution analysis was conducted to deter- mine the percent sand, si It, and clay in the composite sample. Vegetation. Vegetation surveys delineated the major cover types with- in the study area. Within each habitat, the seral stage of development was noted and the plant species were recorded. Qualitative site descriptions were augmented by limited use of quan- titative sampling methods that employed a systematic, nested plot design (James 19781. Strand or patch habitats required "spot" location of nested plots or qualitative description only. Description of the overstory vegetation included the following param- eters: dominant and subordinate tree species, average height and DBH (diam- eter at breast height! of the stand and stand components, and representative ages by species and height class. A I imited number of circular plots (0.04 hal were used to quantitatively sample each habitat. Forester's calipers or a diameter tape, or both, were used to determine tree DBH; tree height was estimated and an increment borer or cross-sectioning method was employed to determine the age of woody plants. Increment cores and cross sections were returned to the laboratory for staining an~ age determination when necessary. Shrub growth within each habitat was descr'ibed by identifying species composition and relative density, average height by species, and representa- tive ages by species and height class. Stem and clump density counts were conducted on a limited number of systematically located, 0.004-ha circular plots. Sefected shrubs were aged by cross-sectioning above the root collar. Evidence of herbivore browsing was noted. 27 Ground cover sampling identified species composition within each habi- tat and provided an estimate of percent surface coverage for each taxon. Percent surface coverage was visually estimated in systematically located, 0.0004-ha plots. P,ercent surface coverage was estimated as follows: if only one plant of a given taxon was present and its coverage was very sparse, it was rated at I percent coverage; if more than one plant of a given taxon was present, but its coverage was less than 10 percent of the plot's surface area it was rated at 5 percent coverage; the percent coverage of alI other taxa was estimated in increments of 10. Wildlife. Evidence of wildlife use of disturbed and undisturbed areas was recorded at each site. Direct observations and evidence of use (tracks, trai Is, nests, dens, runways, food caches, and scats! were keyed to their presence in specific seral stages. Historical use of a cover type was noted (i.e., hedged growth form of preferred browse species! and seral stages critical to certain I ife history stages of wildlife were inspected. The disturbed area was examined for the presence of special attractants or deter- rents to wildlife use of the site. An avian census was conducted in disturbed and undisturbed habitats at all study sites; attempts were made to visit the five intensive study sites during the peak avian activity period. The census in homogeneous habitats employed a Modified Strip Plot technique for three consecutive morn- ings (five mornings at the intensive sites) to obtain data on the species present and habitat utilized. Smal I, isolated habitats were qualitatively surveyed to ascertain avian species occurrence. Waterfowl, shorebirds, and game birds were inventoried by total counts when areas of concentration were clearly visible. Smal I mammals (shrews, voles, and lemmings) were inventoried at alI sites in disturbed and undisturbed habitats using a trap and removal tech- nique. A "I ine" or "spot" trapping configuration was used in all cover types. Trapping was conducted for two nights at nonintensive sites and four nights at regional representative sites with the traps checked, baited, and reset each day. The species, sex, age, and weight of captured specimens were recorded to assess occurrence and characteristics by habitat. 28 c c c c e 0 0 0 c e c ) ) Collection of terrestrial invertebrates was conducted at alI fish intensive sites and at the regional representative sites. Collections were made adjacent to the watercourse at the disturbed site and near the upstream aquatic sampling station to assess the avai labi I ity of potential food sources for the aquatic environment. Sweep nets were used to collect inverte- brates. Specimens were pres€rved in 40 percent alcohol and returned to the laboratory for identification. DATA BASE The data base, the third end product of the gravel removal study, <the Technical Report and Guidelines Manual are the first two end products! consists essentially of alI information collected during site selection and field data collection. Information for each of the 25 study sites includes: • Case history information including mining plans and permits, if avai 1- able; • Biological, hydrological, and water quality field data; • Geotechnical evaluations; • Tabulation of data summations; • Computer printouts for aquatic ecology and hydrology and hydraulics; • Draft site description reports; • Site photographs, including both ground and aerial; • Topographic maps showing site location; and • Depiction of actual data collection areas within each site. 29 The information is in a form to allow any professional to evaluate where the data was collected, what data was collected, and the general conclusions of the original investigator. This data base is on file with the U. S. Fish and Wildlife Service. It wil I not be distributed routinely with the Technical Report and Guide- 1 ines Manual. Due to the mass of information available, a specific need wil I have to be identified before the data relevant to that need can be provided. TECHNICAL REPORT Analyses of field data, beyond the immediate data reduction after site visits, began in winter 1977-78. This initial effort prepared descrip- tions of each of the study sites visited in previous summers and analyzed data specific to each site. Brief summaries of essential information rele- vant to each of the 25 material sites studied during this project are in- cluded in the subsequent chapter. These are included to orient the reader for the discussions that follow in the individual discipline chapters. Data syntheses for alI sites did not begin unti I after the 1978 field season. Analyses of combined site data are contained totally in this report. Each of the six disciplines included in the project, (River Hydrology and Hydraulics, Aquatic Biology, Terrestrial Ecology, Water Quality, Aesthetics, and Geotechnical Engineering!, is discussed in separate chapters. These chapters include some integration with other disciplines. For example, Aquatic Biology is dependent, for some of its data interpretation, on the Water Quality parameters measured, and on the physical changes that are described in the River Hydrology and Hydraulics section. An interdisciplinary overview of the effects of gravel removal follows the discipline chapters. This chapter reviews the analyses of the six disci- plines in terms of the similarities and differences that are evident. An important aspect of this chapter is discussion of the tradeoffs and com- parisons between disciplines that must occur with respect to the siting, 30 c c c e 0 c 0 c J operation, and closing of material sites. Where possible, the similarities in approach of the vari9us disciplines to minimize disturbance from gravel removal are emphasized because these conditions maximize protection of floodplain environments. GUIDELINES MANUAL The Guide! ines Manual (printed separately) is based on the evaluations and recommendations contained in the Technical Report, on the preliminary guide! ines developed in an earlier phase of this project (Woodward-Clyde Consultants 19761, and on stipulations and recommendations used by certain resource agencies when reviewing material site applications and projects. The guide! ines are intended to provide guidance to the persons respon- sible for writing material site permits and for planning resource or indus- trial development in localized areas. The guidelines also are helpful to potential applicants for materia! site permits because they wl!! he!p 1n planning a project characterized by minimal environmental perturbations. The guide! ines are not designed as stipulations to be attached to each permit granted. If used in this manner contradictions in siting, opera- tional, and rehabilitation procedures could occur, thus negating the value of the guide! ines. It is intended that the guide! ines user evaluate the proposed project within the context of the guide! ines, and the proposed area for the material site, to insure that it wi I I develop in an environmen- tally acceptable manner. The guide! ines were developed for use by personnel with some background in an environmental science. Ease of use was considered necessary because, at least on large projects such as pipe I ines and roads, permit agencies can be inundated with applications requiring quick consideration. A set of guide! ines that are cumbersome and inefficient to use, under these circum- stances, could foster disregard of the guidelines or their misuse e.g., attaching the guide! ines as stipulations to a permit. 31 The guide! ines, as mentioned, were developed with the assumption that the potential user has some experience with environmental problems and issues and, thus, appreciates the potential complexities associated with a material removal project. It is strongly recommended that the user read the Technical Report and understand why and how the guide I ines were devel- oped. A comprehension of the total project is considered necessary for intelligent, efficient, and expeditious use of the guide! ines. Without this understanding, the guide I ines could be viewed out of context and used inap- propriately. 32 c c c c e 0 0 c ) J REFERENCES Buchanan, T. J., and Somers, W. P. 1969. Discharge Measurements at Gaging Stations. Book 3, Chapter AS. Techniques of Water-Resources Investi- gations of the U.S. Geological Survey. 65 pp. James, F. C. 1978. On understanding quantitative surveys of vegetation. Am. Birds 32( I l: 18-21. Kellerhals, R. 1971. Sampling procedures for coarse fluvial sediments. J. Hydraulics Div. ASCE 97(HY8l: 1165-1180. Lamke, R. D. 1979. Flood Characteristics of Alaskan Streams. U.S. Geolog- ical Survey Water Resources Investigations 78-129. Anchorage, Alaska 61 PP· Woodward-Clyde Consultants. 1976. Preliminary Report-Gravel Removal Studies in Selected Arctic and Sub-Arctic Streams in Alaska. U. S. Fish and Wildlife Service. FWS/OBS 76/21. Wash. D. C. 127 pp. 33 J D 6 0 c DESCRIPTION OF STUDY RIVERS L. L. Moulton, Ed. As previously mentioned, 25 sites were selected for study. These sites occurred in four geographical regions of Alaska and include a wide variety of Physical Site Characteristics and Gravel Removal Area Characteristics !Table ll. Site locations are shown on Figure I. Table 4 summarizes dis- turbed area size, volume of gravel removal, and period of activity at each site •. SEWARD PENiNSULA General Description of Region The region of Seward Peninsula containing the six study sites is in the foothi I Is of the Kigluaik Mountains, characterized by broad rounded hi I Is with elevations of 250 to 700 m {Figure 2!. The surficial geology at Sinuk River, Washington Creek, and Nome River is dominated by remnants of highly modified moraines and associated drift resulting from Pleistocene glaciation. Gold Run Creek however, is just outside the northern edge of glacial influence and the surficial geology is fine-grained alluvial and col !uvial deposits with rare bedrock exposures. At Oregon Creek and Penny River the surficial geology is characterized by coarse and fined-grained deposits of alluvium and colluvium associated with moderate to steep-sloped mountains and hi I Is. Bedrock exposures are common on the upper slopes and crests. The region is generally underlain with permafrost of variable thick- ness. Normal temperatures range from 3 to 13°C in the summer and -23 to -13°C in the winter. The annual precipitation of the region is about 30-40 em, including approximately 130 em as snow. 35 Table 4. Size and Quantity Values of the 25 Study Sites Drainage basin Area of. Gravel volume Volume/Drainage Average Period of gravel removal removed basin index a depth gravel removal area (km 2) !hal I 1000 m3 1 lml Seward Peninsula Gold Run Creek 67 4 8 1.2 0.2 1963-65 Sinuk River 540 88 174 3.2 0.2 1960-66 Washington Creek 29 3 49 17.0 1.6 1960-63 Oregon Creek 31 7 27 8.8 0.4 1960-65 Penny River 62 15 5~ 8.2 0.3· 1960-65 Nome River 130 2 Late 1950's North S I o~e Ugnuravik River 279 <23 <0.8 <2. 3 1969 Aufeis Creek 255 46 570 22.0 1.2 1972 and 1974 "' Kuparuk River 8500 14 41 0.1 0.3 1969 01 Skeetercake Creek 82 10 38 4.6 0.4 1966 Sagavanirktok River 4700 35 431 0.9 1.2 1974-75 Ivishak River 3600 40 119 0.3 0.3 1972 and 1974 Shaviovik River 410 116 2.8 1972 Kavik River 891 40 247 2.7 0.6 1968-69 and 1973-74 Northern Interior Dietrich River-Upstream 520 35 631 12.0 1.8 1974-77 Dietrich River-Downstream 667 8 129 1.9 I. 7 197~ Middle Fork Koyukuk River-Upstream 2400 20 177 0.7 0.9 1974 Middle Fork Koyukuk River-Downstream 4100 28 215 0.5 0.8 1975-"/6 Jim River 687 II 135 2.0 I .2 1974-76 Prospect Creek 248 6 84 3.4 1.4 ( 974-"/5 Southern Interior West Fork Tolovana River 754 8 132 1.8 I. 7 1975 McManus Creek 14 4 < 75 <54.0 < 1.9 1961 Tanana River-Downstream 44,600 8 310 1.0 3.9 1971 Tanana River-Upstream 38,700 9 135 1.0 1.5 1962-65 Phelan Creek 83 95 575 70.0 0.6 1975-76 ·------ aRatio of volume of gravel removed to size of drainage basin area times 10. bQuant i ty unknown. 0 0 0 n 0 Figure 2. Typical Seward Peninsula terrain. Vegetation within the floodplains consists of dense mature wi I low thickets interspersed with less advanced mi xed woody-herbaceous communities. The valley walls contain occasional wi I low and alder thickets in the moist ravines and pockets, and shrub-tussock tundra on the slopes. The river systems contain both anadromous and resident fish spec i es. Typical anad- romous species include Arct i c char, pink, chum, coho, and sockeye salmon and various whitefish species. Typical resident species include Arctic grayling, resident Arctic char, northern pike, Alaska blackfish, and slimy sculpin. Description of Study Rivers-Location and Gravel Removal Area Characteristics Go I d Run Creek. Go I d Run Creek is a sma I I, sinuous river which or i g i- nates in, the foothi I Is of the Kigluaik Mountains at an elevation of 4 27 m and flow{ through rolling hills for 23 km to its confluence with the Blue- stone River. The study site is app r o x imately 7 km from the mouth at an 37 elevation of 100m. Gravel was removed from this site for construction of the Nome-Teller Highway. Gravel removal occurred by shallow scraping over approximately 3.5 ha between 1963 and 1965 with 7,738 m3 of material ex- tracted. Scraping occurred in the active channel, on mid-channel and lateral bars, and on a vegetated island between the active channel and a high-water channel. Approximately I ha of riparian willow thickets and an accompanying 0.5-m layer of overburden were removea prior to gravel removal. This organic overburden was placed in a stockpile on the edge of the scraped area along the right !northern! floodplain bank downstream from the highway bridge. An additional overburden pile, composed primarily of sand, was located at the downstream I imit of the scraped area. Both stockpiles sti I I remained during the site visit. A 50-m long gravel access road also was present leading from the highway to the scraped area located upstream from the highway bridge. The floodplain bank at the floodplain end of this access road was incised and approximately I m high. Rehabilitative measures were not conducted after completion of gravel mining activities. Sinuk River. The Sinuk River is a medium, split river which originates in the Kigluaik Mountains at an elevation of 425 m. It flows through a narrow, steep-walled valley before entering a broad valley containing the study reach. The lower section flows across a relatively flat coastal plain for 26 km before discharging into Norton Sound. The study site is approxi- mately 19 km from the mouth at an elevation of 30 m. Between 1960 and 1966, 174,221 m3 of gravel were extracted for high- way construction by shallow scraping within the active floodplain and adjoin- c c c c G 0 c ing the active channel of the Sinuk River. Access to the floodplain was () gained via two short !about 30 ml gravel roads leading from the highway. Scraping extended approximately 1,500 m upstream and downstream from the Sinuk River bridge and encompassed 88 ha. Material within the Sinuk River floodplain was described from highway department analyses as stream-deposited sandy gravel with less thah 25 percent greater than 50 mm in size !coarse gravel! and about 2 percent exceeding 250 mm !boulders!. Several !three or four! islands were removed 38 c 0 0 e 0 0 c during the mining operation. These islands were heavily vegetated with wi I low thickets averaging 1.2 min height. These islands comprised approx- imately 35 ha of the site. Stripping of 0.15 m of overburden was necessary in these vegetated areas. In addition, approximately 150m of incised flood- plain bank and 1.2 to 1.6 ha of adjacent tundra were removed from the north- east side of the floodplain to expose gravel deposits. Also, within the active floodplain, debris and soi I from vegetated islands were pushed into a long narrow overburden pile !approximately 450 m in length) in the middle of the material site to expose underlying gravel deposits. The water table was encountered at about 0.75 m below vegetated sand bars with seasonal frost present in the floodplain and· permafrost encountered at depths of 0.9 to 2.4 m in adjacent terraces. It does not appear that this material site was shaped, contoured, or rehabilitated in any way following gravel removal. Various aspects of this site are shown in Figures 2 and I I. Washington Creek. Washington Creek is a smal I, sinuous creek which originates in the foothi I Is of the Kigluaik Mountains at an elevation of about 265m and flows through a wide, V-shaped val ley for about 13~km before entering the Sinuk River. The study site is approximately 5 km from the mouth at an elevation of about 105 m. This study site consists of two gravel removal areas approximately 1,000 m apart on Washington Creek. Both areas were developed between 1960 and 1963 during construction of the Nome-Teller Highway. The lower site was sti I I being used in 1978 to supply gravel for road malntenance. Gravel at both sites was removed by scraping the Washington Creek floodplain and the alluvial fan deposits formed near the confluences of two unnamed tributaries of Washington Creek. A reported 8,000 m3 of ma- terials were removed from I ha in the upstream site, while 41,000 m3 had been removed from 2 ha in the downstream site. Clearing of large amounts of overburden was required for the devel- opment of both sites. Overburden was not removed from the material sites but was collected into large mounds which were sti I I present at the time 39 of our visit. Large stockpiles of clean gravel were also seen at both sites. Efforts to rehabi I itate the floodplain or to maintain the natural character of the channel were not observed during the field study. Dikes, however, were constructed in the downstream mined area to maintain the course of the main channel in its pre-mining location. Various aspects of this site are shown in Figures 12, 38, 39, 43, 53a, 53b, and 67. Oregon Creek. Oregon Creek is a smal I, straight river which originates in the foothi I Is of the Kigluaik Mountains at an elevation of 380m and flows approximately 7 km through a V-shaped val ley to a confluence with Cripple River. The val ley wal Is are steeply sloped over the upper half of its length; the lower half is flanked by moderately sloped hi I Is. The Crip- ple River headwaters lie at an elevation of about 300m and the river flows in a broad V-shaped valley for 40 km before discharging into Norton Sound. The Oregon Creek confluence occurs 15 km downstream from the headwaters of Cripple River at an elevation of 80 m. The material site was developed by scraping gravel bars within and adjoining the active chennel near the Oregon Creek-Cripple River conflu- ence. Scraping of angular gravel and cobbles was conducted west of the Nome-Teller Highway in Oregon Creek from 1960 to 1963 when 20,500 m3 of material were removed from approximately 5.5 ha. Vegetation was removed from 4 ha at the downstream end of this site. Mounds of vegetated overburden along the banks of the broadened channel and stockpiled gravel within the active floodplain were observed during site inspection. Between June and September 1965, 6,000 m3 of gravel were excavated from I ha in the Cripple River immediately downstream from the highway bridge. Various aspects of this site are shown in Figures 13, 40, 41, 53c, 64, and 74. Penny River. The Penny River is a smal I, sinuous river which originates in the foothi I Is of the Kigluaik Mountains at an elevation of 230m and flows approximately 23 km before discharging into Norton Sound. In its upper reaches, the Penny River flows in a narrow V-shaped val ley. The val ley broadens downstream and the val ley floor typically reaches widths of 350m 40 c c (' c e 0 0 c ) ) between moderately sloping hi I Is in the vicinity of the study reach. The study reach is approximately 8 km upstream from the mouth at an elevation of 28 m. The material site was developed by scraping within the active flood- plain and excavation of a pit adjacent to the main channel of the river. Material removed from the 15-ha site was primarily sand and gravel alluvium with some col I uvial debris along the southeast edge of the working I imits. Rock types were quartz mica schist, I imestone, and quartz; rock fragments were subangular to rounded with 3 to 10 percent greater than 50 mm in size and less than 1 percent greater than 250 mm. Clearing and stripping were necessary to remove the dense wi I low (that covered approximately 12 hal and an average 0.6 m of overburden. The water table varied from 0.8 m to more than 1.5 m deep with no permafrost encounter- ed up to a depth of 2. I m. Scraping was conducted during 1960-63 when 3,646 m3 were removed and during August and September, 1965 when 47,034 m3 were extracted. The 1965 operation yielded some select materials, indicating that a processing plant probably operated within the site. A smal I 0.6-ha pit was excavated in the southeast corner of the material site during the 1965 operation. This pit averaged I to 1.5 min depth during the site visits and was directly connected to the main channel. Smal I stockpiles were pres- ent within the disturbed area during field inspection. The site was not shaped, contoured, or rehabilitated in any way following gravel removal. Thus, many shallow depressions, which are not sloped to drain toward the river, collect standing water. In addition to the 0.6-ha pit, scraping occurred to below the water table in several smal I isolated pockets, and these areas were covered with standing water during site visits. Four or- ganic overburden piles and the gravel access road remain on the site. Var- ious aspects of this site are shown in Figures 33, 58, 61, 65, 66, and 85. Nome River. The Nome River is a medium, sinuous river which originates in the Kigluaik Mountains at an elevation of about 230m and flows through a broad val ley for about 57 km to its mouth at Norton Sound. The Nome River drainage basin is long and narrow, with an average width of about 8 km. The study site lies about 37 km from the mouth at an elevation of about 58 m. 41 This material site was developed by scraping 1.5 ha across the entire floodplain width. Scraping apparently occurred in the active channel and on adjacent mid-channel and lateral bars. Vegetative and overburden clearing was not necessary because the site was sparsely vegetated prior to gravel removal. Mining was conducted at this location in the late 1950's during construction of the Nome-Taylor Highway. Access was via a short 60-m gravel road leading from the highway. A gravel fi II ramp protected the 1.5-m in- cised floodplain bank. There was no evidence of site rehabi I itation; the access road remains and its end has been eroded by the river. Material stockpiles and overburden berms were not observed in the floodplain. Various aspects of this site are shown in Figure 25. NORTH SLOPE General Description of Region Eight gravel removal sites from two North Slope physiographic prov- inces, the Arctic Coastal Plain !ACPl and Arctic Foothi I Is !AFHl, were included in this study !Wahrhaftig 1965). Both provinces are underlain by continuous permafrost. The study sites at Ugnuravik River and Kuparuk River are in the Teshekpuk Section of the ACP while the Skeetercake Creek site is in the White Hi I Is Section. Aufeis Creek, Sagavanirktok River, and Kavik River sites are in the Northern Section of the Arctic Foothi I Is Prov- ince while the Ivishak River and Shaviovik River sites are near the border between the two provinces. The Teshekpuk Section of the ACP Province is flat and poorly drained, being very marshy in the summer !Figure 3!. The poor drainage results in part from a continuous permafrost layer from 0.2 to 1.2 m beneath the surface. Ice wedge polygons, beaded streams, and elongated thaw lakes are common in this area. Pingos and incised river channels pro- vide the only rei ief to the flat terrain. The study sites in this section are in an area of coastal delta deposits of interstratified alI uvial and marine sediments with some local glacial drift deposits. In the White Hi lis Section of the ACP Province, the surficial geology contains areas of undifferentiated alluvium and colluvium consisting of 42 c c c c e c c 0 c ) .) J .) Figure 3. Arctic Coastal Plain wetlands. fine-grained deposits associated with greatly sloping hi I Is. Bedrock out- crops are rare in this area. The Northern Section of the AFH Province is characterized in its northern area by gently rolling terrain with occasional isolated hi lis and in its southern area by rolling plateaus and low I inear mountains with broad east-trending ridges (Figure 4l. The surficial geology of the AFH is more complex than that in the ACP Province. The Aufeis Creek study site is near a geologic contact between eolian si It deposits and undifferentiated alluvial and colluvial deposits while the Kavik River and Sagavanirktok River sites are flanked by remnants of moraines and associated drift. The topography surrounding the Ivishak River site, near the border of the ACP and AFH Provinces, is more typical of that of the White Hi lis Sec- tion !Figure 5) while the Shaviovik River site is right at the interface of the two provinces. The area to the south and west of the Shaviovik River site is flat while that to the north and east is predominated by mildly sloping hi I Is up to 360m. 43 Figure 4. Northern portion of the Arctic Foothi I Is. Figure 5. Typical view of the White Hi I Is Section of the Arctic Foothi Its. 44 J J The climate of the North Slope is characterized by long winters, cold temperatures, and frequent winds. Normal temperature ranges are from 2 to 13°C in the summer and -30 to -22°C in the winter. Annual precipitation along the Arctic Coastal Plain is approximately 13-15 em, which includes 30-120 em as snow, while in the Arctic Foothi I Is, the annual precipitation is about 25 em, including 140 em as snow. The Teshekpuk Section of the ACP Province is characterized by flat topography, wet tundra, and numerous lakes and ponds. AI I plants, including woody forms such as wi I low and heath, are low growing. In most areas tundra vegetation occurs up to the stream banks and woody thickets are not pres- ent. The vegetation of the Northern Section of the AFH Province consists of tundra species with small stands of taller riparian shrub thickets (2-5m in height! along the river systems. Smal I river systems of the North Slope contain primarily resident fish species, such as Arctic gray! ing, resident Arctic char, round white- fish, burbot, and slimy sculpin, with estuarine species, such as fourhorn sculpin, ninespine stickleback, and possibly whitefish species, entering lower reaches. Larger river systems, such as the Sagavanirktok-Ivishak drainage, also contain anadromous species, including Arctic char, chum and pink salmon, broad whitefish, humpback whitefish, least cisco, and Arctic cisco, as wei I as the resident species. Description of Study Rivers-Location and Gravel Removal Area Characteristics Ugnuravik River. Ugnuravik River is a medium, sinuous river which originates on the Arctic Coastal Plain at an elevation of 100m and flows across coastal plain tundra for 65 km before emptying into the Beaufort Sea. It is primarily confined to a single channel except for a few short beaded sections in the upper reaches. The study site is approximately 6 km from the mouth at an elevation of 2m. 45 -------·--------------------------------· --------------------------·-- The study site was developed by pit excavation and scraping approxi- mately ha within and adjoining the active channel of the Ugnuravik River. Gravel removal was conducted during the winter from 26 March to I Apri I 1969 with an unknown quantity of sand and gravel extracted from the site. Twenty- three thousand cubic meters had been approved for removal, but the permittee found that the gravel was only a veneer and not in sufficient quantities for their needs. During this short period of operation, gravel was removed from below the water table. Si It accumulation was noted in the gravel removal area; overburden had been stripped and pi led along both banks of the river; and backhoe teeth were observed near the working limits. Various aspects of this site are shown in Figures 26, 36, 83, and 92. Aufeis Creek. Aufeis Creek is a medium, meandering river originat- ing in the foothi I Is near the lmnavait Mountains at an elevation of 670 m and flows approximately 100 km before joining the Kuparuk River. The study site lies at an elevation of 275m approximately 60 km upstream from the confluence with the Kuparuk River. Material removed from this site was used for the construction of faci 1- ities associated with oi I exploration. Faci I ities constructed include a 1,341-m airstrip, a camp work and storage pad, and access roads of approx- imately 7 km in length connecting the stream with the airstrip and camp pad. An estimated 288,000 m3 of material were removed during the winter of 1972. There are two large and distinct gravel removal areas separated by approximately 3,130 m of undisturbed stream. The upstream gravel removal area covers 46 ha along a 2,260 m reach of the stream. The entire f-lood- plain was scraped, including the channel bed itself. Clearing and-removal of approximately 20 ha of vegetation and overburden were required. There is no evidence of rehabi I itation following mining. Mining at the downstream gravel removal area was less extensive and included scraping the inactive floodplain, and in some areas, the adjacent terraces along a 600 m reach of the stream. Deep and shallow scraping, as 46 ( ---··------·- .J J wei I as pit excavation, were uti I ized to remove gravels. The main channel of the creek was apparently not disturbed at the downstream area. Clearing and removal of vegetation and overburden were required in the downstream area. Dikes were also constructed, possibly to protect the integrity of the main channel and prevent its spreading into the mined area. Various aspects of this site are shown in Figures 14, 39, 54, 68a, 68b, 69, 75, and 81. Kuparuk River. The Kuparuk River is a large, braided river which origi- nates in the Brooks Range foothi lis and crosses the Arctic Coastal Plain before discharging into the Beaufort Sea. The study site is located approxi- mately 9 km upstream from the mouth of the Kuparuk River at an elevation of less than 10m. The material site was developed by scraping unvegetated mid-channel and lateral bars within the active floodplain of the Kuparuk River. Approx- 3 imately 41,300 m of gravel was removed from 14 ha between Apri I and August 1969 to provide material for dri II site pads, roadways, and airstrips near the site. The site was scraped to within or slightly below the existing water table. The 5-m incised floodplain bank was protected with a gravel fi I I ramp. Smal I mounds of stockpiled materia! were noted within the materi- al site. Various aspects of this site are shown in Figure 51. Skeeter cake Creek. Skeetercake Creek is a sma I I, meandering stream which originates in the northern edge of the foothi I Is of th~ Brooks Range at an elevation of about 300m and flows approximately 40 km to its conflu- ence with the Toolik River. The study area lies at an elevation of about 160m, approximately 15 km upstream from the confluence. Material removed from Skeetercake Creek was used for oi I dri I I ing operations. Gravel extraction at the site was accomplished during December 1965 by scraping 10 ha of floodplain deposits on three consecutive meanders. Approximately 38,000 m3 of gravel were reportedly removed, much of which apparently was not used; the unused material was pushed into large stock- piles which sti I I remain in the upstream gravel removal area. 47 Vegetative clearing, overburden removal, and berm construction were conducted at each of the three gravel removal areas~ At the upstream area the overburden was formed into an earthen dike, the purpose of which is unclear. The gravel removal areas were not rehabi I itated following distur- bance. Various aspects of this site are shown in Figures 37, 42, and 48a. Sagavanirktok River. The Sagavanirktok River is a large, sinuous river (at the study site) which originates in the Phi lip Smith Mountains of the Brooks Range at an elevation of approximately 1,500 m and flows through mountains, foothi I Is, and coastal plains approximately 300 km before enter- ing the Beaufort Sea. The study site, at an elevation of 335m, is located about I I km downstream from Pump Station Number 3 on the Trans-Alaska Pipe- 1 i ne, 16 km downstream from the mouth of R i bdon River, and 21 km upstream from the mouth of Lupine River. Gravel removal occurred in 1974 and 1975 by scraping vegetated and unvegetated gravel bars totaling approximately 35 ha. About 15 ha had been vegetated with mature riparian wi I low thickets. The original mining plan ca I I ed for scraping to an average of I. 5 m in depth with an average of 15 em of overburden removal required prior to gravel extraction. Approximately 3 3 283,000 m and 148,000 m of gravel were removed from the upstream and downstream gravel removal areas, respectively. Access to the floodplain was gained via a gravel ramp which protected the floodplain incised bank. Prior to site abandonment in 1976, existing stockpiles and berms were I eve I ed and contoured, and the grave I f iII ramp protecting the bank was to be removed. Various aspects of this site are shown in Figures 44, 45, 76, and 82. Ivishak River. The Ivishak River is a large, braided river which origi- nates in the Phi I ip Smith Mountains at an elevation of 1,829 m and flows 80 km through the mountains and 45 km through the foothi I Is before entering the Sagavanirktok River. The study site lies I I km upstream from the conflu- ence of the Sagavanirktok River. 48 c J ) J J Material removed from the Ivishak River was used for the construc- tion of faci I ities associated with oi I exploration. Gravel extraction was accomplished by scraping unvegetated, mid-channel gravel bars within the active floodplain of the Ivishak River. Two separate winter gravel removal operations were conducted at this location with I 15,000 m3 extracted during March and Apri I 1972 and 3,800 m3 extracted during November and December 1974. Information pertaining to the size of the gravel removal area is not available because removal occurred on randomly located gravel bars within the permit area; however, the average depth of excavation planned for the 1972 operation would require approximately 40 ha of exposed material. Three separate gravel removal areas were observed in the field. The upper area is located upstream from the airstrip in the left quarter of the active floodplain. The middle area lies in the middle of the flood- plain covering an area equivalent to the upstream one-third of the air- strip. The lower area lies about one-third of the way across the flood- plain from the left bank, just downstream of the downstream end of the airstrip. Vegetative clearing, overburden removal, or dike construction were not necessary at the site. Grave! ramps were used for access to the flood- plain over the river bank at most points of entry, however, at the down- stream access point the 2-m incised bank was cut instead of protected by gravel fi I I. Two gravel haul roads 90 to 150m long connect the airstrip to the material site. During 1972 and 1974 dozers were used to rip and stockpile material for front-end loader transfer to scrapers and trucks. Maximum excavation depth was to the existing water level at the time of the gravel removal operation. Rehabilitation measures used in 1972 and 1974 were similar: depres- sions were fi I led, stockpiles were leveled and gravel ramps were removed prior to breakup. Various aspects of this site are shown in Figure 71. Shaviovik River. The Shaviovik River is a medium, sinuous river which originates in the Brooks Range at an elevation of 909 m and flows for 95 km 49 before emptying into the Beaufort Sea. The study area is 95 km from the mouth at an elevation of 230 m. Gravel was scraped from unvegetated gravel bars within the active floodplain. The gravel was used in construction of oi I exploration faci 1- ities including a dri I I ing pad, campsite, supply pads, and landing strip. The proposed extraction area encompasssed approximately 2.4 km of flood- plain. Gravel removal was conducted during the winter of 1972 with I 16,000 m3 extracted between March and spring breakup. Vegetative clearing and overburden removal were not necessary before gravel removal. Material was stockpiled with a dozer and loaded into dump trucks with a front-end loader. Excavation below the water table was not permitted under the provi- sions of the mining plan. Access over the river bank to the mined area was by gravel ramp. Upon completion of gravel removal alI excavated sites were to be smoothed by back-blading with a dozer and the gravel access ramp over the stream bank was to be removed. At the time of site inspection the gravel ramp was sti II present and essentially intact. Various aspects of this site are shown in Figures 4, 72, and 91. Kavik River. The Kavik River is a medium river flowing in split channel configuration. It originates in the Brooks Range at an elevation of 1,200 m and flows 125 km to its confluence with the Shaviovik River. The study site is 60 km from the confluence with the Shaviovik River at an elevation of 1~0 m. Downstream from the study reach the floodplain widens and takes on a braided configuration. Approximately 40 ha were mined by scraping mid-channel and lateral gravel bars within the active floodplain of the Kavik River. Gravel was used for construction of an airstrip and road, and for development of four oi I wei I pads. Approximately 196,000 m3 were removed in 1968-1969 with another 50,000 m3 extracted in 1973-1974. The initial gravel removal activ- ity at this site was a tres~ass action and a mining plan is not avai !able. Gravel removal was conducted during the winter with scrapers and belly 50 -----~--------~----------------------------~-~~--~------~-------~-- ( J dumps; gravel removal was completed prior to breakup. Most disturbed gravel bars contained sparse vegetative cover consisting of herbaceous plants and scattered young wi I lows; however, one 2-ha island vegetated with a mature wi I low thicket was removed. The overburden and slash from this island were pi led within the gravel removal area. Diversion dikes were constructed to direct flow from the gravel removal area, and a 2-ha gravel stockpile was located on the edge of the floodplain. The 2-m incised floodplain bank was cut in five locations to gain access to the floodplain or to reach underlying gravel deposits. Approximately 375m of bank were disturbed. Rehabilitative measures were not employed following the activity, hence alI dikes, stockpiles, overburden piles, and cut banks remained during the site visit. Various aspects of this site are shown in Figures 5 and 77. NORTHERN INTERtOR General Description of Region AI I six study sites in this region are located in the Koyukuk River watershed. Four sites, Dietrich River-Upstream, Dietrich River-Downstream, Middle Fork Koyukuk River-Upstream, and Middle Fork Koyukuk River-Down- stream, are in the Central and Eastern Brooks Range Section of the Arctic Mountains Physiographic Province, while Jim River and Prospect Creek, are in the Kokrine-Hodzana Highlands Section of the Northern Plateau Physiographic Province (Wahrhaftig 1965). The Central and Eastern Brooks Range Section is characterized by flat-floored glacial valleys and east-trending ridges that rise to elevations of approximately 1,800 m (Figure 6l. Minor tributaries typically flow east and west, parallel to the structure imposed by the belts of sedimentary and volcanic rocks. Valley walls are dominantly coarse rubble deposits associated with steep sloped mountains which have a high percentage of bedrock exposures. The valley bottom in the vicinity of the Middle Fork Koyukuk River study sites consists of unmodified moraines and associated drift. The area is underlain by continuous permafrost. The Jim River and Prospect Creek sites, in the Kokrine-Hodzana Highlands, are in an area of 51 Figure 6. M.F. Koyukuk River valley looking upstream. coarse and fine-grained deposits associated with moderate to steep sloped mountains and hi I Is; bedrock exposures are I imited to upper slopes and crest I ines (Figure 7l. The area is underlain by discontinuous permafrost. Normal temperature ranges in the Northern Interior are from 2 to 20°C in the summer and -30 to -8°C in the winter. The annual precipitation is about 28-38 em, which includes 190-210 em as snow. The valleys in the Dietrich River-Middle Fork Koyukuk River region are heavily wooded with both steep, timbered slopes and gently sloping terraces adjacent to the river. The slopes are vegetated primarily with stands of white spruce and paper birch. In the Jim River-Prospect Creek area, the valleys are heavily wooded with white spruce and paper birch and a thick understory. Resident fish species found in the Koyukuk River system include burbot, Dolly Varden or Arctic char, Arctic grayling, long- nose sucker, northern pike, slimy sculpin, round whitefish, inconnu, and 52 Figure 7. Typical terrain of the Kokrine-Hodzana High- lands. other whitefish species. Anadromous species include chum and chinook salmon and possibly a na dromous whitefish spec i es. Description of Study Rivers-Locations and Gravel Removal Area Characteristics Dietrich R i ver -Upstream and Downstream. The Dietrich River is a medium, braided river which originates in the Endicott Mountains of the Brooks Range at an elevation of appro x imately 1,500 m and flows southward through mountainous terrain for I 10 km, joining the Bettles River to form the Middle Fork Koyukuk River. The upstream study site is located appro x imately 4 km, 14 km, and 25 km upstream from the confluence with Big Jim Creek, Snowdon Creek, and Bettles River, respectively. The downstream site is located 17 km and 6 km 53 upstream from the confluence with the Bettles River and Snowdon Creek, respectively, and 8 km from the upstream site. The upstream site was excavatedin an alluvial gravel deposit within the active floodplain of the Dietrich River. Between late summer 1974 and 3 early 1977, 631,000 m of gravel was removed from the 35-ha site for con- struction of the Trans-Alaska Pipe! ine. A dike was constructed across an intermittent channel north of the gravel removal area to divert active flow or seasonally high water away from the material site. Two methods were used to remove gravel. Most of the site was scraped to an average depth of 3m while a pit was excavated by dragline in the southern end of the work area. This pit is approximately 240 x 90 m and was excavated to an average depth of an additional 2m below the scraped portion of the gravel removal area. Within this pit two deeper holes approxi- mately 9 m deep were excavated. Ground springs were encountered during the scraping operation. The ground springs have been diverted through two chan- nels into the deep pit. Aufeis formation was a natural occurrence in this area before gravel removal and was observed downstream from the pit drainage channel during the first winter following excavation. A screening-crushing operation was used to produce pipe I ine padding and bedding material; stockpiled processed material also was stored at this location. The material site was utilized as a concrete fabrication area in August 1975 to produce cement castings of pipeline weights. In the summer of 1977 the area was sloped and contoured to drain water into the gathering channels leading to the deep pit. The southern and north- ern portions were then reseeded with annual grasses. The central portion was left open for access to stockpiled maintenance and operation gravel for the Trans-Alaska Pipeline. The Dietrich River-Downstream site was worked by shallow excavation of a gravel deposit within the active floodplain of the Dietrich River. Gravel was removed from the 7.5-ha site with 128,590 m3 of material ex- ( _} tracted during 1975 for construction of the Trans-Alaska Pipeline. Over- burden within the working I imits required disposition and stabilization outside the active floodplain. Permit provisions required a 90-m undis- turbed buffer between the working I imits of the material site and active channels of the Dietrich River. Braided channels that flowed east of the material site were diverted west of the site by an upstream dike to pre- vent active flow during excavation. Fine to coarse gravel with sand and a trace of si It was excavated to a 0.9 m depth. Rehabilitation measures conduc- ted after mining included sloping of all al iquots to the southwest. Various aspects of this site are shown in Figures 47a and 73. Middle Fork Koyukuk River -Upstream and Downstream. The Middle Fork Koyukuk River is a large, sinuous river which originates in the Brooks Range at the confluence of the Dietrich and Bettles Rivers and flows I 16 km before joining the North Fork Koyukuk to form the Koyukuk River. The Middle Fork Koyukuk River flows in inconsistently spaced reaches of braided and single channel patterns. The upstream study site is located about 92 km from the confluence of the Middle Fork Koyukuk and North Fork Koyukuk Rivers at an elevation of 365m. The downstream study site is 45 km from the confluence with the North Fork Koyukuk River and 47 km downstream from the upstream study site at an elevation of 282m. At the upstream study site gravel extraction was accomplished by shal- low excavation of sparsely vegetated gravel bars associated with the active channel and excavation to the same elevation in the contiguous, vegetated alluvial terrace. From August to November 1974, 135,000 m3 of gravel was removed from about 20 ha. The material site is comprised of two parcels; the upper area encom- passes a high-water channel while the lower area is situated on the inside bend of the next meander downstream. The upper area was unvegetated prior to gravel removal. Scattered stands of shrub thickets occurred within the active floodplain portion of the lower ar.ea and the adjacent alluvial ter- race had to be cleared of mature white spruce and balsam poplar prior to gravel removal. Overburden was not present on the active floodplain area, however, 15 em of organic si It were stripped from the alluvial terrace and disposed of southeast of the lower area. An undisturbed 30-m buffer was maintained between the active chan- net and the working I imits of the lower area; natural depressions and minor channels through the buffer were augmented by construction of perimeter dikes not exceeding 0.3 m above the natural buffer elevation. Caterpi I tar tractors with rippers and self-loading bottom dump scrapers were used to excavate to depths of 0.9 min the active floodplain and 3.0 min the adja- cent alluvial terrace area. The upper area was scraped to a depth of 0.9 m. Material extracted from the active floodplain was seasonally frozen, sandy, fine to coarse rounded grave I. The a I I uv i a I terrace provided frozen, inter layered si tty and sandy gravel to the water table. Screening and stock- pi ling of select material was conducted on the floodplain. Permit provisions required that unused material of si It size and finer be disposed of outside the active floodplai~; unused coarse material from the screening process could be evenly spread in the gravel removal area. During site rehabilitation the disturbed area was graded to an even bottom with cut faces no steeper than 2: I, stockpiles were removed, and outlet channels were constructed at the downstream end to allow high-water drainage. Revegetation within the active floodplain was not attempted due to the likelihood of periodic flooding. Various aspects of this site are shown in Figures 15, 47b, 49, 52, and 88. The Middle Fork Koyukuk River-Downstream site was developed by shal- low scraping of a sparsely vegetated lateral gravel bar within the active floodplain. The gravel removal operation was conducted during the winters of 1975 and 1976 with 215,000 m3 of material removed from 28 ha. Permit pro- visions required overburden encountered within the working I imits to be disposed of and stabilized outside the active floodplain. 56 ( J J A material site investigation conducted prior to removing gravel report- ed wei !-rounded gravel with some seams of fine sand and an absence of perma- frost in test pits. Approximately 38,000 m3 of select material was produced from a screening operation and stockpiled outside the material site working I imits. Rehabi I itation of the site following completion of the gravel remov- al activity did not include seeding or revegetation of the leveled gravel due to the likelihood of periodic flooding. Various aspects of this site are shown in Figure 6. Jim River. The Jim River is a medium, sinuous river which originates at an elevation of 880 m and flows about 96 km before emptying into the South Fork of the Koyukuk River. The study area is located 37 km from the mouth at an elevation of 275 m. Material removed from this site was used for the construction of faci li- ties associated with the Trans-Alaska Pipe! ine. An access road !90 m in lengthl was constructed connecting the site to the Haul Road. Vegetative cover and underlying organics were removed. Gravel extraction was accom- 3 plished by scraping about II ha, yielding an estimated 200,000 m of gravel. The site was worked during winter to a level below the water table. As a result, the site was inundated during summer, leaving, at the time of the survey, a shallow pit consisting of two ponded segments, approximately 5 and I ha in size with a maximum water depth of 1.2 m. The former high-water channel now flows continuously through the site thus connecting the pit area with the main Jim River. Restoration began during the fall of 1976. The site was contoured, including sloping the banks on the south, north, and west sides of the site, and revegetated. The excavated depression was fi lied in restricting water to the east side of the gravel removal area and reducing the inun- dated pit area to ha by 1978. Various aspects of this site are shown in Figures 7, 48b, and 78. Prospect Creek. Prospect Creek is a medium, meandering stream which originates at an elevation of about 600 m and flows 40 km to its conflu- 57 ence with the Jim River. The study site lies at an elevation of 270m approx- imately 5 km from the mouth of Prospect Creek. The site was worked by scrap- ing surface gravel deposits over 6 ha of gently sloping terrain adjacent to Prospect Creek. In addition, a 1-ha pit was excavated on the northern edge (lowest pointl of the gravel removal area to act as a sediment catch basin. Gravel removal was conducted intermittently from Apri I 1974 through Apri I 3 1975 with 63,636 m of gravel removed for construction of the Trans~Aiaska Pipe I ine System. A 45-m wide buffer was ~aintained between Prospect Creek and the gravel removal area, however, a 90-m wide swath was cleared through this buffer zone on 22 May 1974. Gravel removal was accomplished by ripping frozen material prior to conventional loading and hauling methods. Material varied from clean to silty fine to coarse gravel. An average working depth of 2.7 m was planned for the catch basin pit with additional excavation permitted if suitable material was present below this level. A screening operation to produce select material was conducted in the pit. The pit has fi I led with water as a result of intergravel flow during the summer months. During the site visit, this ponded water averaged approxi- mately I m in depth. The pit does not have an inlet, however, an outlet leading to Prospect Creek from the northwest corner was constructed during site rehabilitation activities to allow unimpeded fish passage into and out of the pit. Additional rehabi I itation measures included grading the material site to I percent downslope, ensuring that alI cut slope faces were no steeper than 2: I, and leveling of temporary stockpiles to blend with the natural terrain. Various aspects of this site are shown in Figures 28 and 55. SOUTHERN INTERIOR General Description of Region AI I five study sites in the Southern Interior were located in the Tanana River drainage, which empties into the Yukon River. The study sites 58 ( c c 1 ) are located in three physiographic provinces-the Yukon-Tanana Upland Section of the Northern Plateaus Province (West Fork Tolovana River and McManus Creek), the Tanana-Kuskokwim Lowland Section of the Western Alaska Province (two Tanana River sitesl, and the eastern portion of the Alaska Range Section of the Alaska-Aleutian Province (Phelan Creek) (Wahrhaftig 1965). The Yukon-Tanana Upland Section is characterized by rounded ridges and flat, alluvium floored valleys (Figure 8l. Surface deposits tend to Figure 8. Typical terrain in the Yukon-Tanana Upland Section. coarse and fine-grained a I I uv i um and co I I uv i um. Bedrock exposures are gen- erally limited to upper slopes and ridges. The area is underlain by discon- tinuous permafrost and is subject to extreme temperature ranges, from -45°C in the winter to 32°C in the summer. The average annual precipitation is 33-35 em, which includes 130-150 em as snow. 59 The Tanana-Kuskokwim Lowland Section in the vicinity of the Tanana River study sites is characterized by extensive glaciof luvtal deposits and large alI uvial fans (Figure 9). The area is immedia t ely south of the Figure 9. Glaciofluv i al deposi t s in Dry Creek floodplain. Yukon-Tanana Upland section. The Tanana River basin I ies in an area of discontinuous permafrost. The climate is typified by cold, dry winters and warm, relatively morst summers with an annual precipitation of around 32 em, including about 90 em as snow. The Alaska Range Section is characterzed by glaciated ridges between mountains to 2,900 m (Figure 10). Unmodified moraines and associated drifts dominate the surficial geology. The area is underlain by discontinuous permafrost. Normal temperatures range from 2 to 17°C in the summer and -33 to 1°C in the winter. An annual precipitation of 43 em includes 275 em as snow. 60 J Figure 10. Typical view of Alaska Range Section. The vegetation at the Southern Interior study sites varied because of differences in climate, e l eva tion, and geology of the three physiographic provinces. The West Fork Tolovana River site is in a val ley heavily wooded with white spruce and paper birch with a thick understory, particularly along the river. At McManus Creek, the surrounding hi I lsides have thin stands of white spruce with dense underbrush. The floodplain areas devoid of white spruce are covered with wi I low thickets with woody and herbaceous groundcover. At the two Tanana River sites the adjoining hi I Is ides are covered with dense stands of aspen and paper birch with scattered white spruce while islands in the floodplain are covered by 10 to 20m tal I stands of white spruce with scattered paper birch. The vegetation surrounding the Phelan Creek site consists of subalpine tundra, upland thickets associated with the drainages, and scattered, open stands of white spruce. Resident fish species found in the Tanana River system include Arct i c grayling, northern pike, burbot, longnose sucker, slimy sculpin, various 61 whitefish species, and scattered Dolly Varden populations. Anadromous spe- cies include coho, chum and chinook salmon, and various whitefish species. Species of whitefish found in the drainage include Bering cisco, broad whitefish, humpback whitefish, least cisco, round whitefish, and inconnu. Most of these species show substantial movements within the Yukon River drainage and distribution and anadromy has not been wei I documented for many of the species. Description of Study Rivers-Location and Gravel Removal Area Characteristics West Fork Tolovana River. The West Fork Tolovana River is a medium, meandering river orfginating in the foothi lis of the White Mountains in the Yukon-Tanana Upland Section at an elevation of 915 m. The confluence of the West Fork Tolovana River and Tolovana River, a tributary to the Tanana River, I ies 6 km downstream from the study site. The material site is located on the east side of the river with an undisturbed 60-m buffer strip between the site and the river. The mining occurred in an abandoned channel with the upstream end of the channel plugged to prevent water flow through the site. The outlet, however, is open to a backwater area of the 3 river. The 8-ha site was worked in 1975 by a dragline with 101,500 m of material removed, stockpiled, and screened to produce the required quanti- ties of select materials. The pit fi lied with groundwater and has depths in excess of 6 m. The unflooded portions of the gravel removal area were contoured and sloped to drain toward the pit in 1976. Most of these areas were also reseeded by Alyeska Pipe I ine Service Company with annual grasses. Various aspects of this site are shown in Figures 48c, 56, 59, 62, 63, and 84. McManus Creek. McManus Creek is a smal I, sinuous stream which origi- nates in foothi I Is at an elevation of 1,000 m and flows 25 km to its conflu- ence with Smith Creek, forming the Chatanika River. The study site lies at an elevation of 675 m, approximately 20 km from its confluence with Smith Creek. During the course of its development, McManus Creek has tended to migrate laterally southward, causing a slightly steeper valley wall on the left than on the right. 62 ( r '- J ) J J J J The material site was developed during construction of the Steese Highway by scraping gravel deposits within and adjoining the main channel of McManus Creek. A smal I gravel pit was also dug along the northwest boundary of the site, in an area where the floodplain meets the valley wall. During gravel removal operations, it was necessary to clear and remove the dense vegetation at the 3-ha site. An estimated 75,000 m3 of gravel were made avai !able for use by these efforts, although a considerably smaller amount is thought to have actually been removed. Large mounds of removed overburden and unused gravels were left within the site. Site rehabilitation was not performed following mining activities. The revegetation that has occurred is attributed to natural reinvasion. Various aspects of this site are showo in Figure 89. Tanana River -Downstream and Upstream. The Tanana River is a large, braided river fed by many glaciers in the Alaska Range. The Tanana River- Downstream study site is adjacent to the Richardson Highway approximately 57 km downstream from the Tanana River and Delta River confluence at an elevation of 260m. The site was developed by pit excavation of the central portion of a vegetated island located within the active floodplain of the Tanana River. Excavation was conducted after March 1971 with approximately 310,000 m3 of materia! removed from within the 8-ha working limits. Cleared and stripped surface materials were disposed of in waste areas along the borders of the pit. Permit stipulations required a minimum 91 m buffer along the highway and a minimum 30-m undisturbed buffer along adjacent side- channels of the Tanana River. Maximum depth of excavation in this uncon- nected, water-fi I led pit was approximately 9.4 m. The site was not reha- bilitated. The Tanana River-Upstream study site is adjacent to the Richardson Highway approximately 9 km downstream from the Tanana River and Delta River confluence at an elevation of 290m. The gravel removal area was developed by pit excavation of a vegetated gravel deposit adjacent to an active side channel of the Tanana River. The pit was excavated in two parcels herein called the upper and lower pits, which are segregated from the river by a 30 to 40-m wide vegetated buffer. A single channel at the downstream end of the 63 lower pit connects the excavated area to the Tanana River. Mining operations were conducted between 1962 and 1965 during reconstruction of the Richardson Highway between Shaw Creek and Delta Junction. The actual amount of gravel removed is unknown but 133,600 m3 were approved for removal at this loca- tion. The upper and lower pits total about 7.5 ha. Access to the site was via a 100-m gravel road from the Richardson Highway. Clearing of dense wi I low and alder and scattered white spruce and paper birch was necessary before stripping of 0.6 to 0.9 m of brown silt, fine sand, and organic material. Coarse gravel was present below the over- burden with 10 to 15 percent oversized material. Smal I stockpiles of gravel were noted along the south edge of the pit. In the upper pit the excavation occurred in an irregular pattern over about 3.5 ha, creating numerous is- lands and spits. The lower pit on the other hand was mined contiguously over 4 ha, is of greater average depth, and contains no major elevated land forms within its main boundaries. It did not appear that the site was rehabi 1- itated following gravel removal. Various aspects of this site are shown in Figures 27, 57, 70, and 80. Phelan Creek. Phelan Creek is a smal I, braided river which originates at an elevation above !,200m at the Gu!kana Glacier and flows 19 km through the mountainous terrain of, the Alaska Range before joining the Delta River. The study site is located approximately 3 km upstream from the Richardson Highway crossing of Phelan Creek and 9 km downstream from the terminous of the Gulkana Glacier. The material site was worked by scraping unvegetated exposed deposits in the active floodplain of Phelan Creek during construction of the Trans- Alaska Pipeline System. Approximately 152,000 m3 were removed from the 25-ha original work area between July and October 1975; a 70-ha upstream expansion 3 was approved in late October and yielded an additional 423,000 m . Several high-water channels traversed both the original work I imits and the area encompassed by planned expansion to the east. The major active -channels of Phelan Creek flowed through the original working area at the time of the survey. 64 ( c 0 Vegetative clearing and overburden removal were not necessary for the removal of the sandy gravel with some cobbles and boulders. A 15-m buffer was maintained between the work area and main channel of Phelan Creek; this natural buffer was augmented by dikes across depressions and minor channels. A dike was constructed at the upstream end of the site to divert intermittent channel flow and an outlet channel was provided at the downstream end of the gravel removal area to facilitate drainage. Material was removed to a 0.9-m working depth with conventional loading and hauling methods; permafrost was not present but ripping with dozers was necessary for excavation of seasonally frozen ground. Simi far working depths, excava- tion methods, and diversion/buffer procedures were used during development of the upstream expansion. The site apparently was not rehabi I itated, because several dikes and one stockpile remained during the time of the site visit in 1978. Various aspects of this site are shown in Figure 90. 65 REFERENCE Wahrhaftig, C. 1965. Physiographic Divisions of Alaska. U. S. Geological Survey. Prof. Paper 482. 52 pp. 66 ( ( 0 EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS L. A. Rundquist INTRODUCTION The purpose of the hydrology and hydraulics study was to evaluate the effects of floodplain gravel removal on the river configuration, hy- draulics, sedimentation, ice characteristics, and hydrology at the 25 study sites. The locations of these sites are shown in Figure I. The characteris- tics describing the physical aspects of the site and the gravel removal methods are I isted in Table I .. General descriptions of the sites are pro- vided in DESCRIPTION OF STUDY RIVERS. Previous studies of gravel removal from river floodplains are limited in number. A prei iminary report for this project !Woodward-Clyde Consultants 1976al reviewed I iterature on gravel removal up to that time. Significant results of that review are included and expanded upon in this section. Other pertinent I iterature identified since 1976 are included in this section. A few general statements !from Woodward-Clyde Consultants 1976al con- cerning the behavior of rivers are given in the following paragraphs to provide a basis for the information presented in subsequent sections. A river continually changes its position and shape as a consequence of hydraulic forces acting on its bed and banks. These changes reflect the dynamic condition of the natural environment; they may be slow, gradual processes or sudden morphological changes resulting from an extreme flood event. A river system always strives toward a state of equilibrium in order to convey the water and sediment delivered to it. 67 Similarly, when a stream is altered locally, the change often causes modification of the channel characteristics for considerable distances both upstream and downstream. The river response to changes is quite complex, but alI rivers are governed by the same basic forces. From a review of avai I able I iterature on river response to alterations, some general statements can be made on the basis of past research results !Karaki et al. 1974J. • Depth is directly proportional to water discharge and inversely proportional to sediment discharge. • Channel width is directly proportional to water discharge and to sediment discharge. • Channel shape !width:depth ratio) is directly related to sediment discharge. • Meander wave length is directly proportional to water discharge and to sediment discharge. • River slope is inversely proportional to water discharge and directly proportional to sediment discharge and grain size. • Sinuosity is proportional to valley slope and inversely proportional to sediment discharge. Although these relationships cannot be used to predict the exact re- sponse of a river to alterations, they do reveal the interdependency of the river parameters. Local modifications to a river can induce short-term and long-term responses. During excavation, channel morphology and sedimentation charac- teristics may be changed. After the operation has ceased, the river wi I I tend to readjust to the geometry and pattern that it had previously; if the magnitude of the modification is large enough, the readjustment may take many decades to complete. The short-term responses are usually observable 68 c c 3 and may be measurable; however, the long-term response may be so gradual that the changes wi I I not be noticeable for decades. In addition to these general statements pertaining to alI rivers, a few characteristics of arctic and subarctic rivers are introduced below. Flow stops in many rivers for much of the winter. Those rivers that continue to flow in the channel beneath the ice or in the gravel beneath the channel have the potential to develop aufeis, which is ice that forms upon itself by a series of overflows. The remaining flow is considered vital to fish over- wintering areas. At breakup, the water levels of large snowmelt floods are often in- creased by ice jamming or aufeis in the channel. After the snowmelt flood, flow may decrease significantly for the rest of the summer except for a few short duration events in response to summer storms. Very low summer flow is especially common on the North Slope, which is semiarid, receiving only 150 mm of precipitation annually. In subarctic Alaska, glaciers feed many rivers, resulting in generally more uniform flows through the summer. Diurnal fluctuations are evident in these rivers near their headwater~. Associated with glaciers are glacier dammed lakes that can empty rapidly causing extensive flooding downstream. 69 METHODS OF DATA COLLECTION The hydrology and hydraulics field program was conducted to provide information for the evaluation of gravel removal impacts on the physical characteristics of the river within the study reach. Three consecutive days were available at each of the 25 study sites for collection of these data. The site visit was during the summer when the water level was rela- tively low so that the channels could be more easily crossed. Detai Is on the procedures used can be found in APPROACH AND METHODOLOGY. 70 J METHODS OF DATA ANALYSIS The evaluation of changes resulting from gravel removal operations at the 25 study sites was based primarily on subjective judgement. A few hydrologic and hydraulic analyses were performed to enhance the data base for making further evaluations and biological analyses. A table wa~ prepared that I isted quantitative values for the subjective evaluation of changes, and was used to compare sites and, thereby, to evaluate the relative change. The following subsections describe briefly the methods used in the analyses. HYDROLOGY Mean annual flows and flood frequency curves were developed for the 25 study sites. There were no U. S. Geological Survey gaging stations at the study sites. Nine sites were near enough to gaging stations to use the gaging station data, although none of the station records exceeded 12 years in length. Sta~dard regional regression techniques were difficult to use because of the sparse gaging station network in arctic and subarctic Alaska. The hydrologic analyses thus include a significant amount of judge- ment; thus, the results should be considered as rough estimates. Mean Annual Flow The mean annual flows at six U. S. Geological Survey gaging stations were used as a basis for the analysis. The unit mean annual flow (mean annual flow per square kilometer of drainage basin! was computed for these stations. Nine of the study sites were near enough to the stations to·use the station's unit mean annual flow. At the remaining 16 sites, the unit mean annual flow from the nearest gaging station was modified after con- sidering the difference in mean annual precipitation of the drainage basins for the gaged river and the study site. 71 Flood Frequency Analysis Flood frequency curves for ea~h of the study sites were generated by applying a regional analysis technique described by Lamke ! 1979l. Discharges for the I .25-, 2-, 5-, 10-, 25-, 50-, and 100-year recur- rence intervals were computed. In order to improve these estimates, flood frequency data based on the application of the Log Pearson Type I I I distribution were requested from the U.S. Geological Survey for 17 gaging stations on or in the general area of the study sites. The re- gression equations presented by Lamke were also used on these gaged rivers and the ratio of the Log Pearson Type I I I discharges to the discharges calculated from the regression equations were computed. These ratios were then applied to the study sites if the sites were ! I l on the same river but upstream or downstream from the gaging site, !2l a similar size to that of the gaged river, and !3l if the drainage basin characteristics such as headwaters location, aspect, and drainage basin shape were similar. The resulting discharges were used to develop flood frequency curves for each of the study sites. HYDRAULICS Three analyses were included in the hydraulic investigation: back- water analysis, uniform flow analysis, and hydraulic geometry analysis. Each of these are discussed in the following separate subsections. Backwater Analysis A backwater analysis was performed for most of the rivers included in the study using the standard step method !Chow 1959). Input data to the program included a selected discharge, a corresponding water sur- face elevation at the control section, cross-sectional geometry of each cross section in the study reach, distances between cross sections, and roughness coefficients for each subsection of each cross section. 72 J J Uniform Flow Analysis In addition to the flood flow computations performed in the backwater analysis, values of some geometric and hydraulic parameters at low flows were computed in order to relate these parameters to the corresponding discharge and to provide data for the aquatic habitat evaluation. Use of the backwater program was not appropriate for low flows because of the smal I number and wide spacing of cross sections in the study reaches. The flows at the surveyed cross sections were assumed to be uniform and computations were made using the Manning equation (Chow 19591. The input data to the uniform flow program included the cross-sectional coordinates, roughness coefficients, energy slopes, selected discharges, and initial estimates of stage. The surveyed water surface slope was used as an estimate of the energy slope because most surveys took place when rivers were carrying flow similar in magnitude to the mean annual flow. Similarly, the roughness coefficient was calculated from the measured discharge and geometry rather than from estimates used in the backwater analysis. This calculation technique was used because roughness would I ikely be greater at low flows than that at flood flows due to the greater influence of the bed roughness at sma I I depths. Hydraulic Geometry Analysis Values of the coefficients and exponents in the power relations for the hydraulic geometry (including mean velocity) at a cross section were com- puted for disturbed and undisturbed cross sections at five selected study sites. Power curve fitting was completed for the geometric and corresponding discharge data which were determined by the hydraulic analyses discussed in the previous subsections. The resulting coefficients and exponents were compared with the values obtained for other rivers in Alaska and other parts of the United States. In addition to this quantitative comparison, a qual i- tative comparison_ of power relation coefficients and exponents for disturbed and undisturbed cross sections was made based on plots of the power curves for each cross section of other sites having insufficient data range for a quantitative analysis. 73 QUANTIFICATION OF CHANGES At each of the 25 study sites an attempt was made to quantitatively rate the degree of change of selected river characteristics due to the gravel removal operations. When quantifying changes, the selected charac- teristic should be compared before and after the gravel removal operation under similar flow conditions. Whenever possible, this was done using aerial photographs. Aerial photographs often did not provide the necessary detai I, or the lack of information concerning flow conditions in the photographs mad~ such comparisons less meaningful. Thus, the upstream sample area was assumed to represent the undisturbed condition for many of the comparisons. After comparisons were made, a rating scale was applied to establish the relative degree of change occurring in physical characteristics at the various sites. A sca1e was selected ranging in value from 0 to 10, with 0 being a very large decrease in the quantity of a characteristic, 5 indicating no change, and 10 being a very large increase in the quantity of a character- istic. Intermediate values reflect various degrees of change between the extreme values. More specific meanings of the degree of change for each characteristic are given in the fo! !owing RESULTS AND D!SCUSS!ON section. AI I sites were rated using the rating scales. Sites with more than one physical response to the gravel removal activity were given more than one rating. These sites included Sinuk River, Washington Creek, Oregon Creek, Aufeis Creek, and Middle Fbrk Koyukuk River-Upstream. At alI other sites, the physical changes resulting from the gravel removal operation were similar throughout the site. The gravel removal areas for alI sites are dis- cussed in general in the previous section !DESCRIPTION OF STUDY RIVERS!. The separation of the gravel removal areas for the hydrologic and hydraulic analyses at selected sites is described in the following paragraphs. At Sinuk River, different responses to gravel removal were observed for two gravel removal locations. These locations are shown in Figure I I. An island that split the channel upstream of the highway bridge was completely 74 c Scale in Meters 17 June 1973 0 381 Figure II. Aerial photograph showing the two gravel removal locations at Sinuk River considered separately in the hydrology/hydraulics analysis. 75 removed (this area is designated Area Al. The other location (Area Bl, in and adjacent to high-water channels upstream and downstream from the highway bridge, was separated from the main channel. At Washington Creek, two gravel removal areas were separated by approxi- mately I km of undisturbed river (Figure 12!. The upper (upstream! and lower ( (downstream! gravel removal areas are designated A and B, respectively. At Oregon Creek the major area of disturbance was immediately upstream of its confluence with Cripple River (Figure 13, Area Al. The unvegetated gravel bar (Area Bl immediately downstream from the highway bridge was also used for gravel extraction. At the Aufeis Creek site, the two major gravel removal areas were separated by over 3 km of ri,ver channel (Figure 14!. The upper and lower sites are designated A and B, respectively. Gravel removal at the Middle Fork Koyukuk River-Upstream site was located in a high-water channel and on a point bar (Figure 15!. The upper and lower sites are designated areas A and B, respectively. 76 c Scale in Meters 17 June 1973 0 254 Figure 12. Aerial photograph of Washington Creek showing the upper and lower gravel removel areas. 77 Scale in Meters 18July 1977 0 Figure 1~. Aerial photograph of Oregon Creek showing the upper and lower gravel removal areas. 78 ) Scale in Meters 7July1977 0 305 Figure 14. Aerial photograph of Aufeis Creek showing upper and lower gravel removal areas. 79 Scale in Meters 11 July1977 0 305 Figure 15. Aerial photograph of Middle Fork Koyukuk River-Upstream showing upper and lower gravel removal areas. 80 RESULTS AND DISCUSSION The following subsections present and discuss the results of the data analysis for the 25 study sites. The five subsections represent five cate- gories of river characteristics which exhibited changes resulting from gravel removal operations. These include: • Channel configuration and process, • Hydraulics, • Sedimentation, • Ice characteristics, and • Hydrology. Each subsectibn includes background information that provides the reader with a knowledge of selected characteristics of undisturbed rivers and a description of changes which occurred in these river characteristics as a result of gravel removal operations. CHANNEL CONFIGURATION AND PROCESS The channe~ configuration of a river is the shape of the river chan- nel (s) when looking vertically down at the river. Configurations represented by the 25 study sites include braided, split, meandering, sinuous, and straight. A sixth configuration, beaded, is unique to northern environments, but was not investigated during this study; beaded systems are typically very smal I and are not likely to contain much gravel. Associated with the channel configurations are processes of sediment erosion and deposition which form features characteristic of the configuration. The five channel configurations that were used to describe the studied sites are described in s~bsequent paragraphs. 81 The channel configuration is a function of river stage (water level l; the optimum stage for defining the channel configuration is at low flow. The channel configuration is also a function of location along the river; a river could conceivably exhibit alI channel configurations between its headwaters and its mouth. The channel configurations describing the 25 study sites are those only through the reach studied. Configuration combi- nations, I oca I spatia I variations, and variations over time comp I i cate channel configuration selection. Undisturbed Condition ~raided Configuration. A braided river typically contains two or more interconnecting channels separated by unvegetated or sparsely vegetated gravel bars (Figure 161. Its active floodplain is typically wide and sparsely vegetated, and contains numerous high-water channels and occasional vegetated islands. Active channels are typically wide and shallow and carry large quantities of sediment at high flows. Bars separating the channels are usually low, gravel surfaced, and easily erodible. The lateral stabi I ity of the channels is quite low; channels shift by bank erosion and/or by channel diversion into what was previously a high-water channel. The lateral activ- ity of channels within the active floodplain of a braided river that carries large quantities of bed load, is expected to be high because gravel deposits may partially or fully block channels, thereby forcing flow out of the channel. Maximum depths and corresponding top widths of undisturbed major, side, and high-water channels, at four braided study sites, are plotted in Figure 17. Split Configuration. A split channel river has numerous stable islands which divide the flow into two channels (Figure 181. The banks of the chan- nels are typically vegetated and stable. The split river floodplain is typically narrow relative to the channel width. There are usually no more than two channels in a given reach and other reaches are single channel. One of the two channels in a split reach may be dry during periods of low flow. The channel cross section is narrower and deeper than a braided river with similar flow characteristics. Maximum depths and corresponding top widths of 82 ( :J :J J J PLAN VIEW ... ... Q) Q) ---~a; ~Q) I C • c ,cC ,cC a"' c:n"' --.C ·-.c :ro :ro SECTION A-A Figure 16. Schematic diagram of the plan view and cross section of a typical braided river. 83 2-0 1.0 . 9 . 8 .7 E .6 -:c .5 .... a.. .4 w c :::E .3 :::1 :::E >< .2 oC :::E ..... ..... :::1 u. ..... w z z oC :c (,) LEGEND eAclive Channel !:>High-Water Channel •Side Channel • • • • • 6 • • 6 6 •• ... 2 3 4 5 6 7 8 9 10 20 30 CHANNEL FULL TOP WIDTH (m) • • • • • • 60 . 90 120 150 180210 Figure 17. Maximum depths and corresponding top widths of undisturbed major, side, and high-water channels at four braided study sites. 84 c ) ::_) PLAN VIEW SECTION A-A Figure 18. Schematic diagram of the plan view and cross section of a typical split channel river. undisturbed major, side, and high-water channels, at four split channel study sites, are plotted in Figure 19. Sediment discharge is typically less than that of a braided river. Bed load is deposited at low flow to form gravel bars along the sides or in the middle of the channels. These bars are typically more erodible than the banks. The bars, rather than the banks, are eroded during subsequent floods, resulting in a laterally stable channel. Meandering Configuration. A meandering river winds back and forth within the floodplain (Figure 20). The ratio of the channel length to the downvalley distance is called the sinuosity ratio, or sinuosity. Meandering rivers have a sinuosity greater than 1.5. Flow is contained in a single 85 2.0 1.0 . 9 . 8 .7 :[-6 J: .5 1- ~.4 Q :iii .3 :::1 ! >< c( .2 :iii ...I ...I :::1 ... u: .1 z z c( J: u LEGEND •Active Channel 6High-Water Channel •Side Channel 2 6 66 6 66 6 6 6 66 6 6 6 6 6 6 6 6 5 6 7 8 9 10 20 30 CHANNEL FULL TOP WIDTH (m) • • • • • • tf 6 6 • 6 • • • • 6 6 6 • 6 6 60 90 120 150180210 Figure 19. Maximum depths and corresponding top widths of undisturbed major, side, and high-water channels at four split channel study sites. 86 PLAN VIEW 0 High-Water Channel ~~TPoint Bar SECTION A-A SECTION B·B Figure 20. Schematic diagram of the plan view and two cross sections of a typical meandering river. 87 2.0 1.0 .9 .8 :I; :I .7 .6 :I; .2 )( c( :I; ..J ..J ~ .1 ..J w z z c( l: (J channel, with very few islands. At each bend, the typical cross section contains a point bar on the inside of the bend ~nd a pool on the outside of the bend, resulting in a triangular shaped cross section. Point bars are the primary area of sediment deposition in a meandering river. Between the bends is a crossing, which typically has a wide and shallow cross sec- tion similar to that of a single braided channel. Since the width of the channel in the crossing is similar to that in the bend, the average veloc- ity is often greater through the crossing. Maximum depths and corresponding top widths of undisturbed major, side, and high-water channels at 15 study sites with meandering, sinuous, and straight configurations are plotted in Figure 21. A meandering river shifts in the downval ley direction by • LEGEND eActive Channel • • ~High-Water Channel • •Side Channel • •• • • •• • • .. • • • oL-----------,------,.---.--.4--r.-o-7.-r9,ro------"2o----3ro------~so~~go~~,co-,~,roo~~7o-- CHANNEL FULL TOP WIDTH (m) Figure 21. Maximum depths and corresponding top widths of undisturbed major, -side, and high-water channels at 15 study sites with meandering, sinuous, and straight configurations. 88 a continuous process of erosion and deposition; erosion takes place on the outside bank, downstream from the midpoint of the meander bend and deposition occurs on the downstream end of the next point bar downstream. The rate of downval ley shifting varies from one river to another. The rate and direction of shifting is much more predictable than the lateral shifting of braided channels. A result of nonuniform shifting is channel cutoffs. The floodplain width of a meandering river is often roughly equal to the meander belt width, which is the average width from the outside of one meander bend to the outside of the next opposite meander bend !Figure 20). High-water channels on the inside of point bars are typical on meander- ing rivers. Sediment transport in meandering rivers is typically moderate. Sinuous Configuration. A sinuous river is similar in plan view to a meandering river except that its sinuosity is between 1.1 and 1.5 !Figure 22). In sinuous rivers, point bars are smaller and downvalley shifting is generally less than that of a comparable-size meandering river. Other than the greater stability, sinuous rivers are quite similar in form and hydraulic characteristics to meandering rivers. Straight Configuration. A straight river flows in a single channel with a sinuosity less than I. I !Figure 231. The thalweg, or deepest part of the channel, typically wanders back and forth within the channel with alternate ground bars formed by sediment deposition opposite those locations where the thalweg approaches the side of the channel. The alternate bars may or may not be exposed at low flows. Rivers with a long reach of straight channel pattern are much less common than rivers with other configurations. Banks of straight channels are expected to be relatively stable. Sediment transport is likely to be light to moderate in these systems. Other Processes. Rivers with any configuration may be found in narrow mountain valleys and on alI uvial fans. Rivers in these locations have dif- ferent processes of erosion and deposition than those described for the 1 ~ typical river with the same configuration. Channel configurations of moun- tainous rivers are typically not control led by al !uvial processes, but 89 PLAN VJEW SECTION A-A Figur~ 22. Schematic diagram of the plan view and cross section of a typical sinuous river. PLAN VIEW SECTION A-A Figure 23. Schematic diagram of the plan view and cross section of a typical straight river. 90 J ~ather are control led by geological and morphological features of the val- ley. Mountainous rivers commonly have very little or no floodplain and consequently, have small quantities of gravel. Alluvial fans develop when a steep gradient stream flows onto a substantially less steep terrain; its sediment transport capacity is significantly reduced causing sediments to be deposited. This deposition fi I Is the channel, thus forcing the flow to develop a new channel. This may occur by a gradual migration process or by a rapid abandonment of one channel to develop a new channel. Such processes develop a partial cone-shaped deposit of gravels with the apex being near the end of the steep gradient river valley !Figure 24). The fan may or may not be vegetated; denser vegetation implies greater stability. Figure 24. Schematic diagram of an alluvial fan. Changes Due to Gravel Removal The most common change to the channel configuration resulting from gravel removal was a shift towards a more braided configuration as indi- cated, in part, by an increase in the number of channels. A decrease in lateral stability of the channels was often associated with changes to 91 more numerous channels. These changes were most prevalent in scraped sites and most prominent in single channel sites. Gravel removal at many scraped and pit excavated sites caused a diversion or a high potential for diversion of flow through the gravel removal site. These observed channel config- uration changes were given quantitative ratings for comparative purposes !Table 51. These changes in channel configuration are discussed in more detai I in the following sections. Braiding Characteristics. The two braiding characteristics considered were the number and stability of the channels. The most significant changes in these characteristics resulted from scraping operations in straight, sin- uous, split, and meandering rivers with lesser changes observed in scraped braided rivers. This difference was expected, because braided rivers had such characteristics prior to gravel removal, thus, any change was compara- tively less significant. The locations of the gravel removal operations that caused the most significant change in the braiding characteristics were those which disturbed the bars adjacent to active channels or those which c~used diversion of flow into the material site. Disturbance of the bars adjacent to active channels can hypotheti- cally reduce the flow within the channel during floods because flow spreads out through the mined area. The reduced flow within the channel would reduce the ability to transport sediments; sediment deposition within the channel may result. This deposition would potentially aggravate the problem by further reducing the cross-sectional area available to the flow. This pro- cess can result in widening the channel and the development of mid-channel bars. Although the potential for this hypothetical process exists, it was not observed at the study sites. Braiding characteristics increased at many sites due to the diversion of flow through the site and the lack of a wei 1-defined channel to confine the flow. The flow thus spread through the material site and likely did not have sufficient scour potential to develop a new channel. Thus, numerous poorly-defined channels flowed through the site. 92 ( c c u u u u l.J u u u Table 5. Quantification Ratings of Change in Channel Configuration Characteristics Resulting from the Gravel Removal Operation at Each of the 25 Sites River Gold Run Creek Sinuk River Washington Creek Oregon Creek Penny River Nome River Ugnuravik River Aufeis Creek Kuparuk River Skeetercake Creek Sagavanirktok River Ivishak River Shaviovik River Kavik River Dietrich River-Upstream Dietrich River-Downstream Middle Fork Koyukuk River-Upstream Middle Fork Koyukuk River-Downstream Jim River Prospect Creek West Fork Tolovana River McManus Creek Tanana River-Downstream Tanana River-Upstream Phelan Creek (Footnotes on fo I I owing page l Gravel removal area A B A B A B A B A B No~ of channel sa 5 4 10 5 9 7 9 10 6 9 5 7 5 10 8 6 8 5 6 5 10 8 5 5 5 5 5 5 4 Channel b stab i I it y 5 3 0 4 0 5 0 0 3 0 4 3 I 4 4 5 2 5 5 5 0 4 5 5 5 5 5 5 5 Diversion through pit 7 10 7 8 8 7 7 Diversion through c scrape 6 9 7 10 6 9 6 10 10 9 10 6 7 10 9 7 6 9 7 7 6 10 7 7 6 10 u Table 5. Footnotes aNumber of channels ratings: Number of active channels in the mined area Number of active channels upstream from the mined area 3 < B R 2.5 < BR < 3 2 < B R < 2.5 1.5 < BR < 2 10 9 8 7 6 I < B < 1.5 or other BR values if they are within normal variatio~ ranges of the river 5 I of if other data indicate no change 4 0.67 ~ BR < I or other BR values if they are within normal variation ranges of the river 0-3 Not used bChannel stabi I ity ratings: 6-10 Not used 5 No change in channel stabi I ity 4 Slight decrease in stabi I ity, but within natural stabi I ity vari- ation of the river 3 Moderate decrease in channel stabi I ity due to gravel removal 2 Large decrease in channel stability due to gravel removal Substantial decrease in channel stability due to gravel removal 0 Very substantial decrease in channel stabi I ity due to gravel removal cFiow diversion ratings: 10 High potential for river to divert all its flow permanently through the site 9 Diversion of a significant quantity of flow through the site oc- curred within several years 8 Moderate potential for river to divert all of its flow permanently through the site 7 Moderate to high potential for some of the river flow to divert permanently through the site or for flow diversion through the site during flood events 6 Low potential for river diversion through the site 0-5 Not used 94 c Ten sites had more than twice as many channels in the material site as were up~tream. At four of these sites, Washington Creek, Nome River, Sagavanirktok River, and Middle Fork Koyukuk River-Upstream, the numbers of channels increased more than three times due to gravel removal operations. Most sites (7 of 101 with large increases in numbers of channels also had a 3 very substantial apparent decrease in the lateral stability of those chan- nels. Lateral stabi I ity evaluations were based on subjective judgements of stabi I ity indicators. Lateral stabi I ity ,indicators included the height and erodibi I ity of the gravel bars at the edge of the active channels, the bed load transport characteristics evident at the time of the site visit, and the channel configuration. The Nome River is an example ~f a material site with increased braided characteristics (Figure 251. In this sinuous river, single channel flow was prevalent prior to the gravel removal operation; exceptions to this are the split in the channel immediately downstream from the material site location and two high-water or smal I active side channels adjacent to the material site location. Approximately 20 years after the gravel was removed, the river was flowing in numerous, poorly-defined channels through the material site. The river apparently diverted into the scraped area soon after the op~ration was completed and has attempted to develop a wei 1- defined channel since it diverted. The state of equilibrium between erosion J and deposition in the Nom~ River was disturbed by the gravel removal opera- tion. To restore equilibrium it wi I I probably take several decades from the time of the initial disturbance. Flow Diversion Through Site. Gravel removal operations caused flow diversion or a high potential for flow diversion at 12 of the 25 study sites. Sites with a high potential for the diversion of alI of the flow permanently through the site included upper Washington Creek, Penny River, Nome River, upper Aufeis Creek, Skeetercake Creek, lower Middle Fork Koyukuk River-Upstream, and Phelan Creek. At most of these sites, alI of the flow had already diverted when the site was visited. AI I of these sites were scraped and the lower Middle Fork Koyukuk River-Upstream site was the only site where a buffer was known to have been used to separate the site from 95 August1950 July1977 Scale in Meters 0 130 Figure 25. Comparative aerial photography of the Nome River showing change in channel configuration resulting from gravel removal activities. 96 J J J the active channel. The vegetated buffer was approximately 30m wide and roughly 1 m in height; vegetation was missing in and adjacent to a high- water channel which crossed the buffer. Low !0.3 ml dikes were used to block off this high-water channel. Flow began to divert through the material site during the first breakup following the removal of gravel. The buffer breached, apparently caused by overtopping and subsequent erosion of the top and downstream face during the flood. At the time of the site visit in 1978, 3~ years after the mining took place, 85 percent of the flow was going through the material site. Scraped sites with a large amount, but notal I, of the flow diverted through the material site by the time the site was visited included Sinuk River !in-channel site!, upper Oregon Creek, Ugnuravik River, Sagavanirktok River, and Kavik River .. None of these sites had a vegetated buffer. A major consequence of flow diversion through scraped sites was the devel~p~ent oi braiding characteristics, as was discussed in the previous section. Another consequence was that flow in the former main channel!sl was eliminated or significantly reduced, thus affecting their hydraulics and their regime. Flow through scraped sites that had the potential to aid the replenishment of gravel within the site occurred at Sinuk River ! in-channel site!, Washington Creek, Oregon Creek, Ugnuravik River, Aufeis Creek, Kavik River, and Phelan Creek. At other sites, such as Penny River and Middle Fork Koyukuk River-Upstream, flow through the site was probably eroding more sediments than it was depositing. Most (6 of 71 pit excavated sites had vegetatea buffers separating the material site from the active channel (sJ. The exception is Ugnuravik River (Figure 261, which had only a 5-to 10-m wide gravel bar separating the material site from the active channel. Therefore, the potential for flow diversion through this pit is high; flow has diverted through the site during floods, but the diversion has not yet been permanent. The two pit excavated sites on the Tanana River were judged to have moderate to high potential for some of the flow diverted permanently through the site within several decades following site closure. Both sites had 97 Scale in Meters 7July1977 0 76 Figure 26. Aerial photograph of the Ugnuravik River pit site showing the in- sufficient buffer zone. 98 :) .) approximately 30 m to 40 m wide vegetated buffers. The main channel of the Tanana River has the capability to erode through such a buffer in less than a year. The side channel at the Tanana River-Upstream site (Figure 271 eroded 3m of the widest part of the buffer between early June and mid-September of 1978. At either of the Tanana River sites, it could take several years or sev~ral decades for the river to breach the buffer and flow through the pit, the length of time depending on the lateral direction oi travel of the main channels. The Prospect Creek and West Fork Tolovana River sites were judged to have a moderate potential for all of the flow to divert through the pits. Both sites had vegetated buffers that inc~uded portions of abandoned channels. The upstream end of the abandoned channel, in both cases, causes a zone of weakness in the buffer. Even though, at both sites, the width and height of the buffers were likely sufficient to prevent breaching for several decades, zone~ of weakness in the buffers at the abandoned channels and channel aufeis development in the active channel may cause earlier flow diversion and buffer b~eaching. At the West Fork Tolovana River site, the upstream end was diked off and heavily riprapped; however, in spring of 1979, flow apparently overtopped the dike and scoured the channel lead- ing into the pit, leaving a large delta gravel deposit in the pit. Flood stage was probably high because of aufeis development in the channel. Channel aufeis developmeot also influenced the Prospect Creek site (Figure 281. Aufeis developed in the channel reach upstream from the material site, reducing the channel capacity during the snowmelt runoff period. The runoff thus flowed directly down the valley, rather than following the ice-fi lied channel. The water flowed through the pit causing headcutting of the up- stream edge. The edge was subsequently riprapped to prevent further head- cutting. Doyle and Childers ( 1976) documented this Apri I 1976 occurrence. HYDRAULICS Hydraulics, as used in this investigation, is the study of those param- eters which influence the mechanics of water flow through the study reach. The hydraulic parameters which were considered include hydraulic geometry, 99 Scale in Meters 11 July 1977 0 168 Figure 27. Aeria l photograph of the Tanana River-Upstream site with substan- tial buffer zone separating the pit from the active side channe l. 100 ..) Scale in Meters 11 July1977 0 145 Figure 28. Aerial photograph of the Prospect Creek pit showing wide buffer zone separating the pit from the active channel. lOt channel slope, and local flow characteristics at flow obstructions. Hy- draulic geometry is defined as the geometric and hydraulic variables at a cross section that vary with changes in discharge. The hydraulic geometry variables discussed are top width, hydraulic depth, and mean velocity. Chan- nel slope !gradient! is the reduction of the water surface elevation in the downstream direction. A general discussion of these hydraulic parameters is presented in the following subsection, followed by a description of the effects on these parameters due to gravel removal. Undisturbed Condition The hydraulic geometry parameters considered herein are top width, hydraulic depth, and mean velocity. The top width is the width of the water surface at a given cross section and a given discharge !Figure 291. The "---Cross-Sectional Area (A) Figure 29. Schematic diagram illustrating definitions of channel geometric ana hydraulic variables. hydraulic depth is defined as the cross-sectional area of flow divided by the top width. The mean velocity is defined as the ratio of discharge to cross-sectional area of flow. An estimate of the carrying capacity of the channel is the conveyance, which is defined by: 10~ c ) => where K K c A R (I l conveyance a coefficient related to the roughness of the channel cross sectional area of flow hydraulic radius x =a fractional exponent The discharge is directly proportional to the conveyance with the proportion- ality constant being the energy slope to a fractional power, usually~- The variation in the hydraulic geometry as a function of discharge at a river cross section is an indicator of the shape of the channel cross section. The shape primarily reflects the magnitude of the bank-full dis- charge which typically has sufficient sediment carrying capacity to shape a channel and occurs frequently enough to maintain the resulting shape. The top width, hydraulic depth, and mean velocity at a cross section are often expressed as a function of discharge in the form of power relations: w = a Qb (2) D = c Qf (3) v k Qm (4) where w top width D hydrau I i c depth v mean velocity Q discharge a, c, k coefficients b, f, m =exponents Typical relations for a hypothetical river are shown in Figure 30. Sub- stituting the power relations for the hydraulic geometry variables into the flow continuity equation i I lustrates the interdependence of the variables: Q A V W D V (5) (a Qbl(c Qfl(k Qml (a c kl Q (b + f + ml (6) 103 Thus, for continuity, and a X C X k !7) b + f + m = I (8) .J -:s!A ·3: \ I D ~ ~i '5. CD CA t ~D B L..------_. Discharge Note: All Scales Are Logarithmic Figure 30. Average hydraulic geometry of river channels expressed by relations of width, depth, and velocity to discharge at two locations along a river !modified from Leopold, Wolman, and Mi I ler 1964). If a coefficient or exponent for one hydraulic geometry variable changes due to the gravel removal operation, at least one of the other variables must 104 ,., z_ ( ( ) ) ) J J J ) also change to maintain continuity of flow. Generally speaking, if a channel is widened, it often satisfies continuity by becoming shallower. Similarly, if a channel slope, or gradient, is increased, thus increasing velocity, continuity is commonly satisfied by a reduction in depth. Exponent values for selected study sites and other rivers are given in Table 6. The ex- ponents exhibit a wide range of variabi I ity for different rivers; Rundquist I 1975) found that the exponents and the coefficients can be expressed as functions of the bank-ful I discharge. The coefficient c and exponent f in the power relation for hydraulic depth were found in addition to be a func- tion of the median bed material size. The exponents in the power relations may change at a given site for discharges above bank-ful I because of the typically abrupt change in bank slope at bank-fuiJ conditions. The slope of the water surface profile for a typical river generally wi I I paral lei the bed slope at low flow, often producing a $equence of rif- fles and pools. At flood flows, the pool-riffle sequence is not apparent in the water surface profile !Figure 31 ). -F!ocd F!ow Water Surface Profile Low Flow Water Surface Profile--....l Figur'e 31. Schematic diagram showing change in water surface slope in response to a change in water disc~arge. Naturally occurring flow obstructions in rivers can include vegetation, rock or snow avalanches, aufeis, and boulders. The effect of an obstruction on the hydraulics is to cause a local increase in velocity which often 105 ------------------------------------------------------------------ Tabl_e 6. Values of Exponents for Hydraulic Geometry Power Relationsa River Kuparuk River Sagavanirktok River Shaviovik River Middle Fork Koyukuk River-Upstream Mi ddl"e Fork Koyukuk River-Downstream Average values, midwestern United States b Brandywine Creek, Pennsylvania b Ephemera I streams in semiarid United States b Average of 158 gaging stations in United States b 10 gaging stations on Rhine River b Average of 17 stations in Southcentral Alaskac Average of 30 stations in Upper Salmon River d area, Idaho a W = a Qb D = c Qf V = k Qm bCompi led by Leopold, et al. ;1964) cEmmett ( 19721 dEmmet t ( 1975 l 106 Undisturbed Disturbed areas areas b f m b f m 0.43 0.28 0.29 0.48 0.28 0.24 0.25 0.40 0.35 0.32 0.42 0.26 0.40 0.33 0.27 0.52 0.29 0. 19 0.29 0.44 0.27 0.44 0.33 0.23 0.54 0.28 0.18 0.37 0.29 0.34 0.26 0.40 0.34 0.04 0.41 0.55 0.29 0.36 0.34 0.12 0.45 0.43 o. 13 0.41 0.43 0. 19 0.39 0.42 0.14 0.40 0.46 ~ ( ( \.... r "" J results in erosion of the obstruction or bed scour adjacent to the obstruc- tion !Figure 321. Complete channel relocation is also a potential response to flow obstructions blocking a high percentage of the channel's cross- sect i ona I area. Jli--L--'-.J..-t.....L--J-~-~---....,""'----Close Flow Line ..__ ___ Pr_obable Scour Spacing Indicates High Velocities Figure 32. Schematic diagram illustrating the effects of a flow obstruction on the local hydraulics. Changes Due to Gravel Removal Substantial changes in hydraulic geometry, slope, and flow obstructions resulted from gravel removal operation& at roughly 60 percent of the sites. Typical hydraulic geometry changes in the mined area included increased channel top width, reduced hydraulic depth, reduced mean vel~city, and increased conveyance. Changes in slope due to gravel r~moval operations took 107 the form of increases through the mined reach resulting from channel cutoffs and local slope redistributions affecting the pool-riffle sequence. Flow obstructions in the forms of material stockpiles, diversion dikes, and overburden piles have the potential for causing local scour, ice jam forma- tion, and siltation. Hydraulic Geometry. Gravel removal operations caused changes in the natural cross-sectional shape of the active channels of approximately half of the rivers included in the study. The backwater analysis was not complete enough at some sites to confirm the hydraulic geometry change evaluation. A comparison of power equation exponents for cross sections in disturbed and undisturbed areas (Table 6) indicated a varied response to gravel re- moval. The coefficients in the power equations must also be considered to understand the effects of gravel removal. For example, at the Middle Fork Koyukuk River-Downstream site, the top width increase~ at a slower rate within the gravel removal area than outside of it. However, the coef- ficients in the power relations were greater for the disturbed than the undisturbed cross sections indicating that the top widths were larger at low flows in the disturbed areas than the undisturbed areas and were similar in both locations at higher flows. A qualitative evaluation of this effect can be made by comparing the relative channel widths in the material site at low flow and flood flow (Channel width and Flooded area, Table 7l. The coefficient in the power equation for the top width was greater for the disturbed cross section than the undisturbed cross sections at eight of the sites; this difference resulted from a consistently greater top width at all discharges considered in the hydraulic analysis. The sites at which this occurred were Gold Run Creek, Washington Creek, Nome River, Aufeis Creek, Skeetercake Creek, Sagavanirktok River, and both sites on the Middle Fork Koyukuk River. At Sinuk River the exponent of the power relation for the top width was observed to be greater at the disturbed cross section than at the undisturbed cross section. This difference indicates that the gravel removal area had smaller top widths at low flows, but larger top width at high flows, than the undisturbed cross section. lOB u u u u 0 0 0 u u (.) 0 Table 7. Quantification of Change in Hydraulic Variables Resulting from the Gravel Removal Operation at Each of the 25 Sites Gravel Local removal Channel Flooded Ponded Overal~ slope Flow d wi dt.ha .a a c River area area area slope redistribution obstruction Gold Run Creek 7 6 5 6 5 8 Sinuk River A 6 7 6 5 7 8 B 9 8 8 Washington Creek A 8 10 10 8 7 9 B 6 8 10 5 5 8 Oregon Creek A 10 9 8 6 7 8 B 5 6 5 5 5 5 Penny River 10 10 10 10 5 9 Nome River 10 10 7 7 5 7 Ugnuravik River 7 10 8 7 5 7 0 Aufeis Creek A 8 10 10 7 7 7 \0 B 6 6 6 5 5 5 Kuparuk River 6 7 6 5 5 7 Skeetercake Creek 5 8 10 10 5 10 Sagavanirktok River 8 10 6 6 5 5 Ivishak River 6 6 6 5 5 5 Shaviovik River 5 6 5 6 5 7 Kavik River 6 7 6 6 7 10 Dietrich River-Upstream 5 5 5 5 5 7 Dietrich River-Downstream 6 7 7 5 10 5 Middle Fork Koyukuk R-US A 5 6 9 5 5 5 B 7 9 8 10 5 5 Middle Fork Koyukuk R-DS 9 10 7 7 5 5 Jim River 10 10 8 5 7 5 Prospect Creek 5 5 5 5 5 5 West Fork Tolovana River 5 5 5 5 5 5 McManus Creek 5 10 6 7 5 8 Tanana River-Downstream 5 5 5 5 5 5 Tanana River-Upstream 5 5 5 5 5 5 Phelan Creek 4 2 6 5 5 9 (Footnotes on fo I I owing page) Table 7. Footnotes aWidth and area ratings: W =Parameter in the mined area R Parameter upstream from the mined area where the parameter is: • top width of the channel Is) during the survey period for Channel Width • top width of the channel Is) during floods of appr.oximately bank-ful I flood magnitude for Flooded Area • area of ponded wa~er, excluding pits, for Ponded Area. 3 < WR 2.5 < w < 3 R- 2 < w < 2.5 R- 1.5 < w < 2 R- 10 9 8 7 6 < W ~ 1.5 or other WR values if they are within the natural range o~ variation of ·the river 5 WR ~ I or if other data indicates no change 4 0.67 ~ WR < I or other WR values if they are within the natural range of variation of the river 3 0.50 < WR < 0.67 0-2 Not used bOveral I slope ratings: LR Len9th of disturbed reach after gravel removal Length of disturbed reach before grave I removal s = R 1/L R 10 1.4 < SR LR < 0.71 9 1.3 < s < R-1.4 or 0.71 < L - R 0. 77 8 1.2 < s < R-1.3 or 0.77 ~ LR < 0.83 7 1.1 < s < R-1.2 or 0.83 ~ LR < 0.91 6 1.0 < s < R-1.1 or 0.91 < L < - R 1.0 5 S • L • R = R = I or if other data indicate no change 0-4 Not used clocal slope redistribution ratings: 10 Very steep slope followed by a very long pool 9 Steep slope followed by a long pool 8 Moderate slope followed by slightly longer than average pool 7 Slope and pool length slightly more than that in the undisturbed areas 6 Some local slope redistribution detected or I ikely to have occurred but not I ikely that of the natural river 5 No local slope re.distribution 0-4 Not used dFiow obstruction ratings: 10 Obstructions in an active low-water channel such that flow is diverted 9 Obstructions adjacent to an active low-water channel 8 Obstructions in or adjacent to high-water channels 7 Obstructions in the floodplain but away from any developed .channe Is 6 Smal I obstructions not much different in size from those occurring naturally in the floodplain 5 No obstructions 0-4 Not used 110 c r :) J Associated with the trend towards larger top widths in the gravel removal areas, the hydraulic depth in seven of these areas decreased. Sites with smaller hydraulic depths, in the mined area, for alI discharges in- cluded Washington Creek, Nome River, Aufeis Creek, Skeetercake Creek, Sagavanirktok River, and both sites on the Middle Fork Koyukuk River. The mean velocity was consistently less at the disturbed cross section than at the undisturbed cross section at nine of the sites for the range of discharges included in the backwater analysis. These sites included Gold Run Creek, Washington Creek, Ugnuravik River, Aufeis Creek, Skeetercake Creek, Sagavanirktok River, Dietrich River-Downstream, and both of the Middle Fork Koyukuk River sites. At two sites, the rate of increase of velocity with discharge was different in the disturbed area than in the undisturbed area. At Sinuk River, the velocity increased at a lesser rate at the disturbed cross section than at the undisturbed cross section. At Middle Fork Koyukuk River-Downstream, the reverse was found. The conveyance, or carrying capacity of the channel, was consistently greater in the gravel removal area of eight sites compared with conveyances at undisturbed cross sections. These sites were Gold Run Creek, Sinuk River, Washington Creek, Aufeis Creek, Sagavanirktok River, Kavik River, Dietrich River-Downstream, and Middle Fork Koyukuk River-Upstream. The Sinuk River had a larger exponent or, equivalently, a more rapid increase in conveyance with discharge than cross sections which were not disturbed by the gravel removal operation. Conversely, the conveyance at the downstream site on the Middle Fork Koyukuk River increased with discharge at a slower rate than did the conveyance of the undisturbed cross sections. Significant changes in hydraulic geometry were observed primarily at sites which were scraped, although not alI scraped sites showed a signif- icant increase. Most of the significant changes were observed at meandering, sinuous, and straight rivers. Although no single gravel removal location caused a significantly greater change in hydraulic geometry than others, most of the sites that had significant change were those sites that were excavated by scraping in-channel and immediately adjacent-to-channel loca- tions. Ill The area of ponded water, which includes those low-lying areas which accumulate water but are not effective in the conveyance of flow, was in- creased at roughly half of the study sites. This pending indicated that the site was not smoothed during restoration, was excavated too deeply, or was not properly drained. Table 7 I ists the relative effect of this parameter at the 25 study sites. The impact of the pending to the hydraulics of the systems was not great. However, it was a concern to aesthetics and fish entrapment evaluations. Channel Slope. Channel slope changes took the form of an overall in- crease in slope or a local redistribution of slope. An overall increase in slope was commonly due to the formation of a meander cutoff. A redistri- bution of slope without changing the overal I slope occurred when the slope was increased leading into the gravel removal area and decreased through the gravel removal area. Table 7 indicates those sites which had slope changes. Study sites exhibiting an overall increase in slope due to gravel removal were generally in smal I, nonbraided river systems that were exca- vated by scraping techniques. The location of gravel removal was an impor- tant factor affecting the overal I slope of the system. Sites such as upper Washington Creek, Penny River, Skeetercake Creek, and lower Middle Fork Koyukuk River-Upstream, that were excavated on the inside of bends, mean- ders, and islands most significantly affected the overal I slope of the river system. This influence was expected because significant increases in slope are most I ikely to result from the development of a meander cutoff !reducing channel length and increasing slope!. The Penny River gravel removal operation caused a significant increase in overall slope !Figure 331. The photograph of the site after the gravel was removed shows that the main channel flows in a relatively straight course along the inside of two broad meanders that were cut off in the excavation process. The channel length was reduced by a factor of two in the process, equivalent to doubling the overall slope through that reach. Doubling the slope has the effect of increasing the mean velocity by roughly 40 percent. 112 ( J .) Scale in Meters August1950 July 1977 0 191 Figure 33. Comparative aerial photography of the Penny River showing change in hydraulic characteristics resulting from gravel r emova l activities. I 13 Gravel removal from active and high-water channels generally caused local slope redistribution. Removing gravel from bars and banks immediately adjacent to channels also appeared to cause a local redistribution of the water surface slope. An example of a local slope redistribution, which is simi Jar to the situation at the Dietrich River-Downstream site, is schemat- ically i I lustrated in Figure 34. Surlace Before Gravel Removal After Gravel Removal Figure 34. Schematic diagram i I lustrating an example of a change in local water surface slope that resulted from an in-channel gravel removal operation. Flow Obstructions. Flow obstructions in the form of material stock- piles, diversion dikes, and overburden piles had a larger potential for hydraulic disturbance on smal I rivers than those on medium and large rivers. This larger potential exists because the flow obstructions would have to be placed closer to the active channel due to the typically smaller floodplain width. There were no significant hydraulic impacts observed due to flow 114 ( r '- ) ) obstructions, but the potential exists for bed scour at the base of the obstruction, erosion of the obstruction, and ice jamming at the obstruction. Erosion of a dike at Skeetercake Creek increased siltation as discussed in the following section. SEDIMENTATION Sedimentation includes the processes of erosion, transportation, and deposition of sediment. These are complex processes related to sediment and water flow properties. Attempts to quantify these processes provide, at best, estimates of the quantity. A very brief discussion of sediment size distribution, channel erosion, and sediment transport are given in the following section. Changes to these sedimentation characteristics due to gravel removal are then briefly discussed. Undisturbed Condition Sediment Size Distribution. An important factor influencing most sedi- mentation problems is the size distribution of the sediments. The typical descriptors of the size distribution of sediment are the median diameter and graduation coefficient of the material. Natural sediment distribution tends to be log-normal, which is a two parameter distribution. The median diameter of a distribution has 5~ percent of the material smaller by weight and 50 percent of the material larger by weight. The second parameter, the grada- tion coefficient, gives the slope of the straight I ine resulting from plot- ting the distribution on log-probabi I ity paper. It is defined as I [D D J (J = -50 + 84 2 0 16 °50 I (9) where cr is the gradation coefficient and D is the particle diameter for X which x percent of the material is finer. The gradation coefficient is related to the standard deviation of the material. The material can be described as uniform if its gradation is less than 1.3 or graded if its gradation is greater than 1.3. 115 The median sediment size in the floodplain generally decreases in the downstream direction along a river. Thus, the median size may be cobbles in the headwaters and fine gravel near the mouth. However, the median size can significantly vary around this general average within a smal I area at a specified point along the river. This variation is a consequence of the variation in hydraulic forces from one point in the floodplain to an- other. Channel Erosion. Channel erosion in rivers is generally considered to be either local erosion (scour! or degradation. Both result from an increase in the sediment transport capacity, or a decrease in the sedi- ment load entering the area, or both. Local scour is most commonly a result of local increases in velocity due to flow obstructions or contractions. The increased velocity increases sediment transport capacity. Degradation can result if the channel bed is steepened in a short reach by, for example, a meander cutoff. The sedi- ment transport capacity would be increased through this reach causing ero- sion and a general upstream progression of the steepened slope !Figure 351. Upstream Progression of Steepened Slope ' .......... " ' ............ ... /Steepened ........................ --~' .. ~ Figure 35. Schematic diagram showing degradation process. Slope The progressive erosion continues upstream unti I equi I ibrium is reached. In theory, equilibrium is reached when the slope is equal to the slope prior to I the occurrence of the cutoff, which would require the steepened slope to migrate to the headwaters. In practice, the steepened slope is reduced 116 r ''- during its upstream migration and gradually reaches an equi I ibrium con- dition. However, the degradation may extend over a long reach before equi I i- brium is achieved. Sediment Transport. Sediment transport is the movement of sediments past a specific cross section of a river. The sediment may be transported as suspended load or bed load. Suspended load is sediment that is trans- ported long distances suspended in the water column. Bed load is sediment that is transported by saltation (bouncing!, or by rol I ing or sliding along the river bed. The sediment size distinction between bed load and suspended load varies with variations in discharge. At low flows, assuming the sedi- ments were available, si Its and clays may be transported in suspension and sands and gravels transported as bed load. During floods, suspended 1oad may include clays, si Its, sands, and gravels, with cobbles and boulders transported as bed load. Often, the suspended load is assumed to include clays, si Its, and sands and the bed load includes gravels, cobbles, and boulders. Changes Due to Gravel Removal Very ! itt!e sediment data were collected at the study sites. Direct measurements or observations of bed or suspended transport were not made because site visits were scheduled during periods of low flow when the sites would be most workable. Because the sedimentation characteristics prior to gravel removal were also unknown, the upstream cross section was usually used as the undisturbed cross section. The effects of gravel removal were evaluated by comparing sedimentation features in the gravel removal area to those in the undisturbed upstream area. At six sites, a decrease in the median size of the surface layer, or armor layer, was observed in the mined area as compared with the undis- turbed area. Similarly, an increase or decrease was observed in the median diameter of1 the material underlying the armor layer at eight sites. In many cases it was difficult to evaluate whether the variation in median diameter was a result of the gravel removal operation or simply a result of the 117 natural variation of the median diameter at a site. Degradation was also ob- served at a few sites although at other sites only causative evidence was avai I able to indicate that this process can occur. Sediment transport changes were suggested at several sites where there were observations of bedforms in or downstream from the gravel removal area, observations of changes in the bed material size, computations of changes in shear stress, or observations of sediment sources which remained from the gravel removal operation. The effects of gravel removal activity on these sedimentation characteristics were evaluated and given quantitative ratings for com- parative purposes !Table 81. Sediment Size Distribution. The most common significant change in sediment size distribution resulting from gravel removal was a decrease in the size caused by fine material deposition in the material site. This change was reflected in the surface material at six sites and the subsurface material at six sites. Oregon Creek, Penny River, and Ugnuravik River had significant changes in both surface and subsurface material sizes. At Sinuk River, fine and medium sized gravels were nearly missing from the subsurface samples in the material site, causing an increase in the median size. The explanation for this is unknown. At Washington Creek, the subsurface ma- terial size was larger in the materia! site even though fine materia! depo- sition in the site reduced the median size of the armor layer. A pattern of correlation was not evident between increases or decreases in armor layer median diameter resulting from gravel removal and physical site or gravel removal area characteristics. On& reason for this lack of correlation is that armor layer development is a complex function of several interrelated factors including degree of development of undisturbed armor layer, flooding history since gravel was removed, and flow characteristics in the gravel removal area. If the undisturbed size distribution of the armor layer was not significantly different from that of the material under- lying it, the relative change due to gravel removal would have been less and the time required for recovery to the undisturbed condition would also be less. The time for recovery is also a function of the floods during the recovery period; one large recurrence interval flood may be sufficient to 118 '- u u u u u u u u iJl) u Table 8. Quantification Ratings of Change in Sedimentation Characteristics Resulting from the Gravel Removal Operation at Each of the 25 Sites Gravel Armor Subsurface removal coat material Channel b Bed Suspen~ed River size a size a degradation loadc area load Gold Run Creek 4 6 8 8 Sinuk River A 4 9 5 3 6 / B Washington Creek A 2 8 10 3 3 B 3 5 5 5 Oregon Creek A 2 5 3 8 B 5 4 5 Penny River 2 2 5 3 8 Nome River 2 7 5 4 4 Ugnuravik River 2 0 5 5 8 \() Aufeis Creek A 6 I 5 5 5 B 5 5 5 Kuparuk River 4 7 5 8 6 Skeetercake Creek 5 2 5 9 8 Sagavanirktok River 7 4 5 5 5 Ivishak River 6 4 5 5 6 Shaviovik River 7 5 5 8 5 Kavik River 7 4 5 10 3 Dietrich River-Upstream 5 5 9 5 5 Dietrich River-Downstream 5 5 8 4 3 Middle Fork Koyukuk River-Upstream A 5 5 5 5 5 B I 7 6 9 5 Middle Fork Koyukuk River-Downstream 5 5 5 4 3 Jim River 5 5 6 Prospect Creek 3 3 5 5 5 West Fork Tolovana River 5 5 5 McManus Creek 4 8 5 5 Tanana River-Downstream 5 5 5 Tanana River-Upstream 5 5 5 Phelan Creek 7 5 6 5 5 (Footnotes on following pagel .Table 8. Footnotes aSediment size distribution ratings: D _Median size in the gravel removal area R-Median size upstream from the gravel removal area 10 10 < DR ldue to gravel removal activity! 9 10 (due to gravel removal activity! 2 ~ DR < 8 2 !due to gravel removal activity! 1.2 ~ DR < 7 1.2 ~DR !cause uncertain! 6 I ~ DR < 1.2 5 DR::: I 4 o.a < DR~ 3 DR~ 0.8 !cause uncertain! 2 0.5 < DR~ 0.8 ldue to gravel removal activity! 0.2 < DR~· 0.5 I due to gravel removal activity! 0 DR~ 0.2 ldue to gravel removal activity bChannel degradation ratings: 10 Very substantial degradation upstream of the disturbed area 9 Substantial degradation upstream of the disturbed area 8 Large amount of degradation upstream of the disturbed area 7 A noticeable. amount of degradation upstream of the disturbed area, but not unlike degradation wh-ich could occur naturally 6 Slight degradation upstream of disturbed.area observed or implied; may not be a result of gravel removal 5 No degradation. observed or Imp! ied by tt>e c:ata 0-4 Not used cBed load ratings: 10 Substantial rncrease in bed !oad by erosiori in the gravel removal area 9 Large increase in bed load by erosion in the gravel removal area 8 Increase iR bed load by erosion in the gravel removal area 7 Sed load increase due to gravel removal activity expected but not verified by C:irect evidence 6 51 ight bed load increase potentially due to gravel removal activity 5 No bed load change evident 4 Slight bed load decrease by ceposition in the gravel removal area 3 Moderate bed load decrease by deposition in the gravel rerroval area 0-2 Not used' dSuspended· load ratings: 9-10 Not used 8 large temporary and/or moderate I ong term i ncr·ease in suspended load 7 Temporary increase in suspended load as a result of disturbance of armor coat 6 Potential slight increase in suspended load resulting from gravel removal activity 5 t>:o apparent change in suspen::ed load 4 Potential slight decrease in suspended load resulting from depvsition 3 Moderate amount of deposition of suspended material 0-2 Not used 120 ) ) ) ) ) J ) ) develop an armor layer comparable to that in the undisturbed area. The development of an armor layer in the gravel removal area is also greatly dependent on the location of the area relative to the active channel and the resulting flow characteristics through the site. The location and extent of gravel removal may be such that an armor layer may not develop unti I the area fi I Is in sufficiently to have appropriate hydraulic character- istics for armor layer development. Channel Erosion~ Channel erosion in the form of local scour was not observed at any of the study sites. The potential exists for local scour to develop as a result of flow obstructions in the form of material stockpiles, overburden piles, and diversion dikes. This potential was discussed in the previous section discussing hydraulics. Channel degradation was observed at four sites and may have been devel- oping at three other sites. At Washington and McManus Creeks, obvious degra- dation had occurred upstream from the site in the main channel. At the two Dietrich River sites, degradation was occurring in high-water channels; at the downstream site, one of the high-water channels developed into an active side channel after work completion. Channel degradation resulting from grave! removal activity has been documented elsewhere !Woodward-Clyde Consultants 1976b, Li and Simons 19791. Li and Simons ( 19791 suggest that the installation of check dams can restrict upstream degradation. Sheridan ( 19761 discusses in-channel gravel removal, noting that the pits fi I led in with sediment; a similar situation occurred on Sinuk River with no apparent degradation. Sediment Transport. Changes in sediment transport due to gravel removal were difficult to evaluate. The ratings given in Table 8 are thus highly subjective. A few possible changes which were suggested by the sedimentary features in and around the material sites are discussed below. It is I ikely that most scraped sites exhibited an increase in suspended load during the first flood event and possibly during one or two subsequent events as the material in the gravel removal area was washed clean of the fine grain sizes. This increase was thus likely a temporary increase common at most 121 scraped sites. Long-term increases in suspended load were implied at sites with disturbed areas which contributed fine materials to the flow. Examples of such long-term increases were the access road degradation at Ugnuravik River !Figure 361, the diversion dam at Skeetercake Creek !Figure 371, and several sites with overburden piles or berms containing fine-grained ma- terials. Simi Jar increases in suspended load could occur from accelerated bank erosion at the site. Deposition of fine-grained sediments in several of the gravel removal areas was also observed. Sites with changes in suspended load showed no pattern with the physical site or gravel removal area charac- teristics. Apparent changes in bed load were observed at some sites in the form of gravel dunes or loose gravel deposits in and downstream from the gravel removal area. When these deposits occur in the gravel removal area, they could indicate the inabi I ity of the flow through the area to carry the sediment load delivered to it or generated within it. Deposition occurring downstream from the gravel removal area would imply that the flow through the area is sufficient to erode the loose gravel from the gravel removal area. It is possible that when these gravels reach the main channel they are transported in the form of another bed form or possibly in suspension. Bed !oad changes occurred most often at scraped sites in active and high~water channels, and in locations immediately adjacent to such channels. ICE CHARACTERISTICS Undisturbed Condition Ice jamming can occur during breakup when ice floes moving down the river are blocked, thereby blocking subsequent ice floes. and eventually creating a surface dam to the flow of ice. Ice jams can cause scour due to increased velocity beneath the ice dam; they can also cause the water level to rise, resulting in increased flooding. Ice jams are normally caused by a constriction in the channel width or depth, a reduction in flow velocity, or manmade structures in the floodplain. 122 ·' ( ( ) ) J Figure 36. Upstream view of thermal and fluvial erosion in the access road at Ugnuravik River, acting as a long-term sediment source to the river. Figure 37. View of erosion of a diversion dam which acts as a long-term sediment source to Skeetercake Creek. Dunes in foreground are atypical of the undisturbed river. 123 Aufeis is defined as areas of ice which have developed by a sequence of events of overflowing water on top of the previous ice surface. The general mechanism for the growth of aufeis involves an increase in the hydrostatic pressure due to a reduced flow area; when the pressure exceeds the elevation of the ice surface, overflow onto this surface results and subsequently freezes. The overflow causes the pressure to decrease and ice surface ele- vation to increase. This sequence continues to repeat unti I the source water cannot produce sufficient pressure to exceed the elevation of the ice sur- face. Three requirements for the formation of aufeis are given by Carey ( 19731; ( ll significant ground water or under-ice flow, !2) growth of ice to the channel bed or near the bed, and !3l subsurface constriction such as bedrock, less pervious soi I, or permafrost. Changes Due to Gravel Removal An organized program of winter and spring observations of aufeis and breakup were not included in this study. Therefore, much of the following discussion is based on observations of aufeis and ice jamming potential, rather than of actual aufeis and ice jams. However, at two sites, Washington Creek !Figure 38) and Oregon Creek, large areas of aufeis were observed in early June. Incidental winter observations at a few other sites documented the existence of aufeis. Ice jams could be caused by several aspects of floodplain gravel re- moval. In rivers which are increased in width and depth by the gravel re- moval, such as by in-channel mining, the velocity would decrease causing the ice floes to gather. At the downstream end of the gravel removal area these floes could jam where the channels constrict back to the natural width. This ice jam could cause flooding in and upstream from the gravel removal area and possible bed scour beneath the ice jam. River channels which are widened causing shallower depths, such as by removing bars adjacent to the channel, could cause ice jamming by grounding the ice floes. Another potential mechan- ism for ice jam formation resulting from a gravel removal operation is the blocking of ice floes by flow obstructions in the form of overburden piles, stockpiles, or dikes. 124 ) ) Figure 38. Large area of aufeis at the upper gravel removal area at Washington Creek as it appeared in early June. In evaluating the potential for aufeis development at each of the study sites, it was assumed that wide, shallow channels were more likely to develop aufeis than narrow, deep channels. This assumption is probably valid because sha I I ow channe Is are more I ike I y to freeze to their bed and to have a shallow tal ik (unfrozen zone) than deep channels carrying equivalent flow. The results of this evaluation of aufeis potential ~re I isted in Table 9, along with the identification of those rivers with aufeis activity or po- tential aufeis activity prior to the gravel removal operation. Most of the observations of increases or potentia I increases in aufe is activity were associated with mining activities in straight and sinuous ) rivers, although some activities in braided, split, and meandering rivers also caused potential increases. Increases in aufeis activity were associ- ated with scraping operations. Increased aufeis activity or potential aufeis activity often occurred at those sites where the gravel removal operation ) was located in active or high-water channels and in locations immediately 125 ) T~ble 9. Quantification Ratings of ·change in Aufeis Potential that Resulted from the Gravel Removal Operation at Each of the 25 Sites River Gold Run Creek Sinuk River Washington Creek Oregon Creek Penny River Nome River Ugnuravik River Aufeis Creek Kuparuk River Skeetercake Creek Sagavanirktok River Ivishak River Shaviovik River Kavik River Dietrich River-Upstream Dietrich River-Downstream Middle Fork Koyukuk River-Upstream Middle Fork Koyukuk River-Downstream Jim River Prospect Creek West Fork Tolovana River McManus Creek Tanana River-Downstream Tanana River-Upstream Phelan Creek a~ potential ratings: Grave I removal area A B A B A B A B A B Aufeis ---a potential 10 Large a·ufeis development observed in the disturbed area where no aufeis was previously recorded 9 Moderate sized aufeis development observed in the disturbed area where no aufeis was previOUsly recorded 8 Sma~eis development observed or a strong potential for aufeis occur- rence is inferred 7 Relocation of an existing aufeis area by gravel removal activity 6 Potential increase in aufers-acFivity resulting from gravel removal activity ------ 5 No change in aufeis characteristics 0-4 Not used bRivers with a high potential for icing activity prior to the gravel removal operation. 126 c e c ' J J J ) adjacent to the channels. Such locations, when excavated for gravel, tend to increase channel width, decrease depth, and allow for freezing down to the channel bed. As noted earlier, large areas of aufeis were observed in the Washington Creek and Oregon Creek study sites. Both of these sites had been extensively scraped and that caused numerous channels to form and loss of surface flow to intergravel flow because of loosely compacted gravels. The aufeis may be retarding the recovery of the surface flow by protecting the loose gravels from the flood flows during the snowmelt runoff period. At both sites, the channels flowing during the survey were not flowing where the channel had previously been; it is thus I ikely that the tal ik was not as deep beneath the newly formed channels, thereby providing the aufeis requirement of a subsurface constriction. The shallow channels would I ikely freeze to the bed, thereby satisfying another requirement for aufeis formation. The third requirement, a water source, was already available. Thus, at these two sites the gravel removal operation changed the channel location and cross section sufficiently to provide two of the three requirements for aufeis formation. HYDROLOGY Hydrology is the study of the origin, distribution, and properties of water during the time it is at or near the earth's surface. Of concern in this section is the distribution of the water. More specifically, this section discusses briefly the quantity of water that can be expected at the 25 material sites during low flow and flood flow conditions and poten- tial effects on the quantity due to the removal of gravel. Undisturbed Condition The mean annual flow of a river at a specific point is, as the term implies,, the mean flow during any 12 month period. It is an indication of total annual runoff and may also be used as an approximation of the typical low summer flow. Estimates of mean annual flow for the 25 study 127 3 sites are listed in Table 10. They range from 0.09 m /sat McManus Creek to 540 m3 /s at Tanana River-Downstream. Flood frequency curves show the expected frequency of occurrence.of different magnitude floods at a specific point on a river. The frequency of occurrence is commonly referred to by the recurrence interval of the flood, which is the average number of years between floods of that magnitude. The rec i proca I of the recurrence i nterva I is the probab iIi ty of occurrence of a given magnitude flood in any year. Flood frequency curves were developed for each of the study sites. Discharge values corresponding to selected fre- quencies of occurrence are shown in Table I I. Changes Due to Gravel Mining Hydrologic characteristics are, to a large extent, governed by basin- wide parameters such as climate and geology. Gravel removal operations did not have a significant effect on these characteristics. However, local changes in the ratio between surface flow and subsurface flow occurred at several sites. The local changes were not measured; quantitative ratings shown in Table 12 were asslgned based on a subjective evaluation. A local reduction in mean annual flow occurred at the upper Washington Creek and upper Aufeis Creek sites as a result of a loss of surface flow to inter- gravel flow. At Washing~on Creek, the flow entered the gravel removal area and spread out through loose, uncompacted gravel; a large percentage reduc- tion in surface flow resulted at low flows. This intergravel flow component was sti I I evident in the site 13 years after the site was worked. The rela- tive effect of the loss of surface flow during flood events was I ikely minimal. At Aufeis Creek, surface flow appeared to cease entirely for a period of 2 years, although continuous survei I lance was not avai !able to verify this. Thus, the mean annual flow of Aufeis Creek in this local region was reduced to near zero for 2 years. The effect on flood flows was unknown. Two other sites, the upper Oregon Creek and Penny River sites, had a potential for a similar, but not as extensive, decrease of surface flow lost to intergravel flow. No observations or measurements were avai !able 128 ( .J J J J Table 10. Mean Annual Flow Estimates at Each of the 25 Study Sites River Gold Run Creek Sinuk River Washington Creek Oregon Creek Penny River Nome River Ugnuravik River Aufeis Creek Kuparuk River Skeetercake Creek Sagavanirktok River Ivishak River Shaviovik River Kavik River Dietrich River-Upstream Dietrich River-Downstream Middle Fork Koyukuk River-Upstream Middle Fork Koyukuk River-Downstream Jim River Prospect Creek West Fork Tolovana River McManus Creek Tanana River-Downstream Tanana River-Upstream Phelan Creek 129 Unit mean annual flow 3 2 (m /s/km l 0.013 0.033 0.018 0.023 0.023 0.033 0.0023 0.0044 0.0045 0.0035 0.0083 0.0066 0.0040 0.0062 0.006 0.006 0.0054 0.0054 0.010 0.010 0.0062 0.0062 0.012 0.012 0.063 Mean annual flow !m 3 /sl 0.9 18.0 0.5 0.7 I .4 4.3 0.6 I. I 38 0.3 39 24 1.6 5.5 3. I 4.0 13 22 7. I 2.6 4.7 0.09 539 468 5.2 Table I I. Calculated Discharges in m3 /s Corresponding to Selected Recurrence Intervals for Each of the 25 Study Sites Recurrence interval (years! River 1.25 2 5 10 25 50 100 Gold Run Creek 11.2 19.2 32. I 42.8 53.6 70.2 91.0 Sinuk River 113 171 256 323 391 481 589 Washington Creek 2.58 5.63 10.7 16.6 28. I 39.5 54.9 Oregon Creek 6.21 II. I 19.4 26.3 33.5 44.8 59.3 Penny River 18.2 23.7 31.7 37.0 43.7 50.2 57.0 Nome River 32.4 53.3 86.3 114 142 182 232 Ugnuravik River 31 .4 46. I 71.5 92. I 121 149 180 Aufeis Creek 39.2 56.8 89.3 116 160 196 235 Kuparuk River 905 1355 2165 2848 3906 4840 5912 Skeetercake Creek 10.6 16.7 28.4 38.4 54.6 69.8 87.0 Sagavanirktok River 376 462 592 665 785 863 970 Ivishak River 267 333 432 489 579 641 726 Shaviovik River 35.8 59.6 98. I 130 164 212 272 Kavik River 108 171 271 353 444 559 701 Dietrich River-Upstream 35.6 58.6 102 140 195 253 322 Dietrich River-Downstream 46.9 75.9 131 !78 247 3!8 402 Middle Fork Koyukuk R-US 126 189 302 396 534 661 808 Middle Fork Koyukuk R-DS 190 276 428 552 736 896 1079 Jim River 101 125 156 178 204 228 251 Prospect Creek 33.3 43.6 57.6 67.3 78.5 90.4 102 West Fork Tolovana River 63.9 89.2 130 159 203 242 282 McManus Creek I .65 3.32 7.48 12.0 20.6 29.8 42. I Tanana River-Downstream 1562 1752 1992 2120 2356 2460 2619 Tanana River-Upstream 1341 1518 1738 1857 2069 2169 2318 Phelan Creek 49.3 65.3 92.8 114 146 171 197 130 IE_ " ( ( '-- " -.: f '· <' '- ) J Table 12. Quantification Ratings of Change in Quantity of lntergravel Flow Resulting from the Gravel Removal Operation at Each of the 25 Sites River Gravel removal area Gold Run Creek Sinuk River Washington Creek Oregon Creek Penny River Nome River Ugnuravik River Aufeis Creek Kuparuk River Skeetercake Creek Sagavanirktok River Ivishak River Shaviovik River Kavik River Dietrich River-Upstream Dietrich River-Downstream Middle Fork Koyukuk River-Upstream Middle Fork Koyukuk River-Downstream Jim River Prospect Creek West Fork Tolovana River McManus Creek Tanana River-Downstream Tanana River-Upstream Phelan Creek a lntergravel flow ratings: A B A B A B A B A B a lntergravel flow 5 5 5 9 5 7 ? 7 5 5 10 5 5 5 5 5 5 5 3 5 5 5 5 5 5 5 5 4 4 5 10 AI I surface flow converted to intergravel flow for one summer or more 9 Substantial long-term loss of surface flow to intergravel flow 8 Moderate long-term loss of surface flow to intergravel flow 7 lmpl ied long-term loss of surface flow to intergravel flow 6 Small quantities of surface flow lost to intergravel flow 5 No apparent change 4 Imp I ied increase of surface flow and decrease of intergravel flow 3 Known increase of surface flow and decrease of intergravel flow 0-2 Not used 131 to estimate the magnitude of the decrease. The location of the gravel re- moval area may provide an explanation for the significant intergravel flow at Washington Creek and Aufeis Creek. At these two sites the scraping occur- red near the downstream end of a sharp meander bend ! Figure 39 l. It appeared that the scraping in this location caused most of the flow to leave the confinement of the channe I. The I ack of a we I I defined channe I caused the flow to spread over the gravels in the material site and deposit the sedi- ment load that it was carrying. These deposits were quite loose and un- stable, and thus were very conducive to intergravel flow. Other sites having a similar specific location of scraping were slightly different in configur- ation from that shown in Figure 39; either the bend upstream from the scraped area at these sites was not as sharp or the scraping occurred fur- ther downstream on the bend, thus allowing some of the flow and I ikely much of the bed load to be retained in the original channel. Three possible explanations for the continued loss of surface flow at Washington Creek are ! I l that the suspended load is not sufficient to fi I I the openings in the gravel, !2l the presence of aufeis in the site protects the gravels from the significant snowmelt floods, and !3l water freezes in the gravel, expanding and separating the gravels in the process. Pit sites, such as Dietrich River-Upstream and the two Tanana River sites, had a potential to locally increase the mean annual flow as a result of intercepting intergravel flow and allowing it to surface at the pit. However, the percentage increase in the mean annual flow at these sites is probably quite smal I. 132 c ( r ) 17J~1173 Scale in Meters 0 152 Figure 39. Aerial photographs of Washington Creek (topl and Aufeis Creek (bottom) showing material site locations and approximate channel locations before the disturbance. SUMMARY AND CONCLUSIONS Various physical characteristics of arctic and subarctic rivers were affected by gravel removal operations. These characteristics were divided into five categories: I • Channel configuration and process, 2. Hydraulics, 3. Sedimentation, 4. Ice characteristics, and 5. Hydrology. One or more characteristics from these categories were observed to have changed as a result of removing gravel from the 25 floodplain study sites. CHANNEL CONFIGURATION AND PROCESS Channel configuration and process characteristics that changed as a result of gravel removal operations included braiding characteristics, such as increase in the number of channels and decrease in lateral stabi 1- ity of the channels, and the potential for diversion of flow through the gravel removal area. The greatest changes in braiding characteristics occurred at 10 study sites and resulted from gravel removal operations that disturbed the bars adjacent to active channels or that diverted flow through the material site. Flow diversion through the mined site resulted from having insufficient buffers or no buffers at alI. Gravel removal operations caused flow diversion or a high potential for flow diversion at 12 of the 25 study sites. 134 ( .) HYDRAULICS Hydraulic characteristics exhibiting changes as a result of gravel removal operations included the hydraulic geometry (including width, depth, velocity, and conveyance), overall channel slope, local slope redistri- bution, flow obstructions, and area of ponded water. Increases in channel width, conveyance, overall slope, flow obstruct ions, and ponded water were typical responses to gravel removal, as were decreases in channel depth and velocity. One or more of these effects from gravel removal were observed at a I I of the sites except those pit excavated sites that were separated from the active channe Is by a buffer. Sma I I river systems typ- ically had smaller floodplains which forced the gravel removal operation closer to active or high-water channels, causing hydraulic changes. SEDIMENTATION Sedimentation characteristics which appeared to have changed as a result of gravel removal operations included armor layer and subsurface material site distributions, channel degradation, and suspended and bed loads. The most common significant change in sediment size distribution resulting from gravel removal was a decrease in the size caused by fine material deposition in the material site. This change was reflected in the surface material at six sites and the subsurface material at six sites, three of which were different from those with surface material changes. Channel degradation was observed at four sites and may have been develop- ing at three other sites. Changes in sediment transport due to gravel removal apparently took the form of increases as well as decreases, with apparent changes occurring at I I sites. Most changes in the sediment char- acteristics resulting from gravel removal operations occurred at scraped sites in or immediately adjacent to active and high-water channels and at those sites where fine sediment sources were left in the floodplain near the channel. 135 ICE CHARACTERISTICS Two ice characteristics were identified as potentially being increased as a result of gravel removal activity. They are ice jamming and aufeis formation. These can be affected by a widening of the channel followed by a rapid reduction in width, a reduction in depth, obstructions in the floodplain, and relocating the channel through an area which was previously dry. Aufeis formation was observed at four study sites. HYDROLOGY The only characteristic related to the hydrology of the river which was identified as potentially changing as a result of gravel removal opera- tions was a change from surface flow to groundwater flow or vice versa. This change, although relatively minor at most sites, can have a local effect on the mean annual flow, flow duration curve, and potentially, on the flood frequency curve. Significant reduction of surface flow occur- red at two study sites. RECOMMENDATIONS Listed below are several recommendations concerning gravel removal operations, the purpose of which is to reduce the number or magnitude of changes to the physical characteristics of rivers: I. Sma I I rivers shou I d not be considered as grave I sources. 2. Braided rivers should be considered as primary gravel sources; other river configurations, I isted in order or I ikel ihood of caus- ing the least physical change, are split, meandering, sinuous, and straight. 3. Pit excavations should be located on terraces or possibly inactive floodplains and should be separated from the active floodplain by a buffer designed to maintain this separation for two or more decades. 136 ) J J 4. Material sites within the active floodplain should: • Not disturb the edge of the active channel (sl; • Maintain a high-water channel shape, within the material site, similar to that which enters and leaves the site; • Not increase the bed slope of active or high-water channels locally to more than that of naturally occurring slopes; • Form new high-water channels through the site if flow is expected through the site; • Be shaped and contoured to provide proper drainage; • Have material stockpiles, overburden piles, and dikes removed from near active channels unless they have a specific purpose for being there and are designed to withstand the hydraulic forces; and • Be protected from low flow channels unti I the occurrence of the first flood after the site is completed. 137 REFERENCES Carey, K. L. 1973. Icings Developed from Surface Water and Groundwater. U.S. Army Cold Regions Research and Engineering Laboratory. Mono- graph I I I-D3. 71 pp. Chow, V. T. 1959. Open-Channel Hydraulics. McGraw-Hi I I Book Company, New York, 680 pp. Doyle, P. F., and J. M. Childers. 1976. Channel Erosion Surveys Along TAPS Route, Alaska, 1976. U.S. Geological Survey Open-File Report. 89 PP· Emmett, W. W. 1972. The Hydraulic Geometry of Some Alaskan Streams South of the Yukon River. U.S. Geological Survey Open-File Report. Anchorage. July. 102 pp. Emmett, W. W. 1975. The Channels and Waters of the Upper Salmon River Area, Idaho. U.S. Geological Survey Professional Paper 870-A. 116 pp. Karaki, S., K. Mahmood, E. V. Richardson, D. B. Simons, and M. A. Stevens. 1974. Highways in the River Environment-Hydraulic and Environmental Design Considerations. Prepared for Federal Highway Administration by Civi I Engineering Department. Colorado State University. Fort Col I ins, Colorado. 453 pp. Lamke, R. D. 1979. Flood Characteristics of Alaskan Streams. U.S. Geo- logical Survey Water Resources Investigations 78-129. 61 pp. Leopold, L. B., M.G. Wolman, and J.P. Miller. 1964. Fluvial Processes in Geomorphology. W. H. Freeman and Company, San Francisco, Cali- fornia. 522 pp. Li, R. M., and D. B. Simons. 1979. Mathematical modeling of erosion and sedimentation associated with instream gravel mining, pp. 420-429. In Conservation and Uti I ization of Water and Energy Resources. ASCE Hydraulics/ Energy Division Conference. San Francisco. 8-11 August. Rundquist, L. A. 1975. A Classification and Analysis of Natural Rivers. Dissertation. Colorado State University. Fort Col I ins, Colorado. 377 PP· Sheridan, W. L. 1976. Effects of Gravel Removal on a Salmon Spawning Stream. U.S. Department of Agriculture. Forest Service. 26 pp. 138 ( c c J J J Woodward-Clyde Consultants. 1976a. Preliminary Report -Gravel Removal Studies in Selected Arctic and Sub-arctic Streams in Alaska. U.S. Fish and Wildlife Service. FWS/OBS 76/21. Wash. D. C. 127 pp. Woodward-Clyde Consultants. 1976b. Aggregate Extraction Management Study, County of Yolo California. Prepared for the County of Yolo. Planning Department. Aggregate Resources Management Committee. 128 pp. 139 EFFECTS OF GRAVEL REMOVAL ON AQUATIC BIOTA L. L. Moulton INTRODUCTION Populations of organisms are controlled by physical and chemical fac- tors, often termed their environment, and by biological factors, including predation and competition. Environmental constraints on a particular species determine the usable habitat available to that population and the size of the population is often restricted by the amount of usable habitat. After the maximum number of individuals a particular habitat can support (termed the carrying capacityl has been reached, the population cannot increase with- out an increase in usable habitat. Predation and competition can act on a population to I imit numbers below the carrying capacity, thus undisturbed populations are not necessarily ful iy uti I izing the avai iable habitat. Alterations to the habitat can alter the quality of the habitat, lead- ing to direct changes in the carrying capacity, and consequently, to reduc- tions in the affected populations. Decreases in habitat diversity may reduce the carrying capacity for one species while leaving that for another un- changed. If the two species were in competition, the reduction or removal of one may allow the other species to increase. Generally, decreases in habitat diversity wi I I result in an increased carrying capacity of one species which is able to efficiently uti I ize the more uniform habitat. Conversely, in- creases in habitat diversity generally cause increases in the number of species or life history stages present as new habitat types are added. These species increases are often accompanied by decreas~s in the populations which had formerly been utilizing the more uniform, less diverse, habitat. 141 The decreases may be due either to less available habitat or to competition from species which more efficiently uti I ize the newly created habitats. The types of habitats present in a river are determined by the loca- tion, size, configuration, and water quality characteristics of the river. Features which define specific habitats include depth, velocity, substrate, and cover. Alterations to a river which affect any of these features wi I I also affect the habitat available in the river and may impact habitats downstream from the alterations. Habitat alterations may affect the quality or diversity of the habitat, or both. Reduced habitat quality makes the area less desirable to the species present prior to alteration, while altered habitat diversity may favor one species or life history stage over another. Reduced habitat quality imp I ies alteration of a single habitat type whereas reduced habitat diversity imp I ies reduction in the number of available habitats but the two responses are not independent. Several types of habitats may be used in the I ife cycle or even sea- sonal cycle of an organism, and there is often a critical habitat which controls the size of the population. In the arctic and subarctic environ- ment, the critical habitat for fish populations is often the amount of overwintering habitat. Other critical habitats often control i ing fish popu- lations are spawning and rearing areas. Critical habitats vary from stream to stream and species to species depending on the characteristics of the streams and the I ife cycle requirements of the species. Recent studies have been aimed at quantifying the effects of habitat alteration on stream populations (Stalnaker and Arnette 1976, Bovee and Cochnauer 1977, Binns and Eiserman 1979). Two of the basic requirements of these efforts are detailed measurements of appropriate habitat parameters and an intimate knowledge of the habitat requirements of the species in ques- tion. The emphasis of the present study was on a multiple-disciplinary survey of the effects of floodplain gravel removal on a broad geographical scale. Because of the I imited data on many species and complete lack of data on many of the river systems studied, a detailed habitat analysis was not possible. The 3 to 4 day surveys at each site allowed for gathering of basic 142 a 0 J 0 physical and biological data but not the type of detai I required for sophis- ticated correlation analysis. For these reasons the present analysis was confined to analysis of trends and subjective evaluations of habitat alter- ations and their effects on aquatic organisms. The material sites were visited 2 to 20 years after mining was com- plete, thus the immediate effects of gravef removal operations were not studied. The changes evaluated during the present study were those which persist over a number of years rather than those affecting the biota during the year of disturbance. A literature review of impacts at the time of actual gravel removal was presented by Woodward-Clyde Consultants ! 1976l. 143 METHODS OF DATA COLLECTION As detailed in APPROACH AND METHODOLOGY a variety of standard sampling methods were uti I ized at each study site with the specific methods used dependent on the type of river system and habitat being studied. 144 METHODS OF DATA ANALYSIS The data from each of the 25 sites were first analyzed on a site- by-site basis to determine the effect of gravel removal operations on the aquatic environment at each study site. These individual site evaluations provided the basis for further analysis to identify trends and correlations relating to major site variables (Table I, Major Variable Matrix). These individual site evaluations are not included because of space I imitations but are part of the permanent data base maintained by the U. S. Fish and Wildlife Service. The various physical and biological parameters measured at the dif- ferent sites varied greatly in magnitude and the variation made the direct comparison of data among sites impractical. The various parameters recorded at the study sites were standardized on a scale of 0 to 10 to obtain a relative measure of the degree of change. A rating of 5 indicates that a parameter measured in the mined area had not changed from the same parameter in the upstream area; ratings of 0-4 and 6-10 indicate decreased and in- creased parameter values in the mined area relative to the upstream area. The rating was determined by calculating the percentage change in the mined area relative to the upstream area for each site and subjectively assigning rating values to various percentage intervals such that alI or most of the 0-10 scale was utilized for those sites at which the parameter was evalu- ated. Data from study sites with similar ratings were examined for similar alterations that might lead to a similar parameter response. The analysis of habitat alteration was based on field notes from the site surveys, ground and aerial photographs, direct measurement of habitat parameters, results of hydraulic analysis, and visual observations. Habitat parameters considered in the analysis included changes in substrate type, 145 substrate porosity, configuration of adjoining banks, bank and instream cover, number of channels, pool-riffle frequency, depth, velocity, and wetted perimeters at different flow levels. Additional habitat alterations were noted where appropriate, such as excessive si I tat ion, aufeis formation and creation of new aquatic habitats. Much of the analysis was subjective because many habitat parameters were difficult to quantify, consequently, the analysis was kept conservative. The results of hydraulic analysis, as described in the EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS, allowed for a certain amount of habitat parameter quantification and these results supported the subjective evaluations whenever comparisons were avai !able, indicating that subjectivity was not a major source of error. Analysis of changes in fish populations was accomplished by evalu- ating the types of habitat alterations occurring in the mined area relative to the upstream area. Then the measured parameters that appeared to be most important at the particular site were examined to determine if there had been a change in fish distribution, as indicated by a difference in catch rate between the upstream and mined areas. In this manner the combi- nations of habitat alteration could be evaluated for their cumulative effect on the population of fish present during the site visit. Additional effects were postulated based on known I ife history requirements of the various species. The large number of benthic sample replicates obtained at each study site during the field surveys allowed for an analysis of vari-ance to de- termine if significant differences existed in the densities among sample areas within a study reach. AI I Surber sample data were computer coded and the densities were subjected to an analysis of variance and multiple classi- fication analysis !Nie et al. 1975!. A nonparameteric procedure, the Mann- Whitney U-test !Zar 1974!, was also used to evaluate differences in density. The results of the two tests were compared and, where the results of the two tests differed, the more conservative nonparametric test was used. Addi- tional computer analysis included the calculation of various indices of diversity and similarity, such as the Bray-Curtis and Raabe similarity 146 0 0 0 indices, and Shannon-Weaver and Simpson density indices. The indices respond differently to changes in density and diversity and were used primarily to search for changes in the aquatic macroinvertebrate assemblages vulnerable to Surber samplers. Because the level of identification was to the generic level at best and often only to family or order, the indices were applicable only to the present study. Comparison with results of other studies and extensive anal- ysis of the data are not justified. Often multiple species within a genus were recognizable but the absence of suitable taxonomic aids for arctic aquatic macroinvertebrates inhibited identification. A I ist of collected taxonomic groups by phyletic classification, with associated common names, is included in Appendix A. 147 RESULTS AND DISCUSSION MAJOR GRAVEL REMOVAL HABITAT ALTERATIONS Habitat Quality Alterations of habitat quality observed at many of the sites consisted primarily of substrate alteration and removal of both instream and bank cover. Siltation, commonly associated with instream disturbances, was ob- served at a few sites, but was not a major factor because most of the sites were visited several years after mining had been completed. At three sites where siltation was observed it was caused by eroding berms (Kavik River! or melting aufeis fields (Washington Creek, Oregon Creek! (Figure 401. Two types of substrate alteration were observed: (ll a shift from a moderately compacted gravel substrate to a very loose, unconsolidated sand- grave! substrate, usua! !y with considerable intergrave! f!ow and !2! a shift from a smooth, paved substrate which produced near laminar flow to a more porous, irregular substrate producing turbulent flow. Most of the substrate alterations recorded were Type alterations with only two Type 2 alterations observed. Type I alterations occurred at four of the eight sites where scraping was conducted in an active channel (Washington Creek, Oregon Creek, Penny River, McManus Creek) and at four where flow subsequently increased or diverted to inundate a scraped area (Sinuk River, Kuparuk River, Sagavanirktok River, Ivishak River) (Table 131. The effects of this type of alteration appear to be long-term, because this alteration was noticeable at McManus Creek 16 years after mining. The effect on the sub- strate was caused by removal of the armor layer, loosening of the gravels, and subsequent washing out of fine materials. Formation of ice in the mined areas appeared to prolong the recovery time of this type of alteration. 148 a) Sediment being released by melting aufeis. bl Si It deposited in substrate downstream from aufeis field. F igure 40. Siltation resulting from extensive aufeis field at Oregon Creek mined study area, 20 June 1977. 149 '- Table 13. Major Habit at A Iterations Observed at Sites Mined by Scraping ,. '-(5 = No Change, 6-10 =Trend Towards Parameter, 0-4 = Trend Away From Parameter) N <ll <ll a. a. ~ >->-'-' 1-1-"0 "0 <ll <ll c c () (J) 0 0 :::J "0 tO "0 "0 "0 <ll <ll +-+-<ll <ll <ll (J) L tO tO () L (J) tO () L L :::J tO <ll c <ll <ll "0 L <ll L +-+-<ll <ll L () L > () c L tO tO 0 c <ll c L () +- <ll <ll <ll L tO +-+-> E 0'> <ll ~ tO tO 0 tO c +- L L () <ll tO "0 +-+-L "0 ~ <ll (J)· (J) .;,:. +-.;,:. "0 .0 .0 c (J) tO () c :::J :::J tO c L tO 0 Site en en !D !D !D a.. Seward Peninsula e Gold Run Creek a 5 5 8 5 6 5 Sinuk River 7 5 8 6 9 8 Washington Creek 10 5 10 10 10 10 10 Oregon Creek 10 5 10 10 9 9 8 Penny River 9 5 10 8 9 10 10 Nome River 5 5 10 10 7 (;; North Slope Ugnuravik River 5 8 5 5 6 10 8 Aufeis Cr.eek · 5 5 8 9 10 10 Kuparuk River 8 5 5 5 8 7 6 Skeetercake Creek 5 9 8 5 8 10 c Sagavanirktok River 9 5 5 9 10 10 6 Ivishak River 6 5 5 5 8 6 5 Shaviovik River 5 3 5. 5 6 6 5 Kavik River 5 5 9 8 7 5 Northern Interior .~ Dietrich River-l.Jpstream 5 5 5 5 5 5 5 ..., Dietrich River-Downstream 5 5 5 5 6 7 7 M.F. Koyukuk River-US 5 5 10 5 10 9 9 M.F. Koyukuk Ri ver-DS 5 5 5 5 8 10 7 Southern Interior McManus Creek 7 5 5 5 5 10 5 r ~ Phelan Creek 5 5 5 5 4 2 5 a Dash means parameter not evaluated at this site. J 150 ) 3 Type 2 substrate alterations were documented at two locations, both on medium size North Slope rivers !Table 131. In one case, Ugnuravik River, the upstream area showed near laminar flow that was changed to turbulent flow while in the other case, Shaviovik River, the reverse occurred-the upstream flow was turbulent whereas the flow through the mined area was laminar. Such changes would be expected naturally where localized substrate or s I ope differences a Iter f I ow characteristics. Bank cover is provided by structures on or features of the stream bank that provide shelter from surface predation and reduce visibi I ity. Ex- amples of bank cover include overhanging vegetation and incised or undercut banks, thus bank cover was eliminated when mining removed these features !Figures 41 and 421. These types of bank cover were typically present in straight, sinuous, meandering or split channel rivers, but were less common in braided rivers. Significant bank cover loss was observed at 6 of the 21 scraped sites, Sinuk River, Washington Creek, Oregon Creek, and Penny River sites on the Seward Peninsula, at the Skeetercake Creek site on the North Slope, and at the Middle Fork Koyukuk River-Upstream in the Northern In- terior !Table 13!. lnstream cover is created by obstructions, such as boulders or iogs, that provide slack water· where fish can hold position with minimal energy expenditure and reduce predation from above by being less visible. Water depth can also function as cover, because deep pools and runs offer more overhead protection and often lower velocities than shallow riffles. Certain species, such as Arctic char and Arctic grayling, are often associated with instream cover. lnstream cover was reduced at five sites, Washington Creek, Oregon Creek, Penny River, Kavik River, and Sagavanirktok River, as a result of directly removing boulders and large cobbles or altering flow such that new channels did not possess this habitat !Figures 43 and 441. At six sites, Gold Run Creek, Washington Creek, Oregon Creek, Aufeis Creek, Skeetercake Creek, and Sagavanirktok River, the channel configuration was altered so that the channel was wider and shallower in the mined areas, thus the in- stream cover provided by depth was reduced by lowering the ratio of pools to riff I es. 151 ., a) Undercut vegetated bank typical of Oregon Creek upstream study area. b) Oregon Creek mined study area-notice lack of bank cover, multiple channels. Figure 41 . Remova I of bank cover at Oregon Creek as observed on 24 June 1977. 152 J ) ) ) ) al Skeetercake Creek upstream study area-note undercut vegetated bank. bl Skeetercake Creek mined study area-bank cover absent, flow spread over wide, shallow area. Figure 42. Removal of bank cover at Skeetercake Creek as observed on 18 June 1977. 153 ) a) Sagavanirktok River upstream study area, note predominance of boulders. bl Sagavanirktok River mined study area showing extensive sedimentation and backwaters. Figure 44. Reduction of instream cover as provided by boulgers at Sagavanirktok River, 3 August 1978 (flow level, 60 m /sec,= 155% of estimated mean annual flow). 155 Habitat Diversity The result of decreasing habitat diversity, that is, creating uniform habitats by gravel removal operations, was to favor certain species or I ife history stages over others. One of the main indicators of reduced habitat diversity was increased braiding in the mined area caused where gravel deposits were scraped to below the Water line or where flow subsequently increased to inundate the mined area. This type of habitat alteration oc- curred at 10 study sites !Washington Creek, Oregon Creek, Penny River, Nome River, Aufeis Creek, Kuparuk River, Sagavanirktok River, Ivishak River, Kavik River, and Middle Fork Koyukuk River-Downstream) !Figures 43 and 45, Table 13!. The channels in a braided area usually have a uniform depth, velocity, and substrate with minimal bank cover. The areas were generally characterized by increased wetted perimeter, reduction in channel depth, and reduced mean velocities !Figure 46!. At Washington Creek !Figure 46al, for example, the cross section in the upper mined area !Cross Section 3l had the greatest wetted perimeter at alI flow levels, but most of this was in shal- low open channels with I ittle cover. Similarly, at Oregon Creek !Figure 46bl the wetted perimeter at cross sections in the mined area !Cross Section 2 and 3l was considerably greater than that in the upstream area and ap- proached or exceeded that of the Cripple River cross secttons, a river with greater than three times the estimated mean annual flow of Oregon Creek. Again, the Oregon Creek mined area channels were-wide and shallow, providing low quality and low diversity habitat. The final example, Sagavanirktok River !Figure 46cl, showed a similar pattern with the mined area cross sections having a greater wetted perimeter, but a shallower depth profile than cross sections in undisturbed areas. Habitat diversity was increased in some other mined areas by the crea- tion of new habitats. Three types of new habitats were usually found: ( ll low velocity backwater areas, !2l a side channel off the main river, and !3) a flooded pit forming a pond habitat !Figures 47 and 48). Low velocity back- water areas were found at five sites !Sinuk River, Skeetercake Creek, Sagavanirktok River, Dietrich River-Downstream, and Middle Fork Koyukuk River-Upstream!; side channel formation occurred at three sites !Skeetercake 156 {" '-- ---······--------------------------------- ) ) a) 27 July 1973 -pre-mining b) 2 August 1976-post mining Figure 45. Increased braiding at Sagavanirktok River study site caused by mining mid-channel gravel bars and a vegetated island in the active channel !mining operation conducted during the winter of 1974-1975). 157 ·~ ~7 MAF = 0-53 m3/ sec E a:6 Cross Section w ..... 0 Depth 1 2 3 4 5 6 ~50 ffi Interval US us UM BM LM OS ffi40 Iii 0-10 42% 26% 88% 42% 53% 39% € D. ::::!: 10-20 35 22 12 26 26 28 @30 ~ 20-30 24 19 18 10 14 ..... w 30-40 15 11 7 10 tii2 (.) 40-50 11 3 4 6 ;: 50-60 6 0.4 2 1 60-70 0.7 2 10 30 60 100 c % OF MEAN ANNUAL FLOW a. Washington Creek 30 3 e MAF= 0.69 m3 /sec Oregon Cross Section a: 2.32 m3 t sec 2 3 4 5 6 e w Depth C-..... 2 rn Interval 0-US 0-UM 0-LM ~20 6 Bridge C-LM C-DS a: 5 ffi Q-10 39% 66% 64% 24% 29% 31% w 4 ~-~ 29 32 29 21 24 28 D. 24 4 9 16 19 24 @10 i=. 30-40 9 0.2 15 15 15 ..... ffi 4Q-50 0.3 15 11 2 ..... (.)SQ-60 8 2 w ("' ;: 6Q-70 0.4 '- 10 30 60 100 o/o OF MEAN ANNUAL FLOW b. Oregon Creek = Cripple River Cross Section Depth 1 2 3 4 Interval us UM LM OS (" MAF = 39 rriltsec Q-10 14% 23% 21% 21% "' 15 2 1Q-20 13 21 19 19 2Q-30 13 19 17 17 :§: 30-40 12 16 14 14 3 4Q-50 11 10 11 11 4 5Q-60 7 6 10 7 a: w 6Q-70 5 3 6 5 tii10 ::::!: 7Q-80 4 1 2 3 a: ~80-90 4 0.2 0.4 2 r ; ~ w w 90-100 3 1 D. ~ 100-110 3 1 -11Q-120· 3 3 ~ 12D-130 3 0.2 ~ 13Q-140 2 0.07 140-150 2 KEY 150-160 1 us Upstream 16Q-170 1 UM Uppermlned BM Between Mined r 60 17Q-180 0.4 ·~ 10 30 100 LM Lower Mined 18Q-190 0.4 OS Downstream % OF MEAN ANNUAL FLOW 190-200 0 Oregon Creek c. Sagavanirktok River c Cripple RIVeJ •MAF ·Mean Annual Flow Figure 46. Res,ponse of cross-sectional wetted perimeters to percentage of mean annual flow and percentage of cro.ss sections comprised of selected ,~ depth i n-terva Is at mean annual f I ow at three gravel remova I study sites. 158. ) ) ) ) a) Dietrich River-Downstream-inundated mined study area. bl Middle Fork Koyukuk River-Upstream-backwater in lower mined area. Figure 47. Low velocity backwaters formed by gravel removal at Dietrich River-Downstream ( 13 July 1978) and Middle Fork Koyukuk River-Upstream (18 July 1978), note extensive silt deposition in both cases. 159 Cut-off channel created by mining Original channel a) Skeetercake Creek showing cut-off channel, 4 September 1975. b) Jim River showing side channel created by mining in a high- water channel, 12 August 1978. c) West Fork Tolovana River pit created by deep excavating in an abandoned channel, 29 July 1978. Figure 48. Creation of low velocity side channels and inundated pit following gravel extraction. 160 ) J J J J J J J J Creek, Middle Fork Koyukuk River-Upstream and Jim Riverl; and flooded pits were created at seven sites !Penny River, Ugnuravik River, Dietrich River- Upstream, Prospect Creek, West Fork Tolovana River, Tanana River-Downstream, and Tanana River-Upstream). The changes in habitat diversity were determined by the location of mining and, to some extent, the type of mining. Braiding (decreasing habitat diversity) occurred where the majority of flow went through a mined area, such as where a meander was eliminated !two sites: Penny River, Middle Fork Koyukuk River-Downstream), an inchannel island or gravel bar was removed !five sites: Washington Creek, Kuparuk River, Sagavanirktok River, Ivishak River, Kavik River) or where excavation occurred in an active channel !five sites: Washington Creek, Oregon Creek, Penny River, Nome River, Aufeis Creek). Removal of gravel in active channels created braided areas in what had previously been pool-riffle habitats, thus, in these cases there was often a loss of instream and bank cover, substrate alteration, depth alter- ation, spreading of flow combined with decreased velocity, and loss of pools and riffles. Habitat diversity increased at two sites with incomplete meander cutoffs forming backwater and ponded areas or side channels !Skeetercake Creek, Middle Fork Koyukuk River-Upstream) and with gravel removal in a high-water channel to below the water.table such that it con- tained ponded water !Sinuk River) or annual flowing water !Jim River). Habitat diversity also increased at three sites where recent gravel extraction or channel changes created low velocity backwater areas and braided characteristics were not wei I established !Sagavanirktok River, Dietrich River-Downstream, Middle Fork Koyukuk River-Upstream). Ponded areas or low velocity backwaters were characterized by a sand to si It substrate. The low velocity with associated clear water often allowed increased growth of filamentous algae. Water temperatures were usually increased over those in the active channel because of the dark substrate and poor circulation. Similar effects, although not as great in magnitude, were observed where side channels were formed at Jim River and Middle Fork Koyukuk River- Upstream. Water velocities were reduced and increased silt deposition was observed in the main channel. 161 The three sites with increased habitat diversity due to recent flow were 3 to 4 years old and, in two cases (Dietrich River-Downstream and Middle Fork Koyukuk River-Upstream), flow had only entered the site within a year or two of the site study (Figure 49). The habitat diversity in these areas wi I I probably decrease within a few years as meander cutoffs are completed and braiding characteristics are established. Inundated pits were formed when gravel removal was conducted away from the active channel and the depression, usually deeper than I m, fi lied with water either by direct connection to the river or through intergravel flow. These areas developed characteristics typical of pond habitats, i.e., mud bottom, rooted aquatic vegetation around shorelines, high density plank- ton communities, and macroinvertebrates typically associated with a lentic environment. Two types of pits were included in the study: shallow (< 2 ml and deep (> 2 ml pits (Table 14l. Shallow pits (Penny River, Ugnuravik River, Prospect Creek) normally froze to the bottom in the winter while deep pits (Dletrich River-Upstream, West Fork Tolovana River, Tanana River- Down·stream, Tanana River-Upstream l contained water year-round. Two of the deep pits (West Fork Tolovana River, Tanana River-Upstream) showed dissolved oxygen and temperature stratification in the summer of study while the other two (Dietrich River-Upstream, Tanana River-Downstream) did not (Figure 50). The time at which stratification would be most pro- nounced was missed at Dietrich River-Upstream and Tanana River-Downstream and it is possible that there was some stratification mid-summer; however, the Tanana River-Upstream and West Fork Tolovana. River were thermally strati- / fied from early June to mid-September. AI I pits except the Tanana River- Downstream pit were connected to the associated rivers. The Tanana River- Downstream pit was on a vegetated island and connection to the river was inundated only during annual high water events. This pit had clear water (bottom visible to deeper than 5 ml, very little mud or si It even in the deepest area, and virtually no thermal stratification. Aquatic vegetation was absent except along the shoreline, despite the extreme water clarity. Four of the five deep pits had extensive shallow areas, with over 25 percent of the area less than I m deep. Only at the Tanana River-Downstream was a majority of the area deeper than 2m (Table 14l. 162 ( J ) a) 16 September 1972 b) 2 August 1976 c) II Ju l y 1977 Figure 49. Sequence of aerial photographs showing effects of overm1n1ng the inside of a meander bend at Middle Fork Koyukuk River-Upstream. Immediately following mining (b) there was an i ncrease in backwater areas. The next year (c) the meander was partially cut off, creating a variety of low velocity habitats. 163 Table 14. Percent of Pit Area Composed of Selected Depth Intervals Depth Di€1trich R West Fork Tanana R Tanana R-Upstream interval Penny R Upstream Prospect Ck Tolovana R Downstream Upper Lower (ml (%) (%) (%) (%) (%) (%) (%) 0-1 90a 70.0 90a 54.0 28 23 1-2 lOa 21.0 lOa 32.0 35 38 3i 2-3 0 4.4 0 6.2 34 45 3-4 0 I .3 0 4.2 II 0 0 4-5 0 0.6 0 3.0 13 0 0 > 5 0 2.2 0 0.7 41 0 0 0'\ Mean depth .p. (ml 0.6 1.0 0.6 I .5 4.5 1.6 . I. 7 Maximum depth (ml I .5 7.5 1.5 6.4 9.4 2.7 2.9 Total area (hal 0.6 1.8 1.0 4.5 4.25 7.5 aEstimated. D () () (' ) 14 )( 1 f 2 3 s ! 4 :c t h: 5 w 0 6 )( a. Dietrich -Upstream, 10 July1978 T and DO 2 4 6 8 10 12 14 16 1 t f 2 i 3 1 E i 4 l :c b:: 5 I w )C 0 6 L 7 l c. Tanana-Downstream, 9 Sept.1976 x--x· Temperature (°C) -Dissolved Oxygen (mgft> 2 ~ 3 :c fu 5 0 T and DO )C I b. West Fork Tolovana, 13 Sept.1978 T and DO 2 4 6 X 1 X/ I E :t 1 J :c j h: w 0 d. Tanana-Upstream, 19 Aug.1978 Figure 50. Temperature and dissolved oxygen profi lesat four deep gravel pit study sites. 165 Water Quality Water quality measurements reflected habitat alterations in several ways. First, dissolved oxygen and temperature responded in a predictable fashion to increased braiding. The spreading and shallowing of flow and loss of cover led to an increased rate of heat exhange, with the temperature, and therefore dissolved oxygen, responding more quickly to ambient air tem- peratures in the mined area than in the upstream area. Similarly, areas with ponded water showed increased temperatures and reduced dissolved oxygen !Skeetercake Creek, Dietrich River-Downstream). An increase in dissolved oxygen and decrease in temperature which was not caused by flow alteration was recorded at Dietrich River-Upstream where a spring was uncovered during gravel removal operations. As mentioned, inundated pits functioned as pond habitats with corresponding water quality characteristics. These included higher temperature and lower dissolved oxygen than the associated rivers and in some cases, thermal and oxygen stratifications. A second type of water quality change was a change in conductivity between the upstream and mined areas. A change in conductivity may indicate the existence of a spring water source near or exposed by the gravel removal operation. Such changes were recorded at Aufeis Creek, Skeetercake Creek, Dietrich River-Upstream and Penny River. As already mentioned, the Dietrich River-Upstream was an identified spring exposure. The Penny River had a spring-fed tributary entering the floodplain in the mined area. Springs were not recorded at Aufeis Creek or Skeetercake Creek, but the conductivity changes may indicate their existence. A third type of water quality change was alteration in turbidity or suspended sol ids, or both, in the mined area compared to the upstream area. These changes probably indicate erosional or depositional characteristics of the mined area, but the sampling was insufficient to reach definite conclu- sions on an individual site basis. 166 EFFECTS OF HABITAT ALTERATION ON FISH POPULATIONS Observed Alteration of Summer Distributions or Densities Several types of changes in summer fish distribution were observed in the mined areas; specific types of distributional changes were related to certain types of habitat alterations caused by gravel removal. These changes included: ( ll reduction in the numbers of alI fishes in a disturbed area, !21 replacement of one species by another species, !31 replacement of one age group by another age group, and ( 4 l increase in the number of fish or species, or both !Table 15!. A list of alI species caught during the study and their scientific names is included in Appendix A. Density Reductions. Reductions in numbers of alI fish populations occurred at Washington Creek, Aufeis Creek, and Kavik River sites. The habitat in the upper mined area of Washington Creek was altered in several ways, reducing habitat quality and diversity to an extent that few organisms could utilize the newly created habitat. The density and biomass of Arctic char was significantly reduced downstream of the upstream sample area !Table 16!. The slimy sculpin density and biomass was also reduced in the upper mined area, but increased in the lower sampie areas to densities exceeding those in the upstream area. The sculpin biomass remained low, indicating the slimy sculpin captured below the mined area were smaller than those captured above. Thus, there was a replacement of Arctic char habitat by a habitat more suitable for slimy sculpin in the lower three sample areas. The spe- cific habitat alterations that led to a loss of Arctic char habitat were removal of bank and instream cover and possibly reduced water quality (i.e., increased turbidity! caused by siltation from the melting aufeis f·ield. At the Aufeis Creek site, there was only one I ife history stage of ) Arctic gray! ing present during each sampling trip, thus any changes would have to be density reductions rather than species or age-group shifts. Density reductions were recorded in the upper mined area during the first trip and alI disturbed areas in the second trip. Specific habitat altera- tions that led to reductions in Arctic grayling habitat were: ( ll the reduc- 167 Table 15. Effects of Cumulative Habitat Alterations on Fish Populations in the Mined Area of Study Sites Mined by Scraping Study site Seward Peninsula Gold Run Creek Sinuk River Washington Creek Oregon Creek Penny River Nome River n (I Habitat alterations caused by mining Scraped bars; decreased instream cover; increased ponded water Scraped high-water channel, island, and bank; increased unstab I e sub- strate, slight braiding, backwaters, ponded water; decreased bank cover Scraped active channel; increased siltation, unstable substrate, braiding, backwaters, ponded water, aufeis; decreased bank and instream cover Scraped active channe I; increased unstable substrate, braiding, back- waters, ponded water, aufeis; de- creased bank and instream cover Mu It i pIe meander cutoff; increased unstable substrate, braiding, back- waters, ponded water; decreased bank and instream cover Scraped bars; incl~eased braiding, backwaters, ponded water Continued n (") Effects of total alteration to fish populations in mined area No measurable response (Arctic char, Arctic grayl ingl Arctic char, Arctic grayling, chum salmon fry reduced, slimy sculpin unaffected; potentia I for strand- ing Arctic char eliminated, shift to slimy sculpin below mined area, potential for temporary blockage and stranding Arctic char habitat eliminated, potential temporary migration blockage, stranding Loss of overwintering and spawning areas; species alteration by crea- tion of coho salmon rearing habi- tat Potentia I for stranding and tem- porary migration blockage l""lh u u Table 15. (Continued) Study site North Slope Ugnuravik River Aufeis Creek Kuparuk River Skeetercake Creek Sagavanirktok River Ivishak River u u u Habitat alterations caused by mining Scraped bars; increased braiding, backwaters, ponded water; change from laminar to turbulent flow Scraped active channel; increased braiding, backwaters, ponded water; decreased instream cover Scraped bar; increased unstable substrate, braiding, backwaters, ponded water, possibly aufeis Meander cutoff; increased backwaters and ponded water; decreased bank and instream cover Removal of island; increased unstable substrate, braiding, backwaters, ponded waters, possibly aufeis; decreased instream cover Scraped mid-channel bars; increased unstable substrate, braiding, back- waters, ponded water, possibly aufeis Continued u Effects of total alteration to fish populations in mined area No effect -only a few four- horn sculpin caught Reduction of Arctic grayling, documented blockage due to lack of surface flow Reduction in number of species and I ife history stages; age-l Arctic grayling dominant, docu- mented stranding u Arctic grayling usage reduced where cover was lost, increased in area of partial meander cutoff Increased Arctic grayling, reduced round whitefish, loss of Arctic char habitat; potential for stranding Slight increase in Arctic gray- 1 ing, no significant changes -...1 0 Table 15. (Continued) Study site Shaviovik River Kavik River Northern Interior Dietrich River-US Dietrich River-DS M.F. Koyukuk River-US M.F. Koyukuk River-DS (] Habitat alterations caused by mining Scraped point bars; increased laminar flow, slight braiding, and backwater increase Scraped floodplain; increased si lta- tion, braiding, backwaters, ponded water; decreased instream cover Scraping in high-water channel, ex- posed spring water Scraping in high-water channel; increased backwaters and ponded water-newly flooded depression Partial meander cutoff; increased braiding, backwaters, ponded water; decreased bank cover Scraping in high-water channel; in- creased braiding, backwaters, ponded water Continued Effects of total alteration to fish populations in mined area No measurable changes Arctic char and Arctic grayling both decreased Creation of overwintering area Some use by Arctic grayling, po- t en t i a I for s t r and i n g Altered species composition, round whitefish and longnose sucker in- creased, documented stranding, overall habitat diversity increased Altered species composition- round whitefish, slimy sculpin increased, Arctic grayling de- creased, potentia I for stranding u u u u Table 15. (Concluded) Study site Southern Interior McManus Creek Phelan Creek \ . .) u u Habitat alterations caused by mining Scraping bars; increased backwaters, ponded water, unstable substrate, aufeis Scraping channels and bars; increased ponded water; decreased braiding, backwaters u Effects of total alteration to fish populations in mined area No measurable change (Arctic grayling, slimy sculpin) No fish captured at this site \_.I -....! 1\.) u Table 16. Estimated Densities and Biomass of Arctic Char and Slimy Sculpin at Washington Creek Study Site Based on Repeated Electroshocking of Blocked Sections of Stream, 21-23 June 1977 No. of Area No. of Arctic char S I i my scu I pin sections sampled passes/w Avg density Avg biomass Avg density Avg biomass Study area sampled (m2) shocker a (fish/IOOm2 lb 2 ( gm/ lOOm l . 2 (fish/lOOm l 2 ( gm/ lOOm l Upstream 3 254 12 14 77 12 57 (6-21) ( 37-1 19) (6-21) (32-107) Upper mined 3 209 8 6 2 8 (0-2) (0-13) (0-3) (0-16) Between mined 3 221 10 2 13 II 26 ( 1-2) (8-18) (6-15) ( 18-40) Lower mined 2 125 6 2 23 20 41 (0-3) (0-46) ( 15-25) (32-50) Downstream 2 249 7 2 10 24 44 (2) (5-14) ( 10-37) (21-67) aNumber of times blocked section of stream was sampled with electroshocker. b Value in parentheses is range of estimated values. () ( ' 1 J J tion of the pool-riffle frequency, and (2) increased braiding characteris- tics with the associated loss of bank cover and altered flow regime. At the Kavik RiVer site, habit~t quality was altered by the erosion of berms left in and along active channels, channelizing one section of the river, and creation of a more braided configuration. The densities of Arctic char and Arctic grayling for each study area were estimated by repeated shocking of blocked channels (Table 17!. Total fish densities in the mined area were reduced by a factor of three or greater when compared to the undisturbed areas (Table 18!. The catch of adult Arctic grayling, as de- termined by angling, was also lower in the mined area (Table 19!. The den- sity reductions occurred in both Arctic grayling and Arctic char with neither species apparently favored by the habitat alteration. Removal of instream cover appeared to be a major habitat alteration affecting reduction of fish densities because a channel that contained boulders adjacent to the mined area supported densities of both species comparable to those in un- disturbed areas. Species and Ag~ Group Alteration. Species shifts were observed at nine sites (Washington Creek, Oregon Creek, Penny River, Kuparuk River, Sagavanirktok River, Ivishak River, Dietrich River-Downstream, Middle Fork Koyukuk River-Upstream, and Middle Fork Koyukuk River-Downstream) because alterations in the type of habitat allowed other species to populate an area (Table 20!. A similar response is a change in the age structure of fish inhabiting~ reach of river, as was observed at Kuparuk River, Skeetercake Creek, and Middle Fork Koyukuk River-Upstream. In these areas newly created habitats favored or excluded certain age groups in the areas affected by gravel removal operations. On Kuparuk River, the mined area had a more uniform habitat than the upstream area and numerous smal I channels of simi- lar velocity. Age-0 and age-l Arctic gray! ing and several age groups of slimy sculpin were present in the upstream area while only age-l Arctic gray! ing were captured in the mined area. At the Sagavanirktok River, Arctic grayling juveniles were confined almost exclusively to the mined area, while the upstream area catch was dominated by round whitefish and an unmined channel adjacent to the mined area contained adult (-300 mml Arctic gray- 1 ing. Again, the mined area was changed from a large single channel to an 173 u Table 17. Estimated Densities and Biomass of Arctic Char and Arctic Grayling at Kavik River Study Site Based on Repeated Electroshocking of Blocked Sections of Stream, 1976 No. of Area sections Study area sampled 22-25 July Upstream Mined 2 366 Downstream 2 228 4 - 8 August Upstream 285 Mined 6 2, 190 Downstream 9 2,344 28 August - 4 September Upstream 2 822 Mined 9 2,452 Downstream 6 I ,548 No. of passes/w shocker 8 4 6 6 20 24 8 32 30 Arctic char Avg density (fish/100m2 ! 0.5 (0.5) 3.0 (2.6-3.5) 0.7 0.3 (0-0.7) 0.3 (0-1.0) I. 7 (I. 1-2.2! 0.7 (0-2.2) 0.9 (0-3.9) b . b Avg 1omass 2 (gm/IOOm l 8.4 (7.7-8.7) I II (80-142) 12 17 (0-68) 4 (0-17) 30 (24-36) 19 (0-79) 63 (0-281) aNumber of times blocked section of stream was sampled with electroshocker. b Arctic grayling Avg densityb Avg Biomassb ( fish I I oom 2 l ( gm/ I oom 2 l 0 4.0 (0.9-7.0) 0 0 0.8 {0-4.2) 0.9 (0. 7-1. I l 0.5 (0-2.2) 3.5 (0-10.9) 0 110 (25-195) 0 0 3 {0-20) 35 ( 18-51) 5 (0-30) 9.5 (0-95) Value in parentheses represents range of estimated values. n c ) c '1 C''l t"l (f''l n ( \ u -...J I.J1 u u () 0 u ._;,, Table 18. Comparison of Fish Densities in Mined and Undisturbed Areas as Determined by Electroshocking Blocked Sections of Stream at Kavik River Study Site, 1976 Avera~e fish density No. of Total Mined Undisturbed Undisturbed sections area sampled area areas . Date sampled (m2l (fish/100 m2 l (fish/100 m2 l Mined area 22-25 July 4 594 0.5 7.0 14.0 4-8 August 16 4,819 0.3 0.9 3.0 28 August -4 September 17 4,822 1.2 3.6 3.0 u Table 19. Catch of Arctic Grayling per Angler Hour at Kavik River Study Areas During Summer 1976 Sampling Trips Periods Total Average number of hours of of fish per Area fishing effort angler hour a 22 -24 July Upstream 3 4.7 3.4 ( 1.8-4.5) Mined 3 7.9 2.6 ( 1.3-3.6) Downstream 4 5.6 4.8 (2.2-6.0) 4 -8 August Upstream 2 4.5 3.6 (2.25-4.9) Mined 2.2 2.3 Downstream 2.6 3. I 28 -31 August Upstream 6.0 ! '7 Mined 3.0 0 Downstream 0 0 aVal.ue in parentheses is range of estimated values. 176 "" 'L ff" '- e ""' r~ "'-' e r~ '-' J _) :J Table 20. Change in Catch pe~ Effort end Pe~cent Composition of lnd]cet~ Species at Selectea Study Sites !Selected on Basis of Suitable Semple Sizet Species composition i Che~ i Grey I i ng Obse~ved catch e•~ effort Minnooi Electr-o-All Mejo~ species Rive~ washington Ck O~egon Ck -June -August u UM BM LM 0 u M u M -Sep ternb•~ U M Penny R -June -August -September Kuparuk R Sagavani~ktok R Ivishak R .U M p 0 u M p 0 u M p 0 u ~ u M 0 u M 0 Oiet~ich R-Downstreem U M 0 Middle Fo~k Koyukuk River-upstream Middle Fork Koyukuk River-Downstream u UM LM oc 0 u M D 1.3 0.2 o.o 0.2 2.2 4.15 2.7 I. 7 2.51 0.06 0.20 0.50 15.2 40.5 7.4 24.8 18.2 51.e 12.6 1.3 U • upst~eem LM "' lower mined UM • upper mined p "' pit b + = increased relative to upstream C5 • coho salmon RWF • round whitefish t~ep shock gee~ types lost/gainea0 6.5 12.8 1.0 0 • .56 1.12 0.14 1.155 0.65 1.50 4.2 1.51 4.4 1.8 3.1 I.? 1.3 2.7 26 3 12 22 26 22 II 137 164. 14 30 3.1 3.3 1.51 100 100 0 0 513 78 100 85 0 33 3 71 64 4 85 42 34 0 67 55 4.7 14 5I II 58 513 68 65 36 45 -. eo 87 87 43 Sl4 75 10 61 0 17 8 5 54 751 48 64 44 551 55 25 25 38 8M • between mined OC • original channel 0 • downstream -• decreased relative to upstream AC • Arctic char 177 55= slimy sculpin LNS • longnose sucker +55 +SS +55 -ss +55 +SSIMTl. -SSIESl +55 +CS, +55 +CS +CS -c5 +CS +CS -c5 -ss -55 -RWF +AC +AC -ss +RWF +RWF +RWF,+LNS +RWF +55, +RWF +SS, +RWF +SS, +RwF area criss-crossed with numerous shallow smal I channels. At Skeetercake Creek, gravel removal in the upper mined area created an extensive backwater which was utilized by adult Arctic grayling; at the middle mined area, bank cover and pools were removed and this led to a reduction in the population density of Arctic grayling. At the lower mined area of the Middle Fork Koyukuk River-Upstream site, the single-channel sinuous configuration of the river was changed to a split channel with extensive backwater areas. The catch and species present were similar between mined and undisturbed areas, but the age structure was more complex in the areas affected by gravel removal. Age-0, age-l, and age-2+ Arctic grayling, age-0 round whitefish, and age-l and adult longnose sucker were captured in the mined areas while the·species caught in undisturbed areas were primarily represented by a single age group. Only round whitefish exhibited a more diverse age struc- ture in the undisturbed areas. Similarly, at the Middle Fork Koyukuk River- Downstream site the river was changed from a single channel to a multiple channel braided system with numerous backwater areas. Arctic gray I ing domi- nated the catch at the upstream area, but were replaced in the mined area by round whitefish and slimy sculpin. Potential for Entrapment. Gravel removal in active floodplains created areas of ponded water which were isolated from the active channel. Typically these ponded areas were inundated during high water and became isolated as the water level receded (Figures 51 and 521. Fish often entered these ponded C areas during high water and became stranded as the water level dropped. The mortality rate of these fish was assumed to be high because they were sub- jected to increased temperature, decreased dissolved oxygen, greater vulner- ability to surface predation, desiccation if the area dried completely, and freezing. There were 13 scraped areas at which ponded areas were observed: Sinuk River, Washington Creek, Oregon Creek, Penny River, Nome River, Ugnuravik River, Aufeis Creek, Kuparuk River, Skeetercake Creek, Sagavanirktok River, Dietrich River-Downstream, Middle Fork Koyukuk River- Upstream, and Middle Fork Koyukuk River-Downstream (Table 131. Sampling in these ponded areas revealed significant entrapment at some sites. At Sinuk River the mined area was not heavily utilized by fish. Pink and chum salmon spawn in the river and considerable numbers of chum salmon fry were captured 178 ') J ) ) ) Figure 51. Ponded area at Kuparuk River study site where three seine hauls captured 61 Arctic grayling and 2 slimy sculpin, 9 August 1978 !pool I in T able 21). Figure 52. Ponded area at Middle Fork Koyukuk-Upstream study site where one seine haul captured 28 Arctic grayling, 3 round whitefish and 3 slimy sculpin, 18 July 1978 !pool 2 in Tab I e 21 l. 179 above and below the mined area. Pink and chum salmon are often associated with low velocity water and there was high potential for entrapment of downstream migrants of these two species. The same two species, plus coho salmon, were vulnerable to entrapment at the Penny River site. At Washington Creek, Oregon Creek, and Penny River, the dominant species, Arctic char, are probably not greatly affected by entrapment because they are generally associated with high velocity water and instream cover and would tend to avoid the type of areas which are prone to pending. At the Kuparuk River site, a natural ponded area, apparently enlarged by gravel excavation, contained a high density of age-l Arctic grayling !Table 21, Figure 51l. At the latter site both natural and ponded areas created by gravel removal were present in the study reach. At the Middle Fork Koyukuk River-Upstream, considerable stranding was documented when several isolated pools were sampled !Table 21, Figure 52). The primary species subjected to entrapment in the Middle Fork Koyukuk River system was Arctic grayling. Migration Blockage. Two types of potential mining-induced migration blockages were observed during the study: ( ll blockage due to aufeis for- mation, and !2l blockage due to lack of surface flow. Possible temporary mi~ration blockage due to aufeis formation may have occurred at the Wash- ington Creek and Oregon Creek sites !Figure 53), The principal migrations that could be affected in these particular systems would be upstream and downstream movements of juvenile Arctic char and juvenile coho salmon moving from overwintering areas to feeding areas and downstream migrations of adult Arctic char returning to the sea from upstream overwintering areas, if present. A short-term delay in these migrations may not have a critical effect on these particular species, but a similar blockage for another species, such as an upstream spawning migration of Arctic grayling, may have a great effect on the population in the river. A blockage due to lack of surface flow can occur where flow is spread over a wide area and there is considerable intergravel flow. Under such conditions, alI surface flow may cease. Such a condition occurred at the Aufeis Creek site !Woodward-Clyde Consultants 1976l !Figure 54l and possibly could occur at the Nome River site !K. Tarbox, personal communication). The potential for such a blockage 180 3 ) J J J Table 21. Summary of Catch from Ponded Water Areas Isolated From Active Channels at Two Study Sites No. of Catch per haul seine Arctic S I imy Round Long nose Location Pool hauls gray I i ng sculpin whitefish sucker Kuparuk River 3 20.3 0.7 0 0 M i dd I e Fork 2 28 3 3 0 Koyukuk River-3 20 I 0 'I Upstream 4 0 0 0 0 5 0 0 0 0 6 2 0 0 0 7 2 9 0.5 0 5 181 a) Washington Creek aufeis field, 21 June 1977. b) Washington Creek aufeis field, 21 June 1977. Note sediment layer on ice inside cavern. c) Oregon Creek aufeis field, 7 Jurie 1977. Note sediment layer on melting ice in foreground. Figure 53. Potential migration blockages, aufeis fields at Washi_ngton Creek and Oregon Creek, June 1977. 182 ) a) Ae rial view of Aufeis Creek middle mined study area, 21 July 1977. b) Aufeis Creek upper study area where surface flow disap- peared for three years, 22 July 1977. Figure 54. Region where Aufeis Creek went subsurface creating migration blockage due to lac k of surface flow. 183 existed at several additional sites, such as Washington Creek, Oregon Creek, Penny River, and Skeetercake Creek, but a specific blockage was not ob- served. Creation of New Habitats New aquatic habitat was created at eight sites where mined areas sep- arated from the active channel were flooded subsequent to site closure. These include the Dietrich River-Downstream and Jim River sites as wei I as the pit sites at Penny River, Dietrich River-Upstream, Prospect Creek, West Fork Tolovana River, Tanana River-Downstream, and Tanana River- Upstream. At the Dietrich River-Downstream site, a wide shallow backwater was created in the spring immediately prior to the site survey, 3 years after mining, and was quickly uti I ized by round whitefish and Arctic gray- 1 ing. Less mobile "species, such as slimy ~culpin, had not moved into the : area by the tim~ of the survey I 12-13 Julyl ~ut ~ould probably immigrate into the mined area over the summer period. In the river, the most abundant species was juvenile Arctic gray! ing; the second and third most abundant were slimy sculpin and round whitefish. Removing gravel in an abandoned channel at the Jim River site created a large pool habitat that contained a high density of adult Arctic gray! ing during the summer. Other species captured included juvenile chinook salmon, burbot, and slimy sculpin. In the main river, the catch was dominated by Arctic gray! ing. The present configuration of the Penny River apparently resulted from two separate periods of mining. Originally, the floodplain was scraped adjacent to the channel. The channel subsequently diverted through the scraped site and gravel was removed from the original channel, leaving a shallow pit. During the site visit the present Penny River channel, formed by flow diversion through the original scraped area, was heavily uti I ized by Arctic char juveniles. The pit, created by excavating in the original chan- nel, provided rearing area for coho salmon juveniles and spawning and re·ar- ing areas for Alaska blackfish and ninespine stickleback. The catch in undis- turbed areas was dominated by Arctic char and coho salmon with Arctic char dominant in the spring and coho salmon dominant in the fal I. The occurrence 184 c of both species in undisturbed areas, compared to the single species dom- inance in the mined areas, again reflects the reduced habitat diversity in areas disturbed by gravel removal. The Penny River pit provided coho salmon rearing habitat, which was lim- ited in the river. Arctic char appeared to be more suited to the river environment than coho salmon, and avoided the pit. The pit thus provided ideal rearing conditions for coho with I ittle competition from Arctic char. There was a significant difference in size of coho using the pit as compared to those using the river possibly indicating increased growth rate by those in the pit !Tables 22 and 231. During the winter the coho left the pit and moved to other areas where they poss1bly would be In direct competition with char for space. If overwintering space is I imitlng in this river system, the increased number of larger coho could lead to displacement and subsequent reduction in the numbers of char. The Prospect Creek pit, a shallow pond habitat previously not present in the immediate area, was used as a rearing area by Arctic grayling, round whitefish, chinook salmon, burbot, and slimy sculpin, and also provided a feeding area for adult northern pike !Figure 55). In the upstream area of Prospect Creek the catch In 1977 was dominated by round whitefish, Arctic grayling, and slimy sculpin I isted in diminishing order of abundance. in i978 juvenile chinook salmon appeared to dominate the fish populations in the creek. The Dietrich River-Upstream pit and associated channels provided a deep-water, spring-fed system uti I ized principally by adult Arctic grayling and Arctic char while the main river contained juvenile Arctic gray! ing, ~) slimy sculpin, and round whitefish. The West Fork Tolovana River pit contained extensive vegetated shallow water areas which sloped off rapidly to deep water areas up to 6 m deep, :) thus creating excellent spawning, rearing, and feeding areas for northern pike and feeding areas for adult Arctic grayling !Figure 56). Arctic gray- 1 ing were the only species captured in the river during three sampling trips, while northern pike were abundant in the pit. The only Arctic gray- 1 ing captured in the pit were adults longer than 225 mm; smaller Arctic 185 CX> "' 0 Table 22. Mean Fork Lengths of Coho Salmon Caught by Minnow Trap at the Penny River Study Site During 1977 As e-o A9e-l Mean Mean length Standard Sample length Standard Sample Area (mml deviation size (mml deviation size 4 -10 Ausust Upstream 46.3 2.85 21 76.7 7.59 27 Pit 49.9 3.56 96 85.4 9.29 35 Mined (scraped) 47.8 2.86 50 80. I 6.78 38 Downstream 46.4 2.03 18 79.7 5.70 20 9 -13 seetember Upstream 51.0 5.45 90 85.6 7.33 5 Pit 57.3 5.02 387 89.6 7.55 65 Downstream 52.8 4.47 19 83.3 3.51 3 0 0 ( ) u co -..J u u u u u u Table 23. Differences of Coho Salmon Mean Fork Length Between Sample ~reas and Associated Sig- nificance Levels, Penny River Study Site During 1977 (Using Student's T-Test of Differences Among Lengths in Table 22! A~e-0 A~e-1 Length difference Significance Length difference Significance Areas (mml level (mml level 4 -10 Au9ust Pit-upstream 3.6 p < 0.01 8.7 p < 0.01 Pit-mined 2.1 p < 0.01 5.3 p < 0.01 Pit-downstream 3.5 p < 0.01 5.7 p < 0.05 Mined-upstream 1.5 p < 0.05 3.4 NS Mined-downstream 1.4 NS 0.4 NS Upstream-downstream 0.1 NS 3.0 NS 9 -13 September Pit-upstream 6.6 p < 0.01 4.0 NS Pit-downstream 4.5 p < 0.01 6.3 NS Upstream-downstream 1.8 NS 2.3 NS Figure 55. Prospect Creek study site-shallow pond habitat supporting Arct ic grayling, chinook salmon juveniles, round whitefish, northern pike, burbot, slimy sculpin, 12 August 1978. Figure 56. West Fork Tolovana River study site-deep pond with extensive shallows providing northern pike and Arctic grayling hab i tat, 29 July 1978. 188 ) J grayling either were not entering the pit or were consumed by pike soon after entering. Northern pike were apparently spawning in the pit because many age-0 pike were caught or observed in the shallows throughout the summer. During September, age-0 pike were observed in the river in a large pool opposite the pit outlet, apparently moving from the pit to the river. Thus, the pit may be increasing the number of pike in the river system in general and, given the high density of age~o and age-l Arctic grayling observed in the river near the pit, may lead to a localized increase in the density of river-dwelling northern pike near the pit. Studies by Alt ( 1970) and Cheney ( 1972) indicate that movements of northern pike in the rivers of the nearby Minto Flats region may not be extensive. On a smal I. river, such as the West Fork Tolovana River, a local increase in the northern pike population may lead to )ocal reductions in the Arctic ·grayling population. The upper pit at the Tanana River-Upstream site had a similar habitat and also provided a spawning, rearing, and feeding area for northern pike as wei I as a feeding area for least cisco and humpback whitefish (Figure 57). On a large river, as at the Tanana River-Upstream pit, the effects of the increased numbers of northern pike must be minimal when compared to the river population. The main effect of a deep pit on this type of river system is providing a clear water feeding area that increases the avai iabi iity of desirable species to sport fishing. The lower pit was a more uniform depth with minimal littoral area and was used as a spawning and feeding area by longnose sucker. The connection between the two pits, a shallow (8 em deep) stream, was used by longnose sucker fry, lake chub, and juvenile chum salmon as a rearing area. The lower pit was also utilized as a feeding area by humpback whitefish, least cisco, northern pike, and burbot. The Tanana River-Downstream pit was a deep (maximum depth= 9.4 ml clearwater pit with apparently very low productivity. Fish species captured in the pit were longnose sucker, Bering cisco, and chinook salmon. There was no connection to the river, thus, the fish apparently immigrated during high water and became trapped after the water level dropped. 189 al Upper Tanana River-Upstream Pit, note extensive shallow areas. bl Upper Tanana River-Upstream Pit -area of high northern p i ke density. Figure 57. Tanana River-Upstream upper pit showing extensive vegetation beds, 18 August 1978. Note difference in the extent of vegetative development in this 13-year old pit as compared to the 2 and 3-year old pits in Figures 55 and 56. 190 ) ) ) ) J J J ) Effects on Overwintering Areas Possible effects of gravel removal on fish overwintering areas were observed at several of the study areas. Potential overwintering areas were created at the deep pit sites --Dietrich River-Upstream, West Fork Tolovana River, Tanana River-Downstream, and Tanana River-Upstream --by the pits themselves. The Dietrich River-Upstream pit has been reported as an over- wintering area (W. Anderson, personal communication to A. Ottl. In addition, outflow from the West Fork Tolovana River pit created a potential overwinter- ing area approximately 50 m downstream from the outlet where a deep natural pool with a 1-2 em ice cover existed into March 1979. A possible overwinter- ing area on the Penny River was altered as a spring-fed tributary; Wi I low Creek, that had previously entered the main channel at a deep pool, now entered the river through the scraped area in a series of shallow braided channels (Figure 58l. The pattern of freezing observed during winter studies on six of the pit sites indicated that fish entrapment was not a problem during the 1978- 1979 winter (Table 24l. In those pits studied, the outlet remained open wei I into winter with outlet flow velocities increasing as the sti I I water at the edges of the pit froze, reducing the volume of the pit. Fish appeared to move to the open water found at the outlet areas and the increased veloc- ities may have induced the fish to move downstream to areas of reduced velocity. If fish were holding at an outlet pool and the outlet closed downstream from the holding fish, entrapment could occur. The outlet area in the pits examined was generally quite smal I. However, the number of fish affected compared to the numbers using the pit in the summer would be mini- mal. The outlets of the Prospect Creek and Jim River sites remained open at least unti I late January and possibly into early February, thus fish had ample opportunity to emigrate as flow decreased during freeze-up. Fish were present (caught and observed) at both sites in early November but were not evident in late January. Both sites were frozen to the bottom in March. At the Penny River pit site, fish were caught in the pit in late December and 191 ORIGINAL CHANNEL WILLOW al Wi I low C~eek, a t~ibuta~y of Penny Rive~, showing flow dive~sion following g~avel ~emoval ope~ations, Septembe~ 1975. bl Willow C~eek as it ente~ed Penny Rive~ on 20 March 1979. Figu~e 58. Potential ove~winte~ing a~ea at Wi I low C~eek. This sp~ing-fed t~ibuta~y~ open th~oughout the winte~, had p~e viously ente~ed Penny Rive~ at a deep pool. 192 u u u u u 0 Table 24. Physical Conditions at Pits Visited During Winter Date 16-20 March 1978 6 November 1978 27-29 November 1978 18 December 1978 24 January 1979 ~ 6-8 March 1979 13-14 March 1979 20 March 79 State of out I et Penn~ River Ice thickness/ Water Water depth temperature I em Ia 1°Cib 76115 -0.6 80/0 open through December closed In March Dissolved oxygen lppmlb 12.4 Jim River Ice thickness/ Water Water depth temper at ur e Cern~ 1°CI 1610 2/60 33/36 ·-1.0 90/10 ·-0.5 open through .)anuary closed In March Dissolved oxygen lppml 18.2 5.8 Proseect Creek Ice thickness/ Water Water depth temperature I em) C°CI 155/23 o.o 20/100 107/30 0.0 I 10/0 open through January closed in March ~First number =maximum Ice thickness, second number =maximum water depth from bottom of Ice to bottom of pit. First or one number = surface measurement, second number = bottom measurement. ContInued u Dissolved oxygen lppml 3.5 10.6 u West Fork Tolovana River Ice thickness/ Water Water Dissolved depth temperature oxygen I em) C°CI lppml 80/530 o.o o. 7 20/590 75/535 0.0/3.5 5.8/5.8 closed by late November flow through dam I ni·o March u Table 24. !Concluded) Tanana River-Downstream UJ!~er Tanana Rlver-UJ!stream Lower Tanana Rlver-UJ!Stream Ice Ice Ice thickness/ thickness/ thickness/ Water Water Dissolved Water Water Dissolved Wa:ter Water Dissolved depth temperature oxygen depth temperature oxygen depth temperature oxygen Date lcml 1°CI I ppm I lcml 1°CI I ppm I lcml 1°CI lppml 16-20 March 1978 :n1122 o.o 3.2 100/290 0.010.0 8.016.6 6 November 1978 27-29 November 1978 20/100 0.0/0.0 3.4/2.9 20/163 2.1/3.5 6.2/5.1 18 December 1978 24 January 1979 "' 6-8 March 1979 75/900 -1.0/3.0 6.216.0 105/100 o.o 6.0 90/163 0.5 11.4 ~ 13-14 March 1979 20 March 1979 State of outlet no outlet closed In November open through November open In March closed In March u u 0 0 C:) () 0 0 the outlet was flowing at that time. By March all flow in the pit had ceased and the pit and outlet were frozen to the bottom. The spring-fed tributary, Willow Creek, however, remained open and flowing into March, but fish were not detected either in the tributary or in the Penny River downstream from where the tributary entered the mined area. At West Fork Tolovana River, the outlet was blocked at the time of the first winter visit, 29 November 1979, because the deep, low velocity arm connecting the pit to the river was frozen and the other arm flowed through a beaver dam. Flow out of the pit through the beaver dam persisted through March !Figure 59). Fish were not detected during any of the winter visits. There was sufficient water and dissolved oxygen to support overwintering fish in mid-March 1979 and the persisting outflow through the beaver dam indicates the pit may be receiving some intergravel flow from the river. The Tanana River-Downstream pit was visited only on 6-7 March 1979; fish were not captured but as emigration after the previous September visit was not possible, fish were probably present. The dissolved oxygen should not have been depleted because of the depth, I imited phytoplankton pro- duction, and absence of littoral vegetation, and, in fact, was 6.0 mgt~ in March !Table 24l. At the two Tanana River-Upstream pits, a more dynamic pattern of freezing was observed. On 27-28 November 1978, the connection between the two pits was frozen solid, thus isolating the upper pit. The surface of the ice in the upper pit was approximately 1.5 m higher than the surface of the lower pit. A burbot and possible lamprey were observed with an underwater television system. The outlet of the lower pit was open to the Tanana River with a school of juvenile salmon and two species of whitefish holding in the outlet current. Burbot were captured by set I ine in the lower pit. On 6-7 March 1979, the ice surface of the lower pit had risen to the level of the upper pit and the connection between the two pits was open, approximately 30 em deep and flowing at about 0. I m/sec into the lower pit. The outlet to the lower pit was frozen solid. Dissolved oxygen at the upper pit had increased from 3.4 to 6.0 ppm between November and March. Fish were not detected in either pit in March. 195 f . a) Flow out of beaver dam at pit outlet, 29 November 1978. bl Deep pool (>I ml with thin ice cover approximately 50 m downstream from beaver dam, 15 March 1979. Figure 59. Creat i on of a potential overwintering area at West Fork Tolovana River downstream from pit. 196 0 The above observations indicate that after November the outlet froze, then the side channel of the Tanana River adjacent to the pit started flow- ing through grave I into the upper pit, opened the connection between the two pits and flowed back into the side channel through an intergravel pathway. The raising of the surface of the lower pit appeared to have been caused by overflow on top of the existing ice and snow. Oxygen depletion was a poten- tial problem at the upper pit because of the dense stands of aquatic vege- tation (the March 1978 dissolved oxygen was 3.2 ppml but these were absent in the lower pit and the dissolved oxygen was consistently higher than that of the upper pit. The net effect was the creation of one and possibly two overwintering areas, depending on the minimum winter oxygen levels at the upper pit. Assuming an adequate water depth, the main factor determining the suitabi I ity of a pit as an overwintering area is an adequate level of dis- solved oxygen through the winter. A pit with sufficient depth for over- wintering but with an extensive, heavily-vegetated I ittoral area may ex- perience an anoxic period following the initial snow cover. Barcia and Mathias ( 1979) found that winterki II in eutrophic prairie lakes was closely corre I a ted to the mean depth of a I ake and deve I oped a method to estimate the potential for winterki II based on the initial oxygen storage, rate of oxygen depletion and the mean depth. The critical mean depth for the lakes studied was approximately 2.0-2.5 m. Lakes with an average depth less than 2.0 m experienced regular winterki I I, lakes 2.0-2.5 m experienced occasional winterki II, and lakes with an average depth greater than 2.5 m generally did not experience winterki I I. The indications were that a productive pit with an average depth of less than 2.5 m may have marginal uti I ity as an over- wintering area, especially during years of early heavy snowfal I. The upper Tanana River-Upstream and West Fork Tolov~na River pits had the characteristics to fit this type of pit (Table 14). The 6 m deep area in the latter pit may have provided sufficient volume to maintain a suitable dissolved oxygen level, but both of these pits should be considered marginal overwintering areas. lntergravel flow from the adjoining river, however, adding a continual supply of oxygenated water, could maintain sufficient 197 oxygen levels throughout the winter. The lower Tanana River-Upstream pit did not contain a great average depth, 1.7 m, but the lack of I ittoral vege- tation reduced the probabi I ity of oxygen depletion. The water in the pit was turbid during the summer, I imiting production of aquatic vegetation. The lower pit maintained higher dissolved oxygen than the upper pit during the winter (Table 24l. The Dietrich River-Upstream and Tanana River-Downstream pits both contained deep, clear water regions and did not have wei !-devel- oped I ittoral vegetation. Oxygen levels probably remained high through- out the year. The depth and lack of productivity combined to make these two pits excel lent overwintering areas; the same features limited the'ir value as rearing areas. There are other possible effects of gravel removal on overwintering areas, but they are difficult to assess because of the absence of data on the study sites before gravel removal. A primary effect is the loss of overwintering areas due to diversion of flow from an original channel, as occurred at four sites (Penny River, Dietrich River-Downstream, Middle Fork Koyukuk River-Upstream, and Middle Fork Koyukuk River-Downstream). In these cases, complete or partial diversion of flow could lead to loss or reduction of overwintering habitat. Another effect is the loss of overwintering hab- itat due to increased braiding and the associated changes~~ loss of pool- riffle sequence and reductions in depth and velocity which promote rapid freezing. In some areas, gravel removal created or aggravated the formation of aufeis fields, thus leading to a reduction in water avai fable for over- wintering downstream (Washington Creek, Oregon Creek, McManus Creek, pos- sibly some of the North Slope sites). EFFECTS OF HABITAT ALTERATION ON AQUATIC MACROINVERTEBRATES Observed Effects on Density and Species Assemblage Habitat alterations expected to affect.assemblages of riffle macro- invertebrates would be changes in velocity, substrate, depth, and water quality. During the present study, habitat alterations resultinlf in a change of each of these parameters were accompariied by changes in the riffle com- munity (Table 25). 198 ( c c n u u \0 \0 u u u (11 u u Table 25. Response of Aquatic Riffle Macroinvertebrate Taxa to Habitat Alterations Observed at Selected Study Sitesa Study site Washington Creek Oregon Creek -June -August -September Penny R -June -August -September Nome River Habitat alteration caused by mining Increased aufeis, unstable substrate, braiding Increased aufeis, unstable substrate, si It, braiding Increased unstable substrate, braiding Increased unstable substrate Increased unstable, substrate, braiding, aufeis Increased unstable substrate, braiding Increased unstable substrate, braiding Increased braiding Taxa showing density decreases in area of major a Iteration Cinygmula, Brachycentrus, Chironomidae, Empididae 01 igochaeta, Nemoura, Bae- tinae, Centropti fum, Cin- ygmula, Chironomidae,---- Hydracarina Nemoura, Cinygmula, Epeorus, Chironomidae Nemoura, Cinygmula Oligochaeta,. lsoperla, Nemoura, Paraperla, Bae- tinae, Cinygmula, Glos- sosoma, Chironomidae;- Simuliidae OJ igochaeta, Nemoura, Para- per.! a, Cinygmula, Epeor us,· Chi ron om i dae OJ igochaeta, Nemoura, Eccl isomyia, Glossosoma, Apatania, Chironomidae Glossosoma Continued Taxa showing density increases in area of major alteration Tipul idae None Capnia, Baetinae Capnia, Ephemerel Ia Tipulidae Baetinae, Athericidae, Tipulidae Capn i a, Ephemere I I a, Tipulidae AI Ioper fa, Epeorus, Ephemerel Ia, Athericidae u N 0 0 Table 25. (Con·~inuedl Study site Aufeis Ck -July -August Kuparuk River Skeetercake Creek Sagavanirktok River Ivishak River $haviovik River Kavik R-July -early August -late August Habitat alteration caused by mining (I Increased braiding Increased braiding Increased unstable substrate, braiding New channel Increased unstable substrate, increased braiding Increased braiding Increased substrate alteration Increased si lta- tation, braiding Increased s i Ita- t ion, braiding Increased si lta- tion, braiding (') Taxa showing density decreases. in area of major alteration None Baet i nae, Ephemere I I a, Simul i idae 01 igochaeta, Baetinae, Chironomidae Chironomidae, Simul i idae None 0 I i gochaeta Capnia Nemoura, Cinygmula, S i mu I i i dae Simuliidae Simul iidae Continued Taxa showing density increases in area of major alteration Baet i nae., Ephemere I I a, Cinygmula Tipul idae None Limnephi Ius Bae'tinae, Cinygmula, Epheme- rella, Rithrogena, Brachy- centrus, Chironomidae, Empididae, Simul i idae, Hy.dracar ina Diura, Baetinae, Chirono- midae, Simul i idae, Tipul idae Nemoura, Cinygmula, Chironomidae, Simul i idae None None None ( 1\ ( 'I 1\) 0 u u Table 25. (Concluded) Study site McManus Ck -June -July -September u u Habitat alteration caused by mining Increased aufeis, unstable substrate Increased unstable substrate Increased unstable substrate u u Taxa showing density decreases in area of major alteration u 01 igochaeta, AI Ioper Ia, Cinygmula, Rhyacophi Ia, Chironomidae 01 igochaeta, Rhyacophi Ia 01 igochaeta, Paraperla, Rhyacoph i I a Taxa showing density increases in area of major alteration None AI Ioper Ia, Nemoura, Baetinae, Apatania, Chironomidae, Tipul idae AI Ioper Ia, Centropti lum, Cinygmula, Chironomidae, Psychodidae, Tipul idae aSites omitted had very low macroinvertebrate densities or involved pit mining rather than river mining. Response to Substrate Alteration. The two types of substrate alter- ations observed during the study (a shift to unstable substrate and change from laminar to turbulent flow! significantly affected the total numerical densities of aquatic macroinvertebr~tes in the mined area as compared to undisturbed areas (Table 26!. At Washington Creek, Oregon Creek (June and August!, all Penny River, Kuparuk River, and McManus Creek (May! site visits, macroinvertebrate densities in mined areas were significantly less than those in the upstream area. At alI five sites there was a shift from a moderately compacted gravel substrate to a very loose, unconsolidated sand- gravel substrate (Table 25!. A similar habitat change at the Sagavanirktok River and Ivishak River sites resulted in a significant increase in the density of aquatic macroinvertebrates. In five of the eight cases in which there were total density decreases, there were density reductions in the ephemeropteran genus Cinygmula while in seven of the eight cases, there were reductions in the dipteran family Chironomidae. The density increases at the Sagavanirktok River and Ivishak River sites both contained density increases in the ephemeropteran subfamily Baetinae and dipteran family Chironomidae, as wei I as some other taxa. At two sites there was a change from laminar flow to turbulent flow caused by substrate alteration. At both Ugnuravik River and Shaviovik River sites, there was a significant decrease in total macroinvertebrate density, c primarily because of a decrease in Simuli idae densities. At Ugnuravik River, C the laminar flow was in the upstream (control! area, while at Shaviovik River, laminar flow occurred in the mined area. At three of the five sites where there were decreased densities in the mined area (Washington Creek, Oregon Creek, McManus Creek! there were also aufeis fields associated with the mined area (Table 25!. AI I three sites were visited early in the summer so that any aufeis effects would have been measured at their greatest magnitude. Later visits at two of the sites (Oregon Creek, McManus Creek! indicated that densities in the mined area increased to levels similar to those in the upstream areas. At Oregon Creek, the summer recovery from aufeis effects was not complete for population densities of Nemoura and Cinygmula, which remained below the densities 202 --~------------~------~~~~ ~~~-- c n u 0 u u '> 0 .., u u u u w u Table 26. Changes in Aquatic Macroinvertebrate Densities at Sites Exhibiting Type I and 2 Substrate Alterations Mean denslty 2 lor9anisms/m I Mined or Down-Significance level Major taxonomic grougs Upstream a upper mined stream ANOVAb Mann-Whltneyc experiencing change Ty~e I alteration Density decreases Washington Ck 1121101 56191 791101 0.018 ** 6, 9, II, 12 Oregon Ck -June 5091151 151 I 151 0.000 ** 4, 5, 6, II -August 1221 I 151 8151141 0.030 ** 6, 7, II Penny R -June 10021151 2781 151 0.000 ** 4, 6, II -August 17021151 11681151 5991151 o.ooo NS 6, 7, II -September 6501151 4981151 3331151 0.004 NS I, 3, II Kuparuk R 4431151 771151 1751151 0.000 ** I, 4, II McManus Ck -May 1521151 461141 2741151 o.ooo ** I, 2, 10 Density increases Sagavanirktok R 1531151 301 I 151 1951151 0.016 ** 4, 6, 8, II Ivishak R 2951151 501 I 101 2081141 0.003 ** 4, II, 13 Ty~e 2 alteration Ugnuravik R 50461101 7561101 681101 0.000 ** 13 Shaviovik R 6691151 13321151 9221151 0.010 NS 13 a Number in parenthesis is sample size. b Significance level from ANOVA test, rounded to three decimal places. c Significance level from Mann-Whitney U-Test between upstream and mined areas,**= p < 0.01, NS =not significant. d Code to taxonomic groups: I = 01 igochaeta, 2 = Allo~er Ia, 3 = Nemoura, 4 = Baetlnae, 5 = Centro~llum, 6 = Clny9mula, 7 = E~eorus, 8 = E~hemerel Ia, 9 = Brachycentrus, 10-Rhyaco~hl Ia, II -Chlronomldae, 12 = Empidldae, 13-Simul i l·dae. reached by the same genera in the upstream area. The August and September population densities of Capnia and Baetinae, however, exceeded those re- corded in the upstream area. At McManus Creek, the mined area densities of 01 igochaeta and Rhyacophi Ia did not reach those recorded in the upstream area; the mined area densities of AI Ioper Ia, Chironomidae, and Tipulidae exceeded the up- stream area densities on each of the two succeeding trips. The failure of the mined area densities of some taxa to reach upstream densities, while those of other species exceeded the upstream densities, indicated that there was a long-term habitat alteration which has led to an alteration in species composition of the mined area. Another site which showed a similar response, but where an aufeis field was not identified, was the Penny River site, where mined area densities of Oligochaeta, Nemoura, Cinygmula, Chironomidae, and others were generally lower than upstream densities. In the Penny River mined area, population densities of Tipul idae and, at times Capnia, Baetinae, Epheme~el Ia, and Athericidae were higher than those in the up- stream area. The shift in taxa at the above sites appeared to be related to the occurrence of unstable substrate possibly aggravated by an aufeis field. Other sites with a similar substrate alteration (Washington Creek, Kuparuk River) also showed density reductions of most organisms but the site was only visited once and this precluded any analysis of recovery or sea- sonal patterns. At Kuparuk River, densities of all species were lower in the mined area than in the upstream area while at the Washington Creek upper mined area, only Tipulidae densities exceeded those in the upstream area. In summary, certain taxa, primarily 01 igochaeta, Nemoura, Cinygmula, and Chironomidae were reduced in areas of unstable substrate while others, primarily Tipul idae, but also Capnia and Baetinae, showed increased den- sities. Response to Increased Braiding. Aquatic macroinvertebrate responses to these alterations were colonization by taxa which are more suited to lower velocity waters with higher organics. Clinging ephemeropterans, as found in the family Heptageniidae (Cinygmula, Epeorusl, were replaced by sprawlers 204 and climbers, e.g., Baetidae. Trichopterans often increased in these areas and the dipteran family Tipul i idae was often associated with the finer sediments found in mined areas. At two sites on large rivers showing in- creased braiding as wei I as altered substrate !Sagavanirktok River and Ivishak River) there was an increase in the density of virtually all taxa in the mined area as compared to the upstream area !Table 24). The riffles in the mined area in these two cases were in small shallow channels with exten- sive riffle area while the riffles in the upstream area were in large chan- nels, were less extensive, and composed of a more coarse material. The riffles in the mined area had greater detrital accumulation, and the de- creased depth and velocity associated with the braided areas may have allowed greater periphyton production. Such a situation would increase the quality of the habitat for most of the species unless a critical parameter, such as velocity, had been lost or altered. The increased braiding at other sites, such as Oregon Creek and Penny River, may have contributed in a similar manner to the altered species composition. The increased braiding at many of the sites led to changes in the water temperature and dissolved oxygen in the mined area. An examination of the seasonal variation in the riffle macroinvertebrates at Aufeis Creek revealed a pattern of density changes which indicated a possible effect of the al- tered temperature and dissolved oxygen regime on the apparent densities of certain macro invertebrates !Figure 60). In the ephemeropteran taxa, Baetinae and Cinygmula, the densities in the upstream area increased from the July to August trip while those in and below the mined area decreased. Simul i idae densities decreased between the two trips in the upstream area with simu- 1 i ids absent in and below the mined area in August. The temperature at the area between the two mined areas was 2.8°C !July) and 1.2°C !August) higher than that in the upstream area. The immature stages of the three taxa ap- parently emerged earlier in the areas affected by gravel removal than in the unaffected upstream area. The altered water quality parameters may have altered the emergence times of these three taxa because temperature and dissolved oxygen can affect developmental rates !Hynes 1972). 205 . ---~~~----~--·--·---~------------------------~------~--------------~---------------------------------------------·---------~--- 5000 1000 500 100 -('I E 50 ~ E Ul ·c: CIS Cl ... 0 ->-!- (j) z w 0 10 5 1 • Baetinae • Ephemeretla • Simuliidae Shaded -lJpstream Area Halt-Shaded -Upper .Mu.tArea- Open-8etween Mined Area OL---------------~----~------~----------------July August Figure 60. Densities of selected aquatic macroinvertebrates at Aufeis Creek study areas during 1977 sampling trips. 206 <!' "" " ..... 0 An indication of a similar effect was seen at McManus Creek where AI Ioper Ia nymphs were present in the upstream area in densities exceeding those in the mined and downstream areas. An emergence of adult plecopterans was occurring in the mined area during the site visit, however, and this probably caused the reduced densities of nymphs. Thus, the low nymphal densities of AI Ioper Ia in the mined and downstream areas may have resulted from an earlier emergence time rather than a lack of suitable habitat. The observed density differences between upstream and mined areas, at sites which were only sampled once, must be viewed with caution because of the possibility that emergence periods were altered due to an altered thermal regime. A major period of emergence may have occurred in one area just prior to ·the site visit, thus leaving the area with low densities relative to an area with a later emergence period. At present there is not enough infor- mation on the natural emergence patterns, and the effects of temperature and dissolved oxygen on those patterns, to predict how the arctic macroinverte- brate species would respond to changes in these habitat parameters. Creation of Pond Habitat. The creation of pond habitats allowed aquatic macroinvertebrates typically found in a lentic habitat to colonize these areas !Table 27l. In these cases the change was from terrestrial to aquatic habitat so there was not a direct effect on river communities. Indirect effects could be enrichment of downstream communities by phytoplankton and nutrients being carried out of the pit. The Southern Interior deep pits (West Fork Tolovana River, Tanana River-Downstream, Tanana River-Upstream) had a higher diversity of organisms than the pits in other regions, probably reflecting a more stable habitat. The age of the pit did not seem to exert much effect because the West Fork Tolovana River and upper Tanana River- Upstream pit both had similar configuration and similar fauna and density but the former was 10 years newer than the latter. The low productivity of the Tanana River-Downstream pit was evfdent; the density of chironomids at the Tanana River-Upstream pits, about 50 km upstream, was 5 to 20 times greater than those at the downstream pit at a similar time of year. 207 Table 27. Densities of Aquatic Macrolnvertebrates Collected at Inundated Pit Sites, 1976-1978 !Densities In Organlsmstm2 , from Ponar Sampler I Dietrich R Tanana R Tanana R-Upstream Penny R Ugnur av.l k R Upstream Jim R Prospect Ck West Fork Tolovana R Downstream u~~er ~it Lower ~It 10 Aug. 26-28 Aug. 8-11 July 2-5 July 24 July 10 June 30 July 13 Sept. 10 Sept. 4 Jun'e 17 Aug. 19 Sept. 4 June 17 Aug. 19 Sept. ln=41 ln=51 ln=41 ln=51 ln=51 ln=51 ln=51 ln=51 ln=61 ln=51 ln=51 ln=51 ln=51 ln=51 ln=51 Nematoda 5 Ollgochaeta 1871 19 23 15 4 4 191 269 119 Ephemeroptera Ameletus 4 4 ~ 4 6 8 Caenls II .. 3 calllbaet Is 8 8 19 27 Centro~t i I urn 3 8 E~hemere II a 4 ·SI~hlonurus 4 Odonata Enallagma 27 lschnura 3 II 27 Llbellulldae 4 Hemiptera Corlxldae 42 4 3 4 Coleoptera Dytlscldae 5 Hallplldae 4 .., Trlchoptera 4 4 g Le~toce II a eo Oecetls 4 4 89 27 Phryganea II 16 4 Polycentro~us Diptera 4 4 4 19 8 Ceratopogonldae 19 4 19 19 73 4 4 38 8 23 Chlronomldae 445 983 859 7025 8060 555 3670 16,472 487 4789 7220 9681 1983 1623 2438 Empldldae '19 4 4 4 46 4 8 Slmullldae 4 Mol'lusca 4 Lymnaea 4 6 119 Physldae 10 4 Planorbldae 4 42 69 8 Valvata 4 4 8 Plsldlum 4 8 Gammarldae 4 8 100 4 4 Hydracarlna 43 II 38 4 4 II Total 2374 998 883 7025 8136 606 3747 16,602 788 4843 7259 10,090 2274 1919 2635 No. of taxa 5 3 3 I 4 9 7 14 12 9 6 14 8 7 8 (I (') 0 0 SUMMARY AND CONCLUSIONS EFFECTS OF GRAVEL SCRAPING ON RIVERINE HABITATS Gravel removal by scraping in floodplains resulted in a number of alterations to aquatic habitats with the biota showing a variety of re- sponses to these habitat alterations. Important habitat alterations in- cluded: (I) the creation of braided channel areas with associated changes in various habitat parameters, (2) removal of bank and instream cover, (3) increased habitat diversity, (4) creation of potential migration blockages, and (5) creation of potential entrapment areas. Increased Braiding Characteristics This habitat alteration occurred at 15 study sites where active channel deposits were scraped to below the water line or where flow subsequently increased to inundate the mined area. The main effect of braiding on spe- cific habitat parameters was to reduce velocity and depth by spreading flow over a wider area. The populations of both aquatic macroinvertebrates and fish utilizing these areas were altered with shifts in species and I ife history stages. The reduction in velocity led to increased detrital accum- ulation, deposition of fine materials, and often altered the temperature and dissolved oxygen regime. The altered temperature regime led to altered emergence periods of aquatic insects; the effect of this alteration on reproductive success and overall population stabi I ity is unknown. Fish populations responded to increased braiding in a number of ways, but the general pattern was a reduction in the diversity of the fish com- munity. The number of species and age groups usually decreased in the braid- ed areas. 209 The increased braiding also increased the probability of aufeis forma- tion in the mined areas. This effect was documented at Washington Creek and Oregon Creek and was indicated at McManus Creek and Penny River. There may have been additional ice formation at some of the North Slope sites, such as Kuparuk River, Sagavanirktok River, and Ivishak River. The formation of aufeis fields seemed to prolong the recovery of the site as the channels and substrate remained unstable and si I tat ion persisted during the melting process. In addition, the water needed to create the aufeis field became unavailable downstream, thus reducing water available for overwintering, often the factor limiting fish populations in arctic rivers. Removal of Bank and lnstream Cover Reduction of bank cover occurred whenever a portion of incised or undercut bank was removed. At sites with this habitat alteration, the bank was scraped to remove overburden in order to access underlying gravel de- posits. The former bank with cover was changed to a gravel bar following removal operations. Certain species, such as Arctic char and Arctic gray I ing were strongly associated with bank cover and the loss of this cover led to reduced population densities in the mined areas. Similarly, loss of instream cover led to reduced densities in mined areas. Increased Habitat Diversity Habitat diversity increases were documented at three scraped sites, but these were viewed as temporary increases at newly inundated sites. The habitat diversity wi I I decrease as btaiding characteristics are established, the channel cutoffs are completed, and the habitats become more uniform. Migration Blockages The combination of increased wetted perimeter and decreased depth in mined areas created a situation that could lead to migration blockages during periods of low flow. Such a situation occurred at the Aufeis Creek site and possibly could occur at the Nome River site. The potential for 210 c c :J migration blockage was present at sites, including Oregon Creek and Washington Creek, where the entire active channel was scraped. Because of the known complexity of fish movements throughout arctic watersheds, migra- tion blockages can have a significant, but as yet unstudied, effect on popu I at ions. Potential Entrapment Areas The potential for fish entrapment was high at areas with extensive backwater, as was found at newly inundated areas !Dietrich River-Downstream, Middle Fork Koyukuk River-Upstream! and areas with increased braiding !many sites, including Sinuk River, Kuparuk River, Sagavanirktok River, Ivishak River, and Middle Fork Koyukuk River-Downstream!. At these sites, areas of ponded water became isolated from the active channel as the water level dropped, trapping fish and invertebrates that had moved or been carried into these depressions during the high water. Mortality of stranded fish and invertebrates is assumed to be high because they are subjected to high summer water temperatures, low dissolved oxygen, increased predation from terrestrial predators, winter freezing, and total loss of aquatic habi- tat as the isolated pools often dry up if the river continues to drop. EFFECTS OF INUNDATED PIT FORMATION ON THE ASSOCIATED RIVER BIOTA The direct effects of pit excavation on the river biota were difficult to assess because the river habitat was not directly affected; inundated pits were created from previously terrestrial habitat. Because of this, the pits represented a new habitat and the fauna inhabiting the pits was con- siderably different from that inhabiting the associated river. Summer Utilization by Fish Two of the pits, Dietrich River-Upstream and Tanana River-Downstream, were deep clear water pits with low productivity and fish utilization. At Tanana River-Downstream this low utilization was easily explained because there was no connection to the river and immigration into the pit occurred 211 only at infrequent high water levels. The Dietrich River-Upstream pit, however, was connected to the active channels but fish were apparently not utilizing the pit for feeding. Benthic macroinvertebrate densities in both these pits were low when compared. to those of other pits. The spring-fed channels upstream from the Dietrich River pit were utilized by adult Arctic gray! ing and the pit itself was reported to be an overwintering area. AI I other pits were highly productive and heavily utilized by fish as summer rearing areas. The shallow pits, Penny River, Prospect Creek, and Jim River side channel {this site had some characteristics of a pitl supported high densities of juvenile salmon {coho in the Penny River, chinook in the latter twol as wei I as some species associated with both a lacustrine environment {Alaska blackfish, burbot, northern pike) and stream environment {round whitefish, Arctic gray! ing, slimy sculpinJ. The productive Southern Interior deep pits, West Fork Tolovana River and two Tanana River-Upstream, contained a more lacustrine fish fauna with northern pike dominating the fauna and humpback whitefish, least cisco, and burbot also present in the Tanana River-Upstream complex. Potential for Winter Mortality and Winter Survival Areas The creation of shallow pits and subsequent heavy summer usage by fish created the possibi I ity for entrapment during freezeup and subsequent winter mortality when the pit freezes solid or decay of vegetation consumes the dissolved oxygen. The pattern of freezing observed during winter studies indicated that during the year of observation, entrapment was minimal and probably not a significant problem. The creation of deep pits connected to the river could create over- wintering areas; this was documented or suggested at several study sites. AI I pits studied, with the exception of Tanana River-Downstream, however, had a mean depth insufficient to preclude winter mortality. lntergravel flow appeared to maintain the abi I ity of some pits to support winter fish sur- vival, but this is an unpredictable factor in the design of pits. 212 ( ( 0 J J ) ) RECOMMENDATIONS 1. It is recommended that mining practices leading to an increased braided configuration be avoided. This is best achieved by avoiding active channels and by mining above the water table. 2. Undercut and incised vegetated banks should not be altered. 3. Critical habitats, such as spawning and overwintering areas should be avoided. 4. Formation of isolated ponded areas that cause entrapment should be avoided by contouring and sloping to provide drainage. 5. Pits should be excavated to a sufficient depth to preclude winter mor- tality. Generally, a mean depth of at least 2.5 m should ensure winter sur- vival. 213 REFERENCES Alt, K. T. 1970. Sheefish and pike investigations of the upper Yukon and Kuskokwim drainages with emphasis on Minto Flats drainages. Alaska Dept. of Fish and Game. Fed. Aid in Fish Restoration, Annu. Prog. Rept. 1969-1970, Proj. F-9-2, I I :321~330. Barcia, J., and J. A. Mathias. 1979. Oxygen depletion and winterkil I risk in small prairie lakes under extended ice cover. J. Fish. Res. Bd. Canada 36!81:980-986. Binns, N. A., and F. M. Eiserman. 1979. Quantification of fluvial trout habitat in Wyoming. Trans. Am. Fish. Soc. 108!31:215-228. Bovee, K. D., and T. Cochnauer. 1977. Development and Evaluation of Weighted Criteria, Probability-of-Use Curves for lnstream Flow Assess- ments: Fisheries. lnstream Flow Information Paper No. 3. Coop. lnstream Flow Serv. Group, Fort Col I ins, Colorado. 39 pp. Cheney, W. L. 1972. Life history investigations of northern pike in Tanana River drainages. Alaska Dept. of Fish and Game. Fed. Aid in Fish Res- toration. Annu. Prog. Rept. 1971-1972, Proj. F-9-4, 13:1-30. Hynes, H. B. N. 1972. The Ecoiogy of Running Waters. University of Toronto Press, Toronto, Canada. 555 pp. Nie, N. H., C. H. Hull, J. G. Jenkins, K. Steinbrenner., and D. H. Bent. 1975. Statistical Package for the Social Sciences. Second Edition. McGraw-Hi I I, Inc. 675 pp. Stalnaker, C. B., and J. L. Arnette !eds.l 1976. Methodologies for the Determination of Stream Resource Flow Requirements: An Assessment. Utah St. Univ., Logan, Utah. 199 pp. Woodward-Clyde Consultants. 1976. Preliminary Report-Gravel Removal Studies in Selected Arctic and Sub-Arctic Streams in Alaska. U. S. Fish and Wildlife Service. FWS/OBS 76/21. Wash. D. C. 127 pp. Zar, J. H. 1974. Biostatical Analysis. Prentis-Hall, Inc. Englewood Cliffs, N. J. 620 pp. 214 ----------~-----~~~~~ c ( c '~ EFFECTS OF GRAVEL REMOVAL ON TERRESTRIAL BIOTA M. R. Joyce INTRODUCTION The ecological importance of floodplain and riparian terrestrial habi- tats in temperate regions has been wei I documented in the ecological I itera- J ture. These habitats, particularly the riparian zones, have high primary and secondary biological productivity and typically support a diverse and abun- dant flora and fauna. These biotic zones frequently provide temporary and pe~rmanent refuge for many of our rare and endangered species. The signifi- cance of these floodplain and riparian habitats has recently been recognized and incorporated into the management plans of several Federal agencies !Johnson and Jones 1977; U.S. Army Corps of Engineers l979l. Arctic and subarctic floodplain and riparian habitats are no less significant in their importance and ecological value. The riparian zones develop dense shrub thickets dominated by willows and alder in all four study regions. Overstory forest dominated by white spruce and paper birch also frequently inhabit the riparian zones of the Northern and Southern :.:1 Interior regions. !Scientific nommenclature for terrestrial flora and fauna is presented in Appendix A. l High primary productivity in these zones pro- vides optimum feeding, nesting, and cover habitat for a diverse fauna usu- ally dominated by smal I mammals and passerines. These riparian habitats in ~ interior Alaska frequently support over 100 birds per 40 ha during the nesting season !Spindler and Kessel 1979l. Some birds, such as the yellow warbler and northern waterthrush, very seldom nest in habitats other than riparian shrub thickets. These zones also are preferred habitats for tundra voles and singing voles. The more dense riparian shrub thickets provide critical feeding and cover habitats for moose and ptarmigan during winter. 215 The unvegetated and sparsely vegetated areas within arctic and sub- arctic floodplains provide equally valuable habitat for a d1fferent segment of fauna. Many of the major floodplains provide key migratory corridors for large numbers of waterfowl, shorebirds, and caribou moving to and from wintering zones and summer nesting and calving territories. Unvegetated areas of larger floodplains are used as prime nesting and feeding habitat by numerous shorebirds, gul Is, terns, and waterfowl. The delta areas of larger rivers also are prime juvenal rearing habitats for shorebirds and waterfowl. Along coastal regions, these river deltas also are key nesting sanctuaries for geese, brant, swans, gul Is, terns, and shorebirds, and during late summer and early fal I they provide protected habitat for large concentra- tions of molting waterfowl. Due to the high secondary productivity of these areas, predators including bears, wolves, eagles and jaegers also frequently concentrate their feeding activities along floodplains. Unfortunately, from a biological viewpoint, floodplains also provide easily accessible gravels that are available in large quantities and fre- quently close to development sites. As previously noted, arctic and sub- arctic conditions, primarily associated with the presence of permafrost, place large demands upon gravel resources by alI development projects. During the construction of the Trans~Aiaska Pipeline System, over 3,300 ha of unvegetated floodpJain habitat and approximately 1,000 ha of riparian habitat were affected by gravel removal operations !Pamplin 1979!. The proposed construction of a gas pipe I ine through Alaska, depending upon final route selection and the degree of use of existing construction facilities, could require similar gravel supplies. Other development projects are expec- ted to increase the future demand upon gravel resources. Previous to this study, natural resource managers had I ittle indepth knowledge, relative to arctic and subarctic terrestrial floodplain eco- systems, of how to best mitigate the-use of floodplains as gravel removal sites. The short-term effects of gravel removal operations were believed to be associated with reduction of habitat, probable decrease in local fauna population sizes, and potential indirect effects through reduced habitat quality in adjacent and downstream habitats. However, the variations in the 216 --------~ ------------------- ( -------~---- .J levels of influence and the durations of influence between differing gravel removal sites and methods of operation were not completely known. Also, there were no data on long-term effects in the arctic or subarctic. Factors such as the size and location of the site, and the characteristics of the stream and floodplain were believed to be influencing parameters, but their relationships to short-term and long-term detrimental effects were not understood. To help answer these questions, a terrestrial study was incorporated into this project. The study was designed to be compatible with the hydrol- ogy and aquatic biology programs and organized to provide answers on: (I l the degree of flora and fauna change resulting from gravel removal opera- tions; (21 the rate of habitat recovery at disturbed sites respective to the characteristics of the gravel removal operation and the characteristics of the river and floodplain system; and (31 how the detrimental affects of gravel removal operations could best be mitigated. 217 METHODS OF DATA COLLECTION As previously described in APPROACH AND METHODOLOGY, terrestrial data were collected at alI 25 study sites, with individual site visits occur- ring either during the summer of 1976, 1977, or 1978. Standard procedures were used to collect field data on flora, soi Is, birds, and mammals. Site locations are identified on Figure I. Sites occurred on the Seward Peninsula, North Slope !in both the coastal plain and Arctic foothil lsl, Northern Interior !between the Brooks Mountain Range and Yukon Riverl, and Southern Interior !between the Alaska Mountain Range and the Yukon River). One study site, selected as being most representative with respect to river type and biological conditions in each regional study area, was sampled during a 5-day visit. We attempted to coincide this visit with the peak of the avian nesting season. AI I other sites were surveyed during a 3-day visit. Within each region, the 3-day visits were spaced throughout the spring, summer, and fal I to measure seasonal fluctuations in species compo- sition and abundance. The selected approach to meet the objectives of this project was to document the presence and establish the habitat relationships of the flora and fauna of the disturbed area and compare these to predisturbance flora and fauna populations and habitat affinities. A control area which was most representative with respect to physical site characteristics !i.e., inside or outside meander) and habitat characteristics !i.e., dense riparian shrub thickets, or unvegetated floodplain) was selected to establish pre-gravel removal biological conditions and flora-fauna relationships. In addition, surveys were conducted in floristic seral stages representative of the disturbed area during the time of the field visit, and in seral stages representative of anticipated future disturbed-area vegetative development. 218 ( J These areas were surveyed to identify flora-fauna relationships during various site recovery stages. The Major Variable Matrix Table !Table I l identifies the variety of sites studied. Study sites varied from large braided rivers to smal I, single-channel streams located in four major geographical regions of Alaska. Selected sites were studied from 2 to 20 years after disturbance, allowing data gathering on short-term and long-term response and recovery by the terrestrial biota. Characteristics of gravel removal areas included: scrap- ing operations of surface gravels within and adjacent to active channels; scraping in areas separated from the active channels; and pit excavations separated from active channels. This range of sites allowed comparison of the effects of d.ifferent techniques and site locations on terrestri~l biota. 219 METHODS OF DATA ANALYSIS Data analysis initially resulted in the identification of the degree of change in measured parameters at each study site. A numerical rating ranging from 0 to 10 was assigned to indicate an increase (ratings 10 through 6l, no change (rating of 5l or a decrease (ratings 4 through OJ. These ratings indicate the degree of change at the time of the site visit between the pre-gravel removal conditions (i.e., extent of shrub thicket cover, or number of passerines presentl and the post-gravel removal conditions. Each numerical unit increase (6 through IOl or decrease (4 through OJ approxi- mates an alteration similar to a 20 percent level of change in that param- eter. Each site was analyzed to determine how measured parameters (vege- tation, soi Is, birds, and mammals) interacted, and how they responded as a whole to the Physical Site Characteristics (such as river size and config- uration) and Gravel Removal Area Characteristics (such as type and location of gravel removal l. After individual site analysis, alI sites were compared to evaluate similarities and differences in the degrees of change in biolog- ical parameters. Fauna directly respond to the presence (and typel or absence tive development, consequently, the degree of change and the rate covery at the gravel removal sites received major emphasis in the data analysis. Factors that influence vegetative recovery (e.g., ditions and aufeis development!, also were thoroughly reviewed. of vegeta- of re- vegetative soi I con- Selected biological data were subjected to a computerized hierarchical clustering routine to identify similar responses in a measured biological 220 ( c c r '- J J parameter between rivers. This analysis grouped similar sites and simi Jar responses (increase or decrease! by biological parameters. AI I data were thoroughly reviewed to identify any correlations between Physical Site Characteristics, Gravel Removal Area Characteristics, degree of change by the terrestrial biota, and short-term and long-term recovery rates. The following sections include the results of data collection and analysis. 221 -------~ RESULTS AND DISCUSSION Changes in selected terrestrial parameters that were induced by gravel r ernoval ate ide-11ti Fied in Table 28. These changes were based Ypon measured levels of variation in each parameter at each site. In general, the degree of both short-term and long-term changes in local faunal communities strong- ly reflected the extent of disturbance to floodplain and riparian vegetative communities . . VEGETATIVE COMMUNITIES OF STUDY AREA FLOODPLAINS Vegetative communities of floodplain and riparian zones at the study sites were typical of those occurring throughout arctic and subarctic regions. In general, the Seward Peninsula rivers and the smaller North Slope rivers usually were meandering or sinuous in configuration with wei !-defined (incised! outside meander banks !Figure 611. This configuration and profile created a relatively narrow floodplain 130 to 60 ml and allowed extensive development of mature shrub thickets adjacent to single channel rivers. These shrub thickets usually were dominated by Salix alaxensis. On inside meanders !point barsl and in more active portions of floodplains !lateral and mid-channel barsl herbaceous, woody pioneer and early wi I low communities occurred adjacent to unvegetated gravels bordering the river. Meandering and sinuous rivers of the Northern and Southern Interior were similar in pattern and were characterized by extensive shrub thickets with dense stands of advanced and mature successional stage boreal forest communities at the edges of active floodplains (Figure 621. White spruce usually dominated these stands, but paper birch and balsam poplar also were common. Similar pioneer and early shrub successional stage communities occupied point bars and edges of lateral and mid-channel gravel bars. 222 ( c (j u u u u u u Table 28, Quantitative Changes In Selected Terrestrial Biological Parameters at Gravel Removal Study Sites a Seward Peninsula North Sloee Northern Interior Southern Interior Sl te age II 10 13 13 II 20+ 7 5 9 II 3 3 5 7+3 2 3 4 2 2 2 3 16 4 13 3 I years I ... L CD (f) (f) CD "" > (f) (f) :::> a > "" CD :::> a I I (f) • L CD 0:: L I I "' (f) "' • .. L CD ... L 0:: 0:: "' a :::> CD L > L u "' L > .. .. .. .. "' I I • u "' "' .. 0 CD > > "' "' .. c CD L L "' b ... CD ... "' .. ~ .. ... > 0:: L " " L "' CD .. ., .. .. c • .. ... "' "' "' CD IX 0:: "' "' u > L > > .. > 0 b ~ .. "' ... 0:: .. .. 0:: "' > " " L. 0 u L. c ... > u u > .c .c >->-.. ... "' "' u " 0:: en IX ii .> "' L. c "' "' u u 0 0 > u 0 Ul ., 0:: c c .. •• " .. .. .. 0 "' "' " ,_ " .. c "' 0 >-L ! ... ... > .c > "' .l: .l: "' Q. c c c " .., " .c en c s ·" " .. .. .. .. " ., " c .. .. c c Q. .. "' " > .. .. ... u. E 0 ... ~ c c " ~ .. L. .. "' " " "' .. ~ .c .. -E -E L. " .. .c II) .. 0 ... z :::> < "' II) II) "' "' a 0 Q. ;<: ,_ ,_ Q. Hectares of removed vegetation I 35 2.5 4 12 0.5 0.3 20 0 7 15 0 0 4 35 7.5 10 7 II 6 8 3 8 9 0 Percent of disturbed area 30 40 85 65 eo 35 25 45 0 70 45 0 ·0 10 100 100 50 25 100 100 100 80 100 100 0 Vegetation Overstory forest 5 5 I 5 I 4 I 4 0 3 5 Shrub thickets 3 I I I I 4 4 I 5 I I 5 5 4 I 3 3 3 I 3 I 4 7 I 5 E~rly mixed shrub-herbaceous 9 Cl 7 3 7 4 5 4 5 7 3 5 5 4 3 3 7 4 3 3 3 6 7 3 5 .... l:;l Sol Is Texture 7 7 9 7 7 6 5 4 5 5 7 5 5 6 7 5 7 5 8 7 7 6 7 7 5 Nutrients 5 5 4 5 6 3 5 5 6 \5 3 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Birds Passerlnes 3 I I I I 3 5 I 5 3 I 5 5 3 I 3 I 4 I I I 5 I 3 5 Water birds 5 3 6 6 9 5 5 8 5 6 6 5 5 4 6 7 6 5 9 5 9 5 5 9 5 Ptarmigan habitat 3 I 3 3 I 5 5 3 5 3 I 5 5 4 I 4 4 5 I 3 I 4 6 3 5 Mammals Smal I mammals I 5 3 3 7 3 5 7 5 5 I 5 5 7 3 5 7 5 0 0 4 7 5 7 5 Ground squirrels 5 7' 7 5 7 5 6 5 5 9 5 5 5 6 6 5 5 5 5 5 5 5 5 5 5 Moose habitat 3 I 3 3 I 5 5 3 5 3 I 5 5 4 I 4 4 5 I 3 I 4 6 3 4 8 Degree of change from original conditions was measured as an Increase 16 through 101, no change 151, or a decrease 14 through 01. Each numerical unit corresponds to an approximate 20 percent degree of change, A dash Indicates no appllcab Ill ty. Figure 61. Penny River undisturbed floodplain showing typi- cal North Slope and Seward Peninsula floodplain character- istics of sinuous channel bordered with dense shrub thick - ets with incised outside meander bank, and narrow gravel point bar on inside meander. Figure 62. West Fork Tolovana River showing typical South- ern and Northern Interior medium river floodplain character- istics with shrub thickets and white spruce-paper birch stands along the riparian zone. 224 The larger rivers within alI four regions typically flowed in braided or split channel configurations. These floodplains were more hydraulically dynamic, with much wider active areas, and contained advanced seral stage vegetative communities only along floodplain borders and on isolated mid- channel islands. Much of the floodplain in these large, braided rivers contained expansive areas of unvegetated gravels or were sparsely vegetated with herbaceous and woody pioneer or early shrub thicket communities. This very briefly describes in general terms the normal vegetative patterns of floodplains in the area of study. For a more detailed descrip- tion of normal patterns, refer to the "Preliminary Report Gravel Removal Studies in Selected Arctic and Sub-Arctic Streams in Alaska" (Woodward-Clyde Consultants 1976) and for a detailed description of the vegetative structure which occurred at each study site refer to the Project Data Base. VEGETATIVE COMMUNITY CHANGES AT GRAVEL REMOVAL SITES The observed changes in vegetative communities of the study sites varied from no significant change to long-term loss of habitat. Habitat loss and alteration (both short-term and long-term) repeatedly resulted in signif- icant secondary changes within the bird and mamma! populations that inh~b ited study area floodplains. These faunal responses are discussed in a foi iowing section. Significant areas of existing floodplain vegetative cover were removed at 18 of the 25 sites (Table 28). Lost vegetative habitats usually consisted of mature shrub thickets on the Seward Peninsula and North Slope sites, and a mixture of shrub thickets and advanced successional stages of boreal forest floodplain communities in Northern and Southern Interior regions. At alI sites these habitats supported a diverse and abundant fauna dominated by passerines and smal I mammals prior to clearing and gravel removal activ- ities. Refer to the Project Data Base for a complete listing of recorded flora and fauna at each study site. Vegetative habitat removed at these 18 sites averaged 10 ha and ranged from approximately I ha at Gold Run Creek to 35 ha at Dietrich River- Upstream (Table 28). 225 In general, sites separated 'from the active floodplain frequently disturbed the most vegetative habitat as a percentage of the total disturbed area. For example, Table 28 identifies seven sites that were entirely ( 100%) vege t ated pri or to gravel removal and alI were separated from the active floodplain. At alI seven sites vegetative cover and associated organic overburden were completely cleared prior to gravel removal. Long-Term Loss of Vegetative Habitats Long-term loss of terrestrial habitat occurred at those sites where: (I l the gravel extraction method !either pit excavation or deep scraping) removed gravel to depths that resulted in permanent flooding; or !2l the specific site location and material site characteristics resulted in r i ver hydraulic changes which annually affected the site. Permanently Flooded Material Sites. Eight of the study sites were excavated pits, either totally or in part !Figure 63l. Pits varied from an Figure 63. West Fork Tolovana River showing permanently flooded pit excavated adjacent to the active floodplain with a downstream connection. 226 average of 1.5-m in depth at the Penny River to over 7 m deep at the Dietrich River-Upstream, West Fork Tolovana River, and Tanana River- Downstream sites. The pits were either connected or unconnected to adjacent active river ch anne Is, however, in a I I cases they were permanent I y f i I I ed with ponded water (Figure 63l. Surface areas ranged from 7.5 ha at Tanana River-Upstream to 0.1 ha at Ugnuravik River. Six of the eight sites were separated from the active floodplain and were completely vegetated with mature white spruce-paper birch and/or wi I low and alder shrub thickets prior to excavation. At these sites the depth and subsequent flooding created aquatic habitats that led to long-term loss of terrestrial habitats. At the two other pit sites, the excavations occurred in unvegetated point bars (Ugnuravik Riverl and unvegetated lateral bars (Kavik River). Thus, no vegetated habitat disturbance occurred. Excavation of deep pits, however, was not the only gravel removal method that led to development of permanently ponded water and consequently the long-term loss of terrestrial habitats. The combined gravel removal and site location characteristics at the Jim River and Dietrich River-Downstream sites also led to permanent ponding. At the Jim River, gravel was scraped from within and immediately adja- cent to a high-water channel. The resulting profile at the completion of the scraping operation resulted in an almost circular depression in the middle of the worked area. The high-water channel traversed this depression. Since this channel carries summer flow, it consequently had formed an annually ponded area of approximately 4.5 ha over this centrally depressed portion of the I I ha site. Before clearing and gravel removal, with the exception of the approximately 10-m wide high-water channel, this site contaioed a di- verse complex of mature and intermediate-aged white spruce-paper birch stands with scattered willow and alder thickets. The Dietrich River-Downstream site was scraped to an average depth of I to 1.5 min a rectangular shaped 7.5 ha. The area was separated from the active floodplain by approximately 150m prior to the activity. However, the depth of excavation w~s the probable cause of a permanent channel change by a major side channel of the Dietrich River. This channel entered the pre- 227 viously dry site during the second spring breakup following the activity. ihis channel change caused flooding of approximately 90 percent of the material site. This condition wi I I remain as long as this side channel flows through the site. Thus, at both the Jim River and Dietrich River-Downstream sites, mining depth and site location characteristics also created permanently ponded aquatic habitats which wi II lead to long-term loss of terrestrial habitats. Annual Hydraulic Stress. In addition to the creation of permanently ponded sites, long-term loss and alteration of habitat occurred at sites where the gravel removal operation resulted in significant changes in river hydraulics. Examples of such changes include shifted channels, annually f loaded sites, and aufeis development within the material site. On the Seward Peninsula, the Penny River and Oregon and Washington Creeks are smal I rivers with relatively narrow, densely vegetated flood- plains. Penny River and Washington Creek flowed in a sinuous configuration, while Oregon Creek flowed in a straight configuration. The portion of the total disturbed area which was vegetated by dense, mature shrub thickets prior to disturbance at each site was extensive !Oregon Creek 65 percent; Penny River 80 percent; and Washington Creek 85 percent) !Table 28). At alI three sites, the working area !which was scraped to a level equal to or slightly below normal water levels) extended across the entire floodplain and at Washington and Oregon Creeks the disturbed area extended approxi- mately 9 to 15m beyond the floodplain banks and into the adjacent shrub- tussock tundra. The resulting effect of these scraping operations created: an unvegetated, flat floodplain which was 2 to 3 times wider than upstream or downstream reaches; a floodplain that was equal to, or only slightly higher in elevation ( 10 to 20 em on the average) than normal summer flows; and a wider channel with increased braiding, straighter configuration and shallower flow !Figure 64). The effects of these induced hydraulic changes created direct impedi- ments to vegetative recovery and thus they also resulted in long-term altera- tion of the habitat structure of the disturbed reach in these floodplains. 228 ( -~--------~------~~-----------------~- ) ) ) Figure 64. A view of Oregon Creek looking downstream through the mined area showing site conditions that remain 13 years after gravel removal. The specific changes that retarded vegetative recovery and development at these sites were related to induced aufeis development and increased annual high-water stresses. At Washington and Oregon Creeks, extensive aufeis fields annually developed within the material sites. This ice, which is known to last unti I late June throughout the 6isturbed areas, severely impeded vegetative recov- ery at these sites. No significant vegetative communities had developed within the disturbed areas of either site during the 13 years following the gravel removal operations. There is no evidence of aufeis development at the Penny River site. However, the area was scraped in an irregular surface pattern over 15 ha to a depth equal to or slightly below normal summer flow levels (Figure 65J. The site was visited I I years after gravel was removed. As a result of the depth of scraping, much of the site contained either smal I pools of ponded 229 Figure 65. Penny River mined area looking upstream. Note the f looded conditions with i n the disturbed area, and the overburden piles in the center of the site (circled on p ho t og r aph ). water or wa t e r satura t ed so i Is. A sma I I 0.6 ha, I .5 m qeep p i t was dug in t he southeast corner of the sit e . The hydrau! ic anal y s is s hows that the Penn y Riv e r site is fl o oded f or short dur a tions during hi gher fl ows o n an ann ual a n d possibly semiannual basis. Flows of only appro xi mately 150 per- cent of mean annual flow begin to flood the material site. During the II growing seasons following the disturbance, only sparse, scattered pioneer and early wi I low f l oodplain communities had developed within the scraped portions of the Penny River site. These early succes- sional habitats were not present in the undisturbed floodplain reach which, as previously stated, consisted almost entirely of mature shrub thickets. Thus, the structure of the vegetative community within the mined site changed for the long-term from one dominated by dense mature shrub thicket habitats to one dominated by scattered and low-density immature herbaceous and woody species that are adapted to wet soi I conditions. Repeated stress from annual or semiannual high water, combined with the continuously 230 G 0 0 :J water-saturated soi Is over much of the Penny River site, were probably the key factors impeding vegetative recovery (especially by woody species!. Another example of gravel removal and site location characteristics which resulted in known short-term (the site was visited 3 years after disturbance!, and probably long-term annual hydraulic stress occurred at the Sagavanirktok River study site. At this site 20 ha of a complex mixture of mature and advanced, seral-stage shrub thickets was removed and the under- lying gravels excavated to an average depth of I .5 m. This area was located between a high-water channel and the main river channel. The Sagavanirktok River was a large river with moderate channel slope that flowed in a sinuous configuration. This gravel removal operation resulted in a permanent shift of much of the main channel through the material site. Hydraulic analysis at this site shows that extensive flooding is expected to occur on an annual basis with water potentially influencing the site for up to 70 days each year. The site was visited during the third growing season after disturbance, and no vegetative recovery had occurred. As long as the river continues to flow through and annually flood the material site, it is not expected that significant vegetative recovery wi I I occur in the long-term. Short-Term Alteration of Vegetative Habitat Structure Short-term alterations, in the types of vegetative habitats present within disturbed areas, occurred at those sites where vegetation was re- moved, but where some natural vegetative recovery began within or 2 years post-mining and continued thereafter unimpeded. At no instance did an entire disturbed area naturally revegetate over the short-term. However, in par- tions of 13 sites pioneering communities became wei I established within or 2 years (Table 29!. This development most frequently occurred in those portions of the disturbed areas which: were not influenced by normal or high water flows; had a plentiful seed source or contained root stocks and other woody slash; and/or consisted of well drained but moist soi Is with high si It 231 -------~~-·-·----·----~------·------·--~·------·-------------~----- 0 1\.) \.N 1\.) Table 29. Location, Response Time, and Community Characteristics of Vegetative Recovery at Selected Study Sites Site Gold Run Creek Sinuk River Washington Creek Penny River Aufeis Creek Skeetercake Creek MF Koyukuk River-Downstream Jim River Prospect Creek West Fork Tolovana River McManus Creek Tanana River-Downstream Tanana River-Upstream u Location of first vegetative recovery Overburden piles Overburden piles Overburden piles Overburden piles Broadcast slash and debris at edge of floodplain Inside meander of abandoned channel Broadcast slash and debris at edge of floodplain Sloping banks above ponded water Sloping banks above ponded water Sloping banks above ponded water Overburden piles Overburden piles surrounding ponded water Overburden piles surrounding ponded water Community characteristics Herbaceous (few shrubs) Herbaceous with woody shrubs Herbaceous with woody shrubs Herbaceous with woody shrubs Herbaceous with woody shrubs Herbaceous (few shrubs) Herbaceous with woody shrubs Herbaceous with woody shrubs and trees Herbaceous with woody shrubs and trees Herbaceous with woody shrubs and tree's Herbaceous with woody shrubs Woody shrubs Herbaceous with woody shrubs Site age at initiation of vegetative recovery (years) Unknown Unknown 2 2 1'1'\ and sand content. The results of sol I sample analysis indicated sol I nutri- ents were not I imiting factors influencing vegetative recovery at any of the 25 study sites. The initial recolonization of these disturbed areas most frequently oc- curred by seed development; at several locations, however, wi I lows had reinvaded through development of adventitious stems and roots from old woody slash and root stocks. Adventitious stem development occurred most often in overburden piles where woody slash was placed. AI I overburden piles occurred in sites developed before 1971. More recent regulation of gravel removal activities require overburden and woody cover to be removed completely from floodplain sites. In general, herbaceous species dominated in those pioneer communities which were developing from seed. However, Salix alaxensis was a frequent member of these communities in alI four geographic regions, and seed I ing Betula papyrifera and Populus balsamifera commonly occurred in pioneer communities at several Northern Interior sites. Taxa that most often were dominant in these invading communities included Epilobium latifol ium, Salix alaxensis, Salix spp., Equisetum variegatum, Stel laria spp., Hedysarum Mackenzi i, Astragalus spp., Oxytropis spp., Juncus spp., Carex spp., Eriopho- ~ spp., Calamagrostis spp., and Poa spp. In sol Is that were less moist and more coarse, Artemisia spp., Crepis nana, Aster sibiricus, and Erigeron spp. frequent! y occurred as ! nit i a I invaders. Overburden was piled either within the disturbed area or at its edge at many of the older sites. At the Penny River and Washington ~nd McManus Creeks these overburden piles contained many organics and woody slash, root stocks, and debris. At Penny River, three piles of material were located within the 15-ha site !Figure 65l. At Washington Creek, one pile was placed in the middle of the 3-ha site and one on its edge, and at McManus Creek the organic overburden was alI piled on the edge of the 4-ha disturbed area. These piles averaged !Figure 66l. to 2m in height, however, a few were 5 to 7 m At alI three sites, herbaceous and woody vegetation were wei I estab- 1 ished on the overburden piles within I year after disturbance. Development 233 ---~-------~------~----------------~~-----~------- Figure 66. Close-up view of an over~urden pile in the Penny River mined area. Note the development of herbaceous and woody vegetation during the II years following gravel remova I. on these piles preceded other disturbed area revegetation at Penny River and McManus Creek by approximately 6 to 7 years. At Washington Creek, which was visited 13 years after Disturbance, the only significant revegetation of the site occurred on overburden piles (Figure 67). At alI sites, the initial Figure 67. Washington Creek mined area showing vegetative recovery only present on the overburden pile 13 years after gravel removal. 234 --------~~----- J ) .) .) shrub development was through adventitious stems (Figure 68). Wi I lows, primarily S. alaxensis, most frequently developed from old slash and root stocks. a. View of broadcast slash and 2-year-old stems. b. View of old root stock with new stem. Figure 68. Woody revegetation occurring through develop- ment of adventitious stems. 235 Simi lar rapid development of woody shrubs through adventitious stem development occurred in 1-to 2-ha area~at both Middle Fork Koyukuk River- Downstream and Aufeis Creek study sites.However,at these sites the slash and woody debris were not pi led,Qut were spread over the ground at the edge of the disturbed areas (Figure 69). Figure 69.Distribution of woody slash debris and other organics over the ground on the edge of the gravel removal area at Aufeis Creek.. At the Tanana River-Downstream site overburden from the 5-ha pit was placed in contoured banks surrounding the flooded pit.These overburden pi les were approximately 2 to 3 m deep inversely pi led (top material covered by bottom material),and consequently contained no organics or woody remains near the surface.However,an early shrub community dominated by Populus balsamifera,~.alaxensis,and Alnus crispa,with a density of 230 stems per 0.004 ha,was present during the fourth growing season fol lowing gravel removal.This shrub community developed from seed and invaded in mass during the first growing season.The shrubs occurred in uniform density over approx- imately 60 percent of the gently-sloped,20 to 25 m wide overburden banks surrounding the pit. Rapid natural recolonization of disturbed areas was not always limited to overburden pi les.At the Jim River,West Fork Tolovana River,and Prospect Creek,pioneer communities were wei I developed at the end of the 236 J ) .) first full growing season following disturbance. At these sites the com- munities were developing on the contoured side slopes of the permanently ponded areas. An average of 13 species, with a range of 7 to 21 species, occurred in 0.0004-ha sample plots located in these habitats during the second (Jim River and Prospect Creek) and third (West Fork Tolovana River) growing seasons following disturbance. Wi I lows, alders, birch, and spruce occurred with the herbaceous taxa in these habitats at alI three sites. Although these sites have not been inspected since 1978, the pioneer com- munities wi I I probably develop unimpeded and quickly lead to early and advanced sera! stage shrub communities. The Tanana River-Upstream site was very similar to the West Fork Tolovana River site with respect to Physical Site Characteristics and Gravel Removal Area Characteristics. The mined site was 10 years old during site inspection, and 13 years old at the time of data collection (summer 1978). Shrub thickets dominated by Salix arbusculoides and Alnus tenuifol ia had developed surrounding much of the pit and on spits and islands which remain- ed above the water level of the upper pit (Figure 70). These communities had Figure 70. View of the upper pit at Tanana River-Upstream showing diversity of shore I ine configuration -and develop- ment of woody and herbaceous vegetation 13 years after gravel removal. · 237 reached an advanced shrub stage with densities as high as 990 stems per 0.004 ha by the 13th year. Thickets averaged 2 to 3 m in height. During site in~pection these thickets most I ikely were equally as dense and practically as ta I I. At most above mentioned sites, following rapid invasion and development of pioneer communities !both by seed and adventitious stems), early shrub communities usually were wei I established in 3 to 5 years. The majority of these areas were smal I !0.5 to 2 hal and were usually scattered throughout the scraped sites or surrounding the flooded sites. Usually only one to three isolated patches of early shrub communities occurred in the scraped sites. Those sites that were of sufficient age (including Penny River, Oregon Creek, Washington Creek, Sinuk River, McManus Creek, and Tanana River-Upstream) began to provide sufficient cover for nesting and feeding passerines and summer and winter cover for smal I mammals about 10 years after initial disturbance. Thus, at sites that provide areas !of various sizes) for revegetative growth without severe stresses from flooding or aufeis scour, habitats that provided food and cover for passerines and smal I mammals !primary shrub thicket occupants) were naturally replaced about 10 years after completion of gravel removal activities. No Significant Change in Vegetative Habitats Contrasted to long-term loss of habitat and short-term alteration of habitat structure are gravel removal operations that resulted in no measur- able change in the vegetative structure of the study areas. Gravel mining did not affect vegetation at 5 of the 25 study sites, either because of the disturbance location, or the floodplain character- istics, or both !Table 281. At two additional sites, the Nome River and Kavik River, only slight reduction? in vegetative cover were observed. Three of the five sites with no vegetative disturbance were large flood- plains with large-and medium-width channels flowing in braided patterns. At 238 c c c c c c c c J ) .) alI three sites large quantities of gravel were removed by shallow scraping surface layers over a broad area. Specifics on these sites are: Study site Ivishak River Kuparuk River Phelan Creek Scraped surface area 40 ha 14 ha 70 ha Quantity of gravel removed 3 120,000 m 3 42,000 m 3 575,000 m Although Phelan Creek was a wide (approximately 1,000 m) unvegetated floodplain, and the Ivishak and Kuparuk Rivers also had extensive unvege- tated gravel bars, the latter two sites also contained numerous islands with densely vegetated shrub thicket stands (Figure 71 ). At the Ivishak River and Figure 71. View of the Ivishak River floodplain looking downstream showing typical braided channel characteristics with extensive gravel bars . and isolated, vegetated islands. Kuparuk River sites, operators conformed the configuration of their gravel removal areas to avoid the vegetated islands. At the Phelan Creek site, gravel was scraped from a uniformly shaped and contiguous area, because the floodplain was entirely unvegetated within the work area. 239 The best example of avoiding disturbance to vegetated areas on a mean- dering or sinuous river occurred at the Shaviovik River study site (Figure 72). This river flowed in a medium width, single channel and in a sinuous Figure 72. View of both undisturbed (background) and mined (foreground) reaches of the Shaviovik River . Note that gravel removal maintained natural point bar contours and shapes and did not disturb riparian vegetative zones. configuration. With these characteristics the floodplain consisted of broad (averaging approximately 40 to 50 m in width) unvegetated point bars at every inside bend and numerous unvegetated lateral bars located between point bars. Gravel removal consisted of shallow scraping on every point bar and lateral bar over a distance of several river kilometers. Smal I quan- 3 tities were taken from each location, however, a total of I 16,000 m was removed. The actual scraping of unvegetated gravel deposits throughout most of the Shaviovik River site was conducted in a manner that caused minimal, or no biological disturbance. Gravel bars were scraped only in their unvege- tated portions and riparian shrub thickets were not disturbed. Also, the mining operation maintained natural contours and shapes on gravel bars and 240 c c c c 0 0 0 0 0 c did not mine adjacent to the river. Thus, the Shaviovik River has maintained its natural channel and configuration. FACTORS AFFECTING VEGETATIVE RECOVERY RATE Several factors found to be influencing vegetative recovery already have been discussed. The composition of faunal communities using disturbed areas was directly related to the habitat. types avai !able, thus, an under- standing of how factors at the study sites influenced the rate of natural vegetative recovery warrants further discussion. Overburden piles, woody slash, and debris, an abundant seed source, and displaced organic mats enhanced recovery rate. Hydraulic stress such as aufeis development, perman- ent pending, actual channel shifts, and increased flooding impeded develop- ment. Soi I conditions and growing season, depending upon site specific characteristics, either enhanced or impeded vegetative recovery. Impediments Among the factors believed to be impeding vegetative recovery, hydrau- 1 ic stress influenced most sites and had the strongest and most long-term effect. These stresses resulted from changes induced by gravel removal in floodplain elevations, dimensions, and configurations. They included: • Permanent or annual flooding, • Increased frequency and duration of temporary flooding, • Long-term channel changes (increased braiding and channel width and decreased channel stabi I ityl, and • New or increased aufeis development. The specific known causes for these induced hydraulic changes are presented in detai I in EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS. In general, they most frequently resulted because sites were excavated too deeply (excluding pit sites) without maintaining buffers or stable channel banks, or because the gravel removal method and character- istics were not correct for the chosen location. 241 At 13 sites the gravel removal method led to significant hydraulic changes that secondarily impeded the vegetative recovery rate !Table 30!. Permanently ponded water and aufeis development caused the most significant impediment. Permanently ponded water occurred at those sites where the mining plan cal led for excavated pits, but also at sites where depressions were scraped below summer water levels. The latter occurred at sites that were directly connected to an active channel !Jim River!; at sites that were not directly connected to an active channel !Penny River!; and at sites that were originally not connected, but where gravel extraction caused an active channel to reroute through the deep depression !Dietrich River-Downstream!. Aufeis impeded vegetative recovery at four sites !Washington Creek, Oregon Creek, Middle Fork Koyukuk River-Downstream, and Jim River!, alI of which were directly connected to active channels. Aufeis development is believed to occur annually at all sites, and affects the entire disturbed area at Washington Creek and Oregon Creek and most likely affects much of the disturbed areas at Jim River and Middle Fork Koyukuk River-Downstream. Two additional factors were impediments to vegetative recovery under certain conditions: soi I condition and length of growing season. Vegetative recovery was occurring to some degree under a wide variety of soi I type, texture, nutrient, and moisture levels. Differences in the degree of develop- ment and the species composition reflected the wide range of xeric and mesic soi I conditions. Soi I nutrients were not found to be I imiting factors at any site regardless of its age, original condition, or final condition. However, vegetative invasion was restricted by very compacted surface layers at several of the more recent sites. These areas most frequently were associ- ated with access routes over gravel surfaces leading to and from the mined sites. At Dietrich River-Downstream, heavy equipment compacted the flood- plain gravels approximately 25 em adjacent to the gravel removal area !Figure 73!. This site was visited 3 years after completion and vegetation had not invaded this access road although the unflooded banks of the materi- al site were supporting pioneer communities. Another soi I condition which restricted vegetative development 13 years after site work, occurred at Oregon Creek. Inorganic materials were scraped 242 c c c c c 0 G e c c a 0 l:j 0 0 0 0 Table 30. Quantification of Change in Selected Hydrology Parameters Which Were Impeding . . a Vegetative Recovery at Study S1tes site - Hydrology parameter Study Age Channel Flooded P.onded Aufeis in years Braiding width area area potential Sinuk River -10 9 8 Washington Creek-13 10 8 10 10 10 Oregon Creek -13 9 10 9 8 10 Penny River -II 9 10 10 10 Nome River -20 10 10 10 7 1\.) Ugnuravik Creek - 7 10 8 .p.. Vol Aufeis Creek - 5 9 8 10 10 Skeetercake Creek -II 8 10 Sagavanirktok River - 3 10 8 10 Dietrich River-Downstream - 3 7 7 Middle Fork Koyukuk R.-Upstream -4 10 7 9 8 Middle Fork Koyukuk R.-Downstream -2 8 9 10 7 8 Jim River -2 10 10 8 8 aRe fer to EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS for explanation of parameters and quantification of change values. Figure 73. Compacted surface gravels in an access road leading to the Dietrich River-Downstream site. from the site and placed in piles along the northern boundary of the mined area (Figure 74). Piles of this material supported no growth, while adjacent Figure 74. Inorganic overburden pi led on the edge of the Oregon Creek site which supported no vegetation 13 years after gravel removal. 244 0 0 c 0 0 0 0 c c piles of organics, silts and sands supported advanced seral stage shrub thickets. The undesirable material was of unknown substance, but appeared to be a mica-like material. The average growing season varies from approximately 130 to 150 days in the Souther Interior, from 100 to 120 days on the Seward Peninsula, and from 75 to 95 days on the North Slope <Mitchel personal communication!. This factor was believed to be strongly influencing the rate-of vegetative recov- ery at the two most northern study sites (Ugnuravik and Kuparuk Rivers). Both sites were only 6 km inland from the Arctic Ocean and at both sites vegetative recovery in nonflooded areas was progressing very slowly even when compared to similarly aged North Slope sites (7 and 9 years! located 80 to 90 km inland. Enhancements Several factors were found to enhance vegetative recovery, the most significant of which appeared to be the presence of organic soil with woody slash and debris. This material was most effective when placed in piles that were higher than frequent flood levels, or broadcast in those portions of the disturbed site where it would not get washed downstream or frequently flooded by high water. Overburden piles occurred at I I of the 25 study sites, however, only at those sites where this overburden contained organics with fine textured soils (silts and sands! and woody slash and debris, was vegetative recovery most enhanced. Instead of being placed in piles, this material was broadcast over the surface at two additional sites <Aufeis Creek and Middle Fork Koyukuk River-Downstream). At both sites, this material was placed in areas where it was not stressed by high water levels. At both sites these 2-to 4-ha areas were the first to begin natural revegetation and supported the most diverse and most developed communities. Revegetation began the first growing season following completion of gravel removal at both sites. Develop- ment of adventitious stems was the prime method of revegetation by willow <Figure 751. 245 Figure 75. Close-up of dense and diverse vegetative devel- opment in an area of surface broadcast of woody slash and organics. Note the wi I low adventitious stem development. Other factors that enhanced vegetative recovery were the presence of silt deposits, an abundant seed source, and the deposition or grounding o1 d i spiaced organic vegetative mats. At several sites (including Kavik River, Skeetercake Creek, Kuparuk River, Sagavanirktok River, and Dietrich River -Downstream) the deposition of pockets of si It in low depressions within the disturbed areas quickly led to the development of a pioneer community dominated by wetland plants adapted to wet and silty soi Is. These areas frequently were dominated by Carex spp., Juncus spp., Eriophorum spp., Equisetum spp., and Salix spp. (Figures 76 and 77). Their size was highly variable and dependent upon river characteristics (suspended load) and site characteristics (disturbed area profiles and shapes). At several of the permanently ponded sites (Jim River, Prospect Creek and West Fork Tolovana River) the development of herbaceous and woody plants was found to be frequently most concentrated at old and recent high water 246 Figure 76. Distant view of e large si It depositional area at the Sagavanirktok River study site. Figure 77. A si I t depositional area of the Kavik River supporting a wei !-developed pioneer vegetative community. 247 I ines (Figure 781. These water bodies concentrated avai !able seeds on their surfaces and then deposited them al~ng the shore! ine. Figure 78. Close-up of a concentration of wi I low seed! ings at the shore! ine of the Jim River ponded area . The erosi on, downstream transport, and subsequent deposition of iarge, intact vegeta t ed organic mats also was found to initiate vegeta t ive recovery of gravel mined sites (Figure 791. Howeve r , this process was not overal I significant because it most often occurred on a smal I scale and was not widespread. It most frequently occurred in the larger more dynamic rivers. Most observations of this occurrence were of mats that were believed to have been deposited I or 2 years prior to site visits. In the type of river where they most frequently occurred, they were vulnerable to continued downstream movement during floods. However, in a few locations the root systems of woody species had penetrated the underlying gravels and these mats appeared to be firmly established. FAUNAL COMMUNITY CHANGES AT GRAVEL REMOVAL SITES Terrestrial fauna either displayed no response to gravel removal opera- tions or displayed one of four different reactions depending upon fauna 248 J ) Figure 79. Vegetated organic mats that were washed down- stream and grounded during high water on Tool ik River floodplain gravel bars. type, habitat preferences, and home range size. Most responses were directly related to the removal of floodplain vegetation. A response was recorded at 19 of the 25 study sites !Table 28). In all cases where no differences in populations (particularly birds and small mammaisi were recorded, vegetation was either not removed (Kuparuk, Ivishak, and Shaviovik Rive rs and Phelan Creek) or only very sparse vegetative cover was removed (Ugnuravik River and Middle Fork Koyukuk Rive~-Downstream). At those sites where significant quantities of floodplain vegetation were removed, faunal responses basically consisted of four different reactions: • Population Reductions-passerines and smal I mammals responded to the loss of vegetative habitats. • Population Increases-water birds and ground squirrels responded to the removal of heavy vegetative cover, and, in the case of ground squirrels, also to the presence of overburden piles. 249 • Altered D1stribution-overwintering moose and ptarmigan most I ikely responded to the reduction of food and cover habitat provrded by floodplain thickets, by either increasing their winter rei lance upon adjacent undisturbed thickets, or by shifting their local w1nter distribution and movement patterns. • No Apparent Response-large mammals !such as caribou, bears, and wolves) showed no significant response to floodplain alterations created by gravel removal operations. Population Reductions At 18 of the 25 study sites significant areas of vegetated habitat were removed prior to gravel mining. These habitats usually were of a~vanced or c c c c~ mature vegetative stages and were dominated by a diverse and abundant passer-C: ine and smal I mammal community in alI four regions. In Southern and Northern Interior regions red squirrels also were dominant members of these commu- nities at sites that contained stands of mature spruce, or mixed spruce and birch. On the North Slope and Seward Peninsula, the passerine· populations inhabiting riparian shrub thickets most frequently were dominated by yellow warblers, Wi I son's warblers, orange-crowned warblers, white-crowned spar- rows, fox sparrows, tree sparrows, gray-cheeked thrush, American robins, common redpol Is, and yellow wagtai Is. Although population sizes were not est.imated, at sites with extensive development of riparian shrub thickets as many as 50 individual birds of 13 species were present in an area of approxi- mately 3.5 ha !Penny River!. In Southern and Northern Interior ~ites, many of the above passerines were joined by yel low-rymped warblers, gray jays, black-capped chickadees, dark-eyed juncos, and alder flycatchers. At many sites smal I mammals also were common to abundant in heavily vegetated habitats. Tundra voles were the most frequently captured species, and were recorded in alI four regions. They were captured in a wide variety of vegetated habitats and appeared to be more tolerant than other smal I mammals of the low-lying habitats which frequently contained water saturated 250 c G e c 0 c c 0 0 0 0 0 0 0 soi Is. Singing voles and red-backed voles also were commonly captured in alI regions. Most singing voles were captured in habitats that were more removed from the active portions of the floodplains, while red-backed voles were most abundant in the mature spruc~-birch forest of the Jnterior sites. The most important aspect of clearing advanced and mature shrub thick- ets and spruce-birch stands was the loss of feeding, nesting, and cover habitats for passerines and small mammals. No small mammals were observed or captured in unvegetated or sparsely vegetated portions of d~sturbed areas at any of the 25 study sites. Also, passerines displayed no dir~ct association with these areas, and only were observed on a few occasions feeding or drinking in these habitats. As identified in previous sections, character- istics of the gravel remova.l operation~ and subsequent hydraulic changes most frequently tesulted in long-term loss of terrestrial habitats. Thus, the local passerine and small mammal populations, primarily at the larger sites, most likely were significantly reduced as a result of lost habitat. Population Increases At some sites the grave I remova I operation created habitats that were more desirable to some species than predisturbance habitat conditions. Population levels of water birds (including waterfowl, shorebirds, gul Is, and ternsl increased within the disturbed area at 12 sites (Table 28J. These sites included those where mining resulted in permanently ponded areas (such as Jim River, West Fork Tolovana River, or Tanana River-Upstream) and where mining removed dense vegetation creating ponded water or backwater areas and/or mud flat and gravel bar habitats (Penny River and Aufeis Creek). These habitats provided the preferred feeding and nesting areas for these birds. Many of the most significant increases occurred at sites where the adjacent upstream and downstream floodplain was heavily vegetated, and the gravel excavation provided habitats that were not readily avai I able in the immediate floodplain vicinity (Penny River, West Fork Tolovana River, and Tanana River-Upstream). Birds that were most frequently associated with gravel and mud flat habitats in material sites included semipalmated 251 plovers, Arctic terns, western sandpipers, ruddy turnstones, spotted sand- pipers, glaucous gulls, northern phalaropes, and semipalmated sandpipers. At sites that provided desirable conditions, primarily abundant food supplies, the disturbed areas supported abundant shorebird populations. At the Penny River, 56 individuals of 8 species of water birds were using the 15-ha mined site during the nesting season, while at Aufeis Creek 100 individuals of 13 species of water birds were present within the site during the post-nesting period. At both study sites, these numbers were a several factor increase over the numbers of individuals and species present in the undisturbed reaches of these floodplains. Flooded pits provided feeding and/or nesting habitat for waterfowl !most frequently green-winged teal, mal lard, red-breasted merganser, pin- tal I, bufflehead, and Barrow's goldeneye>. Tree, violet-green, and bank swallows, Arctic terns, mew gul Is, and herring gul Is also were frequently observed feeding in these pits. At seven sites ground squirrels were found to be more abundant within the disturbed areas than within adjacent undisturbed zones !Table 28!. At six of the seven sites this response was directly related to the presence of overburden piles located within or at the edge of the material sites. These piles provided denning sites, convenient observation posts, and the first avai I able food source !through vegetative development! within the mined s~te. At several sites !Washington Creek, Penny River, and Skeetercake Creek) the only ground squirrels observed were in the mined site. In addi'tion, at West Fork Tolovana River, Tanana River-Downstream, and Tanana River-Upstream, beaver were actively using the ponded waters in these pits. Muskrat also were encountered at the Tanana River-Upstream pit. Altered Distribution Moose and ptarmigan concentrate many of their winter activities in dense floodplain thickets. Evidence of their past presence was recorded at most sites and in alI four regions. These animals normally move throughout large areas, hence the localized removal of vegetated habitat was not be- 252 c c c c 0 e c c c 0 c 0 0 0 0 G c I ieved to have significantly affected their population levels. However, at sites where large areas of vegetati~n were removed !including Dietrich River-Upstream, Sinuk River, Sagavanirktok River, Penny River, and Jim River) the loss of habitat may influence the winter distribution and move- ment patterns of these animals. No Apparent Response Mammals that have large home ranges !including bears, caribou, wolves, and foxes) generally displayed no apparent attraction to or avoidance of the disturbed floodplain areas. Hence, the only apparent effects of gravel removal on these animals would be those associated with reducing their cover and food supplies !vegetation, sm·all mammals, passerines, and fish) or increasing their cover and food supplies !water birds, ground squirrels, and fish l. An exception to this pattern was recorded at a few of the sites located aiong the Trans-Alaska Pipeline corridor. At these sites !Jim River, Dietrich River-Upstream, West Fork Tolovana River, and Middle Fork Koyukuk River-Downstream) individual bears and wolves have become attracted to these areas by associating them with discarded food and garbage. FACTORS AFFECTING RECOVERY RATE OF FAUNAL COMMUNITIES For species whose populations were reduced as a result of gravel min- ing, specifically passerines and small mammals, the rate at which they began to recolonize disturbed areas was directly related to redevelopment of vege- tative habitats. Vegetative recovery was most directly influenced by hydrau- lic parameters as discussed in previous sections. At sites that were of sufficient age and contained sufficient vegeta- tive recovery, passerines did not begin to again use the disturbed areas as nesting and feeding habitat unti I shrub thickets of an intermediate stage with densities approaching 200 to 300 stems per 0.004 ha and 1.0 to 1.5 min height were present. In addition, smal I mammals did not begin to use vege- tated areas as primary habitats unti I the ground cover developed to a multi- layered cover with densities of at least 60 to 70 percent surface coverage. 253 As stated in discussions of vegetative recovery, some sites began to provide habitat of this level in portions of the disturbed areas approxi- mately 10 years after disturbance. Mo5t frequently this occurred in over- burden piles. At four sites (Sinuk River, Washington Creek, Penny River, and Kavik Riverl, the only significant use of the disturbed area by passerines and smal I mammals occurred at the overburden piles even though these sites averaged over 10 years in age. Thus, at sites where gravel removal created a site subject to frequent hydraulic stresses, overburden piles not only provided areas for rapid vegetative recovery, but frequently provided the first useable nesting, feeding, and cover habitat for passerines and smal I mammals. AI I vegetated overburden piles were found to be of sufficient size to support at least one pair of nesting passerines and one resident smal I mammal. The smallest overb~rden pile sampled was approximately 9 m x 15m, while the largest was approximately 15m x 100m. As was anticipated, the larger piles supported the larger populations. PERMANENTLY PONDED SITES Many gravel removal operations resulted in significant long-term loss and reductions in vegetative habitats and associated passerine and smal I mammal populations. However, one gravel removal method frequently led to an increase in local habitat diversity, even though it resulted in a permanent change from original habitat conditions. This increase~ habitat diversity also frequently led to increased fauna diversity. This method created perman- ent aquatic habitat either by excavating a pit separated from the active floodplain or by scraping a deep depression adjacent to an active channel. Eight sites provided this lacustrine habitat. (Note: the Kavik River and c c: c c c 0 G Ugnuravik River pits were not considered in this evaluation; the Kavik River e pit had fi I led in prior to the site visit and the Ugnuravik pit was very smal I ( 10 to 15m in diameter) and primarily covered with main channel flow.) Several parameters at pit sites were qualitatively evaluated !Table 31 l. Increased fauna use was associated with those ponded waters that had high border cover, irregular pit shape, vegetated or graveled islands, high food avai labi I ity, and a diversity of water depths. Also, pit size appar- ently was a I imiting factor, because both Penny River and Prospect Creek 254 c c 0 0 0 0 0 0 0 Table 31. Qualitative Evaluation of Habitl;!t Quality and Fauna Use at Permanently Ponded Gravel Removal Sites sIte Tanana River-Upstream Dietrich River-Downstream West Fork Tolovana River Tanana River-Downstream Jim River Dietrich River-Upstream Prospect Creek Penny River Rank by habitat value ldiversityla 4 2 8 3 7 6 5 Age 13 yrs 3 yrs 3 yrs 4 yrs 2 yrs 2 yrs 2 yrs II yrs. Pit size 7.5 ha 6.5 ha 4.5 ha 4.25 ha 4. I ha 1.8 ha 1.0 ha 0.6 ha Border cover High & diverse Low Medium & dIverse Medium but low qualIty Pit shape Very irregu- lar & diverse Islands present Vegetated gravel lrregu-None lar lrregu-Gravel lar Regular None Medium & lrregu-None diverse I ar Low Regular None Medium & Regular diverse Low Regular None None Water depth Food avallabi I ity Diverse Abundant & diverse Shallow Abundant benthos Diverse Abundant & diverse Very deep Low Shallow Abundant & diverse Deep Very low Sh,a I I ow Abundant & diverse Shallow Abundant & diverse Detrital organics present High High High Very low High Very low High High 0 Fauna use Very high & diverse Medium water birds. High & diverse Very low High water birds Very low Low Low .aA subjective evaluation and relative ranki.ng of overall habitat quality based upon habitat parameters of border cover, pit shape, presence of water depth, food availability, and presence of detrital organics: 0 appeared to provide adequate habitat with sufficient food supplies but both received low fauna use. They were both I .0 ha or less in size. Tne Tanana River-Upstream pit, which was 13 years old, provided the most desirable lacustrine habitat. This 7.5-ha pit had a very irregular shore! ine with heavy vegetative cover; contained numerous shrub-thicket vegetated islands in its southern half (upper pitl and graveled islands in its northern half (lower pitl; had an abundant food supply dominated by fish and macroinvertebrates; and had a variety of deep and shallow water zones (Figure SOl. During the site visit 147 individual birds of 39 species were Figure 80. Tanana River-Upstream showing shoreline diver- sity and vegatative development in the upper pit. recorded in the entire study area and four individual beaver, at least two muskrats, and three moose were observed using the pits. The avifauna observ- ed are identified in Table 32. The West Fork Tolovana River pit was smaller (4.5 hal and not as old (3 years) but otherwise was similar to the Tanana River-Upstream pit. Avifauna observed at this site are identified in Table 33. Due to the young age and sparse vegetative cover, the avifauna in the disturbed area included few 256 0 Mature spruce Gray jay 1}1 Yellow-rumped warbler 131 Alder flycatcher 131 Dark-eyed junco 121 Common raven Ill "' "' ... Totals 5 1121 0 0 0 0 0 0 Table }2. Bird Observations by Habitat Type Within the Control and Disturbed Areas at Tanana River-Upstream }-7 June, 1978. Control Intermediate-aged mixed deciduous Yellow warbler 151 Dark-eyed junco 121 Fox sp·arrow 121 Gray-cheeked thrush (I) Black-capped chickadee Ill American robin Ill Ptarmigan· Ill 7 1131 Numbers Indicate Minimum Individuals Known to Occur In Each Habitat Type. Deciduous swamp Northern waterthrush 121 Belted kingfisher Ill 2 131 Disturbed Intermediate-aged Carex wetland mixed deciduous Yellow warbler 141 Rusty blackbird 121 Gray-cheeked Spotted sand- thrush 121 piper 121 Ye llow-rumped Lesser yel lowlegs warbler I II (I) Common f I I ck er WhIt a-crowned Ill sparrow Ill Dark-eyed junco Savannah spar~ow Ill Ill Ptarmigan Ill Common snipe Ill 6 I 101 6 IBI Bare gravel/ mud flat Herring gull Mew gull 141 161 ArctIc tern 121 Semlpalmated plover 121 Spotted sand- piper 121 Lesser yellowlegs (I) Bald eagle Ill American golden plover Ill 8 1211 Gravel removal area Early willow/ Ponded water in pits herbaceous WhIt a-crowned Tree swallow 1101 sparrow 121 American robin Ill Barrow's goldeneye 1101 Savannah sparrow Herring gull 181 Ill Bank swallow 181 Spotted sand-Violet-green swallow 161 piper Ill Bufflehead 151 Mew gu II 141 Lesser yellow legs 131 Canada goose 121 Red-breasted merganser 121 Arctic tern 121 Semipalmated plover 121 Northern phalarope 121 Spotted sandpiper 121 Green-winged teal 121 American golden plover (I) Bald eagle I II western sandpiper Ill Belted kingfisher Ill Plntai I (I) Greater scaup Ill Mallard (I) 4 151 22 1751 0 Table 33. Bird Observations by Habitat Type Within the Control and Disturbed Stations at West Fork Tolovana River 9-1 I June, 1978. Mature spruce/ deciduous Gray jay 141 Dark-eyed junco 141 Black-capped chickadee 131 Alder flycatcher (3) Hermit thrush 121 Varied thrush 121 American robin 121 Common ravin 121 Common flicker 121 American kestrel (II Totals 10 1251 Numbers Indicate Total Individuals Known to Occur in Each Habitat Type. Control Riparian shrub/ backwater slough Spotted sandpiper 141 Northern water- thrush 141 Fox sparrow 131 Rusty blackbird 131 Yellowlegs 121 Yellow warbler (II 6 ( 171 Intermediate-aged deciduous Dark-eyed junco (31 Wi I son's warbler (31 Black-capped chickadee 13) Alder flycatcher 121 WhIte-crowned sparrow (21 American robin (21 Yellow warbler (I I Hermit thrush (II 8 ( 171 0 River shore- ! I ne and water surface Spotted sand- piper (21 Canada geese (21 Red-breasted merganser Ill 3 (5) Bare gravel islands and spits Bufflehead ( 131 Spotted sand- piper· 141 Semipalmated plover 121 Green-winged teal 121 Mallard 121 Canada geese 121 Mew gul I 121 Common golden- eye (II Red-breasted merganser (I I 9 1291 Gravel removal area Flooded area of pit Bufflehead ( 141 Bank swallow (51 Bonapart 's gu 1 1 ( 3) Mew gull 131 Canada geese 121 Mallard 121 Green-winged teal 121 Common golden- eye ( I I Red-breasted merganser I I I 9 '(331 Incised bank of pit Bank swa 1.1 ow (51 I 151 c 0 0 0 0 0 0 0 0 G passerines. However, vegetative recovery had become wei I established on the gravel islands and shore I ine and it is believed this site wi I I soon provide the same quality of habitat as the Tanana River-Upstream. One colony of beaver also were using the West Fork Tolovana River pit. Permanently ponded material sites of sufficient size (at least larger than I to 2 hal wi I I provide a high quality habitat if they have: • A diversity of shoreline configuration and water depth, • Dense border cover, • Islands or peninsulas or both, and • An abundant fish and macroinvertebrate food supply. SIMILARITIES OF RESPONSE BETWEEN BIOTIC AND STUDY SITE PARAMETERS A computer analysis for similarities in response between terrestrial biotic parameters and study site characteristics was conducted (Table 34l. Ten biotic parameters were selected for analysis. The analysis demonstrated that responses of biotic parameters could be categorized into three groups. Each parameter within each group displayed a simLiar reaction to specific gravel removal operations. When comparing the responses of the biotic param- eter groups for alI 25 sites, 5 site response combinations were found !Table 34). After these analyses, the material site characteristics were compared for each site response group. Biotic Parameters The biotic parameters reacted in three groups of similar response to gravel removal induced changes. Group I included passerines, shrub thick~ts, moose habitat, and ptarmigan habitat; Group I I included soi I nutrients, ground squirrels, early shrub communities, and smal I mammals; and Group I I I included soi I texture and water birds. . 259 Table 34. Two Way Coincidence Table Displaying a Hierarchical Clustering of Similar Sites and Similar Biotic Parametersa Biotic parameters Group I Group It Group Ill .... ., "' "' "' Q) .0 ... ... .... I.. !?. ., "' Q) c I.. "' Q) .s::: ~ Q) .0 "' I.. "' u "' ::> ::> E ::> "0 c .0 Q) I.. CT I.. E .... I.. ., ., .s::: c .... 1/) .s::: "' X Site "' .s::: ::> 1/) E Q) .0 I.. c "0 .... E Q) .0 Q) c >-I.. responge I.. 1/) ::> 1/) ::> Q) "' 0 I.. 1/) 0 I.. "' .... group .... 0 .s::: "' 0 I.. "' E 0 "' 0.. :e (/) 0... (/) <!> Ll.J (/) (/) == Shaviovik R Phelan Ck Ugnuravik R Kuparuk R Ivishak R A M.F. Koyukuk R-DS Nome R Dietrich R-DS + Kavik R + McManus Ck + B M.F. Koyukuk R-DS + + + Tanana R-DS + + + Oregon-Ck + Dietrich R-US + W.F. Tolovana R + * c Sagavanirktok R + + Jim R + * Prospect Ck + Aufeis Ck + * Tanana R-US + + * D Penny R + + + + * Gold Run Ck * + Washington Ck + + * E Sinuk R + + Skeetercake Ck * + a Symbols used for computer analysis were adapted from quantification of change ratings !Table T-Il ~s follows: !O,ll equals =; 12,31 equals -; 14,5,61 equals b; !7 ,Bl equals+; and !9,101 equals *· Note: all b's !no response or weak response) were-eliminated from this table to remove c I utt_er. b Responses by group were: A-essentially no response. B-minor decreases in biotic parameter Group I; minor increases in biotic parameter Groups I I and I I 1. C-significant decrease in biotic Group I; minor decrease in biotic Group I I; increase in biotic Group I I I. D-significant decrease in biotic Group I; increase in biotic Group I I; significant increase in biotic Group I I I. E-decrease in biotic Group I; increase in biotic Groups I I and Ill. 260 c c c c G 0 e c c- c (; 0 c c c c 0 0 0 0 In general, Group I parameters either showed no response, or displayed a significant decrease resulting from gravel removal induced changes. This was directly related to clearing of significant quantities of vegetation which passerines, moose, and ptarmigan used as primary habitat. Group I I parameters displayed no response at sites where vegetative habitats were not disturbed. However, alI parameters except soi I nutrients decreased at sites that were subjected to permanent or frequent hydraulic stresses !aufeis, pending, and flooding) and did not contain overburden piles. At sites that were subjected to hydraulic stress but which contained overburden piles, smal I mammals, ground squirrels, and early shrubs increas- ed. Soi I nutrients basically displayed no response. Group I I I parameters either displayed no response at sites where the floodplain character was not significantly disturbed, or they increased. Both parameter responses were once again directly related to removal of extensive vegetative cover. Water birds increased in response to the in- crease in aquatic, gravel bar, and mud flat habitats, while sci I texture increased due to the removal of organic, silt, and sand overburdens and the exposure and deposition of coarse gravels and cobbles. Physical Site Characteristics The Physical Site Characteristics that were analyzed are those identi- fied in the Major Variable Matrix Table !Table I l. They included: drainage basin size, channel width, channel configuration, channel slope, and stream origin. Responses of biotic parameter groups at the 25 study sites displayed five basic combinations. These are labeled Site Response Group A through E on Table 34. Eight sites occurred in Group A, where no significant responses were measured in any of the biotic parameter groups. These sites were mostly of medium to large channel widths, of braided or sinuous configuration, and of mountain or foothi I I origin. However, these site characteristics were not considered to have significantly contributed to the minimal disturbance at these sites. Of greatest significance was the minimal vegetative disturbance which occurred during the gravel removal operations. 261 Site Response Groups B through E did not display any apparent similar Physical Site Characteristics. Thus, it was judged that drainage basin size, channel width, channel configuration, channel slope, or stream origin were not significant factors in governing the responses of terrestrial biota. Gravel Removal Area Characteristics The most significant similarities in Gravel Removal Area Character- istics were those that led to permanent or frequent hydraulic influence within the disturbed area. This annual stress led to a significant and often long-term impediment of site vegetative recovery. Two similar Gravel Removal Area Characteristics were observed that produced this result. They were: scraping within the active channel at any location along the river coarse; and scraping adjacent to an active channel primarily on an inside bend, and without an adequate buffer along the channel. Scraping Within the Active Channel. Wherever gravel was scraped from within the active channel, the scraping also extended beyond the original channel to adjacent gravel bars. In these areas gravel was scraped to depths equal to or slightly below normal water' levels. This characteristic produced a long-term decrease in Biotic Group I !primarily shrub thickets and passer- inesl. The hydraulic changes that occurred in these areas were the prime factor found to be influencing site vegetative recovery. These changes are discussed in further detai I in EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS. Scraping Adjoining the Active Channel on an Inside Bend. At seven sites gravel removal occurred on a point bar or inside meander but did not extend into the adjacent active channels. AI I sites were of sinuous or meandering configuration and were scraped on sharp inside bends. At five of these sites c c c c~ G 0 G !Penny River, Ugnuravik River, Skeetercake Creek, Middle Fork Koyukuk River-~ Upstream, and Middle Fork Koyukuk River-Downstream! the scraping occurred to within or below the water level. Except at Middle Fork Koyukuk River- Upstream, no buffer was maintained between the scraped area and the main river channel. At the Middle Fork Koyukuk River-Upstream site a 30-m wide vegetated buffer was maintained. However, within a few years the rivers had formed cut-off channels through the scraped areas at alI five sites. 262 c 0 0 0 0 0 0 G 0 0 Thus, scraped sites located on sharp inside bends led to the formation of cut-off channels unless extensive vegetated buffers !Jim River) or natur- ally contoured channel slopes !Shaviovik River) were maintained during the gravel removal operation. These cut-off channels subjected the mined areas to frequent or permanent ponding and flooding which impeded vegetative recovery. Additional Similarities. Overburden piles, as previously discussed, were a positive addition at sites annually subjected to ponding, flooding, and aufeis development. At sites wher~ piles occurred, Biotic Group I I !primarily smal I mammals, ground squirrels, and early shrub communities) increased !Site Response Group B, D, and E, Table 341. However, at sites where overburden piles did not occur, but the site received annual hydraulic stress of flooding, permanent ponding, or aufeis development, Biotic Group I I decreased !Site Response Group Cl. Overburden piles occurred in a variety of shapes and sizes and were placed in various locations within the material site. From a revegetative viewpoint the most effective pile compositions were those with a mixture of si Its, organics, woody slash, root stocks, and debris. These piles only occurred at the o I der sites and a I I were at I east I to I. 5 m above norma I water levels. It is not known if additional piles of lower height originally occurred and had been eroded and removed by flood waters. Also, alI piles that were within the central portions of the mined areas were either not directly in the path of main currents or were placed in windrows oriented parallel to the current. Overburden piles that remained in the middle of large scraped sites were judged to be of more overal I benefit than those placed on the edge of the disturbed areas. These piles provided immediate denning habitat for ground squirrels and, within several years, began to provide cover and nesting habitat for smal I mammals and passerines within the central portions of large mined areas. The effectiveness of natural buffers was related to their location and dimensions in relation to river size and configuration. Twelve of the 25 study sites included some use of buffers. Two types were employed: 263 • Undisturbed gravel bars separating scraped sites in active flood- plains from active channels, and • Incised banks and associated riparian zones separating scraped and pit sites located in i nactive floodplains and terraces from active floodplains. The level of understanding that was obtained regarding the effective- ness of these buffers does not allow conclusions to be drawn. Accurate data describing original buffer characteristics !such as width, height, veget- ative structure, and soi I composition) were not available for many sites, however, several trends were observed. At smaller rivers of sinuous and meandering configuration, buffers !primarily incised banks and associated riparian zones) of widths in the range of 10 to 15m were effective in conta inin g active channels at sites that were 5 to 16 years old !Figure 81). Figure 8 1. Undisturbed buffer along the original stream channel at Aufeis Creek !downstream disturbed area on ly). 264 0 c 0 0 0 0 0 c c In larger rivers, most natural buffers that were maintained to protect scraped sites in active floodplains failed within a couple years. At Middle Fork Koyukuk River-Upstream a 30-m wide, 1-to 1.5-m high heavily vegetated buffer protecting an inside meander site was breached in I year; at Sagavan- irktok River, a 30-m wide, 0.5-m high gravel buffer protecting a mid-channel site was breached in I year; and at Dietrich River-Downstream a 50-m wide and 0.5-to 1-m high gravel and sparsely vegetated buffer protecting a site on the edge of the active floodplain of a braided river was breached in 2 years. These buffer failures have alI created permanent channel changes through the mined areas of these sites. At pit sites located in inactive floodplains and terraces, buffers composed of incised banks and heavi~y vegetated riparian zones ranging from 50 to 90 m in width were sufficient in protecting the pits from active channel diversion at sites up to 13 years old. However, most of these sites !three of fivel are located on smaller rivers with relatively stable chan- nels and are on the inactive side of the floodplain. On the other hand, at the oldest pit site !Tanana River-Downstream) a 50-m wide buffer separated the pit from an erosional zone of a side-channel of this braided river. During 1977 and 1978 this buffer was being actively eroded. It is not known how wide the buffer was at the completion of the mining activity. One mining method !pits) and one site location (separated from the active floodplain) frequently led to the creation of high quality habitat that resulted in an increase of water birds !Biotic Group I I I l. As previous- ly discussed, this method created a habitat type that frequently was not readily avai !able in adjacent floodplain reaches. The quality of this habi- tat was related to its size, shore! ine diversity (configuration), water depth diversity, shore! ine cover, presence of islands, and food avai labi I ity. Other characteristics occurred that were not directly related to the location or operation of the material site but that reduced detrimental impacts to the terrestrial biota. At those sites where access to the flood- plain had to pass an incised bank, gravel fi I I ramps !Figure 82l reduced the overal I impact. At sites where incised banks were cut for access severe 265 Figure 82. Gravel fi I I ramp used to protect the incised bank at the Sagavanirktok River study site. erosion frequently resulted. In permafrost areas both thermal and hydraulic erosion induced by surface travel on unprotected banks can, and at the Ugnuravik River site did, create uncontrol !able problems (Figure 83l. At sites separated from active channels by buffers, a heavy layer of rip rap on the buffers significantly increased their effectiveness (Figure 84). 266 ) ) ) ) ) ) Fi gure 83. Thermal and hydraulic erosion of permafrost in duced by multiple passes of a tracked vehicle across an unprotected incised floodplain bank and adjacent tundra. Figure 84. Armored bank protectfng the West Fork Tolovana River pit from a channel diversion into the mined site. 267 SUMMARY AND CONCLUSIONS Overal I, gravel removal from floodplains frequently had a detrimental long-term effect upon local terrestrial biota. Specific site locations coupled with the depth of scraping proved to be the most influencing fac- tors. VEGETATIVE REMOVAL At 18 of the 25 study sites gravel removal operations cleared signif- icant quantities of riparian vegetated habitat. This loss most significantly affected passerines and smal I mammals which rely upon these riparian zones for primary feeding, nesting and cover habitats. At most of these sites this habitat reduction led to long-term changes in fauna utilization and .com- munity structure. At 4 of the 25 sites, gravel removal operations did not alter existing vegetative communities, and consequently did not lead to changes in local faunal communities. Three of these sites were located in floodplains with large and medium width channels that flowed in a braided pattern. At alI three sites large quantities of gravel were removed by shallow scraping of surface layers over a broad area. The fourth occurred on a sinuous to mean- dering river. At this site a large quantity of gravel also was removed by shallow scraping unvegetated portions of lateral bars and point bars. This scraping maintained ~atural point bar profiles and subsequently did not induce any channel changes. MINING DEPTH AND LOCATION Gravel removal operations that scraped to within or slightly below the water table and that occurred at inside bends or immediately adjacent to, or 268 c 0 within the active channel also produced a long-term negative response (de- crease in numbers! from terrestrial biota. At 13 of the 25 study sites gravel removal operations with these characteristics caused hydraulic changes (such as permanent channel shifts, aufeis development, or increased flooding! that impeded subsequent vegetative recovery of the disturbed areas. However, at those sites where gravel removal created permanently ponded areas, or extensive gravel and mud flat habitats with pockets of ponded water or backwater areas, water birds !including waterfowl, shore- birds, gul Is, and terns! frequently increased utilization of the area. OVERBURDEN Overburden piles containing· si Its, organics, and woody slash and debris faci I itated rapid and continued vegetative recovery within the mined site. These areas provided islands of useable passerine and smal I mammal habitat within a relatively short-term period. At many sites overburden piles were providing vegetated habitats that were being used by these species within 10 years after gravel removal. Ground squirrel populations frequently showed immediate response to available denning habitat provided by overburden piles. At most sites where piles occurred these animals were significantly more abundant within the mined site than in adjacent floodplain reaches. When this overburden material was broadcast over the ground in areas where it would not be washed downstream it was equally effective in facil- itating rapid vegetative recovery and development. PERMANENTLY PONDED HABITATS At eight sites the gravel removal operation !primarily through pit exca- vation! created permanently ponded habitats. Although this operation led to a long-term change from natural terrestrial conditions, at several sites this mining result led to the development of a diverse habitat that provided high quality feeding, nesting, and cover areas for passerines, smal I mam- mals, water birds, and furbearers. Factors that were found to influence the fauna response to these areas were: shore I ine configuration, shoreline vegetative cover, water depth profiles, presence of islands, pit size, 269 avai labi I ity of food, and connection to an active channel. Fauna uti I ization of the area significantly increased at several sites with a high diversity of these factors. RECOMMENDATIONS Gravel removal operations in floodplains should attempt to incorporate the following recommendations into site selection and site operation de- cisions in order to minimize long-term disturbance to terrestrial flora and fauna: I. Whenever possible, avoid vegetated habitats. 2. When scraping in active or inactive floodplains, maintain buffers that wi I I contain active channels to their original locations and configurations. 3. 3 When smal I quantities are required (approximately 50,000 m l, select sites that wi I I scrape only unvegetated gravel deposits. 4. W~en large quantities are required (approximately in excess of 3 50,000 m l, select large rivers containing sufficient gravel in unvegetated areas, or select terrace locations on the inactive side of the floodplain and mine by pit excavation. 5. If pit mining, design a configuration with high shoreline and water depth diversity and provide islands. 6. If mining in vegetated areas, save ~I I overburden and vegetative slash and debris to use during site rehabi I itation to faci I itate vegetative recovery. This material should be pi led or broadcast in a manner so it wi I I not be washed downstream. Detailed elaboration and expansions of these recommendations are pre- sented in the Guidelines Manual. 270 ( ( REFERENCES Johnson, R. R., and D. A. Jones, !tech. coord.l 1977. Importance, preservation and management of riparian habitat: A sy.mposium. Tucson, Arizona. July 9, 1977. USDA For. Serv. Gen. Tech. Rep. RM-43, 217 pp. Pamplin, W. L., Jr. 1979. Construction-related Impacts of the Trans- Alaska Pipeline System on Terrestrial Wildlife Habitats. Joint State/Federal Fish and Wildlife Advisory Team. Special Report No. 24. 132 pp. Spindler, M.A., and B. Kessel. 1979. Forty-second breeding bird census: Census 167. American Birds 33( I 1:99-100. United States Army, Corps of Engineers. 1979. Wetland Values: Con- cepts and Methods for Wetlands Evaluation. Research Report 79-RI. 109 pp. Woodward-Ciyde·consultants. 1976. Pre I iminary Report -Gravel Removal Studies in Selected Arctic and Sub-Arctic Streams in Alaska. U. S. Fish and Wildlife Service .• FWS/OBS 76/21. Wash., Q.C. 127 pp. 271 ) ) ) ) ) ) ) ) ) EFFECTS OF GRAVEL REMOVAL ON WATER QUALITY L. L. Moulton INTRODUCTION Water quality parameters were measured in conjunction with the aquatic biological studies at the 25 gravel removal sites. Since the sites were visit- ed from 2 to 20 years after gravel removal had been completed, the results of the monitoring program reflect only long-term effects on water quality con- ditions. The sites selected for study represented a broad range of Physical Site Characteristics and Gravel Removal Area Characteristics, which are des- cribed in the Major Variable Matrix !Table ll. Instruments and procedures used are described in APPROACH AND METHODOLOGY. Changes in water quality during gravel extraction were not measured because active gravel removal sites were not avai !able for study. A review of avai iab!e information on this aspect was included in an earlier report !Woodward-Clyde Consultants 1976l. 273 Table 35. Selected Alaska Water Quality Standards Parameter Dissolved oxygen !mg/JI,) Temperature ( oc> Water supply >75% saturation or >5 mg/JI, Dissolved solids <500 mg/JI, !mg/JI, or ~mhos/em> !~Boo ~mhos/em> specific conductance> Turbidity !JTUl Suspended solids !mg/JI,) <5 JTU Beneficial use Aquatic life >7 mg/JI, <2.2 °C over natural, no changes if naturally <I8°C Avoid chronic toxicity <25 JTU except when natural degradation a 80 mg/JI, Recreation >5 mgn <25 JTU except when natural degradation aNot an Alaska Standard, but 80 mg/JI, is considered potentially hazardous; 25-80 mg/JI, also has potentia! ly detrimental effect on aquatic I ife !National Academy of Sciences 1973). 274 9 :_) :J J J Table 36. Water Quality Parameters Measured at Gravel Removal Sites Which Exceeded Alaska Water Quality Standards !Values are the Average of Two to Eight Measurements! Specific Suspended conductance Turbidity sol ids Study site Area lllmhos/cml I JTUl !mg/R-l Dietrich-Upstream Upstream 275 56.0b 8 July 1978 Mined 365 I .2b Downstream 342 56.0 Dietrich-Downstream Upstream 324 I I.Ob II July 1978 Mined 340 29.0 Downstream 330 18.0 MF Koyukuk-Downstream Upstream 320 6.30a 20 August 1976 Mined 300 5.20a Downstream 300 2.60 Phelan Ck Upstream 77 154.0a 21 August 1978 Mined 79 270.0a Downstream 56 186.0a aValue exceeds Alaska water quality standard for a defined beneficial use !see Tab I e 351. b May have some effect on aquatic I i fe !see Table 351. 275 RESULTS AND DISCUSSION POST-MINING EFFECTS OF GRAVEL REMOVAL OPERATIONS General Water Quality Conditions Temperature, dissolved oxygen, specific conductance, turbidity, suspend- ed sol ids, oxidation-reduction potential !ORPI, and pH were measured up- stream, downstream, and within the gravel removal area at most sites. Measurements were taken in conjunction with the aquatic biological surveys. Temperature, specific conductance, turbidity, and suspended sol ids values varied substantially among the different sites. However, dissolved oxygen, ORP, and pH values were relatively similar at alI sites. The parameter values measured at each study site were compared to the Alaska Water Quality Standards !Table 351. The water quality standards were established to pro- tect various beneficial uses of receiving waters. The most important bene- ficial uses associated with arctic and subarctic streams include water supply, aquatic life, and recreation. At the 25 study sites, aquatic life was the most common beneficial use being supported. Alaska does not have a water quality standard for suspended solids, but a value of approximately 80 mg/R. suspended so I ids is usua I I y considered potentia I I y hazardous for aquatic life. Waters containing 25-80 mg/R. suspended sol ids have been shown to have a lower yield of fish than water with less than 25 mg/R-(National Academy of Sciences 19731. Water quality standards were exceeded for turbidity, and suspended sol ids at a few river sites !Table 361 while temperature, dissolved oxygen, specific conductance, and pH criteria were not exceeded. The high suspended solids value at Phelan Creek was due to the glacial origin of the creek; the 276 a ) 0 sample site was approximately 9 km downstream from the foot of the glacier. Other high suspended sol ids and turbidity values were recorded at the Dietrich and Middle Fork Koyukuk River sites. Turbidity measurements recorded at the Middle Fork Koyukuk River- Downstream site exceeded water quality criteria for water supply. The only other beneficial use standard exceeded was the aquatic life standard for turbidity at Phelan Creek. This parameter was exceeded by approximately 340 percent during August. Phelan Creek water should sti I I be considered con- sumable, depending on other !unmeasured) parameters. Most values exceeding the Alaska Water Quality Standards reflected a natural situation with only suspended sol ids at Dietrich River-Downstream possibly induced by gravel removal. The pH and ORP values measured at alI sites reflected a basic condition that was neither oxidizing nor reducing. The ORP values were relatively high because of the high dissolved oxygen concentrations. The pH and ORP values showed that there were very little organics in the monitored waters and that most of the heavy metals would be insoluble. Some of the pH values were slightly high ! i.e., at Tanana River-Upstream~ pH= 8.5-9.0 in the two pitsl and may be associated with some heavy metal sol ubi I ities. Water Quality Changes at Gravel Removal Sites. Most of the water quality changes observed as the receiving waters passed through the aban- doned gravel removal sites can be associated with physical changes in the stream. A major change was reduced.water velocity within the mined area promoting sedtmentation, warming of the water, and stratification. At other sites physical changes affecting water quality conditions include a steep- ening of the bottom gradient through the mined site, which would increase the velocity of the water and increase the scour of the bottom sediments. Turbidity and suspended solids changes were observed between the up- stream and mined, mined and downstream, and upstream and downstream study areas at 19 of the sites !Table 371. The changes are expressed as the per- centage change occurring from the upstream samples to the downstream 277 Table 37. Changes In Turbidity and Suspended Solids Between Sample Areas at Selected Study Sites Percent chanae In turbldlt~ Percent chanae .In suseended solids Site characteristics Upstream Mined Upstream Upstream Mined Upstream Years Channel Volume to to down-to down-to to down-to down-since slope re~oved Study site mined stream stream mined stream stream mining rm/kml lm l Seward Peninsula Gold Run· Ck 5 35 42 II 6.8 7,740 Sinuk R 14 0 14 10 2.1 174,000 Washington Ck 158 29 233 -33 1.87 100 13 12.4 20,500 Oregon Ck June 34 620 13 II .8 20,500 1\> August 3 -67 13 II .8 20,500 .... CD September -3211 25 13 11.8 20,500 Penny R June 1.88 5900 II 4.5 50,700 August 122 -24 70 0 -17 -17 II 4.5 50,700 September 45 -24 10 'lO -43 -20 II 4.5 :50,700 Nome R 73 -78 -63 17 7 25 20+ 2.6 unknown North Slope Ugnuravlk R -48 192 52 7 23,000 Aufeis Ck July 53 -10 42 0 0 0 5 3.0 288,000 August -25 -'83 -87 5 288,000 Kuparuk R 260 0 260 9 41,300 Skeetercake Ck II -33 -25 0 0 0 II 2.0 ,38,000 Sagavanirktok R -32 93 32 3 431 ,000 Ivishak R -15 -10 -24 -85 275 -43 3 2.1 119,000 Continued. () (') / \ u u u u u u u u Table 37. (Concluded! Percent chanae In turbidity Percent chanae In suseended solids Site characteristics Upstream Mined Upstream Upstream Mined Upstream Years Channel Volume to to down-to down-to to down-to down-since slope re~oved Study site mined stream stream mined stream stream mining lm/kml lm l Shaviovik R -5 -5 -10 -75 100 -50 5 2.8 116,000 Kavik July 3 -7 -5 29 II 43 5 7.0 247,000 early August 41 -40 -15 29 II 43 5 7.0 247,000 late August -8 4 -4 0 -12 -12 5 7.0 247,000 1\l Northern Interior -..J 10 Dietrich-Downstream 164 -38 64 3 128,600 MF Koyukuk-Upstream 0 50 50 4 135,000 MF Koyukuk-Downstream -17 -50 -59 2 I. 3 215,000 Southern Interior McManus Ck June 0 3 3 42 -41 -17 16 22.4 75,000 July -24 34 3 -25 33 25 16 22.4 7.5,000 September 0 3 3 -12 37 56 16 22.4 75,000 Phelan Ck 75 -31 21 3 575,000 samples. Negative values signify a.decrease in the parameter while a posi- tive value indicates an increase. The column entitled "upstream to down- stream" for each parameter indicates the net affect of the mined site on the water quality during the site visit. There was significant seasonal vari- ation, as indicated by the results from Oregon Creek, Penny River, Kavik River, and McManus Creek, which makes complete analysis of the data of questionable value. There appeared to be some sedimentation associated with remnant instream depressions and this sediment was subject to scour during high flow. Changes in other parameters were observed with temperature and dis- solved oxygen showing the greates~ frequency of change !Table 38). The temperature and dissolved oxygen changes resulted from the reduction of velocity and spreading of flow over the mined area, a situation which occur- red at many of the study sites. The ORP values did not change significantly, indicating the absence of heavy organic loading. Conductivity values changed in the mined area at several study sites, possibly indicating the exposure of a spring. The differences, judging by the age of the mined areas !i.e., 2 to I I years!, were probably not caused by the dissolving or precipitation of substances in the mined area. Spring sources were identified at Penny River and Dietrich River-Upstream, both of which showed altered conductivity. A spring source may be indicated at the Aufeis Creek and Skeetercake Creek mined areas, but the conductivity change at McManus Creek may have been a meter malfunction because the change was not observed during the other two site visits. The water quality parameters in inundated pits were generally quite different from those in the associated river !Table 39!. Summer temperatures were normally higher and dissolved oxygen levels lower in the pits. An excep- tion was the Dietrich River-Upstream pit where spring flow kept the water temperature low throughout the summer. Thermal and oxygen stratification were evident at the West Fork Tolovana River and Tanana River-Upstream pits. 280 ( ( n u J u f\) ()) u u u u u u u u Table 38. Relative Change of Water Quality Parameters Between Upstream and Downstream Sample Areas at Selected Study Sites (5=no Change, 0-4=Decrease in Downstream Parameter, 6-IO=Increase in Downstream Parameter) Study Dissolved Suspended Oxidation-reduction site oxygen Temperature Conductivity Turbidity so I ids potential Seward Peninsula Gold Run Ck 8 4 5 6 Sinuk R 7 6 5 5 Washington Ck 5 3 5 10 9 5 Oregon Ck June 8 5 7 10 5 August 2 10 7 5 2 5 Sept. 6 5 6 4 6 5 Penny R June 9 3 3 10 10 5 August 3 9 6 9 4 5 Sept. 4 9 3 5 4 5 Nome R 5 5 6 3 6 5 North Slope Ugnuravik R 7 2 5 7 Aufeis Ck July 3 9 10 7 5 August 7 7 10 Kuparuk R 4 6 5 10 5 Skeetercake Ck 2 9 10 4 5 5 Sagavaniktok R 5 7 5 6 7 Continued u Table 38. !Concluded! Study Dissolved Suspended Oxidation-reduction site C)xygen Temperature Conductivity Turbidity so I ids potential Ivishak R 8 5 4 3 Shaviovik R 3 6 5 5 2 5 Kavik R July 6 5 5 5 7 August 8 5 5 5 7 Sept. 7 2 5 5 5 1\) Northern Interior CD 1\) Dietrich R-Upstream 9 0 8 5 Dietrich R-Downstream 3 10 5 8 6 MF Koyukuk R-Upstream 4 7 6 7 4 MF Koyukuk R-Downstream -7 5 2 Southern Interior· McManus Ck June 5 7 5 5 4 July 6 10 5 6 5 Sept. 5 3 5 5 7 5 Phelan Ck 5 8 4 6 4 c: ) { ) ilfl'\ ( l ) ) ) ) ) J J J Table 39. Average Measured Values of Selected Water Quality Parameters at Study Sites with -Inundated Pitsa Study site Penny R 6 June 1977 8 August 1977 Dietrich-Upstream 8-11 July 1978 Jim River 3-5 July 1977 Prospect Ck 7 Jul_y 1977 WF Tolovana R 8-12 June 1978 Parameter I un i tsl T 1°Clb DO lmg/JI.lc d Cond l11mhos/cml T 1°CI DO lmg/11.1 Cond l11mhos/cml T 1°Cl DO lmg/ll.l Cond l11mhos/cml T 1°CI DO. lmg/ll.l Cond l11mhos/cml T 1°CI DO lmg/ll.l Cond 1)1mhos/cml T 1°CI DO lmg/11.1 Cond 1)1mhos/cml i 1-13 Sept. 1978 T t°Cl Tanana R-Downstream 9-10 Sept. 1976 Tanana R-upstream 4 June 1978 18 August 1978 18 Sept. 1978 DO lmg/11.1 Cond 1)1mhos/cml T t 0 CI DO lmg/11.1 Cond 1)1mhos/cml T 1°CI DO lmg/11.1 Cond ()1mhos/cml T 1°CI DO lmg/11.1 T 1°CI DO lmg/1..1 Cond 1)1mhos/cml Inundated pit surface· bottom 2.0 12.8 140 12.1 9.8 510 4.5 10.6 400 13.2 9.8 60 16.7 8.4 70 17.8 320 10.4 9.3 185 13.0 10.2 280 17.2 10.7 288 15.2 9.4 9.0 10.0 280 4.2 15.8ml 9, 7 15.8ml 7.1 14.3ml 7,5 14.3ml 0.2 14.3ml 12.9 17.2ml 9.9 17.2ml 14.0 12.7rill 9.8 12.7ml 8.2 12.7ml 5.6 12.7ml 6.2 11.4ml 4.6 ( 1.4ml aSample sizes and variance estimates omitted to simplify Table. bT = temperature. cOO ~ dissolved oxygen. dCond,. conductivlty. 283 Active channel I upstream) 4.0 12.0 65 10.6 11.6 250 .14.1 8.5 275 9.1 10.2 55 11.5 11.9 55 7.5 11.4 225 8.0 10.2 235 7.0 12.7 85 SUMMARY AND CONCLUSIONS Few changes in water quality parameters were measured that could be attributed to gravel removal; most of the observed changes were within the range of that expected by natural variation. The major reason for a lack of measurable effects was the age of the sites, as most were visited several years after mining had ceased. The few changes thaf were observed were related to physicaJ changes in the rivers, generally due to a reduction in velocity and spreading of flow. 284 ( c 0 J :J j REFERENCES National Academy of Sciences. 1973. Water Quality Criteria 1972. Environ- mental Studies Board, National Academy of Engineering, Wash. D. C. 594 pp. Woodward-Clyde Consultants. 1976. Preliminary Report -Gravel Removal Studies in Selected Arctic and Sub-Arctic Streams in Alaska. U. S. Fish and Wildlife Services. FWS/OBS 76/21. Wash. D. C. 127 pp. 285 3 EFFECTS OF GRAVEL REMOVAL ON AESTHETICS D. K. Hardingera INTRODUCTION Aesthetics pertains to manmade modifications of natural landscape fea- tures to a degree that public concern may be expressed. Aesthetic concerns of State and Federal government include maintenance of visual resource values by minimizing undesirable modifications to natural landscapes. Visual resource values of natural landscapes are the particular physical components of an area that have been identified as having high value based on any number of measurable criteria. These could include unique cultural, historical, recreational, geological, or biological significance. Typically the management objectives of an agency having statutory powers for maintaining visual resource values are to protect land areas identified as having high aesthetic values. The agencies may do this by diverting proposed construction to less valued locations, modifying the construction plan, or requiring the application of mitigating measures where construction-related visual impact proves unavoidable. Maintenance of visual resource values has become increasingly important to the American people. Federal legislation has recognized this concern by establishing the visual resource as an integral and coequal resource under the multiple-use concept of land management. At the same time, there is an increasing dem~nd for other resource developments that may not be compatible a This section was reviewed and input was provided by B. Sharky of Land Design North. 287 with the management of visual resources. In order to resolve potential con- flicts, it has become necessary to develop a system than can identify visual resources and provide measurable management standards that are practical to implement. Numerous systems for identifying visual resource values and evaluating visual impact have been developed. The systems vary considerably both in procedures followed and criteria applied. On Federal lands there are two principal visual resource management !VRMl systems in use today. One was developed by the U.S. Forest Service and the other by the U.S. Bureau of Land Management !BLM). Both systems have the capability to: • Identify areas of significant visual resource value; • Establish land units with each unit having measurable, homogeneous qualities; and • Prioritize the land units through establishment of units of low visual quality, hence requiring minimal management protection, and units having high visual quality requiring maximum management protection. The major components of each system involve a systematic field inventory including {I) scenic quality or visual variety, !2) visual sensitivity, and !3) degree of visibi I ity. Generally, the field inventories are conducted from an on-the-ground perspective. Visibi I ity from the air is generally not considered except under specialized circumstances. Definitions of the three key VRM inventory components of scenic quality, visual sensitivity, and degree of visibi I ity follow. Inventoried systemat- ically using the BLM system, these components yield a land unit rating system divided into five classes. Each class provides various degrees of resource management control over prospective resource development proposals, including gravel removal operations from arctic and subarctic floodplains. 288 c c J SCENIC QUALITY Establishing a scenic quality rating begins by using physiographic prov- inces to distinguish landscape character units having common visual qualities and to provide a regional context for the specific area being evaluated. Within each major landscape unit there may be areas having significant visual differences. These differences might include variations of typical landforms that would be classified as character rating units. Each rating unit is fur- ther classified according to the degree of scenic quality or variety as being distinctive, common, or minimal. Generally any landscape has recognizable parts that can be descr1bed in terms of form, line, color, and texture. These basic visual elements exert various degrees of influence and their composition wi II determine the scenic quality of a given landscape unit. The premise is that landscapes with the most variety or diversity have the greatest po- tential for high scenic value. Several key factors are inventoried in determining the scenic quality of the landscape and are used to delineate VRM land classes. • Land form. • Vegetation. • Water. • Color. • The influence of adjacent scenery. • Scarcity (distinctive features) or uniqueness. VISUAL SENSIT~VITY Visual sensitivity levels measure the public concern for the scenic quality of the landscape and for the changes that may alter the existing landscape character. The degree of sensitivity is determined by user attitude and use demand (volume). User attitude can be measured by a survey of private citizens and public officials, or indirectly by public documents such as recreation plans, trai I systems, scenic highways, and other items. These documents indicate areas of general concern. Use volume identifies areas of pedestrian and motorized vehicular use and rates them high, medium, or low 289 based upon frequency and duration of use. User attitude and use demand are frequently combined in a matrix to determine final sensitivity levels. DEGREE OF VISIBILITY A distance zone is the area that can be seen from a sensitivity area, and l is described as foreground, middleground, background, or seldom seen. Distance zones are delineated on the premise that the ability to perceive change or detai I in the landscape is a function of distance. Specific site information !Scenic Quality, Visual Sensitivity, and Degree of Visibi lityl is initially displayed on separate topographic maps. A hier- archy of importance is established and the maps are combined. The resulting classifications are the basis for defining minimum management objectives and the degree of acceptable alteration for each landscape classification. The determination of the degree of acceptable alteration for each landscape unit is defined utilizing a numerical rating system that enables a decision maker to see exactly what feature !landform, water, vegetation, structures) is being affected and to what extent. This method allows some flexibility in determining appropriate mitigation measures. 290 ( J J J APPROACH The aesthetic analysis of gravel removal from the 25 project study sites utilized the premises and criteria of the VRM system developed by the Bureau of Land Management. However, an actual VRM inventory and classification was conducted on a site by site basis rather than on a regional basis as would normally occur. Each project study site was analyzed for scenic quality, visual sensitivity, and degree of visibi 11ty. Project aerial and on-site ground photography, USGS togography maps, and project site descriptions were the primary data sourc& for the scenic quality and degree of visibility anal- ysis. Visual sensitivity data sources are limited in Alaska; therefore, user attitude and use volume were interpreted from the public documents cited in the bibliography and by communications with persons familiar with the loca- tions under study. After the sites in each general region were inventoried for existing visual resources, a contrast evaluation was conducted. The contrast evaluation outlines specific visual effects of gravel removal according to BLM definitions. 291 THE VISUAL RESOURCES OF THE STUDY REGIONS Characteristic landscape descriptions are needed in order to assess the degree of change or contrast that is created by floodplain gravel removal. The following section describes the physical characteristics of each region or site location in terms of the basic visual elements of form, I ine, color, and texture. Although site specific physical descriptions are found else- where in this text, the purpose here is to create an over a I I impression of the landscape quality in the vicinity of the study sites. When avai I able, information documenting public concern and use (or visual sensitivity! in each region is also included in this section. SEWARD PENINSULA Scenic Quality Seward Peninsula sites include Gold Run Creek, Slnuk River, Washington Creek, Oregon Creek, Penny River, and Nome River. The typical landform in the vicinity of alI sites is characterized by broad, smooth textured, rol I ing hi lis with moderate to gentle slopes (Figure 85!. The hi lis are separated by sharp V-shaped valleys near stream headwaters; these valleys become wider near the coast. AI I study sites on the Seward Peninsula are located in narrow valleys or at the point where a narrow valley opens into a broad valley. The panorama at these sites includes both gentle and moderately steep slopes. Angular, rugged mountains are visible in the distance from alI Seward Penin- sula sites, but do not significantly influence or enhance the local scenic quality. The study site rivers on the Seward Peninsula usually flow in sinuous configuration with moderate to swift currents. The Sinuk River is the largest 292 c J Figure 85. Typical Seward Peninsula landform at Penny River. river and it flows in braided pattern through the study reach. The other rivers have a single wei 1-defined active channel with occasional side channels or islan ds. The presence of occasional reaches of steeply eroded river bank do not create strong, visibly apparent vertical I ines. Some river edges are of coarse texture with cobbles and boulders. AI I river systems enhance the scenic quality of the immediate surroundings, but they are not the most dominant element in the large scale landscape. In the Sew ard Peninsula, riparian vegetation grows in various densities and heights. In most cases low-growing shrubs ( 1-2 ml are interspersed with other ground cover species (herbaceous and woody). Islands frequently are vegetated with similar vegetative communities. The Penny River in particular has extensive, wide bands of tal I (2 to 3 ml riparian wi I low. The greener shrub thicket vegetation also extends up adjacent valleys providing a sharp color and texture contrast with the matted brown tundra on the surrounding hi I lsides. Dense shrub thickets also are a common feature along old diversion ditches, seeps, and other water sources; these create contrasting bands and clumps of dense green color across the brown hi I lsides. 293 The predominant summer colors of the region are provided by the vege- tative patterns. Common patterns include: bright green near water sources and dul I green or brown on the hi I lsides. During fal I the floodplains turn bright yellow, while red and golden yellow colors dominate the hi I lsides. Ridges of nearby hi I Is are barren and appear gray in color with occasional dark brown rock outcrops. Cultural modifications are visible from every site in the Seward Penin- su~la. The Nome-Teller Highway intersects and/or pa~al leis five of the region's study sites, and the Nome-Taylor Highway paral leis the Nome River near the sixth study site in this region. The roadways are the most visible cultutal modifications, but the lines they create generally blend into the lines of surrounding landscape. Several streams are crossed by bridges of varied de- sign. These bridges create vertical and horizontal lines that are not fre- quently found in these landscapes. Access roads frequently lead from main highways to river floodplains. Drainage ditches constructed during early gold mining periods frequently can be seen as they follow the contours of adjacent hi I lsides. These ditches were constructed to collect and provide water at upland gold mining sites. Several trails traverse the local terrain and are visually disruptive. Some cabins are situated within sight of roadways, but none are noticeable from within the study sites. There also is evidence of other gravel removal and gold mining sites throughout the region. Visual ~e~sitivity and D~gr~e of Visibi!ity The Seward Peninsula study sites are located within immediate or fore- ground view of the Nome-rei ler and Nome-Taylor Highways. There are only three established highways for vehicle travel on the Seward Peninsula and alI radi- ate from Nome, the largest population center on the peninsula. Ar"l of the study sites are within a 40 km:radius of Nome. There is an established BLM campground about 24 km north of the Nome River study site. This campground and the historical gold mining districts near Nome attract additional summer tourist travel along these routes. Commercial tours of the peninsula usually begin in Nome and branch out along these roadways. Any changes or alterations of the landscape that occur in the foreground along these roadways would be 294 c c c c c c ) ) highly visible. However, lower use volume than in other parts of the State, and less resource agency concern for the quality of this landscape !no wild- 1 ife refuges, wild and scenic rivers, etc. I, give the study areas only a moderate visual sensitivity. NORTH SLOPE Scenic Quality North Slope study sites include the Ugnuravik River, Aufeis Creek, Kuparuk River, Skeetercake Creek, Sagavanirktok River, Ivishak River, Shaviovik River, and the Kavik River. The Kuparuk River and the Ugnuravik River sites are located on the Arctic Coastal Plain which is characteris- tically flat to slightly rol I ing. The steeply incised river banks accentuate the strong horizontal I ine of the coastal plain and also provide vertical rei ief !Figure 861. The remaining sites are located in the Arctic Foothi I Is Figure 86. Typical view of an Arctic Coastal Plain floodplain. which is a transition area between the coastal plain and the Brooks Mountain Range. Gentle, undulating slopes with occasional isolated, ·round and rol I ing 295 hi I Is characterize the landform of the foothi I Is (refer to Figures 4 and 5 in DESCRIPTION OF STUDY RIVERS). Incised river banks or terrace banks establish horizontal I ines that contrast with the characteristic undulating terrain. The landform features appear to be smooth with few surface rock outcrops. Rivers, tributaries, lakes, and ponds are common features of the North Slope landscape. On the coastal plain the abundance of these water features comprise approximately 75 percent of the land's surface. However, no single landform or water feature stands out or is visually significant. The braided river systems with their islands create variations in I ine, texture, and color that contrast with the surrounding homogeneous landscape. The rivers of foothi II region study sites are more visually significant elements in the landscape due to the diminishing frequency of other water features and their prominent, focal location traversing foothi II valley floors. The vegetation of the North Slope study sites is relatively rich in color and texture. Riparian vegetation usually consists of low-growing com- munities of dense wi I low thicket interspersed with herbaceous and woody ground cover species. These riparian communities develop irregular outlines created by irregular channel patterns and uneven texture. Occasionally there are concentrated stands of taller, more mature willow that become a visual focus due to the contrast in height with surrounding low-growing vegetation. The color variation of the North Slope landscape is varied particularly in the fal I. The most significant color contrast exists between the greens of the riparian shr~b thickets and the tans and browns of unvegetated flood- plains. ~·,.... . . Some form of culf~ral modification is evident near all North Slope sites. Most modifications are the result of oi I and gas exploration. Several gravel access roads parallel and intersect the floodplains near many of the study sites. Gravel dri I I pads, camp pads, and airstrips are adjacent to several sites. These surface materials with various bui !dings sharply contrast the form, I ine, color, and texture of the surrounding undisturbed landscape. 296 c ) In addition, the Trans-Alaska Pipeline and Haul Road are within I I km and 1.5 km, respectively, of the Ivishak and Sagavanirktok River sites. These features are visible from the floodplain banks at both sites. The dominant visual feature of elevated sections of the Trans-Alaska Pipeline consists of the vertical pipe supports and the horizontal pipe. The rigid I ines of both elements contrast sharply with surrounding undulating landscape. The North Slope scenery is unusual and intriguing. This vast landscape with its subtle variety pr0vides a sustaining viewer interest and, therefore, yields a fairly high scenic quality rating. VIsual Sensitivity and Degree of Visibi I ity At the present time, there is I ittle visitor or public use near the North Slope study areas. However, several sites are located within or adjacent to areas identified by various groups as lands of national interest. The Ivishak River, for instance, has been recommended as a wild and scenic river. These designations do not guarantee increased pub I ic use, but they are an expression of pub I ic concern for preservation of scenic quality. Increased use could result if and when the Haul Road is opened for public access. Mater- ial sites within view of the Haul Road would have increased degree of visi- bility and therefore higher visual sensitivity. NORTHERN INTERIOR Scenic Quality The landscape of the Northern Interior is among the most spectacular scenery in Alaska. It includes the Dietrich River !two study sitesl, Middle Fork Koyukuk River !two study sitesl, Jim River, and Prospect Creek. The sites on the Dietrich River and Middle Fork Koyukuk River-Upstream are located in flat glaciated valleys surrounded by steep, rugged mountainous terrain !Figure 87l. The steep angular mountain wal Is are often crested with massive I ight colored rock outcrop and cut by jagged ravines. Near the Middle Fork Koyukuk River-Downstream site and the Jim River and Prospect Creek sites 297 Figure 87. Dietrich River valley. the valley widths fluctuate and mountainous features diminish in visual domi- nance (Figure 88). The slopes are more gentle and the surrounding mountains are more rounded in form. Figure 88. Lower Middle Fork Koyukuk River valley. 298 ) 9 ) River systems of the Northern Interior exert varying degrees of influence on overall scenic quality. The large, active floodplain of the Dietrich River covers nearly one half of the valley floor. This river flows in braided pat- tern over much of its length. Numerous light colored unvegetated gravel bars in the active floodplain sharply contrast with the remaining vegetated val ley floor and val ley wal Is. The Middle Fork Koyukuk River varies from a large, sinuous single channel to a braided system with a large main channel. Through- out, there are many abandoned channels, vegetated islands, and terraces. Both Jim River and Prospect Creek are smaller, sinuous to meandering and less dominant in local scenic quality than the Dietrich and Middle Fork Koyukuk Rivers. AI I Northern Interior study sites are in an enclosed landscape where the rivers become a focal point given their prominent and central location. The vegetation along the floodplains and hi I !sides is a diverse mixture of coniferous and deciduous trees of varying ages and densities. Dark-green white spruce trees contrast with the rounded, I i ghter green deciduous trees and wi I low thickets. High-water and abandoned river channels have created broken patterns in the vegetation throughout the floodplain. A rich, complex visual texture has developed because of the variable heights and colors of the vegetative communities. Color variety is furthe~ enhanced by the gravel deposits in the flood- plains, local patterns of vegetation, and in some areas extensive rock out- crops. During fal I, vegetative changes introduce another dimension of color variety with the seasonal colors of red, orange, and yellow added to the land- scape. The most noticeable cultural modifications in the Northern Interior are those associated with the Trans-Alaska Pipe! ine System. Facilities adjacent to the study sites include construction and maintenance camps, airstrips, ma- terial and disposal sites, and elevated and buried pipe I ine. Spur dikes have been bui It into the floodplain in several locations along the Dietrich and Middle Fork Koyukuk Rivers. The light colored gravel materials used to con- struct the pipeline work pad, Haul Road, and camp facilities sharply contrast 299 with the rich natural color variety of this region. The pipeline and Haul Road of ten create contrasting I i nes in the natura I I andscape. The scenic quality of the Dietrich and Middle Fork Koyukuk Rivers can be characterized as a region of high diversity. This diversity is a result of a rich and comp I ex texture of co I or, I and form, and contrasts. The degree of diversity provides the region with a somewhat unique capabi I ity of accom- modating limited manmade encroachments in comparison with the North Slope landscape where manmade structures would produce highly visible results. Although the scenic quality is not as distinctive, Jim River and Prospect Creek have greater recreation potential than the Dietrich and Middle Fork Koyukuk Rivers. This recreation potential may have an overriding influence on the final outcome of the visual analysis. Visual Sensitivity and Degree of Visibi I ity The Northern Interior (at the time of this evaluation) is accessible to the recreation and tourist oriented pub I ic only by air or by foot~ hence, pub I ic use is I imited at the present time. The Bureau of Land Management has several proposals that would affect the use patterns in this region if the Haul Road is opened to the public. Most development would be restricted to presently disturbed areas with an emphasis on maintaining scenic quality. Not all study sites are easily visible from the Haul Road because of screening qualities of the natural vegetation. However, current and proposed river recreation use would increase the amount of visible area. In addition, lands of national ahd State interest are adjacent to the Trans-Alaska Pipe I ine System Uti I ity Corridor (proposed "d-2" lands). Hence, there is strong public interest in maintaining the scenic quality of this region. SOUTHERN INTERIOR Seen i c Qua I i ty Most study sites of this region (West Fork Tolovana River, McManus Creek, and Tanana Riverl have some similar landform characteristics. Rounded foot- 300 ( ) ) hi I Is with moderately steep slopes surround the flat-bottomed West Fork Tolovana River valley and the narrow McManus Creek valley (Figure 89l. Lower, gently rolling hi lis border one side of the Tanana River, while the opposite Figure 89. McManus Creek valley. side consists of a broad, flat plain. Rock outcrops and barren soi I are usual- ly confined to the tops o f the higher foothi I Is surrounding these sites. Phelan Creek, however, is located in a mountainous river valley (Figure 90l. The valley walls are steep and angular with rugged ridges of rock out- crop. Mountain glaciers provide added visual interest to the surrounding landscape. The Tanana River and Phelan Creek flow in braided configuration. The Tanana River has numerous gravel bars and vegetated islands in the active floodplain that contrast with each other in visual appearance. On the other hand, Phelan Creek has a gravel floodplain with little contrasting vegetation. The contiguous gray-white color sharply defines the Phelan Creek valley floor. 301 Figure 90. Phelan Creek valley. The West Fork Tolovana River and McManus Creek flow in sinuous configuration through heavily vegetated, more narrow floodplains and do not strongly domi- nate the surrounding landscape. The vegetation at most Southern Interior locations is a diverse mixture of deciduous-coniferous forest and riparian shrub thickets. The rounded decid- uous shrubs and trees contrast with the dark, slender white spruce. The West Fork Tolovana River and Tanana River floodplains have a particularly lush understory that increases the variety of texture patterns. The valley walls near most Southern Interior sites are less obviously patterned with a more sparse understory except near drainages. However, contrasting patches of dark and I ight green can sti I I be seen in most locations. The color variety near the Southern Interior sites includes a complex mixture of greens, browns, grays, and tans with fall vegetative foliage adding reds, oranges, and yellows. 302 .) The Southern Interior sites are in the vicinity of many manmade modifi- cations. The Trans-Alaska Pipeline System is near the West Fork Tolovana River and Phelan Creek sites, with State highways, rural communities, and recrea- tional faci I ities present in the vicinity of alI Southern Interior sites. These faci I ities, with their modifications of landform and vegetation pat- terns, detract from the overal I scenic quality of the surrounding natural landscap·e. Southern Interior sites, with the exception of Phelan Creek, have minimum or common scenic qualities because landforms are not unique and there are a relatively high number of cultural intrusions. Phelan Creek has more landform variety and in some sections is highly distinctive. Visual Sensitivity and Degree of Visibility The Southern Interior sites are located in the vicinity of some of the most heavily used recreation, tourist, and scenic areas in Alaska. In addi- tion, most sites are close to major Alaskan highways connecting the largest population centers in the state. Increasing recreational use of rivers !lead- ing to increased view areal is faci I itated by convenient road access. Nearby campgrounds and waysides i ncr"ease the viewing time in the i andscape. A I I of these factors contribute to high visual sensitivity in the Southern Interior. 303 EFFECTS OF GRAVEL REMOVAL ON VISUAL RESOURCES Gravel removal activities caused alterations in the landscape that in many cases were not visually harmonious with the surrounding landscapes. These alterations are discussed in this section in terms of contrast. Contrast C is determined by the change in the form, I ine, color, and texture of character- istic landscape features such as landform, water, vegetation, and structures. The degree of contrast can vary widely; however, the significance of each contrast wi I I depend upon the scenic quality and visual sensitivity of the characteristic landscape. The contrasts presented in the following sections generally denote a negatJve effect unless otherwise stated. Similar contrasts frequently exist at separate study sites in each region, hence discussions have been grouped by region with exceptions noted. SEWARD PENINSULA Gravel removal activities in the Seward Peninsula created the most signif- icant contrasts in local landform and water features of all study areas. The uneven texture or angular I ines, or both, of gravel stockpiles and over- burden piles present at most Seward Peninsula sites, visually disrupt the existing smooth I ines of the surrounding homogeneous landscape. Scraping and pit excavation have left contrasting rigid, rectangular I ines at several site locations. The presence of water located throughout much of the gravel removal areas in unnatural shapes and configurations ac- centuates this contrast. The construction of access roads has introduced an additional contrasting form and I ine in this landscape. These features are particularly disruptive if there are several at one site JNome River, Oregon Creekl. Landform contrasts are more evident in this region because the vegeta- tion is relatively low growing and cannot effectively screen gravel removal 304 0 activities. The overall color contrast has been increased at all sites by removing riparian vegetation. However, gravel removal has not created signif- icant overall contrasts with the form, I ine, and texture of the existing vegetation patterns except at Penny River where the vegetation is much taller. Rigid blocks of vegetation now define some borders of the gravel removal area at Penny River, thus producing a contrast with the existing random pattern and height variations of the natural vegetation. NORTH SLOPE Very few significant contrasts are visible on the braided rivers of the North Slope. The rivers are large enough to visually absorb the changes in channel and island configuration. The banks, however, are a strong visual focus in many places and are more visually sensitive to change. The height of incisea banks necessitated the use of gravel fi I I ramps in many locations. Some ramps were partially removed after mining was completed and the remnants are sti II visible. In either case, the ramps produce a moderate contrast with the form and line of the river bank. The Kavlk River Is an example of strong contrast in the form and I ine of the landform-water feature. Large portions of the bank were altered at this site. In addition, a large rectangu- lar scraped area adjoins the river. These I ines are not unlike those of the nearby airstrip, but in this case they disrupt the visual I inear flow of the river's edge. The removal of vegetation and overburden in this area has produced a color contrast that accentuates the unnatural rectangular I ines of the disturbed area. Gravel removal created stronger contrasts along the smaller and/or single channel rivers in the North Slope region. The creation of additional water channels and/or ponds at the Aufeis Creek and Skeetercake Creek has signifi- cantly disrupted the natural lines of each system. Removal of vegetated over- burden and stockpiling of gravel created additional contrasts in color and texture. The resulting broken textures and configurations at these sites contrast sharply with the existing natural landform and vegetation patterns. 305 NORTHERN INTERIOR The Northern Interior sites are generally located in areas where patterns of manmade activity already exist and are visibly apparent. Gravel removal sites in vegetated floodplains developed the most significant visual con- trasts. Rectangular excavation boundaries contrast with the curvilinear shape C of naturally vegetated floodplains. The removal of vegetation and overburden created color contrast at the Dietrich Rlver-Upstream, Middle Fork Koyukuk River-Upstream, Jim River, and Prospect Creek. This contrast distinguishes the rectangular I ines of the disturbed areas from the surroundings. Color contrast would not be as signif- icant at these sites if the disturbed area boundaries were developed in config- uration to reflect surrounding landform and vegetative patterns. Sites that have filled with water (Prospect Creek, Jim River, Dietrich River-Upstream, and Dietrich River-Downstream! have produced line and form contrasts because ponding is not a common element in the floodplains of this region. Angular diversion channels at Dietrich River-Upstream were equally contrasting with natural channel patterns. The abrupt and block-1 ike shape of existing gravel stockpiles at Dietrich River-Upstream sharply contrasted with the flat terrain of Northern Interior river valleys. SOUTHERN INTERIOR The presence of tal I white spruce-paper birch stands associated with specific site locations make the study sites of this region less visible from pub I ic roadways than sites studied in other regions. However, the Southern Interior is a High recreational use area and natural screens between roads and gravel removal areas are .not totally sufficient to keep the dis- turbed areas from public view. Landform contrast is the most obvious change in visual quality resulting from gravel mining at the Southern Interior sites. The West Fork Tolovana River, Tanana River-Upstream, and Tanana River-Downstream sites have rectan- 306 ( r '- 9 0 gular, flooded pits with steeply sloped banks. The angle of bank slope and pit shape contrast with the natural flat floodplain form and the curvi I inear I ines of the river systems. Where gravel stockpiles remain within the visible por- tions of the study site !such as at Phelan Creek) they create a contrasting unnatural form. 307 SUMMARY After studying the effects of gravel removal on visual resources at specific sites, some overal.l generalizations can be made. Certain landscape features or conditions wi II be similarly effected by gravel removal in all regions. The deciding factor in determining total impact wi II be the relative pub I ic sensitivity to the specific landscape. The same impact in two different areas may be judged differently depending upon public priority. Theoretically, ( the landscapes that are highly visible and highly regarded by the public wi I I € be more seriously affected than landscapes of lesser priority. The following summarizes the effect of gravel removal on generalized lanoscape features and briefly discusses public priority. Small, single channel rivers bordered with low-growing vegetation experi- enced the most dramatic visual impact. The location of gravel deposits on these rivers usually requires the removal of riparian vegetation and over- burden along incised banks. Along meandering and sinuous systems this pro- cedure frequently results in significantly altered river configuration. The vegetation removal causes a color change that clearly brings attention to the disturbed area. The remaining low-growing shrub vegetation is not of sufficient height to screen the disturbed area. Braided rivers with or without vegetated islands usually can visually absorb mining induced changes if the gravel removal occurs between the flood- plain banks. Any changes to the banks create noticeable visual contrasts. The most frequently observed contrast to river banks result from access roads and fi I 1-ramps, cut banks, and mined banks. Tal I, dense vegetation buffers surrounding the work area often screen many mining sites from public view at ground level. However, the removal of 308 c vegetation from buffer areas at most study sites has caused unnatural line and color contrasts that draw attention to the disturbed areas. Color con- trasts are more visible from an elevated position where a viewer is looking down onto the site. Rectangular, water-fi I led excavation pits, due to their unnatural shape, generally create significant contrasts in alI floodplain landscapes. The contrast is accentuated when the vegetation bordering the pit is tal I an~ conforms to the rectangular shape. Sites that can be viewed from above, where the viewer is able to look down onto a site, generally results in high visibi I ity potential particularly in areas of sparse or low-growing vegetation. Access roads also have resulted in significant contrasts in many study sites. Access roads frequently create a high degree of visual prominence and contrast where they traverse perpendicularly across existing sl.ope con- tours. This contrast is more disruptive in regions of rol I ing or steep ter- rain, having sparse or low-growing vegetation, as exists on the Seward Penin- sula and North Slope. The presence of more than one access road can produce a multiplying effect with respect to increasing visual prominence. The presence of stockpiled gravel and overburden piles often increase visual prominence to a site. Often due to their height or I inear shape, or both, the piled material tends to attract the viewer's attention to a site even though the site itself may not be clearly visible. Large stockpiles are detractive in most landscapes although less noticeable in broad floodplains surrounded by tal I, highly patterned, mixed stands of vegetation. Tal I vege- tation and terrain features can provide a visual screening effect particularly where the viewing location is at ground level. Areas having more or less homogeneous vegetation and terrain generally are more highly visible than those areas that are more diverse. The diverse landscape character types generally can accommodate gravel removal partic- ularly at locations where the potential viewer is at a substantial distance 309 from the site or is at a similar elevation !ground level with respect to the sitel. Visual p~ominence of a site tends to increase where vegetative clearing occurs along straight, long I ines. This pattern is generally true in regions of both high and low landscape character diversity. Less visual contrast results where irregular clearing patterns have been accomplished. Site visi- bility is further reduced where natural vegetative recovery has occurred on sites cleared on irregular patterns. Four different regions of Alaska were included in this study and each region evokes a different public response to visual resources. The regions that appear to be the most pub I icly sensitive to change are the Northern and Southern Interior regions because of exceptional scenic quality or inten- sive ~ublic use. The visual effect of gravel mining activities is expected to be more scrutinized by the public in those areas. Visual standards for gravel removal areas should recognize this pub I ic sensitivity. 310 c ( 9 GEOTECHNICAL ENGINEERING CONSIDERATIONS OF GRAVEL REMOVAL H. P. Thomas and R. G. Tart, Jr. INTRODUCTION The initial geotechnical effbrt on the project consisted of a I itera- ture review and evaluation of questionnaires sent to highway departments around the United States. Results of this effort were presented in a prelim- inary report (Woodward-Clyde Consultants 1976!. This section presents the findings of a geotechnical review that consisted of an office evaluation of the I imited data from the 25 study sites made available to the project geotechnical engineers. This section identifies general geotechnical consid- erations that should be considered in gravel removal projects. The major data sources were: the mining plans that varied greatly in detai I from site to site (for some sites no mining plans are available!; aerial photography that varied from site to site in scale, coverage (both historical and areal l, and quality; and site photographs collected during biological and hydrological field inspections. This section is, in many cases, generic and general in its treatment because of the I imitations of the avai I able data. ~ The objectives of this evaluation were to identify: I l Engineering techniques that led to efficient development and opera- tion of gravel removal areas; 2! Engineering techniques that mitigated environmental disturbance; and 3! Engineering techniques that could have been used in various condi- tions that would have led to more efficient operation with less environmental disturbance. 311 Volumes of gravel removed from each site ranged from approximately 3 3 8,000 m to 630,000 m , with the largest volumes removed from Dietrich River-Upstream, /Phelan Creek, Aufeis Creek, and Sagavanirktok River. Refer to Table 4. Scraping was the most. common removal method used, but four sites were operated as pits and another four sites were operated as combinations of scrapes and pits. Nine of the sites were developed in connection with construction of the Trans-Alaska Pipet ine System. Most North Slope sites were opened in connection with oi I exploration and dri I ling activities, while at I Seward Peninsula and most Southern Interior sites were developed in connection with local highway projects. More detailed information on site use is presented in DESCRIPTION OF STUDY RIVERS. Permafrost conditions at most of the study sites are unknown. There normally is a thaw bulb associated with rivers in permafrost areas. In continuous permafrost, the thaw bulb may be a transitory feature present only during summer flows. However, in discontinuous permafrost and for large rivers in continuous permafrost, the thaw bulb persists year-round although it may shrink considerably in winter. A 1969 study on the Sagavanirktok River I I km south of Prudhoe Bay (Sherman 19731 showed that in summer the thaw bulb associated with the main channel was 12m deep and had a cross- sectional area of 762m2 • In winter, this thaw bulb shrank to 167m2 with a maximum 7 m depth. Depending especially on whether underflow occurs, thaw bulbs may or may not be present outside the main channel. A major gravel use in arctic and subarctic Alaska is directly related to the need to provide a gravel overlay sufficient to carry traffic and to prevent permafrost degradatio~ (progressive thawingl. The minimum overlay thickness to prevent thawing can be calculated as a function of the local thawing index. The thickness is 1.5 mat Prudhoe Bay and increases as one moves southward (e.g., it is 2. I mat Galbraith Lake and in Fairbanks it would approach 6 ml. A 1.5 m gravel overlay has generally been used for roads, dri llpads, airstrips, and other permanent faci I ities at Prudhoe Bay. However, it has been shown that a 60-cm thick gravel overlay wi_th 5 to 10 em of polystyrene insulation is thermally equivalent to 1.5 to 2.1 m of gravel. This represents a 60 percent reduction in gravel thickness and a 64 percent 312 J J reduction in gravel quantity, considering a typical gravel pad with 1!: I side slopes and a crest width of 10m. Gravel needs during construction of the Trans-Alaska Pipeline System were reduced by using this solution for I 10 km of the pipeline workpad on the North Slope. Depending upon relative costs of gravel and insulation, synthetically-insulated embankments may or may not be less costly than their al 1-gravel counterparts lWei lman et al. 1976). 313 APPROACH The main factors considered in the geotechnical evaluation were site selection, access, operation, and rehabilitation. Primary information re- viewed for each site included mining plan information from permitting agen- cies, aerial photographs, ground photographs, and field notes taken by the project hydrologists. Early in the review effort, a geotechnical fact sheet and evaluation form were developed and fi I led out for each site. The purpose of these forms was to assemble relevant information, to draw out observations of project personnel who had visited the sites, and to generally focus the review effort. Although the geotechnical data base was very limited at a number of the study sites, it was believed to be sufficient overal I to allow certain meaningful judgments to be drawn. The following sections contain geotechnical discussions related to gravel removal during principal stages in the life of a material site. 314 ( 0 SITE SELECTION AND INVESTIGATION Selection of a gravel removal site often begins with a comparison of candidate floodplain and/or upland sites in the immediate use area. Upland sites are beyond the scope of this report and wi I I not be further considered. The site selection process includes preliminary selection, site investigation, final selection, and mining plan preparation. pRELIMINARY SITE SELECTION Preliminary selection of one or more candidate sites results from assembling and reviewing available information followed by implementation of an appropriate selection procedure. Sources of Information Primary sources of information used in preliminary site selection are topographic maps, surficial geologic maps, and aerial photographs. Topographic maps of 1:250,000 and 1:63,360 scale are available from the U.S. Geological Survey !USGS!. Similar topographic maps are also available for Canadian arctic and subarctic regions. From these map~, one can obtain a general impression of the size and type of river, potential gravel avai la- bi I ity, desirable access routes, and proximity to the use area. The only currently available surficial geologic map of Alaska is the 1964 USGS map entitled "Surficial Geology of Alaska". With a scale of 1:1,584,000, this map does not show much detai I. However, USGS recently pub I ished a potentially useful set of maps which cover the Trans-Alaska Pipeline route from-Prudhoe Bay to Valdez. 315 Aerial photographs frequently are the most useful sources of informa- tion. Stereo pairs are needed to show rei ief (e.g., height of banksl and a scale of not more than 1:12,000 is preferred. Color photographs are avai 1- able for some areas of the State, and black and white photography is avai 1- able for most areas of the State. For some areas, pre~existing aerial photo coverage can be purchased from local aerial survey companies. However, it is frequently worthwhile to have the area in question flown and photographed in order to obtain the needed coverage. From adequate aerial photographs, one can normally distinguish such features as the physical characteristics of the floodplain (e.g., channel configurations, flow regime, gravel avai la- bility, vegetation patterns) and can select potential access routes and faci I ity locations. Preliminary Selection Procedure The procedure for selecting a gravel removal site usually involves identifying two or three alternative sources that appear to have sufficient quantities of gravel. These alternates are then compared either in an in- formal basis !usually min~mizing haul distance) or in a more formal pro- cedure involving establishing criteria, evaluating significant factors, and ranking sites. The criteria would be specific to the situation, however, factors that may be considered include physical properties of the material avai I able, haul distance, material site size and configuration needed to produce desired quantities, equipment available and equipment needed, re- quired site preparation !e.g., ramps, berms, dikes, overburden), river hydraulics, and floodplain access from nearest point. At this stage the anticipated life-span of the material site also should be considered. If it is desired to use the site for several consecutive years, or for two or more periods separated by inactive periods, the potential bed-load replenishment rate should be incorporated into site selection. It is generally assumed !See EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS! that rivers of glacial and mountain origin, particularly near their headwaters, have greater potential for gravel replenishment than streams of foothi II or coastal plain origin. Non-engineering aspects of site selection are dis- cussed in other sections of this report. 316 ( SITE INVESTIGATION The importance of an adequate on-the-ground site investigation cannot be overemphasized. At the Ugnuravik River site, the investigation stopped with an interpretation of aerial photographs. Subsequent site operations discovered that the gravel was merely a veneer and not present in ~ufficient quantities to meet project needs. In contrast, before construction of the Trans-Alaska Pipeline System rather extensive site investigations were conducted which significantly increased the knowledge of site gravel quan- tity and quality. Types of Data Several different types of data need to be obtained in a material site investigation. Aerial Extent and Depth of Deposit. Estimating the volume of material avai I able depends on establishment of the aerial extent and depth of the deposit in question. If this volume is less than the needed volume, the site wi I I be inadequate to satisfy the material needs. Hence, this is one of the most important types of data to be obtained. Thickness and Aerial Extent of Overburden. Gravel sites frequently have a covering of si It or organic material, over alI or part of the site, which must be removed in order to expose underlying gravel. Mining may not be economical if more than about I m of overburden is present over most of the site. Homogeneity of Deposit. A deposit which appears suita~le on the surface may be unsuitable at depth. This change in deposit quality frequently is a result of fluvial processes involving channel shifting, alternating erosion and deposition, and overbank flows associated with periodic flooding. Test pits or borings from several locations within the site should be analyzed to determine deposit quality. 317 Groundwater Table. It is important to establish the depth to the ground- water table together with spatial and temporal variations in this parameter. Groundwater conditions may vary widely throughout the year in response to changing river levels, thus, several measurements are preferable. The date of measurements should be carefully recorded. Extent of Permafrost. Although permafrost occurrence in the vicinity of rivers and streams can be highly erratic, it should be anticipated in arctic and subarctic regions. The presence or absence of permafrost can be an important factor in developing a gravel removal site. Field Techniques Both borings and test pits can be used for geotechnical exploration. Test pits are generally preferred in granular soi Is because of the diffi- culties of dri I ling and sampling in smal !-diameter borings. However, borings can provide a good indication of overburden thickness, water table, perma- frost conditions, and presence and extent of unacceptable !e.g., si ltyl materials. These borings or test pits should extend to the depth of the anticipated gravel removal. The number of pits or borings would depend upon the size and variabi I ity of the site. Laboratory Testing The required laboratory testing effort varies. Sieve analyses are needed, as a minimum, to classify the material and establish its suitabi I ity for its intended use. For these tests, rather large !50 to 100 kgl bulk samples are desirable. Other tests that may be needed include hydrometer tests (if frost-susceptibi I ity is a concern) and compaction tests if the gravel wi I I be used to support structures. FINAL SITE SELECTION The final site selection is based upon the criteria analysis of the alternative sites. This analysis compares the characteristics of the rna- 318 ( c 0 0 terials found at the avai !able sites to the needs of the project. A major portion of this analysis is the cost-benefit trade off of the options devel- oped during the site investigation process. Sites further from where the material is needed may have gravel that requires less processing; there- duced processing cost may lower total costs despite the added cost of trans- port and road construction. In another case a more distant site may have an existing access road which would, on a cost basis, justify use of the more distant site rather than a closer site. In some instances, such as pipeline bedding and padding, rounded well-graded gravel might be preferable. Spe- cific gradation requirements may be necessary for subsurface drains. Uni- formly graded angular gravel may be a requirement for asphalt pavement aggregate. In final site selection the engineer makes trade offs to choose the site that wi I I provide the required material at the least cost. This engineering analysis is then reviewed and biological resources, hydraulic factors, and aesthetic concerns are considered before the final site selection. MINING PLAN PREPARATION The agency having jurisdiction wi I I generally require preparation and submittal of a mining plan. Minimum elements of the mining plan are: • Planned use of gravel, • Basis for determination of material quality and quantity !e.g., bor- ings, test pits, laboratory tests. l • Site configuration and depth, • Quantity limits, • Project schedules, • Overburden presence, • Access to site, • Buffer locations, • Operation plan, and • Rehabi I itation plan. 319 Specifically, the mining plans should include at least the following information: • A site sketch drawn to scale showing: project location cross-sections of borrow areas, gravel source locations, existing or planned haul road locations, test pit or boring locations !if anyl; • An estimate of the volume of material that is needed; • An estimate of the volume of material that is anticipated at the available sites; • An estimate of the properties of the material required; • An estimate of the properties of the in-situ materials; • An estimate of the type and amount of processing that wi I I be required; • Project schedules for alI major activities; • Preliminary design features of any required support structures, such as access roads, processing plants, culverts, and bridges; and • Description of operational and rehabi I itational aspects of site use. Plans prepared as described above should provide sufficient information to evaluate the appropriateness of the planned development of the gravel sources. Mining plans were prepared and submitted to the appropriate government agency for most of the 25 study sites. However, no mining plan information was found for the Washington Creek, Nome River, or Skeetercake Creek sites. The mining was apparently a trespass action at the upstream Aufeis Cr~ek site and for initial gravel removal at the Kavik River site. Only results of a very limited site investigation were found for the Penny River site; only some correspondence was found for the Ugnuravik River site; and only a right-of-way permit was found for the McManus Creek site. Mining plan infor- mation reviewed ranged from sketchy !for the Seward Peninsula sites) to quite detailed !in the case of the Trans-Alaska Pipeline System sites). 320 ( c ( '- SITE PREPARATION Having selected and gained approval to d~velop a gravel removal site, site preparation activities can begin. These activities may include construc- tion of access roads, removal of overburden, and construction of channel diversions and settling ponds. ACCESS As a part of most floodplain gravel removal operations, haul roads must be bui It to connect the site to the use location or existing roads. This construction poses no special engineering problems in non-permafrost areas or in areas where the permafrost is thaw-stable. However, in areas of ice- rich permafrost, protection of the tundra is of vital importance. From an engineering standpoint; tundra-insulated permafrost, as !ong as it remains frozen, is an excel lent base or foundation for structures whether they be dri i I pads, roadways, pipe I ines, or other structures. When the permafrost begins to thaw two crit.ical things happen. First, there is a tremendous loss in strength, and second, the thawing process is very difficult to stop. Thus, after the tundra is disturbed enough to allow the permafrost to begin this progressive thawing, the same area that formerly was an excel lent base for structures becomes a very difficult, if not impossible, foundation problem for any engineering purpose. Drainage and other related problems also begin to develop and these can have significant adverse impacts on engineered structures. Access roads traversed ice-rich permafrost at several of the study sites with varying degrees of success. In general, where a~ least 0.5 m of gravel depth was used, permafrost integrity was maintained. However, at several sites (Ugnuravik River, Aufeis Creek, Skeetercake Creek, and Kuparuk 321 River) the access roads were less than 0 .5 m in depth and subsidence fre- quently occurred . Access roads to a given site should be I imited in number and confined to prepared surfaces. Both season of operation and long-term effects need to be considered in planning. Access to most of the study sites seemed to be appropriate and usually consisted of short gravel ramps and haul roads, sometimes including gravel bars within the river floodplain. The practice of constructing temporary gravel ramps, as at the Kuparuk, Sagavanirktok, Ivishak, and Shaviovik Rivers sites to provide access over incised permafrost river banks, reduces bank disturbance !Figure 91 ). How- Figure 91. Gravel ramp at Shaviovik River site providing access over a permafrost river bank. ever, cutting into permafrost banks, as was done at the Kavik River, can lead to severe thermal erosion and is not recommended. 322 Winter-Only Access Winter access to a floodplain site is generally easier than summer access because the surrounding terrain is frozen and river levels are low. However, even frozen organic mats need to be protected from mechanical crushing and ripping created from multiple passes over an unprotected access road while bui I ding snow or ice roads. The Ugnuravik River site provides an example of adverse long -term effects: access to the site was via a temporary winter trai I across the f r oze n No r th Slope tundra. As far as is known, the trai I was used only during the last week of March 1969. However, as was commonly done, the tussocks may have been bladed off to provide a smoother riding surface. Compaction and destruction of the vegetative mat started an irreversible process of thermal erosion. When the site was visited in summer, 1977, the road had eroded to a depth of I .5 to 2.5 m over a distance of 90 to 120 m. Erosion was continuing, and a permanent scar had been created on the land- scape !Figure 92; also refer to Figure 83). Based on the current state of Figure 92. Thermal erosion near Ugnuravik River resulting from compaction and destruction of the vegetative mat over- lying ice-rich permafrost soi Is. 323 knowledge, a better solution would have been to construct a snow or ice road !Adam 1978). Year-Round Access A substantial gravel .( 1-3 m thickness! overlay is required where year- round access to a site is needed over ice-rich permafrost. However, place- ment of insulation beneath the gravel would reduce the thickness of overlay required. Year-round access roads must also be above flood stage of the river, which may require placement of culverts at high-water channels crossed by the road. OVERBURDEN REMOVAL The stripping of overburden involves the removal of any material cover- ing the gravel deposit. The overburden material, usually topsoi I and or- ganics, is normally removed from the site and either stockpiled for later use in site rehabi I itation or hauled to approved disposal sites. Stripping is normally done with graders, scrapers, or dozers. Overburden depths were not recorded at alI of the study sites; However, where information was avai I able, the depths ranged from a thin veneer !at six of the sites) to 0.9 m !at one of the sites) and the average was 0.3 m. CHANNEL DIVERSION For efficient gravel removal at some floodplain sites, it may be desir- able to divert river flows, especially those associated with subchannels, away from the area from which gravel is to be removed. This diversion is normally done by constructing earthen dikes or levees upstream from the site. Armoring of the upstream face and outer ~nd of these structures may be necessary to provide erosion resistance. Erosion prevention is discussed further in EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY AND HYDRAULICS. 324 ( ( SETTLING PONDS It is necessary to wash gravel if the mined material has an appreciable si It content. When gravel is washed, it is essential that settling ponds be provided to allow si It to settle out before the wash water re-enters the river. These ponds should be of sufficient capacity to handle the daily volume of wash water or stream flow, or both, considering the settling velocity of the entrained si It particles. Design considerations for settling ponds can be found in Appendix F of the Guide I ines Manual. 325 SITE OPERATION The basic elements of a gravel removal operation are excavation, trans- portation, and material processing. The detai Is of equipment selection, scheduling, and operation procedures are dependent on the composition of the gravel, the season of operation, the topography, the haul distance, and the environmental characteristics of the site. EXCAVATION The two basic gravel removal techniques used at the 25 study sites were scraping and pit excavation. Table I identifies the technique used at the respective sites. Ripping and Blasting Frequently, site operators prefer removing gravel in winter because water levels are low and access is easier. However, winter mining means excavating gravel in a frozen, possibly ice-saturated condition. At the study sites, if the gravel deposits were wei I above water levels and were low in frozen moisture, excavation by scraper was normally not difficult. Ripping frozen gravel was required at at least three of the sites !Middle Fork Koyukuk River-Upstream, Prospect Creek, and Phelan Creek!. It is not known if blasting was uti I ized to remove gravel at any of the sites. Scraping Scraping at larger sites is usually done with belly-dump scrapers. At smaller sites or remote sites, or both, D-9 or smaller caterpillar tractors 326 ( c :) are frequently used. Scraped sites are usually dry when worked, however, caterpi liar tractors can work in shallow water !possibly up to 0.5 ml. Pit Excavation Pit excavation is generally done with draglines or backhoes. Dewatering may or may not be necessary. At the study sites some of the more shallow pits were dewatered, but deeper pits, e.g., Dietrich River-Upstream, West Fork To I ovana River·, and Tanana River-Downstream were excavated underwater. Comparison of Techniques Some engineering and economic advantages and disadvantages of removing gravel via pits versus scraping are I isted below. Advantages of Pits Versus Scraping • Greater quantity from smaller area. • Can work within confined property limits !if necessary!. • Less clearing required. • Less stripping required. • Can provide si It trap. Disadvantages of Pits Versus Scraping • Dewatering or underwater excavation required. • May provide less gravel per unit time than scraper operation. • Cannot be restored as closely to original condition. TRANSPORTATION AND STOCKPILING Transportation of gravel from the material site to the stockpile or processing plant may be done with scrapers or front-end loaders and dump trucks. Stockpiling gravel removal operations greatly reduces scheduling problems. It is possible to load trucks directly for long-haul transport to ultimate-use areas without stockpi I ing, but a great deal of coordination is 327 required between the excavating and transporting activities. It is advan- tageous to maintain a stockpile of at least moderate size to serve as a buffer between excavating and transporting. Gravel stockpiles remained on or immediately adjacent to nine of the study sites, however, only Dietrich River-Upstream, Jim River, and Phelan Creek stockpiles were sti I I being used. PROCESSING Gravel processing can involve screening, washing, crushing, mixing, or combinations of these. Materials of the study sites frequently were fairly uniform, subrounded to wei 1-rounded, hard gravels with varying amounts of sand and cobbles. Such materials are suitable for road embankments with I ittle or no processing. However, silt content should be limited to approxi- mately 10 percent to minimize frost susceptibi I ity. Processing apparently was only conducted at those study sites used for construction of the Trans- Alaska Pipeline System where screening and some crushing were done to pro- duce bedding and padding material for the below-ground pipeline. 328 ) J J J SITE REHABILITATION Engineering concerns contribute to rehabilitation mainly if future site development (e.g., erecting of structures! is planned. In this situation, long-term integrity of structures is the primary concern of site rehabi I ita- tion. Otherwise, the primary purpose of site rehabilitation is erosion control. The main function of erosion control is to prevent degradation of disturbed and adjacent areas. Some rehabi I itation was done at alI study sites worked since 1972. There was no evidence of rehabi I itation having been done at any of the older sites. Where final site grading was conducted, it typically included sloping or flattening of stockpiles and overburden piles to blend with the terrain, contouring the site to a maximum 2: I slope, and removal of gravel ramps !not done at the Ivishak and Shaviovik Rivers!. 329 REFERENCES Adam, K. M. 1978. Winter Road Construction Techniques, pp. 429-440. In Proceedings of ASCE Conference on Applied Techniques for Cold Environ- ments. Vol. I. Anchorage, Alaska. Sherman, R. G. 1973. A Groundwater Supply for an Oi I Camp near Prudhoe Bay, Arctic Alaska, pp. 469-472. In Proceedings of the Second Inter- national Conference on Permafrost-.-Yakutsk, USSR. Wellman, J. H., Clarke, E. S., and Condo,. A. C. 1976. Design and Construc- tion of Synthetically Insulated Gravel Pads in the Alaskan Arctic, pp. 62-85. In Proceedings of Second International Symposium on Cold Regions Engineering. Fairbanks, Alaska. Woodward-Clyde Consultants. 1976. Preliminary Report-Gravel Removal Studies in Selected Arctic and Sub-Arctic Streams in Alaska. U. S. Fish and Wildlife Service. FWS/OBS 76/21. Wash. D. C. 127 pp. 330 ' '- INTERDISCIPLINARY OVERVIEW OF GRAVEL REMOVAL E. H. Follmanna INTRODUCTION This chapter presents a general overview of the effects of gravel removal in contrast to the preceding disciplinary chapters that rely more heavily on analytical treatments of data collected at the 25 study sites. Each of the Major Variables identified in the Matrix !Table I) is discussed relative to its influence on the effects of a gravel removal operation. These characteristics directed the early phases of the study, including the site investigations, and form, for the most part, the framework of the gravel removal guide! ines. The disciplinary chapters on gravel removal effects did not necessarily treat each of these characteristics because some were not relevant or they did not influence the evaluations or syntheses sufficiently to warrant individual attention. Thus, this overview chapter constitutes the functional bridge between the Guide! ines Manual and the Technical Report. Few problems were encountered in the discussion of the Physical Site Characteristics and their interact~on with gravel removal projects because the categories are mutually discrete, i.e., a river cannot be both meander- ing and straight within the study reach. The categories under each of the Gravel Removal Area Characteristics, however, are not mutually exclusive ahd, thus, cause difficulty in the development of that discussion. The sites selected encompassed at least several individual locat·ions from which gravel a E. H. Fol !mann is presently associated with the Institute of Arctic Biology of the University of Alaska. 331 was removed. Sites such as Aufeis Creek on the North Slope and Penny River on the Seward Peninsula each included 8 of the 12 specific site locations that were possible !Table I). This complexity made it difficult to identify any specific floodplain changes with specific gravel removal locations. For these sites, the overall effect on the floodplain resulted from the total gravel removal operation and specific effects were masked. The problem of sites with multiple Gravel Removal Area Characteristics was unavoidable because almost all of the over 500 sites originally considered reflected the same situation. The major result is that, in some cases, generalities are discussed with I ittle or no reference to specific material sites. If none of the sites clearly exhibited the relationship being discussed, none were cited as examples. However, the generalities discussed are considered ac- curate because of the analyses and conclusions reached in the preceding disciplinary chapters. 332 0 PHYSICAL SITE CHARACTERISTICS The Physical Site Characteristics considered in this project were: drainage basin size, channel width, channel configuration, channel slope, and stream origin (Table ll. Following study of the 25 material sites and analyses of data, it was established that channel configuration was the most important floodplain characteristic affecting environmental change when combined with gravel removal activities. Drainage basin size (channel widthl was found to be less significant, and channel slope and stream origin were found to have little influence on the effects of gravel removal. The follow- ing discussion is subdivided according to these categories. CHANNEL CONFIGURATION The channel configuration or pattern of a river is the shape of the river channel (sl as seen from the air. The channel configurations considered in this study were braided, split, meandering, sinuous, and straight. Braided A river with a braided channel pattern typically contains two or more interconnecting channels separated by unvegetated gravel bars, sparsely vege- tated islands and, occasionally, heavily vegetated islands. Its floodplain is typically wide and sparsely vegetated and contains numerous high-water channels. The lateral stability of these systems is quite low within the :~ boundaries of the active floodplain. Four braided systems used for material sites were studied. Ivishak River on the North Slope, Dietrich River in the Northern Interior, and Tanana River and Phelan Creek in the Southern Interior. These systems usu- 333 ally contain large quantities of gravel and, therefore, are often uti I ized as gravel sources (Figure 93). The bed load carrying capacity of these rivers is large, thus faci I itating the replenishment of extracted gravels after site closure. Braided river systems are dynamic and lateral shifting of channels from year-to-year is common, therefore, any channel shifting resulting from lower- ing bars through gravel removal would be similar to the natural processes. For example, any diversion of a channel through an area that was lowered by the removal of gravel possibly would have occurred naturally sOmetime in the future. Material sites in these areas typically are scraped because required quantities of gravel usually can be obtained over large areal extents and it is more efficient to work a site above the existing water level. Due to the bed load carrying capacity of these systems, the typical shallow scraped sites are subject to sedimentation rates similar to natural depressions occurring in these floodplains. Therefore, the minded sites can return relatively quickly to near natural conditions. This recovery is particularly true if the site is located near the active channel. An example of rapid recovery is the Ivishak River site, which was shallow scraped over a large area of unvegetated gravel bars. After several years the only evidence of gravel mining is the presence of access roads and fi I I ramps that connected the material site with an airstrip and dri I I pad. Long-term effects of gravel removal on water quality were not evident at the four sites located in braided systems. Due to the relative insta- bility of channels in a braided river system, any channels routed through an abandoned material site probably would be affected in a manner similar to a channel being rerouted due to natural hydraulic processes. An exception would be where an aliquot of a material site was used as a settling pond during a gravel removal operation. The accumulated fines could be suspended during subsequent high flows if this material was not armored and was left in the depression during site closure. None of these situations was en- countered at the study sites, however, the possibi I ity would exist in simi- lar site conditions. 334 c € c Sp II t Meandering Sinuous ) Straight ) Figure 93. Configurations of study rivers. 335 The aquatic organisms in braided systems are adapted to the seasonal dynamics of the channels and, therefore, any channel changes resulting from gravel removal operations provide situations for which the organisms are already adapted. An exception to this generalization occurs where a pit is separated from the active channel !Tanana River-Downstream) or is within the floodplain !Dietrich River-Upstream) and connected to an active channel. In these cases, organisms that are more adapted to lentic environments become established. Also, certain fish species may use the calmer waters of these pits for spawning, rearing, and feeding areas. These pit sites are the excep- tion, because scraping is the usual procedure selected to excavate sites in braided systems. Excavating aspects are discussed further in the following section on Types of Gravel Removal. Terrestrial species that utilize braided river systems similarly are I ittle affected by the usual scraping operation. Since non-vegetated bars are favored gravel removal sites, few smal I mammals or passerines are af- fected. The water-associated birds that use the various channels and back- waters for feeding are also I ittle affected by the material sites because the usual result of these operations is to provide habitats already present. Due to the dependence of smal I mammals and passerines on vegetated islands, gravel bars, and banks present in braided systems, any removal of vegetation to expose a gravel deposit would totally displace birds and eliminate small mammals from the disturbed site. Similarly, these areas, which often have associated dense shrub thickets, are used by moose and ptarmigan, especially during winter. Loss of this habitat would cause lo- calized displacement of these animals. Maintenance of the scenic quality of an area can be achieved by de- signing a material site to complement the natural setting. Material sites in braided systems did not detract from the visual quality of the floodplain where gravel removal was restricted to unvegetated grav~l bars. The ex- pansive floodplains typical of these SY.stems are somewhat uniform in ap- pearance, yet the numerous channels and gravel bars endow these areas with a complexity that permits material sites to be located with I ittle effect. 336 u ) ) ) ) ) J J J The usual mining technique for these sites is to scrape unvegetated gravel bars rather than to excavate deeply, thus, any rearrangement of channels through an abandoned site would closely resemble the natural annual pro- cesses of lateral channel migration. In summary, braided river floodplains can be desirable locations for extracting gravels !Table 40l. The abundance of wei I graded materials and the potentially smal I effect on the physical, biological, and aesthetic char- acteristics suggest the desirabi I ity of these areas for material sites. This conclusion assumes that the procedures of shallow scraping of unvegetated gravel bars with minimal disturbance to active channels, banks, and vege- tated areas, and complete rehabi I itation of sites during site closure, are adhered to. Split Channel A river with a split channel pattern has numerous islands dividing the flow into two channels. The islands and banks are usually heavily vege- tated and stable !Figure 93l. The channels tend to be narrower and deeper and the floodplain narrower than in a braided system. Four split channel rivers were included in this study: the Kavik, Kuparuk, and Sagavanirktok Rivers on the North Slope and the Sinuk River on the Seward Peninsula. Although the bed load carrying capacity of split channel rivers is less than for braided systems, they often have a greater carrying capacity than equivalently sized meandering or sinuous rivers. The narrower flood- plains and lack of numerous gravel bars restrict the extent of potential gravel removal areas. Channels, islands, and banks are often used for extrac- tion, as was the case at the four sites studied. Islands and banks typically are vegetated and relatively stable, consequently, there is a direct effect on smal I mammals, passerines, ptarmigan, and moose uti I izing these areas. The long-term terrestrial disturbance is directly related to the extent of vegetation removal and the rehabi I itation practices used during site clo- sure. 337 Table 40. Interdisciplinary Rating of Cumulative Effect of Scraping,·Using Various Study Sites Visited from 1976 to 1978a Indices of Change, on Selected H~drau I I c effects AquatIc effects Terrestrial effects Macro inver-Index of Degree of Fish tebrate Water Environ- increased hydraulic habitat standing Riparian bird mental River type Study site LocatIon braiding alteration diversity crop vegetation habitat change Braided Ivishak R North Slope 6 6 5 8 5 5 1.8 Dietrich R-US Northern Interior 5 5 8 5 I 6 1.3 Dietrich R-DS Northern Interior 6 6 7 3 3 8 1.8 Phelan Ck Southern Interior 5 5 5 5 5 5 0.0 Sp I it Slnuk R Seward Peninsula 6 7 2 5 I 6 1.8 Kuparuk R North Slope 6 6 2 I 5 5 1.5 "' Sagavanirktok R North Slope 8 7 8 9 I 8 3.2 "' Kavlk R North Slope 8 7 3 3 4 6 1.8 CD Mean-Aufeis Ck North Slope 9 8 I 5 7 2.8 dering Skeeterceke CK North Slope 7 8 4 5 6 1.8 Sinuous Gold Run Ck Seward Peninsule 5 6 5 5 3 5 0.5 Washington Ck Seward Peninsula 10 9 0 2 I 6 3.7 Penny R Seward Peninsula 10 10 2 4 I 9 3.7 Nome R Seward Peninsula 10 8 4 8 4 5 2.2 Ugnuravik R North Slope 7 7 5 10 4 5 I. 7 Shaviovik R North Slope 5 6 5 5 5 5 0.2 M.F. Koyukuk R-US Northern ·Inter I or 9 7 9 2 3 7 2.8 M.F. Koyukuk R-DS Northern Interior 7 7 4 9 3 6 2.0 McManus Ck Southern Inter I or 5 7 5 5 4 5 0.5 Straight Oregon Ck Seward Peninsula 10 8 0 3 6 3.3 al5 =no change, 0-4 = d·ecrease in parameter, 6-10 = increase in parameter) blndex of environmental 6 change IIECI = E h-51 where xi = rating values of disciplinary indices; IEC ranges from 0-5. l=l -6- ( l t l Cl (''\ (') ("l\ (''\ ( l ) J ) ) ) ) ) ) Lowering islands and banks by removing gravel, even if maintained above the existing water level, can result in reduced stabi I ity of channels during high water. Material sites wi I I then be inundated at least tempo- rarily. Spreading water over a broader area reduces its velocity, causing deposition of suspended and bed load materials. Some of this reduced vel- ocity may function to replenish materials in the abandoned material site but this process would probably require a longer period than would be expected in a braided system. Spreading of water and reduction of velocity is conducive to changing water temperatures during the open water season. Altered water temperatures may influence the abundance and diversity of aquatic biota by altering the amount of usable habitat for particular species. The reduced stability of the channels that could occur after site closure could be detrimental to the establishment of permanent biotic popu- lations, in particular, benthic organisms. In addition, entrapment of fish in pockets and pools in the disturbed site may occur as water recedes into the active channels following high-water conditions. The increased deposition of both suspended and bed load materials could be detrimental to the establishment of benthic communities. Fine materials would I ikely be deposited in these areas, thus changes in the structure of benthic communities could be expected. These changes would be from organisms adapted to coarse substrate to those able to exist on finer less stable substrate. Changing channel configuration by removing islands, removing gravel deposits from banks, and locally widening the active floodplain wi I I affect the scenic quality of an area. This aesthetic effect was quite noticeable at the Sinuk and Kavik River sites where care was not taken to preserve natural contours and channel configurations. In addition, stockpiles and remnants of diversion berms were left in place. The net effect of these conditions was to form a major contrast with the natural conditions occurring both upstream and downstream of the site. 339 In summary, the split channel system is one that contains a relatively large quantity of gravel material, but its narrow floodplain with stable islands and banks restricts the areal extent where gravel can be easily obtained. Use of vegetated areas wi I I directly affect terrestrial organisms by either complete removal or displacement to undisturbed areas. Similarly, the tendency for localized widening of the floodplain wi II reduce lateral stabi I ity of channels, faci I itate the possible formation of a braided chan- nel pattern, decrease water velocity, increase sedimentation rates and, perhaps, increase water temperature. These changes wi I I affect aquatic organisms by increasing secondary productivity, by changing benthic com- munity structure, by providing rearing areas for some species of fish, and perhaps by affording situations conducive to fish entrapment !Table 40l. Meandering A meandering river winds back and forth within the floodplain. The meandering channel shifts downval ley by a regular pattern of erosion and deposition. Few islands are found in this type of river and gravel deposits typically are found on the point bars at the insides of meanders !Figure 93). Sediment transport in meandering systems is usually less than for braided and split-channel river systems of equivalent size. The size of individual gravel deposits in a meandering river depends on the size of the river. On a large river, point bars can be quite ex- tensive while on smaller rivers the point bars are characteristically smal- ler. The areal extent of these gravel bars determines, to a large extent, the degree of change which gravel extraction has on a meandering system. For example, if a large point bar is used to supply gravel for a smal I project, the operation of a material site may cause little change to the river sys- tem. However, when projects with large gravel requirements are situated close to a smal I meandering river or where the gravel requirements exceed that avai table on a large point bar, potential effects to the river system increase greatly. The alternatrve mining procedures are to completely remove the point bar, use several point bars, or remove vegetated deposits back from the channel. In all cases, varying degrees of impact can be expected, but all wi II depend on the manner in which the gravel is extracted. 340 c .) Four material sites on meandering systems were studied on this project !Table ll. Two were dug as pits and two were scraped. Pit Sites. The material sites at Prospect Creek and West Fork Tolovana River were dug in abandoned channels. In neither case was there a change in the lateral stabi I ity of the active channel. There was loss of terrestrial vegetation and associated fauna because the material sites were located back from the active channels. Aquatic fauna in the active channel apparently did not change. Change, if any, was due to the presence of an adjacent flood- ed pit. Similarly, water quality did not change in the active river channels but, as expected, water qualify in the pit was different from that in the active channel. These differences and changes are discussed in the section on Type of Gravel Removal because they were not unique to meandering sys- tems. Formation of a permanently flooded pit within a floodplain, that other- wise contains few ponds or lakes, changes the appearance of the area by in- creasing the diversity of physical features. These pits are quite visible when seen from the air or from a high terrestrial vantage point. Tal I vege- tation in the areas of these two material sites contributed greatly to blocking view of the sites. Many meandering river floodplains contain a multitude of oxbow lakes that are formed by channel cutoffs. In these cases, a pit could blend e,asi ly into the natural landscape, thus greatly reducing the visual effect of gravel removal operations. However, most pits are dug with angular perim- eters which create a visual contrast in the floodplain. This contrast is a generic problem and wi I I be discussed further under Type of Gravel Removal. Scraped Sites.' The material sites on Aufeis Creek and Skeetercake Creek were scraped. The environmental changes were quite different at the two sites resulting principally from differences in their locations relative to the channel !Table 401. The gravel at Aufeis Creek was scraped from across the entire channel, which changed the channel from a single to a braided configuration. The short-term influence was so severe that surface flow was 341 nonexistent the year following site closure but, over 3 years surface flow was re-established. Although the site was not studied when surface flow was absent, the effect on fish would have been to prohibit passage. Epibenthic communities would have been reduced due to the lack of surface water. Fol- lowing re-establishment of surface flow, benthic communities characteristic of riffle zones would be most common due to channel spread and reduced water depth. The change from a single channel to a braided channel can significantly affect the local distribution of aquatic organisms. The altered community would be similar to that typically found in a naturally braided system. Reduced water velocity enhances sediment deposition and can alter water temperatures. During the study, changes in water temperature were noted between the upstream and disturbed sample areas, but a difference in sus- pended solids was not found. The impact on the terrestrial environment frequently entai Is removal of vegetation and other habitats along the bank. Little change to the ter- restrial environment would be expected when gravel is mined only on unvege- tated gravel bars, unless the hydraulic characteristics of the channel are changed significantly following site closure. Also, I ittle change would be expected in the scenic quality of an area as a result of gravel removal, unless vegetation is removed. At Aufeis Creek, changes in both the ter- restrial environment and scenic quality resulted from the gravel removal operation because of the area disturbed, the site location, and operating procedures that were used, none of which complemented the floodplain char- acteristics. At Skeetercake Creek the hydraulic changes were somewhat different. The exposed gravel deposits were limited because this was a smal I river. Thus, gravel was mined from vegetated areas in the floodplain, with concom- itant effects on the terrestrial fauna. The gravel removal activity affected channel stability by faci I itating a channel cutoff, however, the channel did not braid due, at least in part, to the restricted floodplain. The cutoff formed an oxbow lake in the abandoned site. The floodplain in this reach of 342 the river had few oxbow cutoffs, consequently, mining changed the appearance of the area, However, the presence of overburden and gravel stockpiles detracted far more than the altered channel. Aquatic habitat changes at Skeetercake Creek were not as great as would be expected if the channel had become braided. The narrowness of the natural channel imparted a greater significance to the value of bank vegetation. Loss of this cover can change the distribution of fishes. The change from an incised channel to a shallow riffle area through the abandoned site caused the water temperature, during the study, to be higher in the disturbed area than upstream. However, changes in suspended solids were not noted. Summary. Scraping point bars can have I ittle environmental effect assuming that the operation is conducted in a manner that minimizes changes t~ the hydraulic characteristics of the channel and adjacent vegetated areas. If change is minimized, the effects on aquatic and terrestrial biota, and water and scenic quality are greatly minimized. Meandering rivers provide usable deposits of gravel from point bars, in inactive floodplains, and terraces. The potential effects on such a system vary depending on whether only point bars are used or whether the adjacent inactive floodplain and terrace also are mined. Sites in inactive flood- plains and terraces often are dug as pits while point bars in active flood- plains are scraped. Pit sites remote from the active channel have caused some problems during spring breakup at sites visited during site selection, but not studied as primary sites in this project !unpublished datal. When channels are blocked with ice, melt water must flow over the ice and may overflow the bank and spread across the entire floodplain. Pits located in these flood- plains are then subject to fi I I ing which can faci I itate diversion of flow through the site. This diversion is particularly possible where pits are dug within the inside of a meander. Depending on the size and inherent st~bi I ity of the undisturbed buffer between the pit and channel, the flow may cut 343 through the buffer zone and permanently divert flow. Ultimately, the meander wi I I be cut off through sediment deposition and form an oxbow lake. Other effects can be anticipated when pits are dug in the floodplain of meandering systems, however, they are characteristic of pit mining. There- fore, these aspects are discussed under Type of Gravel Removal. Sinuous Sinuous channels are similar to meandering channels except that the winding pattern is less pronounced. The channel may contain smaller point bars and have less tendency for downval ley shifting. Also, the channels are more stable with respect to lateral shifting. Ten of the sites studied on this project were on sinuous rivers (Figure 93!. Their similarity to meandering channels suggests that the effects from gravel extraction are also similar, with the major influence determined primarily by the site location and the removal method. Due to this simi- larity only a few characteristics of mining gravel at sinuous channels are discussed. The smaller point bars in sinuous rivers, as compared to meandering rivers, I imit the quantity of exposed gravel that is locally avai !able for removal. This limitation can magnify the need for using multiple point bars or vegetated areas back from the channel to fulfi I I the gravel requirements of larger projects. Floodplain areas adjacent to the channel contain gravel deposits that are typically overgrown with vegetation. Floodplain width usually is roughly equivalent to the meander belt width, thus, the floodplain of a sinuous river tends to be narrower than in a meandering system. Therefore, the area in the floodplain that is avai !able for gravel extraction is more limited. This places restrictions on the areal extent of potential gravel resources, and may require that a greater length of floodplain be used to extract grave I. 344 c ) The potential effects of removing gravel from sinuous channel rivers are increased because of these I imitations. If point bars are scraped too deeply, or if incised banks and the adjacent floodplains are disturbed, the potential for decreasing channel stability is greatly enhanced. The initial disturbance from site clearing, and the changes resulting from a poorly located and operated site, wi I I have multiple effects. The decreased channel stabi I ity and tendency for braiding wi I I affect both benthos and fish by altering aquatic habitats. Benthic communities adapted to riffles, fine sediment bottoms, and a relatively unstable bottom, wi I I become established. Loss of bank cover and potentially reduced current in the disturbed site wil I affect fish distribution and perhaps species composition. In addition, reducing water depth and velocity could change water temperatures and affect the level of dissolved oxygen. Fish could become trapped in the disturbed site when water recedes f.ol lowing high flows. Terrestrial vegetated habitat wi I l be destroyed when the floodplain adjacent to the channel is used as a material site. This destruction of vegetation wi I I cause either elimination or displacement of terrestrial fauna. If the stream banks are affected the decreased hydraulic stabi I ity in the area could reduce the potential for re-establishment of vegetative com- munities, thus creating a long-term rehabi I itation problem. Gravel removal from a sinuous river wi I I have effects on the scenic quality similar to those discussed for a meandering system. The degree of effect is fully dependent on the diversity of landforms in the area of the site and the amount of disturbance. Single channel river systems are seen- leal ly more sensitive than multiple channel systems particularly those single channel rivers located in areas with low growing vegetation, such as on the North Slope. In summary, the amount of environmental change that can be anticipated in a sinuous river system is largely dependent on the location of the ma- terial site and the methods of operation. Anticipated effects are similar to l 345 those for a meandering system but, because floodplain~ generally ~re more narrow and contain sma I I er point bars, the potentia I for permanent a I tera- tion is generally greater !Table 40l. Proper placement of the material site and operational proce~ures can minimize permanent change and these should be selected to prevent or m~nimize changes to the hydraulic characteristics of the channel. Straight Straight channel patterns are less common than other types. The thalweg of a straight river typically winds back and forth within the channel. Gravel bars form opposite where the thalweg approaches the side of the channel (Figure 93). These gravel bars may not be exposed during high flow. Banks of straight systems typically are stable and floodplains are usually narrow. These river systems are considered to be an unusual configuration in transition to some other configuration. Only the material site studied at Oregon Creek was situated on a straight channel system. As with other types of single channel systems the major potential effect from scraping floodplain gravels is decreased stabi I ity of the chan- nel and a tendency to develop a braided configuration. These are probable occurrences because of the typically narrow floodplains and the limited number of exposed bars available. Often the adjacent floodplain will have to be disturbed, or even the channel itself, because of the limited area avail- able. The Oregon Creek site typified the extensive long-term changes that can occur when gravel is removed from within the channel and the adjacent floodplain (Table 40l. The channel stabi I ity was greatly reduced and the channel had become braided within the confines of the abandoned site. These conditions exist 13 years after the site was closed and probably wi I I remain in that condition for many more years. The change from a single to a braided channel alters water quality parameters and aquatic biota ~s discussed in previous sections on sinuous and meandering systems. These alterations include the potential for changing water temperature and increasing sedimentation in the disturbed site where 346 € J J J the water fans out and becomes sha.l lower and slower in velocity. Dissolved oxygen and conductivity levels can also be altered. Benthic communities may change from a community associated with the relatively stable channel of a straight river to one that is better adapted to the less stable substrate characteristic of braided areas. Removal or alteration of vegetated banks and changes in pool:riffle ratios can alter the distribution of fish within the immediate vicinity of the disturbance. Fish passage is obstructed if the spreading of water sufficiently reduce its depth. The disturbances at the Oregon Creek site provided a situation con- ducive to the formation of aufeis. Aufeis could have direct effects on fish by eliminating or greatly reducing the flow downstream from the ice field, thus threatening overwintering areas and spawning beds. Similarly, during breakup, delayed thawing of the ice field could obstruct fish passage. Benthic communities would be later in establishing at the disturbed site due to the delayed melt of the ice field. The terrestrial environment wi I I almost always be subject to distur- bance for any site situated on a straight channel river. This vulnerability is due to the rarity of large exposed gravel bars in the channel which necessitates mining the adjacent vegetated floodplain banks or terrace. At the Oregon Creek site the vegetated overburden was removed and placed in a row at the edge of the terrace. The gravel was removed from the exposed area and from within the channel causing extensive spreading of the flow through the exposed floodplain. Inundation of this area during high flow and the build-up of an aufeis field greatly minimized the potential for stabi li- zation and revegetation of the disturbed area. This stabi I ization and revege- tation had not occurred after 13 years, thus the I ike I ihood of th~ site revegetating in the near future is remote. The appearance of the floodplain was greatly affected at the Oregon Creek site. This altered appearance wi I I exist for a long time and wi I I only diminish when the channel begins to narrow and when adjacent areas revege- tate. The potential for major changes in the appearance of a straight chan- nel floodplain, that is mined, is great because of the limited availability 347 of exposed gravels, which necessitates the disturbance of adjacent vegetated areas. The magnitude of effect increases with a decrease in river size. In general, the rarity of ~traight channel rivers probably is fortunate from the standpoint of gravel requirements. The relatively few exposed gravel deposits and the narrow floodplains suggest the major problems that can result from gravel removal operations in these systems. Major distur- bances probably wi I I occur in any river of this type unless precautions are taken to protect the area. When mining is restricted to exposed gravel deposits a major length of floodplain wi II be disturbed if gravel require- ments are large. The latter problem can be prevented by restricting mining to the adjacent vegetated floodplain. Straight channel systems should be avoided where it is possible to select a1ternate areas to mine. DRAINAGE BASIN SIZE (CHANNEL WIDTH! Drainage basin size and channel width are closely related from a hydro- logical standpoint and analysis of only the former would be sufficient for assessing change from gravel removal activities. However, channel width was included in the Major Variable Matrix (Table ll because it is a measure- ment easily obtainable in the field while drainage basin must often be estimated from topographical maps. Because of the close relationship between these two parameters, the following discussion applies to both. Drainage basin size (channel width! was considered to be the second most important Physical Site Characteristic influencing the amount of change in a floodplain from gravel removal activities. In general, the effects of mining were considerably greater on small rivers than on large ones. The determining factor is the amount of exposed gravel material available within the floodplain. In larger systems, gravel deposits can be numerous and any given deposit usually contains a large quantity of material. The situation is the opposite in a small river-the few exposed deposits generally do not contain much material. 348 E E c c 0 0 0 0 In large rivers, a given amount of gravel can be removed from exposed deposits with relatively less effect on the floodplain than at a smal I river. If gravel requirements are very large, the alternatives are to use multiple gravel deposits along the channel, or to expand the areal extent of one site to inc I ude adjacent vegetated areas. 1-n a sma I I river system, there are no real options. Gravel has to be removed from adjacent vegetated areas, or from the active channel, or both. This solution was the case for seven of the small rivers studied. The Gold Run Creek site exhibited less change than the other smal I river systems (except for the site at Phelan Creek where vegetation was not removed). At Gold Run Creek the gravel removal operation was restricted principally to gravel bars and an island in the channel. A bank was removed but the degree of floodplain disturbance was less than for the sites on Washington, Oregon, and McManus Creeks, and Penny River. At these latter sites, extensive adjacent floodplain disturbances tended to either greatly expand the channel width or divert the channel. Phelan Creek is a braided system and has a smal I drainage basin above the material site. Although the site is situated near the headwaters, the channel is of medium width because of flow carried in the summer during glacial melt. In this case the large exposed gravel deposits were scraped and the material site included neither vegetated areas nor channels carrying f I ow. Even though this is a sma I I river system, the I o·ng-term effects are minimal because of other overriding factors. Minima! effects are usually not the case, however, on smal I rivers. Location of the material site is most critical on smal I river systems because of the limited availability of exposed gravel deposits and the rela- tively narrow floodplain. Extensive damage can occur to the entire flood- plain reach being mined in these systems, while on large rivers the effects are not as great because the material sites cover a smaller proportion of the floodplain. Location of sites and potential effects are discussed in a subsequent section. 349 CHANNEL SLOPE AND STREAM ORIGIN Neither of these Physical Site Characteristics was found to greatly influence the effects of gravel removal in floodplain environments. Both channel slope and stream origin are closely related to such factors as drainage basin size and channel configuration, therefore, their influence on the effects of gravel removal are dependent on these factors. The Physical Site Characteristics are discussed separately because of specific imp I i- cations involved. Channel Slope. Removal of gravel from a channel wi II affect the channel slope within the site and, perhaps, immediately upstream and downstream. Usually this effect entai Is increasing the slope, which can have localized effects on the floodplain. The main effect is to increase water velocity. Localized changes that can be expected due to the relationship of increased velocity and increased slope are scour and alterations of aquatic communities. Increased scour in a disturbed site can increase downstream deposition of bed load materials where the water slows to the velocity characteristic of the undisturbed channel. The greater scour potential in the disturbed site decreases the stabi I ity of bed materials thus affecting habitat for benthic organisms. Increased water velocity can directly affect benthic organisms by displacing those not adapted to higher velocities and favoring those adapted to these conditions. Similarly, fish may become redistributed locally be- cause of water velocity changes. Those fish species or age groups preferring lower velocities may displace to areas upstream or downstream. Altered velocity is not expected to change the terrestrial environment ( ( or the scenic quality of an area. Indirectly, an effect might occur to water-r associated birds that are dependent on benthic organisms as a food source. Any alterations to benthic communities could alter feeding sites for these birds. 350 '- Significant changes in slope most often reflect changes in channel length. If a channel is shortened by mining then the slope is increased; if the channel is lengthened, the slope is decreased. At all study sites the slope was either unchanged or it increased. The I ikel ihood of decreasing channel slope by lengthening the channel is slight because water tends to flow downvalley over the shortest distance. However, if channel lengthening should occur by diversion through a site, then the effects would reflect reduced velocities. Stream Origin. The origin of the stream was found to have little or no relationship to the effects of gravel removal activities. Origin can in- fluence, at least in part, other characteristics of a river system, e.g., channel configuration and shape. Therefore~ the preceding discussio~s are indirectly related to this characteristic. The origin of a stream determines greatly the quality and quantity of gravel materials avai I able in downstream areas. The original purpose for including stream origin in the study was to maximize diversification of the types of sites to be studied. The origins of streams included were mountain, foothi I I, coastal plain, and glac1al. Twelve of the sites studied were of mountain origin, 9 were of foothi I I origin, and only 4 were of glacial or coastal plain origin. The avaJ lability of gravels in streams of coastal plain origin is generally low and the materials are finer in texture than those found in other systems. Within the geographical limits of our study, only the Seward Peninsula and North Slope have coastal plains. The coastal plain of the Seward Peninsula is so narrow it precludes the existence of such river systems. On the North Slope material sites were located on the Sakonowyak, Putul igayuk, and Ugnuravik Rivers, but only the latter was studied. Gener- ally, these sites are not favored and are only used if alternative sites are not available. The lack of rock in the headwaters and the low mean annual discharges are the reasons that gravel materials are only minimally avai 1- able in coastal plain streams. If these sites are uti I ized, the potential for replacement of gravel sources is very low even over extended time 351 .. __ ,,_, ____________________ _ periods. The minimal areal extent of exposed gravel bars also generally leads to extensive damage to the river system either by use of extended lengths of river channel or by disturbing vegetated floodplains. Glacial origin streams are not common in the area of study; only three sites situated on this type of river were studied. These were on Phelan Creek and the Tanana River. Because these systems are of mountain origin, the availability of weathered parent materials is not limiting and usually large quantities are available. The Phelan Creek site was situated near the glacier and gravel was abundant across a wide area. The proximity of the site to the glacier strongly influenced the seasonal fluctuations in dis- charge. During winter, water flow from the glacier is greatly reduced and is supplemented by that from associated springs. This reduced flow exposes vast expanses of gravel for extraction. The Tanana River sites are wei I downstream from the river origin, there- fore, water flows throughout the year because of the numerous spring-and groundwater-fed tributaries entering the river. Affects include those associ- ated with braided channels that flow in winter. In these systems, however, ice cover on channels is more of a factor than on a system like Phelan Creek, near its origin. The avai labi !ity of gravels in glacial origin rivers makes them a viable source of materials even when needed in large quantities. This is basically true for systems of alI sizes although on smaller rivers the localized deposits are more restricted. Most rivers in northern and interior Alaska are of mountain or foothi I I origin. The weathered parent material in the headwaters provides large quantities of gravels, particularly in the mountain systems. These rivers are fed by springs, melt water, and runoff and, therefore, discharge fluc- tuates seasonally. Spring-fed systems can be expected to have at least intergravel flow in winter. Moderate to steep channel slopes are normal in the headwaters but these slopes are influenced by the length of the river and the topography through which it flows. Bed load movements are usually 352 ( c 0 D 0 0 0 0 0 0 higher than in rivers with mild slopes. These rivers generally have large quantities of gravel available even near the mouth. The size of the system and other hydrological and hydraulic factors also influence availability of gravel. The abundance of mountain and foothil I origin rivers and the fre- quent availability of suitable gravel materials generally combine to favor the location of material sites in these systems. The geographical location of these rivers, and the topography through which they flow, directly affect the type of channel configuration, a factor discussed in a previous section. 353 GRAVEL REMOVAL AREA CHARACTERISTI~S In the preceding section on Phy~ical Site Characteristics it was ap- parent that not alI characteristics were important in evaluating the po- tential floodplain change caused by gravel removal activities. In contrast, alI of the factors discussed in this section were found to greatly influence the amount of change to a river system. The three main features discussed are type. of gravel removal (pit or scrape!, location of the material site relative to the active channel (sl, and the occurrence of dikes and stock- piles. Singularly and in combination these factors caused varying degrees of. change at the 25 study sites, in some cases, irrespective of the specific physical site characteristics. TYPE OF GRAVEL REMOVAL There are two basic types of material sites: pits and scrapes. Pits are dug deeply, usually with draglines or backhoes, and are flooded year- round after site closure. In many cases pits are flooded during gravel extraction unless water is pumped out to keep the site relatively dry. Eight pit sites were studied and they represented two types, those connected to an active channel and those completely separated from an active channel by a buffer zone. Pits usually are situated away from an active channel. In a scraping operation, gravel deposits are removed with bul I dozers or scrapers in active and inactive floodplains and terraces. Gravel is extracted by successive removal of thin layers, and scraping depths usually are sufficiently shallow to minimize the occurrence of surface water. At certain study sites, gravel was extracted below the water table, thus water ponded in the site. This situation is not conducive to a scraping operation and, therefore, is usually avoided unless it is required for other reasons. 354 c c c c 0 c c c c (; J J Pits Pits are usually excavated away from an active channel and cause I ittle or no change to the natural hydraulic processes of the channel. Where pits are connected to a channel, either year-round or seasonally~ some change to the hydraulics of a river can occur. The most obvious alteration occurs when spring breakup or other high water flows spread throughout the floodplain; much of the water can flow out of the channel because it is often fi I led with ice. A pit in the floodplain probably would fi I I during high flows and then, through erosional processes at the upper and lower ends, function as a channel. The inlets or outlets (or bothl connecting the pit to the channel could enlarge significantly and reroute flow through the excavated pit. Depending on site conditions this could be only temporary, for example, where a pit is adjacent to a relatively straight reach of channel. In this case, following high breakup flows, the water would again flow down the original channel because the downval ley distance is shorter than if the water flowed through the channel formed by the pit. A permanent alteration to flow is more I ikely to occur where a pit is located on the inside bend of a meandering stream. Even with undisturbed buffer zones separating the pit from the channel, spring breakup flows can overflow the pit and exit into the downstream reach of the meander surround- ing the pit. If the stabi I ity of the buffer zone is low, erosion can breach the buffer zone, thus, connecting the pit to the active channel. The down- val ley distance is shorter through the pit, consequently, there would be a tendency for permanent redirection of flow through the pit and eventual cut off of the meandering channel. Excavation of a pit separate from the channel does not affect the water quality of the active channel. As would be expected, however, the water qual- ity is different in a flooded pit than in the channel. In comparison to channel waters, pit waters typically have higher temperatures during ice free conditions, the dissolved oxygen levels are lower, and sometimes there is stratification of both temperature and dissolved oxygen. Differences in water quality parameters could be less in situations where channel flow is 355 through a pit. This difference depends on the size of the pit and the amount of mixing. A pit could faci I itate deposition of suspended and bed load ma- terials if flows are through a pit and velocity is decreased. The aquatic biota of pits differ depending on whether there is an op~ortunity for exchange between the pit and the active channel. Those pits that are separated (e.g., Tanana River-Downstream) or have I ittle potential for exchange (Dietrich River-Upstream) typically are unproductive. The Tanana River-Downstream pit is situated in the middle of an island and is completely surrounded by a broad undisturbed (except for an access road) timbered buffer zone. The I ikel ihood for injection of nutrients and organ- isms into this pit is remote, except during high flows. The aquatic surveys reflected this. The occurrence of a few fish suggests that overflow may occur at irregular intervals. The Dietrich River-Upstream pit, on the other hand, is connected by its outlet to the channel. A spring, exposed during excavation, floods the pit and exits through a channel. The pit system has been used by overwintering fish but the pit itself is relatively unpro- ductive. AI I other pits studied were highly productive and the diversity of the fish community was usually increased over that in the river channel. All of these pits were connected to the river channel through either inlets or outlets and thus exchange was possible between the two systems. The sti I I waters in the pit, which are warmer than the river water, provided con- ditions more suitable for primary and secondary productivity. Fish such as Arctic grayling entered presumably to uti I ize the pit as a feeding area. This situation is particularly good for feeding by fish of younger age classes because of the greater supply of food available and the lack of a current. Fish well suited to a sti II water environment, such as northern pike and burbot, also did wei I in some of these pits and, being piscivorous, had an abundance of young age classes of other fish to feed upon as they entered the pits to feed and rear. Northern pike also utilized two of the pits as spawning areas. The potential for the pits to provide a more diversified 356 c c c c 0 c e c c e 0 0 0 0 D fish community in the river also exists because of the connection between the two systems. This increased community diversity may b~ restricted to the are a of t he c h anne I i n t he i mme d i a t e v i c i n i t y of t he p i t. Pit depths are important to fish uti I ization. Obstructions to movement are not a factor during open water periods if either an inlet or outlet are avai !able for fish movement between the river and the pit. A potential for fish entrapment exists, howeve_r, during winter when ,ice cover is present on the river, the pit, and the intercol]necting channel. In the latter situation the pit must be sufficiently deep so it does not freeze to the bottom and decomposition of aquatic vegetation does not decrease the oxygen content of the water below that necessary for fish survival. The creation of a pit in a floodplain constitutes a major change to the local terrestrial environment. Pits are usually situated on vegetated flood- plains, consequently, terrestrial habitat is almost always destroyed. The depth of excavation and the permanent inundation that results also greatly retards or prevents on the long-term, the re-establishment of predisturbance conditions. What most frequently occurs, however, is the creation of a more diverse habitat with concomitant changes in faunal communities. The creation of a pit in meandering river floodplains, that contain oxbow lakes, merely adds to the habitat diversity in a localized area. Where pits are located in floodplains lacking natural lakes and ponds, the effect is again principally local, but has imp I ications thai affect a much larger system. In these cases, the newly formed body of water can attract migrant waterfowl and shorebirds cind perhaps even provide habitat suitable for- nesting and rearing that did not previously exist" The higher aquatic produc- tivity of many of these ponds could afford a significant food source for those species adapted to feeding in pond and lake environments. The effect of creation of a pit, on the scenic quality of an area, is totally dependent on the diversity of the floodplain environment. A pit wi II have less effect where lakes and ponds occur natural :ry than where these types of aquatic systems do not occur. Where lake~ ahd ponds do not 357 occur location should be selected so that view of the site is blocked from vantage points. For example, the Tanana River-Downstream pit, which is large and contains very clear water, is in a floodplain where the river channels are highly turbid, thus, offering a dramatic visual contrast. However, the site is situated on an island completely surrounded by a heavily wooded buffer zone which blocks view of the site from the Richardson Highway. The pit is visible only from the air. Pits are often excavated with angular perimeters that ignore natural land contour. Since angularity is not characteristic of naturally formed aquatic systems the usual pit site offers some contrast even in areas where lakes and ponds occur naturally. Excavating these sites with perimeters that blend with natural land contours, such as in abandoned river channels, de- creases the visual diversity that wi I I result from development of pit sites. The West Fork Tolovana River and Tanana River-Upstream sites are excel lent examples of this management technique (refer to Figures 63 and 70l. Pit sites require considerably less area to obtain a given amount of gravel than do areas that are surface scraped. Because of the ·depths nor- mally required, subsurface waters are exposed,. usually filling the pit during site operation. This water poses problems for the efficient extrac- tion of materia Is but, s i nee drag 1 i nes or backhoes are usua I I y used for excavation, the presence of water does not prevent the removal of gravels. Pumping is the only method used to eliminate the water but even this is impossible in some systems because of the volume of subsurface flow through floodplain gravels. During mining, the water in a pit is usually highly turbid and should not be pumped into adjacent channels. In summary, there is I ittle doubt that the excavation of a pit materi- al site creates significant change in a floodplain environment (Table 41 l. If situated and operated properly, the hydraulics of the river system are I ittle affected whereas significant changes occur to the terrestrial system and the scenic quality of the area. Differences in water quality and aquatic biota can be expected between a pit and the adjacent channel regardless of whether they are connected. The increase in both aquatic and terrestrial 358 c c c c G c 0 c c c c 0 VI "" 10 0 Table 41. 0 0 0 u lnterdiscipl inary Rating of Effects of Pits on Associated Floodplains at Selected Study Sites Visited from 1976 to 1978 Using Various Indices of Changea Potential for flow diversion Aquatic habitat Terrestr i a I Partial Fu II Fish Benthos Disturbance u u habitat Water PIt lrelativeb !potential habitat d standi~g to riparian bird suitabi I ity II fel c River type Study site Location frequency I buffer diversity crop vegetation habitat index Braided Dietrich R..:us Northern Interior 3 4 2 2 7 3.2 Tanana R-DS Southern Interior 9 8 3 I 0 7 4.7 Tanana R-US I lowerl Southern Interior 10 6 5 4 I B 7.8 Tanana R-US I upper) Southern Interior 10 8 10 9 9 5.7 Sp II t None studied Mean-Prospect Ck Northern Interior 4 9 7 10 3 6 6.5 dering W.F. Tolovana R Southern Interior 6 10 10 5 I 9 6.8 Sinuous Penny R Seward Peninsula I 4 5 3 2 6 3.5 Ugnuravik R North Slope 0 0 0 2 4 5 1.0 Jim R Northern Interior 0 3 3 10 I 9 4.3 Straight None studied a(Unless otherwise defined below, 5 =·no change, 0-4 =decrease in parameter, 6-10 = increase in parameter. l bEstlmated frequency of some flow being diverted through site ranges from 0 = frequent I I or more times per year I to 10 = infrequent 15-10 years). cEstimated potential length of time before buffer becomes ineffective ranging from I =within a decade to 10 =greater than 3 decades. dRelative to pits studied. e· Mean of the six ratings at.a particular pit, potential range= o-.o. fScraped side channel acquired some characteristics of a pit following rehabi I itatlon. habitat diversity is reflected in a more diverse faunal community. Pit sites are a viable alternative for material extraction in areas where changes to the river hydraulics can be avoided or greatly minimized. When major hy- draulic changes occur the effects on the environment can be damaging from many standpoints. Scraped Sites Scraped sites can occur essentially anywhere in a floodplain from within the active channel to vegetated areas in the inactive floodplain and terrace. Location of the site greatly affects the potential impacts that can be expected from a scraped site. Although scraping implies that material sites are operated by shallow removal of gravel, certain sites studied on this project were excavated below the water table and thus resulted in permanent flooding. These sites, however, were worked with scrapers or bul !dozers and not draglines or backhoes as might be implied by depth of excavation. Scraped sites have several operational advantages; usually the sites are dry, providing better working conditions and more efficient gravel extraction. Additionally, excavated materials require less hand I ing when using scrapers to remove the gravel because only one machine is normally used to excavate, transport, and deposit at the construction site. This is not feasible using a bul I dozer on a scrape or when digging pits with drag- lines or backhoes. Given the same gravel requirement, the scraped site wi I I generally disturb a larger area than a pit site because the excavation is more shal- low. In the study sites, the large area affected was often the greatest problem of scrape-mining because there were few restrictions regarding avoidance of channels and areas adjacent to channels. Locations of extrac- tion sites are discussed in the subsequent section. Scrapes are generally situated in active floodplains adjacent to active or high-water channels. Lowering these areas spreads water flow, at least 360 c c c c G c G c c c c c 0 0 D 0 0 G c during high flows, and in some cases forms a braided configuration through the disturbed site. When this occurs on unvegetated gravel bars in braided systems, the effect on the floodplain is relatively minor because the ef- fects are similar to natural hydraulic processes. After site clos~re, unless stockpiles or dikes are present, the disturbed site can return to a rather natural configuration within a maximum of a few years. This, however, is not the case where lateral bars are excavated to include removal of adjacent banks. Bank removal is discussed in the subsequent section. The potential for causing braiding from scraping operations within the active floodplain, is usually insignificant in a river system that already has a braided channel configuration. However, in split channel and single channel systems braiding constitutes a significant change to the aquatic environment and alters the aquatic biota; species which benefit are those better adapted to riffle areas, to less stable substrates and, perhaps, to substrates less granular than those found in the natural system. These habitat changes primarily affect the distribution of organisms. This study generally found a local decreased diversity of the fish community as a result of braiding. There is a potential of blockage to fish passage, at least &uring low flow conditions, as occurred at the Aufeis Creek site because the water flows over a wider area than in the undisturbed channel. Blockage is most severe if the entire active floodplain is disturbed, not just the lateral bars. Entrapment of fish, in depressions created by scrap- ing, is also possible during periods when water is receding from high flows. Effects on the terrestrial environment depend greatly on the river type involved and on the location of the work area within the floodplain. In braided systems mined in the active floodplain, there essential ry is no effect. However, on split and single channel systems, braiding caused by gravel mining can provide feeding habitat for shorebirds that uti I ize ben- thic organisms. Destruction of banks with associated vegetation removes habitat used by terrestrial fauna; the effects are the same as removal of vegetation for pit sites. 361 The potential for re-establishment of natural configurations and flow patterns after site closure are totally dependent on the degree of change to the hydraulic processes characteristic of the river system. Long-term effects can be expected where major changes to the stabi I ity of channels occur. The major terrestrial effect of scraping resulted where deep scrapes occurred in areas immediately adjacent to the channel. Channel flow often diverted through these depressions and caused year-round pending which retarded the re-establishment of vegetation. These deep scrapes usually were inadequate as qua·l ity habitat for waterfowl and shorebirds and unsuitable for fish. To minimize short-and long-term effects, scraped sites should not be excavated beyond certain depth I imits. These restrictions are discussed in the Guidelines Manual. The effects of scraping operations on the scenic quality of a braided floodplain can be minimal if the material sites are restricted to the active floodplain. Where banks and vegetated areas are altered, significant effects can be anticipated. In split and single channel systems the establishment of a braided configuration in the disturbed area produces an unnatural condi- tion in the floodplain, thus affording a visual contrast. Properly located scraping operations that avoided or minimized disturbances to the hydraulic characteristics of a river, minimized long-term environmental change.· How- ever, where sites were poorly located and caused significant changes to the channel hydraulics, major long-term effects were evident on the scenic quality of the area. In summary, scraping operations typically occurred in both active and inactive floodplains. Both vegetated and unvegetated areas were used but the fewest long-term disturbances occurred where only exposed gravel de- posits were scraped. The potential for broadening or diverting channel flow in split and single channel systems is great if depths of excavation are excessive and locations of sites are poor. The potential for braiding in these situations was increased with concomitant changes in aquatic biota. Terrestrial effects were greatest when the depth of excavation was excessive and led to permanent pending which retarded recovery to predisturbance 362 c c c c G c 0 c c c c J 0 0 c conditions. Visual effects of scraping operations depend greatly on the type of river system, the location of the site, and the areal extent of the site within the floodplain. LOCATION OF GRAVEL REMOVAL Location of a gravel removal operation in relation to the channel of a river was found to be the most important aspect influencing long-term change to a floodplain environment. Whether a pit or scrape, in general, the loca- tion of the site was a more important consideration than the type of site. Site location in this section is discussed with minimal reference to the type of site although the latter is a factor influencing the extent of change. In-Channel Locations As used in this project, in-channel gravel removal includes areas in the active channel, high-water channels, and abandoned channels. Fourteen of the sites studied on this project were situated in high-water channels and 7 of the 8 sites located in the active channel also included areas in high- water channels. From hydraulic and hydrological standpoints, material sites in active and high-water channels caused the greatest long-term change to the floodplain environment. Active Channel. Gravel removal operations in the bed of an active channel cause a series of changes all basically related to changes in the depth and location of the thalweg. The degree of change depends on the type of channel configuration, principally whether it is a braided or a single channe I. In a braided system the channe Is genera I I y shift throughout the active floodplain on an annual basis. This is due to the lateral instability of the individual channels. In these systems removal of gravel has the effect of perhaps causing greater instability in the area of the distur- bance. Changes occurring in a single channel river caused by removing bed material are unknown because all seven sites with this mining location had substantial alteration to adjacent deposits or banks. 363 Removing gravel from within.the channel is accomplished either by dredging or by scraping the bed after flow has been diverted. Either method can result in a deepening of the thalweg and, if the edges of adjacent gravel bars or banks are removed, a widening of the channel. Depending on the location of the material site, this operation could alter the pool: riffle ratio in the river. Where the channel is dredged, turbidity in and downstream of the site wi I I increase greatly during mining. Turbidity should reduce quickly after the operation has ceased. If the channel is diverted during mining, the effects on water quality entai I suspension of the fines exposed during mining when water is diverted back through the site. This suspension wi I I result in a temporary increase in turbidity. Reduction in the velocity of water entering the excavated hole wi I I cause sedimentation of both bed load and suspended materials. This wi I I aid in rapid replenishment of the grave! materials removed from the site. Being in the active channel, the replenishment rate IS considered high compared to other areas fn the floodplain. Excavation of the channel bed can remove spawning areas. During a dredging operation fish probably wi I I redistribute to less turbid waters. Benthic organisms adapted to si It-laden areas wi I I establish following excavation and remain unti I the natural gravel bed becomes established. Assuming that the disturbances resulting from gravel removal are re- stricted to the channel, and do not include the banks or edges of gravel bars, I ittle long-term effect on the terrestrial environment is expected. Changes could occur if hydraulic changes in the channel affect adjacent banks. Aesthetically, the in-channel material site has little or no effect. Hydraulic changes resulting from in-channel disturbance that affects banks can cause some effect. 364 c c c c G 0 0 c c c 0 High-Water Channel. High-water channels flow only during high-water periods. The hydraulic effects of removing gravel from high-water channels are not as great as they are in the active channel where the disturbed area is subjected to flow throughout the year. The changes that can be expected are similar to those described for the active channel although they occur only during the period when the site is subjected to flow. Effects on water quality are only evident during the high-flow period. Localized widening or deepening of the high-water channel would slow the water velocity and thus faci I itate deposition of both bed load and suspended materials. Depending on the degree of change to the channel this deposition would reduce the time required to re-establish near-natural conditions in the area. Also, any fines exposed during mining would be available for suspension during high flows. Removing gravel from a high-water channel could trap fish and benthic organisms in the depressions of the disturbed areas as flow recedes. Many benthic organisms that are adapted to a riffle community and most fish species would not be able to survive in such a habitat. Since high-water channels are subjected to less flow than active chan- nels, they tend to be more stable and are usually bordered by established terrestrial vegetation. Any disturbance to these channels causing lateral instabi I ity during high flows could faci I itate erosion of adjacent banks and thus serve to reduce the areal extent of vegetated areas. Loss of habitat would cause localized elimination of smal I mammals and displacement of birds and larger mammals. Having water pooled in the high-water channel during low-flow periods could attract shorebirds, particularly where a benthic fauna has become established to serve as a potential food source. The most serious effect from a gravel removal operation in a high-water channel is bank destruction which often occurs with this type of operation. This aspect is discussed in a subsequent section on removing gravel from banks. 365 The effect of mining gravel from a high-water channel on the scenic quality of an area is minimal if the disturbance is restricted to the chan- nel. If banks are destroyed the effect would be more significant. Since the high-water channel is active only part of the year re-establishment of pre-existing conditions wi It require a longer time. Formation of pits in high-water channels would have effects similar to those described in the section on Type of Gravel Removal. Abandoned Channel. Abandoned channels carry water only during major flood events. Normally, these channels are considered to be dry during most years. Since they represent old river channels they usually contain reason- ably large quantities of gravel, depending on the type of river with which they are associated. Only two of the sites studied wer~ located on an aban- doned channel, Prospect Creek and West Fork Tolovana River, both in meander- ing systems. Abandoned channels are common in this type of floodplain be- cause of the formation of cutoffs that result from the fluvial processes of meandering channels. Location of material sites in abandoned channels causes I ittle problem with regard to changes in river hydrology and hydraulics because the sites are separated from active flow. Where pits are dug in abandoned channels and are connected to the active channel, flow can be diverted through the site during high flows. The magnitude and duration of this change is dependent on the nature of the connection between the material site and the channel and the integrity of the undisturbed buffer zone separating the site from the active channel. Where the once-abandoned channel carries water annually during high-flow stages, the effects to the floodplain would be similar to those described for sites in high-water channels. Where an abandoned channel is scraped and the water table is not reached, water quality does not become a problem. Where pits become flooded, the water quality would be different than that occurring in the active channel, as is discussed in the section on pits. ?66 c c c: c c 0 c c c G D 0 0 0 G 0 Aquatic biota wi I I not be affected in a scrape operation located in an abandoned channel, however, if a pit is dug, aquatic biota could become established. In these cases the effect depends on whether the gravel removal operation alters the site sufficiently to cause it to be subjected to annual high f I ow or whether it is connected to the active channe I. In the former case, there is potential. for entrapment of fish during high flow as was discussed for high,-water channels. In the case of a site connected to a channel, the effects are those discussed in the section on pits. The effects of removing gravel on the terrestrial environment can be greater in an abandoned channel than in other in-channel locations. Aban- doned channels are rarely subjected to hydraulic forces, consequently, vegetation usually is established, and the stage of succession is dependent on the time since the channel ceased to carry flow. Thus, vegetation must be removed from these sites to expose gravel deposits. Removal of this habitat results in a loss of feeding, nesting, and cover habitat for those smal I mammals and passerines that utilize riparian shrub thickets. Larger mammals, being more mobile, are displaced to adjoining areas. If the abandoned channel is scraped above the water table, the dis- turbed site wi II initiate primary plant succession following site closure. The time required to reach the predisturbance stage of vegetational succes- sion is dependent on the geographical region and the vegetative charac- teristics of the area. This process is the same as occurs in other recently abandoned high-water channels and entai Is the same vegetational and faunal communities. If the site is a pit that is permanently flooded, the site would not return to a terrestrial environment in a relatively short time. However, overall habitat diversity is increased. Further discussion of these aspects is included in the section on pits. The effects of siting a gravel removal operation in an abandoned chan- nel, on the scenic quality of an area, reflect the changes occurring to the terrestrial vegetation. The short-term effect is to expose an area that was previously vegetated. The long-term effect in a scraped site depends on the rate of revegetation of the disturbed area. Where a pit is dug the altera- 367 tion is long-term but, in fact, could blend more with the interspersion of cutoffs and lakes occurring naturally in the floodplain. Adjoining Channel Locations The Major Variable Matrix (Table ll includes four subdivisions under adjoining channel locations. These are: point bar, lateral bar, mid-channel bar, and bank. To thoroughly characterize the 25 study sites it was neces- sary to uti I i ze a I I of these subdivisions but the grave I remova I effects are similar for some. Therefore, the following discussion combines the three bar locations and discusses banks separately. Remember, at a given material site these bars and banks are associated with one of the three channel types discussed in the previous section. Point, Lateral, and Mid-Channel Bars. This discussion only considers removing gravel from unvegetated bars with exposed gravel deposits. AI I three gravel bars are usual iy numerous in braided systems but, in single channel systems, usually only point and lateral bars are found. The effect of removing gravel from a bar is to lower the elevation of the bar thus allowing flow to inundate an area that was previously above the low-flow water line. These sites are usually scraped. Maintenance of the integrity and conformation of the bar wi II cause I ittle permanent change to channel hydraulics and wi I I faci I itate replenishment of the gravel during subsequent high flows. Changes in the active channels can and probably wi I I occur where bar integrity is not maintained. In a braided river system this change wi I I be similar to the natural processes and the long-term effects will be minimal. In a single-channel system redistributing flow by removing bars can have long-term effects by changing the local hydraulics of the channel. This hydraulic change could either decrease the lateral stabi I ity of the channel or widen or deepen the flow because the cross-sectional area is larger. Where the banks are stable, the river eventually wilj equilibrate itself by reforming gravel bars as upstream bed load materials become avai 1- able during subsequent high flows. Where banks are less stable it is pos- 368 c c c c c c e c c c c 0 0 c sible that subsequent high flows wi I I cause erosion due to the hydraulic forces acting on the once protected banks. This could significantly alter the local reach of a river. This effect is less likely to occur in straight and perhaps sinuous river systems because the flow is relatively unidirectional down the flood- plain and direct hydraulic forces on the banks would be less than in a meandering system. The effect on a meandering river could be to faci I itate the formation of cutoffs by increasing the hydraulic force on the inside bank at the upstream end of a meander. Removal or lowering of gravel bars wi I I faci I itate the spreading of river flow when water levels are higher than during the gravel removal opera- tion. This flow spread has the effect of reducing the depth and velocity of the water and wi II increase sedimentation rates of both bed load and suspen- ded materials. Additionally, water temperature and dissolved oxygen contents could change. Benthic communities would develop that are adapted to riffles and less stable substrate. Fish would become redistributed with younger age classes perhaps being attracted to the disturbed site where currents would be less. The effects to the terrestrial environment, of removing gravel from a bar, are minimal if the integrity of the bar is basically maintained. The only changes that could be expected are if the hydraulic regime of the river channel is altered, thus, causing changes in adjacent vegetated areas. The spreading of flow between the banks when bars are removed might attract shorebirds for purposes of feeding. These effects would only be expected in single-channel systems. Removing gravel from isolated material sites using accepted mining techniques from bars in braided river systems would have I ittle or no effect on the scenic quality of a floodplain. The lateral instabi I ity of the chan- nels that characterize these systems would cause any changes resulting from gravel removal to blend in with natural processes. Removal of bars in a single channel system wi II locally affect the appearance of the river sys- 369 tern, the magnitude of effect depending completely on the degree to which the bar was disturbed. Any significant changes to the hydraulic geometry of the reach causing subsequent disturbance to adjacent vegetated areas wi II lo- cally alter the appearance of the floodplain. Banks. Probably the most consistent long-term changes to a floodplain occurred when banks were destroyed or greatly modified during a gravel removal operation. In these cases significant changes to the hydraulic geometry of the river occurred. Banks typically are stable and function to restrict the flow of the river to the channel except during high flows. When these are removed or disturbed the river is no longer contained and it begins to wander and erode the adjacent floodplain. This wandering results from the hydraulic forces of the river impinging on newly exposed bank.ma- terial. Where banks are made of stable materials the degree of erosion shou I d not be greater on the new I y exposed bank than what -occurred natura I I y before the site disturbance. Where the newly exposed bank materials are not stable erosion wi I I occur at a rate faster than occurred previously. Also, if the newly exposed bank is situated at an angle to the flow different than what occurred naturally in that reach of the river, erosion could be aggra- vated because of the increased hydraulic force on the bank. Generally, channel width increases with bank destruction. Previous discussion identified that increased channel width can result in reduced water velocity, reduced water depth, changes in water temperature, and dissolved oxygen, and increased sedimentation. Aquatic biota would reflect these altered habitat conditions by changes in benthic communities to those that are adapted to riffle areas with unstable substrate and changes in distribution of fish in the reach affected by the distur-bance. Undercut and vegetated banks are heavily uti I ized by fish as cover and removal of this habitat can greatly reduce the local abundance of certain species. The effects on the terrestrial environment include destruction of riparian habitat during site clearing with resultant effects on faunal distribution. The decreased lateral stability of the channel can cause more destruction after site closure if hydraulic forces erode newly exposed 370 c c c c c 0 G c c c c J 0 0 0 areas. In addition, even if the newly exposed banks are stable the hydraulic forces occurring over the disturbed site would retard the re-establishment of terrestrial floodplain habitat. The effect on the scenic quality of the area wi I I reflect the changes occurring to the terrestrial environment and to the hydraulic geometry of the river channel. Major changes to th~se aspects wi I I greatly alter the appearance of the floodplain in the affected reach. Locations Separated From Active Channel The flve specific site locations identified in the Major Variables Matrix (Table I l that are separated from the active channel are not mutually ~ discrete locations. That is, a site can exhibit a combination of these locations by for example, being located near the channel on the outside of a meander. Hence it is more difficult to assess the potential impact for these locations than for those previously discussed. The following discussion has been separated into two sections: inside and outside of meanders, and islands. These then are discussed from the standpoint of whether a material site is near or distant from the active channel. The essential factor with sites in alI of these locations is whether diversion of the water out of the active channel and through the site is possible. The distance between the material site and the active channel is of major concern, but the height of the intervening bank certainly would be a necessary consideration in this evaluation. Inside and Outside of Meanders. The location of a site on the outside of a meander is possible on any sized river system regardless of the areal extent of the material site. This, however, is not the case on the inside of meanders. In smal I river systems the areal extent of the floodplain or terrace circumscribed by the meander can be quite smal I. In cases where these were used for material sites, the surrounding areas, including the channel, were often disturbed by the gravel removal operation. Therefore, to 371 I imit activities to the inside of a meander and maintain undisturbed buffers the site must be located on at least a medium sized river. Any activity inside a meander, that would reduce the integrity of the banks or weaken the cross-sectional area, could lead to premature cut off of the meander. In many Alaskan rivers during breakup, water often flows over the ice in the channel and, if sufficiently high, over the banks and down the floodplain. A depression resulting from a material site located near the channel on the inside of the meander would aid in channeling the water through the site. Depending on the erodabi I ity of the soi I separating the material site from the channel, a channel could erode at both the upstream and downstream portion of the meander and thus eventually establish a cut- off. The erodabi I ity of the soi I would govern the length of time required for this natural event to occur. When a pit material site is connected to the active channel, the probability of a cutoff occurring could be enhanced greatly, even in a very short time. Such an event occurred at Skeetercake Creek on the North Slope. The inside of a meander of this smal! river was mined for gravel and when the site was studied I I years after site closure, a cutoff had occurred. The time required for this event to occur is unknown. A pit visited during site selection, but not studied in this project, that showed a potential for channel diversion, was located at Hess Creek in the Southern Interior region. The buffer strip was breached during the first spring breakup following site opening while the site was being op- erated. The initial breach was temporary and the water remained in the active channel when the flow receded. The key point of concern when mining in the inside of a meander is maintenance of a sufficiently wide undisturbed buffer zone between the active channel and the perimeter of the material site. The size wi I I depend greatly on factors such as the discharge of the river, flood frequency, and soi I erodabi I ity and must, therefore, be determined on a site-specific basis. In order to maintain the integrity of the channel over the long-term it may be necessary to dig deeper to obtain needed gravel volumes, rather than decrease the buffer width. 372 c c c c G c e c c c c ) Buffer zones are similarly important to separate the active channel from material sites located on the outside of meanders. A breach occurring in this situation would lengthen the meander. This breach probably would be a temporary event during high flow periods and the river would maintain its main flow through the active channel during lower water levels because of the shorter downvalley distance. Periodic and aggravated damage t.o the area between the material site and the active channel and perhaps the creation of a backwater area in the material site, would occur from an outside meander breach. It is obvious that the closer a material site is to the active channel the greater the probability of a permanent breach occurring in a short time. Placement of a material site either on the inside or outside of a meander has no effect on water quality, regard I ess of the distance sep- arating the site from the channe I. However, if water is ponded the water in the pit would differ from that in the channel, as described in the section on pits. Changes in water quality could result if a breach occurs. These also are discussed in the section on pits. Change wi I I not occur to aquatic biota when material sites are located away from the active channel. However, if high flow conditions reach a material site, and cause either temporary or permanent pending, fish could become trapped in the site when the water recedes. Effects similar to those described for connected pits could occur where the buffer is breached and a pit site becomes connected to the active channel. In general, locating material sites back from the active channel wi II necessarily entai I destruction of vegetative habitat. This wi I I result in localized loss of smal I mammals and displacement of birds and larger mam- mals. If the area is scraped and does not become flooded during high water the site eventually wi II return to the predisturbance condition through processes of primary and secondary plant succession. The length of time required wi II depend on the regional characteristics. If the site is flooded 373 because it was dug as a ~it, or because depressions are at least temporarily flooded, vegetative re-establ lshment wi I I be retar8ed. Because of the soi I binding characteristics of vegetation, maintenance of the vegetation on the buffer zone between the material site and the active channel is important. The wider this zone the less the likelihood of a breach. If a buffer breaches, the progressive erosion of soi Is and loss of overlying vegetation wi I I result In prolonged Impact to the terrestrial environment. Concern for maintenance of the natural hydraulic geometry in the floodplain while selecting a material site location, and while operating the site, will limit terrestrial change to the area of the disturbance. The usual need to remove vegetation to operate a site away from the active channel wi I I affect the scenic quality of the floodplain environment. The magnitude of effect wi I I depend much on the shape of the site, whether it conforms to natural land forms, and what the vegetative structure is in the area. If the site is not visible from a road or other accessible vantage point, the overall impact wi II occur only from the air. The distance of the site from the active channel would not necessarily be related to the mag- nitude of impact on the scenic quality but this would be determined on a site-specific basis. Islands. Material sites located on islands require the removal of vegetation. The distance between the perimeter of the material site and the active channel is the major consideration In the development of these sites. Islands are situated In the active channel most of the time, thus, the maintenance of buffer zone intregity is of greatest concern. If buffer zones are removed or greatly disturbed the net long-term effect could be the loss of the island, perhaps changing the hydraulic geometry significantly enough to cause other changes within the floodplain. Sites that have been located on islands where the .banks were disturbed or eliminated have had greater effect on the floodpla'in t.han those where the site was developed totally separate from the channel (e.g., Tanana R i ver-D·ownstreaml. In the I at ter case there was no change detectab I e to the 374 c c c c G 0 G c c c c ) J 0 G 0 hydraulic regime of the channel. In the other cases, induced erosion of the disturbed banks has had more prolonged effects than where this erosion has not occurred. Again, of prime concern with material sites on islands, as with other sites separated from the channel, is maintenance of the natural hydraulic geometry of the river channel. If natural hydraulic forces erode islands in a given reach of a river, the presence of a material site, whether a pit or scrape, wi I I weaken the integrity of the island after natural bank erosion reaches the perimeter of the site. Development of material sites on islands where the perimeters of the sites are separated from the channel, wi I I have I ittle effect on water quality and aquatic biota. If the material site is flooded because it was deeply dug, the contained water wi I I be different than the water in the active channel, as discussed under pit sites. If the site is flooded regu- larly during high-flow conditions there is a potential for fish entrapment as the water recedes. The long-term effect on aquatic biota depends on whether the site is permanently flooded and the depth of the water. If the site becomes connected to the active channel by breaching of the buffer zone, the effect may be development of a braided section with the accom- panying changes. Flooding of depressions in the disturbed area could cause fish entrapment before the establishment of a braided pattern. Terrestrially, the loss of vegetated habitat would result in loss of both smal I mammals and perhaps some larger ones. Loss would depend on the size relationship of the material site to the island, but would occur regu- larly where a large proportion of the island is disturbed for the material site. The mortality would occur as a result of animals not being able to cross the river channel (sl to adjacent floodplain habitat. The loss of vegetation on an island reduces the amount of bird nesting habitat. This could affect the total productivity of an area more than if an equivalent amount of vegetation were removed along the edges of the flood- plain. This assumes that the island provides some protection from mammalian predators unable to cross the intervening channels. Otherwise, the mobi I ity 375 of birds allows them to redistribute in the floodplain just as large mammals do that are dependent on floodplain habitat. Material sites on islands wi I I affect the scenic quality of the flood- plain, but the type of vegetation characteristic of the area would determine the long-term visibility of the site. Where stands of timber block view of the site except from the air, as with the Tanana River-Downstream site, I ittle change would occur. Where such timber is not present the material site could be quite conspicuous and affect the appearance of the floodplain environment more than if the site was located along the edge of the flood- plain. In either case, maintenance of an undisturbed buffer zone between the material site and the active channel reduces the induced disturbances that could further detract from the natural appearance of the floodplain. Summary. The problems associated with material sites located separate from the active channe I are essent i a I I y dependent upon maintenance of the integrity of intervening buffer zones. Where this is maintained, and the hydraulic geometry of the river is not affected, very little or no change would be expected relative to hydrology-hydraulics, water quality, and aquatic biota. The terrestrial system and scenic quality of the floodplain wi I I be affected because usually vegetation must be removed to expose under- lying gravel deposits. Generally, sites located back from the channel are favored from a practical standpoint because they can be operated in a dry condition making for a more efficient and easier operation. Excavating a pit would be an exception because the depths of excavation would normally be below the water table. DIKES AND STOCKPILES The location of certain material sites and the gravel removal opera- tions require the construction of a protective structure and/or the stock- piling of overburden and gravel in or near the material site. Protective structures prevent water from entering the material site and include channel plugs and diversion dikes. Overburden piles consisting of brush, slash, groundcover, and organic soi I are located either permanently or temporarily, 376 c c c c c c 0 c c c G ) J D 0 usually at the edges of sites. Gravel stockpiles are considered to be tem- porary and are located within the material site. Dikes and stockpiles of unused gravel were sometimes left intact when the site was abandoned, thus, contributing to the long-term effect of the gravel removal operation. Any dikes or stockpiles deflecting or otherwise modifying flow patterns cotild aggravate the long-term hydraulic effects of the material site. Flow alterations could significantly modify the hydraulic forces in the local reach of the affected floooplain and cause other damage. Alterations to natural flow patterns in the winter could induce or aggravate aufeis forma- tion. The water quality of an area could be affected by the location of these structures in the floodplain. Any erosion of overburden piles by active flow could introduce large quantities of organic materials for suspension and eventual downstream deposition. Also, any structures that would impound waters, after high flows have receded, would result in differences in the water quality between the active channel and impounded waters. Aquatic biota could be affected by the presence of obstructions. Fish could become entrapped behind any structures that impound water. The suspen- sion of fines in the water column as a result of erosion could cause redis- tribution of fish and reduction of riffle invertebrates. Overburden piles provided a nucleus for revegetation of abandoned material sites. The organics, and particularly the root stocks and slash, faci I itated re-establishment of vegetation in localized areas of the site. Overburden piles were used for denning by ground squirrels and, because they were vegetated, provided habitat for smal I mammals and nesting passerine birds. Abandoned stockpiles of gravel were less prone to provide these conditions. In the long-term, any alterations of flow patterns that resulted from abandoned structures probably would be detrimental to vegetative recovery 377 on the site. Revegetation in these cases would only occur on the area above the high flow levels. Abandoned structures in most cases further detract from the already af- fected scenic quality of a floodplain. Where the site is hidden from view except from the air abandoned structures would not alter the overal I impact. However, in places characterized by tundra and low riparian vegetation, these abandoned structures can attract attention to the floodplain site. 378 c c c c c 0 0 c c c c ) \ J ) ) J SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS SUMMARY Not alI of the major variables used to characterize the 25 material sites were significant determinants of gravel removal effects. Amo~g the Physical Site Characteristics, channel configuration was the most important. Potential floodplain change is least for a braided river and greatest for a straight river. Size of channel is a significant factor, with the least change to be expected in a large system and the greatest in a smal I system. This assumes equally sized material sites. Combining these two variables, (channel configuration and size) gravel removal operations can be expected to have the least effect on large braided rivers and the greatest effect on smal I straight rivers. Influencing Phy~ical Site Characteristics related to configuration and size are the availability and size of unvegetated gravel bars, floodplain width, and the distance that can be maintained between the mining site and active channel. For example, in a smal I straight river system the floodplain is narrow and gravel bars are neither plentiful nor large. Thus, to extract gravel, either a significant length of active floodplain or the adjacent inactive floodplain and terrace must be disturbed. In the latter case the narrowness of the floodplain forces the operation to closely encroach upon the active channel. In large river systems these problems can be less signif- icant because gravel bars are larger and, if the inactive floodplain or terrace are used, the wider floodplain allows maintenance of a broader undisturbed buffer zone between the material site and active floodplain. 379 In the present study, channel. slope and stream origin did not correlate with changes resulting from gravel mining. However, channel slope influences the bed load carrying capacity of a stream --steeper slopes indicate greater carrying capacity. This relationship is useful in evaluating po- tential replenishment rates in a disturbed site after mining. Also, stream origin has an influence because rivers of mountain and glacial origin charac- teristically have larger quantities of gravel available than do rivers of coastal plain origin. AI I of the Gravel Removal Area Characteristics were found to signifi- cantly influence the effects of gravel mining. The location of the material site relative to the active channel is considered to be the most important factor. Whether a material site is scraped or pit-excavated is important, but often pits are located away from an active channel, avoiding the types of changes that can be associated with scraping in active floodplains. The major effects of pit sites located in inactive floodplains and terraces are the loss of vegetated habitat, the possibi I ity for fish entrap- ment, a change in the appearance of the floodplain, and long-term delay in there-establishment of predisturbance conditions. Where pit sites are situated wei I away from active channels they have I ittle effect on the active channel and, there is I ittle chance of contributing to channel diver- sion. When situated close to active channels, particularly on the inside bends in meandering systems, the possibi I ity exists for diversion of the channel through the pit, eventually forming a channel cutoff in the meander. This problem high I ights the importance of providing a buffer between the material site and the active channel. Where pit sites are of suitable size, of sufficient depth, and have contoured perimeters, they can increase local habitat diversity and provide conditions suitable for fish and various species of terrestrial fauna. Scraped material sites in active floodplains have minimal effects on the floodplain environment when exposed gravel bars are only excavated above the water level and slope and contours are maintained resembling those of natural bars. Removal of vegetated areas or banks, which results in 380 c c c c c c G c c c ) ) ) decreased lateral stability of active channels, oral lows water to spread over a large area, is not desirable. De~reased water depth and velocity increases sedimentation rates, alters water temperature, and alters dis- solved oxygen levels. These chang~s in aquatic habitat usually affect the local distribution and community structure of benthos and fish. The effects of scraping in vegetated areas of inactive floodplains and terraces can be similar to those described for pits. However, long-term changes typically are minimal becaus~ the lack of standing water in the closed site wil I facilitate re-establishment of pre-mining vegetation con- ditions. In-channel locations that are dredged have the potential for causing the least change to channel hydraulics, terrestrial biota, and aesthetics; however, they can have the greatest effect on water quality and aquatic biota. Gravel replenishment rates are highest in this location. Mining exposed gravel bars in active floodplains potentially has the least effect on terrestrial systems. Sites in inactive floodplains and terraces affect the terrestrial biota and scenic quality most, but potentially have no affect on the aquatic system. In general, the farther a material site is located from a channel the greater the potential effect on the terrestrial biota.and scenic quality and the smaller the effect on the channel hydrology-hydraulics, aquatic biota, and water quality. This relationship constitutes the major tradeoff consideration in locating material sites in floodplains. If material sites are located and operated to prevent or greatly mini- mize effects on channel hydraulics, and to utilize only exposed gravel bars, the probability of major localized changes to a floodplain is generally greatly reduced. Where exposed gravel bars are not available or are inade- quate, a tradeoff decision between sites must be made that weighs the poten- tial effects of aquatic disturbances against terrestrial disturbances. In these cases, minimization of hydraulic change to active channels should be important in the decision major hydraulic changes can have a greater long-term effect on terrestrial systems than the control led disturbances 381 associated with a site located in a vegetated inactive floodplain or ter- race. Dikes and stockpiles of gravel and/or overburden left in a material site after closure, have potential effects on the floodplain. These struc- tures can alter channel hydraulics locally if they are subject to high flows. During high water the fines and organic debris may be introduced into the water and result in downstream sedimentation. Depending on their position and orientation relative to flow, dikes and stockpiles can also cause fish entrapment. Where overburden piles are above high-water levels, they can facilitate the establishment of vegetation after site closure. This vegetation provides habitat for smal I mammals and passerine birds. In some cases, revegetation at a site was found only on such overburden piles. This observation suggests that, as long as the piles are situated where they are not subject to inundation or hydraulic erosion, they can provide a source for revegetation of the site. Overburden piles may detract from the scenic qua! ity of a f!oodp!ain. RECOMMENDATIONS The recommendations developed for each of the disciplines are generally in agreement, with several exceptions. AI I recommendations are generally designed to minimize change to the floodplain and to enhance re- establishment of predisturbance conditions. I. River types that should be used in order of decreasing preference are: braided, split, meandering, sinuous, and straight. The major consideration in this preference is the avai labi I ity of gravel from exposed bars. The largest volumes are available from braided systems and the least from straight systems. An additional factor is the decreasing floodplain width of the configuration series identified above. If areas adjacent to the channel· must be used for gravel mining, greater overal I change ~iII result in straight systems. 382 c c c c 0 0 c c c ) ) ) ) 2. River sizes that should be used in order of decreasing preference are: large, medium, and smal I. The rationale is the availability of gravels and width of floodplain. Larger systems have more gravel. The proportionally smaller disturbance in large systems wi I I reduce the overal I effect of gravel removal. 3. Mining gravel ·from active channels should be avoided to reduce detrimen- tal effects on water quality, aquatic habitat, and biota. However, if hy- draulic changes can be minimized, in-channel sites wi I I repJenish more rapidly than other areas and effects on the terrestrial biota and scenic quality of the floodplain wi I I be avoided or greatly minimized. 4. Changes to channel hydraulics should be avoided in alI cases, es- pecially the establishment of a braided configuration in the disturbed site. 5. When possible, exposed gravel bars in large active floodplains should be considered for mining. A properly operated material site in these areas can minimize changes to channel hydraulics during low-flow periods, minimize changes to water quality and aquatic biota, minimize or eliminate affects on terrestrial biota, and maintain the scenic quality of the floodplain. In addition, the probability of gravel replenishment is increased. 6. Although pits reflect a major change from predisturbance conditions, they can increase local habitat diversity if suitably located and developed. They should be located to minimize the probabi I ity of channel diversion through the site. Adequate undisturbed buffers should be maintained between the material site and the active channel. 7. Organic debris and overburden should be spread over or piled in the abandoned site to promote revegetation and establishment of predisturbance conditions. This procedure must be conducted only in situations where there is a low likelihood of this material being eroded into active channels. 383 RECOMMENDED FUTURE STUDIES During the present study a number of subject areas were identified that should be investigated. I. Evaluation of gravel mining from coastal and upland sources; and, preparation of guidelines for users of these sources. These alternatives to floodplain sources have not been studied. 2. Evaluation of the effects of multiple sites on one river system. Such an investigation should be aimed at determining the critical, spatial, and temporal relationships of multiple sites. Gravel replenishment rate pre- dictions should be an integral part of this investigation. 3. Several floodplain gravel removal sites should be investigated before, during, and after mining to assess the adequacy of the Guidelines Manual. 4. Several specific topics of the Guidelines Manual should be studied in detai I to assess their adequacy, i.e., buffers, pit des1gn, and active channel dredging. 384 c C' c c G c 0 c c c c J 0 0 0 0 APPENDIX A Scientific names of flora and fauna identified in the text are presented in Tables A-1 through A-5. References are: Herbaceous Vegetation-Hulten, E. 1968. Flora of Alaska and Neighboring Territories. Stanford Univ. Press. I ,008 pp. Woody Vegetation-Viereck, L.A., and E. L. Little, Jr. 1972. Alaska Trees and Shrubs. U.S. Dept. Agric. Handbook 410. 265 pp. Mammals-Hal I, R. H., and K. R. Kelson. 1959. The Mammals of North America. Ronald Press Co., New York. 2 vols. Birds-American Ornithologists' Union. 1957. Check-1 ist of North American -----Birds. Port City Press, Inc., Baltimore. 691 pp. American Ornithologists' Union. 1976. Thirty-third supplement to the AOU check~list of North American Birds. Auk 93!41:875-879. Fish -Alaska Department of Fish and Game. 1978. Alaska's Fisheries Atlas. Vol. I and 11. Alaska Dept. Fish and Game, Juneau, Alaska. 83 pp. + maps. Bailey, R. M., J. E. Fitch, E. S. Herald, E. A. Lachner, C. C. Lindsey, C. R. Robins, and W. B. Scott. 1970. List of Common and Scientific Names of Fishes from the United States and Canada. Third edition. American Fisheries Soc. Spec. Publ. No.6. 150 pp. McPhai I, J. D., and C. C. Lindsey. 1970. Freshwater Fishes of North- western Canada and Alaska. Fish. Res. Bd. Canada. Bull. No. 173. 381 pp. Morrow, J. E. 1974. Freshwater Fishes of Alaska. Alaska Northwest Publishing Co., Anchorage, Alaska. 78 pp. 385 Table A-1. Vegetation Identified in the Text Common Name Horseta i I Reed Bent Grass Po a Cotton Grass Sedge Rush Balsam Poplar Felt leaf Wi I low Littletree Wi I low Paper Birch American Green Alder Thinleaf Alder Chickweed Milk Vetch Oxytrope Sweet Pea Dwarf Fireweed Siberian Aster Fleabane Wormwood Hawk's Beard 386 Scientific Name Equisetum variegatum Calamagrostis spp. Poa spp. Eriophorum spp. Carex spp. Juncus spp. Populus balsamifera Salix alaxensis Salix arbusculoides Betula papyrifera Alnus crispa Alnus tenuifol ia Stel iaria spp. Astragalus spp. Oxytropis spp. Hedysarum Mackenzi i Epi lobium latifol ium Aster sibiricus Erigeron spp. Artemisia spp. Crepis nana c c c c c c G e c c ) J J J ) Table A-2. Mammals Identified in the Text Common Name Arctic Ground Squirrel Red Squirrel Beaver Tundra Vole Singing Vole Muskrat Gray Wolf Black Bear Grizzly Bear Moose Caribou 387 Scientific Name Spermophi Ius undulatus Tamiasciurus hudsonicus Castor canadensis Microtus oeconomus Microtus miurus Ondatra zibethicus Canis lupus Ursus americanus Ursus horr i b i I is Alces Alces Rangifer tarandus Table A-3. Birds Identified in the Text Common Name Whistling Swan Trumpeter Swan Canada Goose Black Brant Mallard Pinta i I Green-winged Teal Common Goldeneye Barrow's Goldeneye Buff I ehead Red-breasted Merganser Semipalmated Plover Ruddy Turnstone Semipalmated Sandpiper Western Sandpiper Spotted Sandpiper Northern Phalarope G I aucous Gu I I Herring Gu I I Mew Gu II Arctic Tern Alder Flycatcher Tree Swa I I ow Violet-green Swallow Bank Swa I I ow Gray Jay Black-capped Chickadee American Robin continued 388 Scientific Name Olor coluinbianus Olor buccinator Branta canadensis Branta nigricans Anas platyrhynchos Anas acuta Anas carol inensi~ Bucephala clangula Bucephala islandica Bucephala albeola Mergus serrator Charadrius semiphalmatus Arenaria interpres Caldris pusi I Ius Caldris mauri Actitis macularia Lobipes lobatus Larus hyperboreus Larus argentatus Larus canus Sterna paradisaea Empidonax alnorum lridoprocne bicolor Tachycineta thalassina Riparia riparia Perisoreus canadensis Parus atricapi I Ius Turdus migratorius c c c c c c e G e c ) ' __; ) Table A-3. !Concluded! Common Name Gray-cheeked Thrush Yellow Wagtai I Orange-crowned Warbler Yellow Warbler Yel low-rumped Warbler Northern Waterthrush Wi I son's Warbler Common Redpo I I Dark-eyed Junco Tree Sparrow White-crowned Sparrow Fox Sparrow 389 Scientific Name Catharus minima Motaci lla flava Vermivora celata Dendroica petechia Dendroica coronata Seiurus noveboracensis Wi !sonia pusi I Ia Acanthis flammea Junco hyema I is Sp i ze I I a arborea Zonotrichia leucophrys Passerel Ia iliaca I.J.I I() 0 Table A-4. Fish Species Reported and Caught or Observed in Major Geographical Areas Represented by the Twenty-Five Sites Seward Peninsula Common and scientific namesa Arctic lamprey Lamptera japonica Arctic cisco Coregonus autumnal is Bering cisco C. I aurettae Broad-whitefish C. nasus Humpback whitefish · ~· pidschian Least cisco · C. sardinella Round-whitefish Historical b record + + + + Prosopium cylindraceum + lnconnu Stenodus leucichthys Pink salmon Oncorhynchus gorbuscha + Chum salmon 0. keta + Coho salmon 0. kisutch Sockeye salmon 0. nerka Chinook salmon 0. tshawytscha Arctic char Salve I inus alpinus Lake trout S. namaycush 0 + + + + Present c study 2,5 2,5 4,5,6 5 1,2,3,4,5,6 North Slope Historical Present record study + + + + + + + II + + 9 + + 11,12,13,14 + Continued t:} Northern Interior Historical Present record study + + + + + + I 5, I 6 , I 7 , I 8 , 20 + 17 + 18 + + I 7 , I 8 , I 9 , 20 + 15 + n Southern Interior Historical Present record study + + 23 + + 24 + 24 + + + 24 + + 23 + + "' \0 Table A-4. !Concluded) Seward Peninsula North Slope Northern Interior Historical Present Southern Interior Historical Present Common and scientific namesa Historical reportb Present studl Historical Present record study record study record study Arctic grayling Thymal Ius arcticus Pond smelt Hypomesus ol idus Rainbow smelt Osmerus mordax A I ask iibTiiCi< f~ Dal I ia pectoral is Northern pike Esox lucius Lake Chuii --- Couesius plumbeus Longnose sucker Catostomus catostomus Bur bot Lota Iota Ninespine stTCkleback Pungitlus pungitius Slimy sculpin + 1,2,6 + + + + 5 + + + + + + + + 4,5 + 8,9, 10,11 12,13,14 7 ,9,13 + + + + 15,16, 17,18, 19,20 20 17,18 17,18 19,20 + 21,22 + + 21,24 + 24 + 23,24 + 24 ~ cognatus + 2,3,4,5,6 + 9, II, 12 + 15,16, 17,18, 19,20 + 22 Fourhorn sculpin Myoxocephalus quadr i corn is No. of species reported No. of species captured + 20 8 ~Common and scientific names from Bailey et cPrimari ly from McPhai I and Lindsey I 19701, Numbers refer to rivers as I isted: I = Gold Run Ck 6 = Nome R 2 = Slnuk R 7 = Ugnuravlk R 3 =Washington Ck 8 = Aufeis Ck 4 Oregon Ck 9 = Kuparuk R 5 = Penny R 10 = Skeetercake Ck d Possible lamprey obs~rved at upper pit. + 7 21 17 19 7 II II lor 121 al. 119701. Morrow I 19741, and Alaska Department of Fish and Game 119781. I I Sagavanirktok R 12 Ivishak R 13 Shaviovik R 14 = Kavik R 15 = Dietrich R-US 16 = Dietrich R-DS 17 = M F Koyukuk R-US 18 = M F Koyukuk R-DS 19=JimR 20 = Prospect Ck 21 = W F Tolovana R 22 23 24 = = McManus Ck Tanana R-DS Tanana R-US 25 = Phelan Ck I..._} Table A-5. Aquatic Macroinvertebrates Caught at Study Sites During 1976-1978 Field Sampling Taxon Common name Nematoda round worms 0 I i gochaeta earthworms Plecoptera stonef I i es A I I oper I a Arcynopteryx Capnia Diura Hastaperla lsogenus lsoperla Nemoura Paraper I a Ephemeroptera mayf I i es Ameletus Baetinae Caenis Cal! ibaetis Centropt i I urn Cinygmula Epeorus Ephemere I I a Heptagenia Rhithrogena Siphlonurus Odonata dragonf I i es and damse I f I i es En a I I agma lschnura L i be I I u I i dae Trichoptera caddisflies Apatania Arctopsyche Brachycentrus Ecc I i somy i a Glossosoma Homophylax Hydatophylax Lepidostoma Leptoce I I a L imneph i I us Continued 392 c c c c r, ~ c G e c c ) Table A-5. !Concluded! Taxon Common name '"'· J Oecet is Onocosmoecus Phryganea Platycentropus Polycentropus " Pseudostenophylax J Psychoglypha Rhyacoph i I a Hemiptera water bugs Corixidae waterboatman Coleoptera beetles Dytiscidae diving beetle ""'), Ha I i pI i dae J Diptera f I i es Atherlcidae Ceratopogonidae biting midge Chironomidae midge Ephididae J Empididae Psychodidae S i mu I i i dae blackfly Tipulidae crane f I y Hydracarina mites Mo I I usc a mo II uses Lymnaea sna i I ;;; Physidae sna i I Pisidium fingernai I clam Planorbidae sna i I Valvata snai I Amphipoda amphipods Gammaridae 393 ) ) J APPENDIX B GLOSSARY abandoned channel --A channel that was once an active or high-~ater chan- nel, but currently flows only during infrequent floods. active channe I --A channe I that contains f I owing water during the ice-free season. active floodplain--The portion of a floodplain that is flooded frequently; it contains flowing channels, high-water channels, and adjacent bars, usually containing I ittle or no vegetation. aesthetics--An enjoyable sensation or a pleasurable state of mind, which has been instigated by the stimulus of an outside object, or it may be viewed as including action which will achieve the state of mind de- sired. This concept has a basic psychological element of individual learned response and a basic social element of conditioned social atti- tudes. Also, there can be ecological conditioning experience because the physical environment also affects the learning process of attitudes. algae--Primitive plants, one or many-eel led, usually aquatic and capable of elaborating the foodstuffs by photosynthesis. aliquot A portion of a gravel removal area that is worked independently, often sequentially, from the other portions of the area. alI uvial river--A river which has formed its channel by the process of aggradation, and the sediment by which it carries (except for the wash load) is similar to that in the bed. arctic--The north polar region bounded on the south by the boreal forest. armor layer --A layer of sediment that is coarse relative to the material underlying it and is erosion resistant to frequently occurring floods; it may form naturally by the erosion of finer sediment, leaving coarser sediment in place or it may be placed by man to prevent erosion. aufeis --An ice feature that is formed by water overflowing onto a surface, such as river ice or gravel deposits, and freezing, with subsequent layers formed by water overflowing onto the ice surface itself and freezing. 395 backwater analysis--A hydraulic analysis, the purpose of which is to compute the water surface profile in a reach of channel with varying bed slope or cross-sectional shape, or both. bank--A comparatively steep side of a channel or floodplain formed by an erosion a I process; its top is often vegetated. bank-ful I discharge--Discharge corresponding to the stage at which the overflow plain begins to be flooded. bar--An alluvial deposit or bank of sand, gravel, or other material, at the mouth of a stream or at any point in the stream flow. c c c beaded stream--A smal I stream containing a series of deep pools intercon-C nected by very smal I channels, located in areas underlain by permafrost. bed --The bottom of a watercourse. bed load Sand, si It, gravel or soi I and rock detritus carried by a stream on, or immediately above its bed. bed load material --That part of the sediment load of a s}ream which is composed of particle sizes found in appreciable quantities in the shift- ing portions of the stream bed. bed, movable --A stream bed made up of materi~ls readily transportable by the stream flow. bed, stream--The bottom of a stream below the low summer flow. braided river --A river containing two or more interconnecting channels separated by unvegetated gravel bars, sparsely vegetated islands, and, c occasionally, heavily vegetated islands. Its floodplain is typically G wide and sparsely vegetated, and contains numerous high-water channels. The lateral stabi I ity of these systems is quite low within the boun- daries of the active floodplain. carrying capacity, biological --The maximum average number of a given organ- ism that can be maintained indefinitely, by the habitat, under a given regime (in this case, flow). e carrying capacity, discharge--The maximum rate of flow that a channel is capable of .passing. channel --A natural or artificial waterway of perceptible extent which periodically or continuously contains moving water. It has a definite bed and banks which serve to confine the water. configuration --The pattern of a river channel (sl as it would appear by looking vertically down at the water. contour --A I ine of equal elevation above a specified datum. 396 c c l J ) ) cover, bank--Areas associated with or adjacent to a stream or river that provide resting shelter and protection from predators-e.g., undercut banks, overhanging vegetation, accumulated debris, and others. cover, fish A more specific type of instream cover, e.g., pools, boulders, water depths, surface turbulence, and others. cover, instream --Areas of shelter in a stream channel that provide aquatic organisms protection from predators or a place in which to rest, or both, and conserve energy due ·to a reduction in the force of the cur- rent. cross section area--The area of a stream, channel, or waterway opening, usually taken perpendicular to the stream centerline. current--The flowing of water, or other fluid. That portion of a stream of water which is moving with a velocity much greater than the average or in which the progress of the water is principally concentrated (not to be confused with a unit of measure, see velocity). datum--Any numerical or geometrical quantity or set of such quantities which may serve as a reference or base for other quantities. An agreed standard point or plane of stated elevation, noted by permanent bench marks on some solid immovable structure; from which elevations are meas- ured, or to which they are referred. dewater --The draining or removal of water from an enclosure or channel. discharge--The rate of flow, or volume of water flowing in a given stream at a given place and within a given period of time, expressed as cu ft per sec. drainage area --The entire area drained by a river or system of connecting streams such that alI stream flow originating in the area is discharged through a single outlet. dredge --Any method of removing gravel from active channels. drift, invertebrate --The aquatic or terrestr i a I invertebrates which have been released from (behavioral driftl, or have been swept from (catas- trophic drift) the substrate, or have fallen into the stream and move or float with the current. duration curve--A curve which expresses the relation of alI the units of some item such as head and flow, arranged in order of magnitude along the ordinate, and time, frequently expressed in percentage, along the abscissa; a graphical representation of the number of times given quantities are equaled or exceeded during a certain period of record. erosion, stream bed--The scouring of material from the water channel and the cutting of the banks by running water. The cutting of the banks is also known as stream bank erosion. 397 fines--The finer grained particles of a mass of soi I, sand, or gravel. The material, in hydraulic sluicing, that settles last to the bottom of a mass of water. flood--Any flow which exceeds the bank-ful I capacity of a stream or chan- nel and flows out on the floodplain; greater than bank-ful I discharge. floodplain--The relatively level land composed of primarily unconsolidated river deposits that is located adjacent to a river and is subject to flooding; it contains an active floodplain and sometimes contains an inactive floodplain or terrace!sl, or both. flood probability--The probabi I ity of a flood of a given size being equaled or exceeded in a given period; a probability of I percent would be a 100-year flood, a probability of 10 percent would be a 10-year flood. flow--The movement of a stream of water or other mobile substances, or both, from place to place; discharge; total quantity carried by a stream. flow, base--That portion of the stream discharge which is derived from natural storage-i.e., groundwater outflow and the draining of large lakes and swamps or other sources outside the net rainfal I which creates the surface runoff; discharge sustained in a stream channel, not a result of direct runoff and withou~ the effects of regulation, diversion, or other works of man. Also cal led sustaining flow. flow, laminar--That type of flow in a stream of water in which each par- ticle moves in a direction para! lei to every other particle. flow, low--The lowest discharge recorded over a specified period of time. flow, low summer--The lowest flow during a typical open-water season. flow, uniform--A flow in which the velocities are the same in both magni- tude and direction from point to point. Uniform flow is possible only in a channel of constant cross section. flow, varied--Flow occurring in streams having a variable cross section or slope. When the discharge is constant, the velocity changes with each change of cross section and slope. fork length--The length of a fish measured from the tip of the nose to the fork in the tai I. freeze front A surface that may be stationary, which has a temperature of 0°C and is warmer on one side of the surface and colder on the other. frequency curve--A curve of the frequency of occurrence of specific events. The event that occurs most frequently is termed the mode. 398 c c c c c c c e G c ) 1 J ) ) ) ' J gage --A device for indicating or registering magnitude or position in spe- cific units, e.g., the elevation of a water surface or the velocity of flowing water. A staff graduated to indicate the elevation of a water surface. geomorphology --The study of th& form and development of landscape fea- tures. habitat--The place where a population of animals lives and its sur- roundings, both living and nonliving; includes the provision of life requirements such as food and shelter. high-water channel --A channel that is dry most of the ice-free season, but contains flowing water during floods. hydraulics--The science dealing with the mechanical properties of fluids and their application to engineering; river hydraulics deals with mechanics of the conveyance of water in a natural watercourse. hydrau I i c depth --The average depth of water in a stream channe I. It is equal to the cross-sectional area divided by the surface width. hydraulic geometry--Those measures of channel configuration, including depth, width, velocity, discharge, slope, and others. hydraulic radius--The cross-sectional area of a stream of water divided by the length of that part of its periphery in contact with its contain- ing channel; the ratio of area to wetted perimeter. hydrograph --A graph showing, for a given point on a stream, the discharge, stage, velocity, or another property of water with respect to time. hydrology--The study of the origin, distribution, and properties of water on or near the surface of the earth. ice-rich material --Permafrost material with a high water content in the form of ice, often taking the shape of a vertical wedge or a horizontal lens. impervious--A term applied to a material through which water cannot pass or through which water passes with great difficulty. inactive floodplain--The portion of a floodplain that is flooded infre- quently; it may contain high-water and abandoned channels and is usually lightly to heavily vegetated. island --A heavily vegetated sediment deposit located between two channels. large river--A river with a drainage area greater than 1,000 km 2 and a mean annual flow channel top width greater than 100m. lateral bar --An unvegetated or I ightly vegetated sediment deposit located adjacent to a channel that is not associated with a meander. 399 Manning's equation --In current usage, an empirical formula for the calcula- tion of discharge in a channel. The formula is usually written Q = 1.49 R 2/3 5 112 A. n mean flow--The average discharge at a given stream location computed for the period of record by dividing the total volume of flow by the number of days, months, or years in the specified period. mean water velocity--The average velocity of water in a stream channel, which is equal to the discharge in cubic feet per second divided by the cross-sectional area in square feet. For a specific point location, it is the velocity measured at 0.6 of the depth of the average of the velocities as measured at 0.2 and 0.8 of the depth. meander wave length --The average downval ley distance of two meanders. meandering river--A river winding back and forth within the floodplain. The meandering channel shifts downval ley by a regular pattern of ero- sion and deposition. Few islands are found in this type of river and gravel deosits typically are found on the point bars at the insides of meanders. medium river --A ~iver with a drainage area greater than 100 km 2 but less than 1,000 km and a mean annual flow channel top width greater than 15 m but less than 100 m. microhabitat--Localized and more specialized areas within a community or habitat type, utilized by organisms for specific purposes or events, or both. Expresses the more specific and functional aspects of habitat and cover that allows the effective use of larger areas (aquatic and ter- restrial l in maximizing the productive capacity of the habitat. (See cover types, habitat). mid-channel bar --An unvegetated or I ightly vegetated sediment deposit lo- cated between two channels. parameter --A variable in a mathematical function which, for each of its particular values, defines other variables in the function. permafrost --Perennially frozen ground. pit excavation--A method of removing gravel, frequently from below over- burden, in a manner that results in a permanently flooded area. Gravels are usually extracted using draglines or backhoes. point bar An unvegetated sediment deposit located adjacent to the inside edge of a channel in a meander bend. pool --A body of water or portion of a stream that is deep and quiet rela- tive to the main current. 400 c c c c c c e G ) ) ) pool, plunge--A pool, basin, or hole scoured out by fal I ing water at the base of a waterfall. profile--In open channel hydraulics, it is the water or bed surface ele- vation graphed aganist channel distance. reach--A comparatively short length of a stream, channel, or shore. regional analysis--A hydrologic analysis, the purpose of which is to esti- mate hydrologic. parameters of a river by use of measured values of the same parameters at other rivers within a selected region. riffle--A shallow rapids in an open stream, where the water surface is broken into waves by obstructions wholly or partly submerged. riparian --Pertaining to anything connected with or adjacent to the banks of a stream or other body of water. riparian vegetation--Vegetation bordering floodplains and occurring within floodplains. riprap-Large sediments or angular rock used as an artificial armor layer. river regime--A state of equilibrium attained by a river in response to the average water and sediment !oads it receives. run--A stretch of relatively deep fast flowing water, with the surface essentially nonturbulent. scour --The removal of sediments by running water, usually associated with removal from the channel bed or floodplain surface. scrape -A method of remov~ng floodplain gravels from surface deposits using tractors or scrapers. sediment discharge--The volumetric rate of sediment transfer past a spe- cific river cross section. sinuous river--Sinuous channels are similar to meandering channels with a less pronounced winding pattern. The channel may contain smaller point bars and have less tendency for downval ley shifting. The channels are more stable with respect to lateral shifting. sinuousity --A measure of the amount of winding of a river within its flood- plain; expressed as a ratio of· the river channel length to the corres- ponding valley length. slope --The inclination or gradient from the horizontal of a I ine or sur- face. The degree of inclination is usually expressed as a ratio, such as I :25, indicating one unit rise in 25 units of horizontal distance. 401 2 smal I river -A river with a drainage area less than 100 km and a mean annual flow channel top width of less than 15m. split river--A river having numerous islands dividing the flow into two channels. The islands and banks are usually heavi ~y vegetated and stable. The channels tend to be narrower and deeper and the floodplain narrower than for a braided system. stage--The elevation of a water surface above or below an established datum or reference. standing crop --The abundance or total weight of organisms existing in an area at a given time. straight river --The thalweg of a straight river typically winds back and forth within the channel. Gravel bars form opposite where the thalweg approaches the side of the channel. These gravel bars may not be ex- posed during low flow. Banks of straight systems typically are stable and floodplains are usually narrow. These river systems are considered to be an unusual configuration in transition to some other configura- tion. subarctic The boreal forest region. suspended load--The portion of stream load moving in suspension and made up of particles having such density of grain size as to permit movement far above and for a long distance out of contact with the stream bed. The particles are held in suspension by the upward components of turbu- lent currents or by colloidal suspension. tal ik --A zone of unfrozen material within an area of permafrost. terrace--An abandoned floodplain formed as a result of stream degradation and that is expected to be inundated only by infrequent flood events. thalweg--The I ine following the lowest part of a valley, whether under water or not; also usually the line following the deepest part or middle of the bed or channel of a river or stream. thermokarst Landforms that appear as depressions in the ground surface or cavities beneath the ground surface which result from the thaw of ice-rich permafrost material. top width--The width of the effective area of flow across a stream chan- ne I. velocity --The time rate of motion; the distance traveled divided by the time required to travel that distance. wash load--In a stream system, the relatively fine material in near-perman- ent suspension, which is transported entirely through the system, without deposition. That part 9f the sediment load of a stream which is composed of particle sizes smaller than those found in appreciable quantities in the shifting portions of the stream bed. 402 c c c c c c G e c c ) ) ) water quality--A term used to describe the chemical, physical, and biolog- ical characteristics of water in reference to its suitabi I ity for a particular use. wetted perimeter --The length of the wetted contact between the stream of flowing water and its containing channel, measured in a plane at right angles to the direction of flow. wildlife--AI I living things that are neither human nor domesticated; most often restricted to wildlife species other than fish and invertebrates. 403 50272-101 REeORT-DOC.UMENTATIO.N.. l_l· REPORT NO. PAUf" r FWS/OBS-80/08 4. Title and Subtitle GRAVEL REMOVAL STUDIES I_ N ARCTIC AND SUBARCTIC FLOODPLAINS IN ALASKA -TECHNICAL REPORT 7. Author(s) WOODWARD-CLYDE CONSULTANTS 9. Performing Organization Name and Address Woodward-Clyde Consultants 4971 Business Park Blvd., Suite 11 Anchorage, Alaska 99503 12. Sponsoring Organization Name and Address u.S. Fish and Wildlife Service 1011 East Tudor Road 3. Recipient's Accession No. 5. Report Date June 1980, Pub. date 6. 8. Performing Organization Rept. No. 10. Project/Task/Work Unit No. 11. Contract(C) or Grant(G) No. cc> FWS 14-16-0008-970 (G) 13. Type of Report & Period Covered Final Report 1975 -1980 ) Anchorage, Alaska 99503 14. ) 15. Supplementary Notes This report is part of Interagency Energy -Environment Research and Development Program of the Office of Research and Development, u.s. Environmental Protection Agency -1&. Abstract (Limit: 200 words) A 5-year investigation of the effects of floodplain gravel mining on the physical and biological characteristics of river systems in arctic and subarctic Alaska I is described. Twenty-five sites were studied within four geographic regions. The 1 sites were selected such-that within each of the regions the group of sites exhibited a wide range of river and mining characteristics. The field data collection program covered the major disciplines of hydrology/hydraulics, aquatic biology, water quality, and terrestrial biology. In addition, geotechnical engineering, and aesthe- tics site reviews were conducted. A wide range of magnitude and type of physical and biological changes were observed in response to mining activity. Little change was observed at some sites, whereas other sites exhibited changes in channel morphology, hydraulics, sedimentation, ice regime, aquatic habitat, water quality, benthic macroinvertebrates, fish utilization~ vegetation, soil characteristics, and bird and mammal usage. Two major products of the project are a Technical Report which synthesizes and evaluates the data collected at the sites, and a Guidelines Manual that aids the user in developing plans and operating material sites to minimize environmental effects. :J 17. -Document Analysis a. Descriptors J J Gravel Removal, Alaska, Arctic, Subarctic, Floodplains, Streams, Scraping, Pit Excavation, Environmental Impacts, Hydrology-Hydraulics, Aquatic Biology, Terrestrial Ecology, Water Quality, Aesthetics, Geotechnical Engineering, Site Selection, Site Design. b. Identifiers/Open-Ended Terms c. COSATI Field/Group 18. Availability Statement Release unlimited (See ANSI-Z39.18) 19. Security Class (This Report) Unclassified 20. Security Class (This Page) Unclassified See Instructions on Reverse 21. No. of Pages 403 22. Price OPTIONAL FORM 272 (4-77) (Formerly NTIS-35) Department of Commerce *U.S. GOVERNMENT PRINTING OFFICE: 1981>-699-277 REGIONAL OFFICE BIOLOGICAL SERVICES TEAMS Region 1 Team Leader U.S. Fish and Wildlife Service Lloyd 500 Building, Suite 1692 500 N.E. Multnomah Street Portland, Oregon 97232 FTS: 429-6154 COMM: (503) 231-6154 Region2 Team Leader U.S. Fish and Wildlife Service P.O. Box 1306 Albuquerque, New Mexico 87103 FTS: 474-2971 COMM: (505) 766·1914 Reglon3 Team Leader U.S. Fish and Wildlife Service Federal Building, Fort Snelling Twin Cities, Minnesota55111 FTS: 725-3593 COMM: (612) 725·3510 Region4 Team Leader U.S. Fish and Wildlife Service 17 Executive Park Drive, N.W. P.O. Box 95067 Atlanta, Georgia 30347 FTS: 257-4457 COMM: (404)881-4457 Region5 Team Leader U.S. Fish and Wildlife Service One Gateway Center Suite700 Newton Corner, Massachusetts 02158 FTS: 829-9217 COMM: (617)965-5100, Ext. 217 Region6 Team Leader U.S. Fish and Wildlife Service P.O. Box 25486 Denver Federal Center Denver, Colorado 80225 FTS: 234·5586 COMM: (303) 234·5586 Alaska Area Office Team Leader U.S. Fish and Wildlife Service 1011 E. Tudor Road Anchorage, Alaska 99503 FTS: 399.0150 ask for COMM: (907) 276-3800