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HomeMy WebLinkAboutAPA1243TK 1425 .S8 A23 no.l243 SUSITNA HYDROELECTRIC P::IOJECT RIVER MORPHOLaGV JANUARY 1982 "EPARED BY I PREPARED FOR• . __ AL ASKA POWER AUTHORITY __ ____, -.. ,~ .. ~1i~W'~t51t:\[t:;~~~~~:~,~.;-:-<'\:~1;;~: ., ~,---\\ ~~ ... ,-~-~. '~I -~-:-·--~----··..,:_. ................ ~----~-............. n .... .:-t. r,:._-___ :~--· __ > ·:·---~~---·--· __ ·,~~---·----~·-· --~--·-{:·::::;~1jJ~-~~h-· .. ~~~~· ,L:I' -. . . . . -....... ~, . .. . _.._.__~-. ~. -. --------~--------------~~~------------.__........_.... ' i I ,! I ;I I ·~ I > .. .-- I I IJ I ll . 1 E J r: ' •J J f '. ' 'l li ~~ l:' .. J j [ ., 1: • .. .}.;;/ I" ~.:.11 [}{J£rffi~& c ~liD&®©© Susitna Joint Venture Document Number 3) Please Return To DOCUMENT CONTROL SUSITNA HYDROELECTRIC PROJECT RIVER MO~PHOLOGY JANUARY 1982 PREPARED BY I PREPARED FOR• R&M CONSULTANTS, INC. I L~.---_ALASKA POWER AUTHORITY __ , .. ____. ! L t I I ) l l i I I l I I ~ ' ..... - .~ - L - - ~TK -/L(:J5 ,58 .t'td3 Y} C) (;;lf{ 3 ALASKA POWER AUTHORITY • ARI_.~IS SUSITNA HYDROELECTRIC PROJECT TASK 3 -HYDROLOGY RIVER MORPHOLOGY JANUARY 1982 Prepared for: . ACRES AMERICAN INCORPORATED 1000 Liberty Bank Building Main at Court Buffalo, New York 14202 Telephone (716) 853-7525 Prepared by: S. B redthauer & B. Drage R&M CONSULTANTS, INC. P. 0. Box 6087 5024 Cordova Street Anchorage, Alaska 99503 Telephone (907) 279-0483 Al.ask<l Rc:WiHc~s Library & ird'r;Trnanon S(;rv1ces A.nchorag.c. ,,.. ; a.s.tta "'"" - ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT TASK 3 -HYDROLOGY RIVER MORPHOLOGY TABLE OF CONTENTS LIST OF FIGURES LJS1r OF TABLES 1 -INTRODUCTION 1.1 - 1 .2 - 1.3 Background and Purpose of Study Downstream Effects Report Contents 2 -SUMMARY 2. 1 -Basin Overview 2. 2 -Projected Post Project Morphological Changes on the Oownstream River 3 -FLOW REGIME 3.1 - 3.2 - 3.3 - 3.4 - Flow Duration Analysis (Pre-Project Conditions) Post-Project Flows Contribution by Tributaries . Flow Variability index 4 -SEDiMENT REGIME 4.1 - 4.2 - 4.3 - 4.4 - 4.5 - Suspended Sediment Bedload Reservoir Trap Efficiency Bed Material Movement Contribution of Sediment Downstream AR ... ~ ... J.•.·s "' . -·ll' A.l. asic;~ Res(1Jirces Library & lnHi•.,.,...:,1··o·.r· ,:, . ''""'L , )ervtces At1dlll:'J'fage. Alaska iii vii 1-1 1-1 1-1 1-3 2-1 2-1 2-3 3-1 3-1 3-2 3-4 4-1 4-1 4-1 4-2 4-3 4-5 5 -REGIME ANALYSIS 5.1 -River Response Relationships 5.2 -River Pattern and Channel Characteristics System 5. 3 Regime Analysis of Susitna River Reaches 6 -SIDE CHANNELS AND SLOUGHS 6.1 -Present and Projected Flow Regime 6.2 -Expected Changes 7 -ICE PROCESSES 7.1 -Pre-Project Ice Conditions 7. 2 -Post-Project Ice Conditions BIBLIOGRAPHY ATTACHMENT A -RATING TABLES ATTACHMENT B -FLOW VARIABILITY RATIOS ATTACHMENT C -WATER SURFACE ELEVATIONS -jj - Page 5-1 5-1 of Natural 5-2 5-4 6-1 6-1 6-1 .~' 7-1 7-1 7-3 - - ,--·~ - -' - ----- Figure No. 2.1 2.2 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3 .. 8 3 .. 9 3 .. 10 3.11 3.12 3.13 LIST OF FIGURES Title Susitna River basin Susitna River cross-section locations Flow duration curves -Susitna River at Denali, Cantwell, Gold Creek Flow duration curves -Maclaren River Flow duration curves -Chulitna and Talkeetna Rivers Flow duration curve -Susitna River at Susitna Station Pre-and post-project flow duration curves, Susitna River at Gold Creek Pre-and post-project flow duration curves, Susitna River at Sunshine Pre-and post-project flow duration curves, Susitna River at Susitna Station Annual flow duration curves at Susi,tna-Chulitna- Talkeetna confluence Pre-and post-project discharge-stage frequency curves, Susitna River at Gold Creek Pre-and post-project discharge-stage frequency curves, Susitna River at Sunshine Pre-and post-project discharge-stage frequency curves, Susitna River at Delta Islands Pre-and post-project discharge-stage frequency curves, Susitna River at Susitna Station Design dimensionless regional frequency curve annual instantaneous flood peaks -iii - 2-7 2-8 3-26 3-27 3-28 3-29 3-30 3-31 3-32 3-33 3-34 3-35 3-36 3-37 3-38 LIST OF FIGURES -(Continued) Figure No. 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 5.1 5.2 Title Suspended sediment rating curves -Susitna River at Denali and MacLaren River near Paxson Suspended sediment rating curve-Susitna River near Cantwell (Vee Canyon) Suspenged sediment rating curve-Susitna River at Gold Creek Suspended sediment rating curves, Chulitna and Talkeetna Rivers Suspended sediment rating curve, Susitna River at Susitna Station Annual suspended sediment load duration curves Estimated bedload rating curve, Susitna River at Denali Bed material movement curves, LRX-54, -57, -62, -68 Bed material movement curves, LRX -43, -45, -49, -so, -s1 Bed material movement curves, LRX -36, -38, -39, -40 Bed material movement curves, LRX -28, -29, -31 1 -35 Bed material movement curves, LRX -16, -18, -20, -24 Bed material movement curves, LRX -4, -7, -9, -12 Single-channel river pattern Split channel river pattern -iv - 4-19 4-20 4-21 4-22 4-23 4-24 4-25 4-26 4-27 4-28 4-29 4-30 4-31 5-22 5-23 -· - - - - -- LIST OF FIGURES -(Continued) 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 5.19 51.20 51.21 Title Braided channel river pattern Multi-channel river pattern River profiles, Susitna River and tributaries above Sunshine River profiles, Susitna River and tributaries below Sunshine Susitna River reach RM 149 to RM 144 Cross-section, RM 148.7 Susitna River reach RM 144 to RM 139 Cross-section, RM 141.5 Susitna River reach RM 139 to RM 129.5 Cross-section, RM 134.7 Susitna River reach RM 129.5 to RM 119 Cross-section, RM 121.6 Susitna River reach RM 119 to RM 104 Cross-section, RM 108.4 Susitna River reach RM 104 to RM 95 Cross-section, RM 101.5 1951-1980 aerial photo comparison, Susitna- Chulitna-Tal keetna confluence Susitna River reach RM 95 to RM 61 Susitna River reach RM 61 to RM 42 - v - 5-24 5-25 5-26 5-27 5-28 5-29 5-30 5-31 5-32 5-33 5-34 5-35 5-36 5-37 5-38 5-39 5-40 5-41 5-42 ~ .. ' LIST OF FIGURES -(Continued) ., Figure No. Title Page )i -\ 5.22 Synthesized cross-section, Delta Islands 5-43 . i' 5.23 1951-1980 aerial photo comparison, Susitna-Oesh ka confluence 5-44 5.24 1951-1980 aerial photo comparison, Susitna-Yentna confluence 5-45 6.1 Susitna River overflow channels 6-6 ~· - - - - vi - - .... - Table No. 3 .. 1 3 .. 2 3 .. 3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3:.15 LIST OF TABLES Title Period of record 1 Susitna streamgaging stations Susitna River at Gold Creek, pre-project monthly flows Susitna River at Sunshine, pre-project monthly flows Susitna River at Susitna Station 1 pre-project monthly flows Susitna River at Gold Creek, post-project monthly flows (Case A) Susitna River at Sunshine, post-project monthly flows (Case A) Susitna River at Susitna Station, post-project monthly flows (Case A) Susitna River at Gold Creek 1 post-project monthly flows (Case D) Susitna River at Sunshine, post-project monthly flows (Case D) Susitna River at Susitna Station, post-project monthly flows (Case D) Relative contribution of flows at Susitna-Chulitna- Talkeetna confluence (pre-project) Relative contribution of flows at Susitna-Chulitna- Talkeetna confluence (post-project, Case A) Relative contribution of flows at Susitna-Chulitna- Talkeetna confluence (post-project, Case D) Pre-and post-project discharge· and stage frequency analysis Lower Susitna River basin characteristics for mean annaul flood calculations -vii - 3-6 3-7 3-8 3-9 3-10 3-11 3-12 3-13 3-14 3-15 3-16 3-17 3-18 3-19 3-20 LIST OF TABLE -(Continued) Table No. 3.16 3.17 3.18 3.19 3.20 3.21 4.1 4.2 4.3 4.4 4.5 4.6 5.1 6.1 6.2 6.3 7.1 7.2 Title Monthly average ratios, (1-day high and low flow)/ (monthly flow) Monthly average ratios, (3-day high and low flow)/ (monthly flow) Monthly average ratios (7-day high and low flow)/ (monthly flow) Monthly average ratios, (15-day high and 14-day low flow)/(monthly flow) Ratios of annual 1-, 3-, 7-, 14-, 30-, 60-and 90-day low flows to annual low monthly flows Average monthly spill below Devil Canyon Dam Suspended sediment rating equations Bedload transport data, 1981 Bed material size distribution analysis Average velocities at selected cross-sections Susitna River profile data summary Sediment sources downstream of Devil Canyon Susitna River reach definitions Location of blocked and partially-blocked side-channels Water surface elevations in multiple channels at low flow (below 10,000 cfs) Water surface elevations in multiple channels at 22,200 cfs Locations of ice accumulations during freezeup -1980 Ice jam locations during breakup, May, 1981 -viii - 3-21 3-22 3-23 3-24 3-25 3-26 4-6 4-7 4-8 4-9 4-10 4-13 5-21 6-3 6-4 6-5 7-4 7-5 ·· .. !j Mlj• -. .... .... i - ..... 1 -INTRODUCTION 1.1 Background and Purpose Construction of dams at Watana and Devil Canyon will effect the river morphology downstream of Devil Canyon 1 with possible effects on fisheries, vegetation, and wildlife. The possible effects of dams on river morphology are described below. The purpose of this report is to describe the existing flow, sediment and river regimes from Devil Canyon to the mouth of the Susitna River, and · to assess potential morphological changes in the river. 1 . 2 Downstream Effects of Dams The construction of dams on a river system modifies both the natural flow regime and the natural sediment transport regime, thus impacting the r1ver processes downstream of the dams. Before discussing the impacts on the river morphology of the Susitna River downstream of Devil Canyon, a summary of impacts downstream of similar projects is worthwhile. Kellerhals and Gill (1973), Petts (1977), Taylor (1978) and Baxter and Glaude (1980) have summarized channel response to flow regulation. Operation of reservoirs significantly alters the flow regime. There is often an increase in the diurnal variation of flow due to the variation in the amount of water passing the turbines in order to follow the toad demand. Annual peak discharges are reduced not only due to storage. which allows no overflow over the spillway, but also due to the surcharge storage provided by the rise in water level above the spillway crest. Routing through a reservoir with no available storage may reduce some flood peaks by over SO% (Moore, 1969) 1 depending on the characteristics of the spillway, reservoir, and flood hydrograph. , The magnitude of the mean annual flood of the Colorado River below Hoover Dam has been reduced by 60% (Dolan, Howard, and GaJienson, 1974). The total· volume of flow may be reduced due to the increase in time during which seepage and evaporation losses may occur. Base flow tends to be increased due to seepage and to minimum releases to the channel below the dam. Reservoirs with a large storage capacity may trap and store over 95% of the sediment load transported by the river (Leopold, Wolman, and Miller, 1964), with the actual percentage depending primarily on the storage capacity-inflow ratio (Brune, 1953), although reservoir shape, reservoir operation, and sediment characteristics have some influence (Gottschalk, 1964) . The effect of dams on the sediment load must not be considered in isolation but in relation to changes in river sediment transport capacity, to river regime, to channel morphometry, and with rS/a 1 - 1 regard to major tributaries. At tributaries which transport large quantities of sediment into a regulated mainstream with reduced flows and consequently less ability to flush away sediments, the effects include aggradation, an increase in bed slope of the tributary, and trenching of the deposit to form a channel that is in quasi-equilibrium with the flow regime (King, 1961; Kellerhals, Church and Davies, 1977). The increased gradient results in increased velocities, bank instability, possible major changes in the geomorphic character of the tributary stream, and increased local scour (Simons and Senturk, 1976). All of the bedload entering a reservoir is deposited in the reservoir. This reduction in sediment supply is usually greater than that in sediment-carrying capacity, resulting. in erosion downstream of the dam except where an armor layer or an outcrop of bedrock occurs (Petts, 1977). Degradation will occur where the regulated flow has sufficient tractive force to initiate sediment movement in the channel (Gottschalk, 1964). Once the channel bed has been stabilized, either by armoring or by the exposure of bedrock, then the banks, which usually consist of finer material than the bed, begin to fail and the channel will widen. Where armoring or bedrock occur across the width of the channel, a simple adjustment will occur where streamflow is accommodated in the existing channel. The sediment load plays an important role in the process of meander migration across alluvial plains by forming point bars from bed load deposition on the inside bank. These point bars are then aggraded to floodplain levels due to the deposition of suspended sediment in the emerging vegetation. The reduction in sediment load may disrupt this process, with at least local ecological changes. Widening of channels at meander bends and lateral instability may also be expected (Kellerhals and Gill, 1973}. Maximum degradation normally occurs in the tailwater of the dam, but may extend downstream. Rates of degradation up to 15 em per year have been observed both in the United States (Leopold, Wolman, and MiJier, 1964) and Europe (Shulits, 1934}. Channel adjustment to bed degradation and the associated reduction in slope was observed for nearly 250 km below Elephant Butte Dam (Stabler, 1925). When an armored condition occurs where the river is unable to recharge itself to capacity, the river may pick up additional material downstream, as was observed on the Colorado River below Hoover Dam (Stanley, 1951). The channel properties of gravel-bed rivers such as the main stem of the Peace River in Alberta appear to be controlled by floods with a recurrence interval of 1.5 to 2 years (Bray, 1972). Regulation reduces these flows, effectively reducing the size of the gravel-bed river without immediately changing the channel, but certain channel properties will adjust to the channel regime over a r5/a 1 - 2 -· - - ·-.I .,..., i ... ~ - longer period of time. On the Peace River, the entrenched layer of the channel, the proximity of bedrock, and the resistant bed material preclude significant changes in width and depth relationships or in the slope (except near tributary junctions), but deep scour holes at bends will fill to some degree, and gravel bars exposed above the new high water mark will have emerging vegetation ( Kellerhals and Gill, 1973). Vegetation encroachment on the higher elevations of the gravel bars downstream of a dam can be expected due to the reduced summer streamflows and the lower flood peaks, and in time could encroach on present high water channels (Tutt, 1979; Kellerhals, Church and Davies, 1977). The effect of the additional vegetation would be to increase the channel roughness, thus decreasing the channel water conveyance. The channel size and capacity could gradually decrease due to vegetation encroachment, deposition of suspended load in the newly vegetated areas, accumulation of material from the yalley walls and deposition of sediment brought in by the tributaries. During periods of high flow, higher river stages could be expected. The W.A.C. Bennett Dam on the Peace River had a dramatic unplanned impact on the Peace-Athabasca Delta (Baxter and Glaude, 1980). The delta is a series of marshes interspersed with lakes and ponds of various sizes. Before the dam was built, the delta was maintained in this state due to almost annual flooding, which prevented vegetation typical of drier ground from being able to establish itself. The hydrological situation itself was complex. The Peace River, passing to the north of the delta, contributed little to the actual flooding, but its flood waters blocked the exit of the Athabasca River, which entered from the south and caused the actual flooding. After construction of Bennett Dam, the delta started drying up, with dry-ground vegetation establishing itself. The effect of the dam was initially obscured due to lower than normal precipitation for some years previously, but it was eventually concluded that the dam was at least a contributing factor, as flood levels on the Peace River were lowered, resulting in the Peace River no longer blocking the exit of the Athabasca River. 1 . 3 Report Contents A relatively significant amount of data are available for the reach of river between Devil Canyon and Talkeetna. Over 30 years of streamflow and suspended sediment data are available for the Susitna River at Gold Creek. Aerial photography was flown in 1980, and blueline copies made at a scale of 1 11 = 500 1 • Cross-sections were surveyed at 66 sites from Devil Canyon to the Chulitna confluence. Bed material data were gathered at a number of cross-sections. Using crest gage data gathered in this reach, the HEC-2 water surface profile model was calibrated, and water rS/a 1 - 3 surface elevations estimated using results from the model. Ice conditions were observed during the 1980-81 winter and 1981 freeze-up. The available data' base is considerably smaller below Talkeetna. Streamflow, suspended sediment and water quality data have been gathered at the Susitna Station gaging site since 1975. Streamflow suspended sediment and bedload data were collected at Sunshine (Parks Highway Bridge) in 1981. Aerial photography is available at a scale of 1 11 = 500 1 • Cross-sections are available only at U.S. Geological Survey gaging sites and at miscellaneous sites or sloughs along the river. Ice conditions were observed during the 1980-81 and 1981-82 winters. This report compiles, presents and interprets all available information pertinent to assessing changes in the river morphology. The existing river patterns and controlling features are described from Devil Canyon to Cook Inlet. A qualitative assessment is also made to predict the response of the river to post-project conditions. r5/a 1 - 4 - - - - 2 -SUMMARY 2.1 -Basin Overview The Susitna River drainage basin is located in the Cook 1 nlet subregion of the southcentral region of Alaska. The drainage basin covers 19,600 square miles. It is bordered on the west and north by the Alaska Range, on the east by the Talkeetna Mountains and the Copper River lowland, and on the south by Cook Inlet. Climate The upper drainage basin is in the continental climatic zone, and the lower drainage basin is in the transitional climatic zone. Due to the maritime influence and the lower elevations, temperatures are more moderate and precipitation is less in the lower basin than that in the upper basin. In the higher regions, freeze-up starts in early October, and most rivers are ice-free in late April or early May. Topography Tributaries in the western and northern portions of the drainage basin rise in the glaciers of the Alaska Range, which is dominated by Mount McKinley (20,320 feet) and Mount Foraker. Other peaks average 7,000 to 9,000 feet in altitude. Those in the eastern portion rise in the Copper River lowland and in the Talkeetna Mountains. The highest peak is 8,850 feet, with elevations averaging 6,000 to 7,000 feet and decreasing northward and westward. To the northwest, the mountains form a broad, rolling glacially scoured upland dissected by deep glaciated valleys. Between these ranges and the Cook Inlet is the Susitna lowlands, a broad basin increasing in elevation from· sea level to 500 feet, with local relief of 50 to 250 feet. Geology The Susitna River basin derived its present geologic features during Quaternary glaciations. The underlying bedrock consists of granitic batholiths intruded into Paleozoic and Mesozoic volcanic and sedimentary rocks on the south side of the Alaska Range and in the Talkeetna Mountains. Copper, gold, silver, and other minerals are associated with the intrusions. The unconsolidated deposits of the lowlands, which contain· thaw lakes and marshes and are poorly drained, overlay Tertiary coal-bearing rocks resting on Mesozoic rocks 30,000 feet thick. Unconsolidated deposits are extensive and largely derived from glaciers. Glacial moraines and gravels fill glacial-carved U-shaped valleys in the upland areas. Glaciolacustrine deposits are present r31/b 2 - 1 in the lowlands. During the periods of glaciation, convergence of glacial flaw blocked drainage, and preglacial lakes formed. The deposits are laminated 1 rhythmically bedded sand, silt, and clay. Fluvial deposits are present in the major river valleys, and consist of gravels and sands. The drainage basin lies in the discontinuous permafrost zone. In the mountainous areas, discontinuous permafrost is generally present. t n the lowlands and upland areas below 3,000 feet, there are isolated masses of permafrost in areas of predominately fine-grained deposits. Permafrost does not exist in coarse-grained deposits or in deposits adjacent to the main stem river or large water bodies. Soils Gravelly till and outwash in the lowlands and on upland slopes are overlain by shallow to moderately deep silty soils. Windblown silt covers upland areas. Steeper upper slopes have shallow, gravelly and loamy deposits with many bedrock exposures. On the south flank of the Alaska Range and south-facing slopes of the Talkeetna Mountains, soils are well-drained, dark, and gravelly to loamy. Poorfy drained, gravelly and stony learns with permafrost are present on narthfacing slopes of foothills, moraines, and valley bottoms. Water erosion is moderate on low slopes and severe on steep slopes. Vegetation Vegetation above tree line in steep, rocky soiJs is predominately alpine tundra. Well-drained upland soils support white. spruce and grasses, whereas poorly drained valley bottom soils support muskeg. Tideflats are dominated by sedge meadows where drainage is poor, and are bordered by moist tundra grading into spruce-hardwood forests in well-drained loamy soils. Water Resources The Susitna River drainage basin is the sixth largest system in Alaska. The Susitna River is 320 miles long, and major tributaries include the Yentna, Chulitna, and Talkeetna Rivers. Extensive glaciers in the headwaters contribute substantial suspended sediment loads during summer months. Streamflow is characterized by high flows between May and September and tow flows from October to April. High summer discharges are caused by snowmelt, rainfall, and glacial melt. Tributaries are generally turbulent in the upper reaches and slower ·flowing in the lower reaches. On the western side of the basin is the Yentna River, with its tributaries the Skwentna River (entering on the southwest) and the Kahiltna River (entering an the northwest). The Yentna River r31/b 2 - 2 - - - - ~. - - - - - - - <; -j - - rises in the glaciers of the Alaska Range and flows 95 miles southeasterly, entering the Susitna River 28 miles from its mouth. The Chulitna River rises in the glaciers on the south slope of Mount McKinley and flows 90 miles south, entering the Susitna River near Talkeetna. The Talkeetna River rises in the Talkeetna Mountains, flows west, and also enters the Susitna River near Talkeetna, 97 miles from its mouth. The Susitna River and its major downstream tributaries are shown in Figure 2.1. Cross-section locations on the river between the Parks Highway and the proposed Watana Dam are illustrated in Figure 2.2. 2.2 Projected Post Project Morphological Changes on the Downstream River The following summarizes potential changes in the current river morphology that could be expected from flow and sediment regulation. The Susitna River main channel between Devil Canyon and the Chulitna River confluence will tend to become more defined with a narrower channel. The main channel river pattern will strive for a tighter, better defined meander pattern within the existing banks. A trend of channel width reduction by encroachment of vegetation and sediment deposition can be expected. This will tend to gradually increase flow depths at specific discharges above the immediate post-project condition. Downstream of the Susitna-Chulitna confluence the frequency of occurrence of dramatic changes in river morphology will decrease under post-project conditions, resulting in a more stabilized floodplain, decreased number of subchannels and increased vegetative cover. However, it must be recognized that an extreme flood generated by either the Chulitna River, Talkeetna River or both in combination with other tributaries could mask this process and delay observable changes for several years. The project morphological changes for specific river reaches are summarized below: RM 149 to RM 144 0 0 r31/b The channel is stable and little change in form is expected. Portage Creek fan will progress out into the Susitna until equilibrium with the regulated Susitna stage is established. Perching of the stream mouth is not expected. 2 - 3 RM 144 to RM 139 0 0 0 0 0 Erosion of valley walls and terraces will decrease dramatically due. to the armour layer. Reworking of alluvial deposits in the main channel will continue but at a reduced rate. Main channel form will progress slowly to a more uniform sinuous pattern. Subchannels may become inactive. Tributary at RM 144 could become perched. It may not be able to regrade its coarse bed sediments to meet the regulated Susitna water level. RM 139 to RM 129.5 0 0 0 0 0 0 Indian River will continue to extend its alluvial deposits into the Susitna. Indian River should easily grade its bed to meet the regulated Susitna Stage. Gold Creek gradient is presently very steep as it enters the Susitna. The cobble and boulder bed will resist regrading the bed to meet the regulated Susitna stage. Fourth of July Creek gradient is currently relatively flat and should easily adjust to the regulated Susitna stage. Erosion of valley walls, terrace deposits and alluvial banks will reduce dramatically due to the armour layer. Reworking of active gravel bed materials will continue at a reduced rate. Main channel form will slowly progress to a more uniform sinuous pattern. Several of the sloughs and subchannels could be blocked off from the Susitna main channel at the regulated stage. Where these channels rejoin the Susitna, gradual siltation and vegetation encroachment will occur. RM 129.5 to RM 119 0 0 r31/b Erosion of valley walls, terraces and alluvial deposits will reduce dramatically. At RM 128 and 125.5, reworking of gravel bed material wil I continue, but at a reduced rate. Main. channel form will become more uniform. 2 - 4 - ' -· - -· - - - - 0 0 Cobble berms at the side channels and sloughs will control and perhaps block main channel flow from entering them. The river _should continue its preferred and stable route along the west valley wall. RM 119 to RM 104 0 No consequential changes in the channel morphology are expected. RM 104 to RM 95 0 0 0 Chulitna River will continue to expand and extend its alluvial deposits. Decreasing the summer flow magnitude in the Susitna River will allow the Chulitna to extend alluvial deposits to the east and south. This could induce erosion of the east ban kline towards the rail road. Increased deposition at the backwater up the Susitna River. continue after the project. confluence will cause Lateral instability will The Talkeetna River will maintain the ability to create its channel into the Susitna system. No consequential interactions can be foreseen at this time. RM 95 to RM 61 0 0 r31/b Under post-project conditions, the bankfull flood (mean annual flood under pre-project conditions) could be expected to have a recurrence interval of once every five to ten years. This will ·tend to decrease the frequency of occurrence of both bed material movement and consequently of changes in braided channel shape, form and network. Over a long period, a trend towards relative stabilization of the floodplain features should occur. The main channel and major subchannels could progress to a more uniform meandering pattern. The active gravel floodplain may develop a vegetative cover and the minor subchannels become relatively inactive. It must be recognized that an extreme flood generated by either the Chulitna River, Talkeetna River, or both, could mask this process and delay observable changes for several years. 2 - 5 RM 61 to RM 42 0 0 The Delta Island reach is a very complex and unstable channel networ.k. There exists a very broad floodplain filled with varying channel types. Project induced changes in flow and sediment regime realized at this reach will be diluted by contribution from tributaries and by the Susitna satisfying its sediment load by reworking the wide floodplain alluvial deposits. Basic changes in the overall channel network are not expected. Local changes could occur in the main channel lateral position but basic channel geometry should remain relatively similar. To quantity post project morphology changes with respect to the natural system would be extremely difficult, if not impossible. RM 42 to RM 0 0 r31/b Effects of the project on river morphology through this reach of river would be extremely difficult or impossible to quantify. The dilution effect of major and minor tributaries as well as the balancing of changes by the Susitna River system should mask any measurable changes that could occur as a result of the project for several decades .. 2 - 6 ~· - - -' ..... SUNSHINE DEVILS CANYON • GOLD CREEK SUSJTNA STATION Pf~EPARED BY ' R&M CONSUl.TANTS, INC. LOCATION MAP LOWER SUSITNA RIVER : SUSITNA~RIVER BASIN 2-7 PREPARED FOF AGURE 2.1111R ., N I (X) --1 ] ) MILE& I 1 PLATE ...2.._ / .-~ ... OSS-SECTION LOCATIONS 'FIGURE 2.2RIVEA CR , ... , --.. -,,./ ,--~ i I I N I I.C / R&M CONSUl-TANTS, INC. J 1, MILES F i J PLATEJ.- Pr ared for: "FIGURE2.2 CONTINUED_ N I ...... 0 1 ' 1 ~~ 1 R&M CONSULTANTS, INC. -1 1 -i l 1 PLATE 6 IJO l t.IILES ,- 1 ~--D 1 1 FIGURE 2.2 CONTINUED 1 l J r J J' I ) N I ....... ....... 11 l I .. ~ J j I R&M CONSULTANTS, INC. i j 1 " j ~ i D I .1 1 PLAT£ __;z_ MILE II .,. 111 o:, F l l Pr ared for: FIGURE 2.2 CONTINUED - 3 -FLOW REGIME The flow regime defines the amount of time that certain flows, together with the corresponding hydraulic characteristics, can be expected. The information is useful in analysis of the sediment regime and the river morphology, as most of the sediment transport occurs at high flows. It is also important in evaluating the impact of flow regulation on fisheries. 3.1 Flow Duration Analysis A flow duration curve shows the proportion of time that discharge equals or exceeds various values. Pre-project monthly and annual flow duration curves based on averagt= daily flows were developed for the four mainstem Susitna River gaging stations (Denali, Vee Canyon, Gold Creek and Susitna Station) and three major tributaries (Maclaren, Chulitna, and Talkeetna Rivers), and are shown on Figures 3.1 through 3.4. The period of record used for each flow duration curve is shown in Table 3.1. The curves do not necessarily indicate that flows arE~ greater than a given value for a certain number of days for every year, i.e. that 30,000 cfs is exceeded five percent of every year ·at the Susitna River at Gold Creek. In the above examplE!, the flow duration curve indicates only that five percent of all days during the period of record had discharges above 30,000 c1Fs. The annual flow duration curve does not indicate how the sequence of flows occur -annual hydrographs should be examined to determine sequences of high or low flows. The shape of the monthly and annual flow duration curves are similar for each of the stations. The flow duration curves are indicative of flow from glacial river:s. Streamflow is low in the winter months, with little variation in flow ·and no unusual peaks. Flow begins to increase slightly in April as breakup approaches. Peak flows in May are an order o1' magnitude greater than in April. Flow in May also shows the greatest variation for any month, as low flows may continue into May before the high snowmelt/breakup flows occur. JunE! has the highest peaks and the highest median flow. The months of June through July have relatively flat flow duration curves, indicating that significant portions· of flow are within a relatively narrow flow range. More variability of flow is evident in September and October as cooler weather becomes more prevalent. 3. 2 Post Project Flows Daily post-project flows for the Susitna River below Devil Canyon are not available. However, the chcmge in flow durations can be estimated based on monthly flow dur,ation curves. Due to the lack r31/c 3 - 1 of records at Sunshine and the short period of record at Susitna Station, 30 years of pre-project monthly flows were synthesized using records from the Susitna River at Gold Creek, Talkeetna River, and Chulitna River gaging stations. The post-project project flow duration curves are based on the 30-year monthly operation of the Watana and Devil Canyon Reservoirs fo.r Case A (optimal power operations) and Case D (minimal impact on salmon spawning areas in side channels and sloughs above Talkeetna). Tables 3. 2 through 3.10 present the 30-year record of historical and synthesized monthly flows for pre-and post-project conditions at Susitna River at Gold Creek, Sunshine and Susitna Station. Annual and monthly flow duration curves for pre-and post-project conditions for these stations are shown in Figures 3.5 through 3. 7. Also presented on these figures are the corresponding water surface elevations, ba,sed on USGS rating curves. For the ice cover period between November and early May, the water surface elevations shown on the graphs will not be valid. The only reason for their inclusion is that the difference in water levels under pre- and post-project conditions is likely to be of the same order as under open water conditions. The relative contribution of average monthly flows at the confluence of the Susitna, Chulitna and Talkeetna Rivers is shown in Tables 3.11 through· 3.13 for pre-and post-project conditions. The annual flow duration curves for the three rivers, including both post-project flow options for Susitna, are illustrated together on Figure 3.8. The pre-and post-project annual flood frequency curves for the Susitna River at Gold Creek, Sunshine, Delta Islands, and Susitna Station are presented in Figures 3.9 through 3.12. Table 3.14 presents pre-and post-project flood discharges and stages for the four sites. Rating tables and rating curves for the above three sites are presented in Attachment A. 3.3 Contribution by Tributaries As part of Subtask 3.05 -Flood Studies, a regional equation was developed to determine mean annual flood flows based on basin characteristics. A forward stepping multiple linear regression computer program was utilized. Twelve watershed parameters were considered, including: drainage area, main channel slope, stream length, mean basin elevation, area of lakes and ponds, area of forests, area of glaciers, mean annual precipitation, precipitation intensity, mean annual snowfall, and mean minimum January temperature. The most influential parameters in predicting the mean annual instantaneous peak flow are drainage area, stream length, area of glaciers, mean annual precipitation, and mean annual snowfall. r31/c 3 - 2 ,-~ ~· ·~I - - - "' - - - ~ .. The resulting equation was selected as being the most representative for determining the mean annual instantaneous peak flow: Where: Q = 7 . 06 ( 0 . A . ) + 46. 36 ( L) + 697. 14 (G) + 200.15 (MAP) -49.55 (MAS) -2594 D.A. = L = G = MAP = MAS = Drainage Area (mi2 ) Stream length (mi) Percent of Drainage Area Covered by Glaciers(%) Mean Annual Precipitation (in) Mean Annual Snowfall (in) Table 3.15 lists a summary of basin characteristics at various locations along the lower Susitna River that were used in this study to determine flood flows. It is interesting to note the variance that exists within the Susitna basin. For example, the two major western tributaries, the Chulitna and Yentna Rivers, have the highest percentage of glacial area. Susitna River at Gold Creek has the lowest percentage of forested area. Table 3.15 is a good reference for general comparison 01f basin characteristics. The mean annual instantaneous peak was used in conjunction with Figure 3.13, the design dimensionless regional frequency curve for the Susitna River basin. The annual instantaneous peak for selected return periods was deter·mined by multiplying the appropriate dimensionless curve value by the mean annual instantaneous peak determined from the above equation. This procedure was used to determine pre-project flood frequencies at ungaged sites along the Susitna River. Additional discussion of the regional flood frequency analysis can be found in the Regional Flood Studies (R&M,' 1981b). 3. 4 Flow Variability Index Long-term average monthly pre-and post-project streamflows may be used to initially assess the project effects on fishery and wildlife habitat. However, Trihey (1981) notes that average monthly flows do not reflect the seasonal and annual flow extremes which may have significant impacts on habitat. High streamflows may scour eggs from streambed gravels. Low streamflows during salmon spawning periods may concentrate spawners into confined areas. Only monthly flows are availaible below Devil Canyon for post-project conditions. Consequently, an analysis is required to assess the value of monthly streamflow values as indicators of flow extremes. r31/c 3 - 3 The 1-day, 3-day, 7-day and 15-day high and low flow values were determined for each May through October (open-water period) for the periods of record at Susitna River at Gold Creek, Chulitna River near Talkeetna, Tal.keetna River near Talkeetna, and Susitna River at Susitna Station. The ratios of the values to the corresponding average monthly flow were then determined in order to provide an indication of how well monthly streamflow values represent the extremes in habitat conditions (Trihey, 1981). The average 1-, 3-, 7-and 15-day ratios and standard deviations for each stations are presented in Tables 3.16 through 3.19. The ratios for each of the months of May through October for the periods of record are presented in Attachment B. The ratio of annual 1-, 3-, 7-, 14-, 30-, 60-and 90-day low flows to the annual low monthly flow were also computed for the above four stations, together with data from the Susitna River near Cantwell. The ratios are summarized in Table 3.20, and the station values for the periods of record are presented in Appendix B. The annual low daily flows. are closely approximated by monthly flows. The low monthly flows occur in mid-winter, when the rivers are ice-covered. Flow statistics indicate that the ratios of 1-, 3-, 7-and 15-day high and low flows vary both with time and with basin characteristics. On all rivers analyzed, May showed the most variability, as it is usually the month when high breakup flows begin to occur. This large variability in May is also evident on the flow duration curves. The ratios for May also had the greatest standard deviation for high flows, indicating significant changes from year to year. June and July generally exhibited less variability than the late summer months, primarily because flows are usually dominated by snow and glacier melt. In the Susitna Regional Flood Analysis (R&M, 1981), it was demonstrated that June had the greatest frequency of annual floods (55%). Floods in June are dominated by rain and snowmelt storms, resulting in high volume floods with relatively slow changes in daily discharge. Flow variability increases in the August through October period. Heavy rainstorms often occur in August, with 28% of the annual floods occurring in that month. The increase in the ratio of high daily flow to monthly flow for September and October is partially due to rainstorm floods and partially due to the decrease in flows due to cooler weather later in each month as winter approaches. The monthly ratios for high and low flows may be used as indicators of the monthly high and low flow values for the unregulated portions of the river, i.e., that portion of flow on the Susitna River contributed below Devil Canyon. The 2-dam reservoir system will have almost complete regulation of flows up to floods with about a SO-year recurrence interval. Table 3.21 indicates the average monthly spill from Devil Canyon. r31/c 3 - 4 ' ..... ~I ... ~I - - - - The spills are completely regulated, i.e., reservoir outlets are controlled so that average monthly fllows are nearly constant for those months. The 1-day, 3-day, 7-day, and 15-day high flow ratios may be used as indices of the increase in flow contributed below Devil Canyon, so that maximum flows expected between Devil Canyon and the Susitna-Chulitna-Talkeetna confluence may be estimated. Overall, the daily/monthly flow ratio for the Susitna River at Gold Creek will be decreased significantly under post-project conditions. Once the SIJsitna-Chulitna confluence is reached, there will be also be some decrease in the daily/monthly flow ratios due to the storage effects of the reservoirs, but it will not be as significant as _that above the confluence. r31/c 3 - 5 TABLE 3.1 STREAMGAGING STATIONS PERIOD OF RECORD Susitna River near Denali -US.G.S. Station 15291000 Mean Daily Discharge Records: May 1957 -September, 1966 July 1968 -Present MaClaren River near Paxson -U.S.G.S. Station 15291200 Mean Daily Discharge Record: June 1958 -Present Susitna River near Cantwell -U.S.G.S. Station 15291500 Mean Daily Discharge Records: May 1961 -September 1972 May 1980 -Present Susitna River near Gold Creek-U.S.G.S. Station 15292000 Mean Daily Discharge Records: August 1949 -Present Chulitna River near Talkeetna -U.S.G.S. Station 15292400 Mean Daily Discharge Record: February 1958 -September 1972 May 1980 -Present Talkeetna River near Talkeetna -U.S.·G.S. Station 15292700 Mean Daily Discharge Record: October 1974 -Present r31/c 3 - 6 ~! .-· - - i r. J l r·. > GOL[I OCT 6335. 3048. 5571. 8202. 5604. 5370. 4951. '5806. 8212. 4811. 6558. 7794. 5916. 67231 6449. 6291. w 7205, I 4l.63. -...) 4900. 3822. 3124. 5298. 58•17. 4826. 3733. 3739. 7739. 3874. 7571. 4907. 5639. ' J J i l ] J ··-· I j ) J J J li N CREEK UF'MTEI• PRE-PROJECT FLOWS NOV [IEC 2583. 1439. 1300. 1100. 2744. 1900. 3497. 1700. 2100. 1500. 2760 •, 2045. 1900. 1300. 3050. 2142. 3954. 3264. 2150, 1513. 2850, 2200. 3000, 2694. 2700. 21001 2800. 20001 22SO. 1494. 27991 1211. 2096. 1631. 1600, 15001 2353-. 2055, 1630. 882, 1215. 866. 3407. 2290. . 3093. 2510 • 2253, 1465. 1523. 1034. 1700, 16031 19931 1081. 2650. 2403. 3525, 2589. 2535. 1681. ' 2467. 1773. JAN FE I! MAH AF'f( MAY JUN 1027. 788. 726. 870. 11510. 19600. 960. 820. 740. 1617. 14090. 20790. 1600. 1000. sao. 920. '5419. 32370. 1100 I 820. 820. 1615; 19270. 27320. 1300. 1000. 780. 1235. 17280. 25250. 1794. 1400, 1100. 1200. 9319. 29860. 980. 970. !940. 950. 17660. 33340. 1700. 1500. 12001 1200, 13750, 30160. 1965. 1307. 1148. 1533, . 129001 25700. 1448. 1307. 980. 1250. 1'59901 23320. 1845. 1452. 1197. 1300. 15780. 15530. 2452. 175-1. 1810. 2650, 17360. 29450. 1900, 15001 140(), 1700. 125901 432701 16001 1500. 10001 830, 19030. 26000. 1048. 9661 713. 745. 4307. 50580. 960. 6601 900. 1360. 129901 257201 1400. 1300, 1300. 1775. 9645. 32950. 1500. 1400. 1200.' 1167. 15480, 29510· 1981. 1900. 1900. 1910. 16190, 31550, 724· 723. '816. 1510. 11050. 15500. 824. 768, 776. 1080. 11380. 18630. 1442. 1036. 950. 1082. 374So 32930. 2239. 2028, 1823. 1710. 21890. 34430. 1200. 1200. 1000. 1027. 8235. 27800o 874. 777. 724. 992. 16180. 17970, 1516. 1471. 1400. i593. 15350. 323io~ 974. 950. 900. 1373. 12620. 24360. 1829. 1618. 1500. 1680. 12680. 37970. 2029. 1668. 1605. 1702. 11950' 19050. 1397. 1296. 1200. 1450. 13870. 24690. 14541 1236. 1114' 1368. 13317. 27928. TABLE 3.2 Susitna River at Gold Creek Pre-Project Monthly Flows l JUL· AUG 5EF' YR AVG 22600, 19880. 6301. 7972. 22570. 19670. 21240. 9062. 26390. 20920. 14480. 9516. 20200, 20610. 15270. 10035. 20360. 26100. 12920. 9619. 27560. 25750. 14290. 10204. 31090, 24530. 18330. 11412· 23310,' 205401 19800. 10347. 22880, 22540. 7550. 9413. 250001 31180, 16920. 10489. 22980. 23590, 20510. 9649. 24570. 22100. 13370. 10750. 25850. 235501 158901 11531. 34400. 23670. 12320. 1098 1f I 22950. 164401 9571. 9793, 278401 21120 I 193501 10117. 19860, 21630. 11750. 9395. 26800, 326201 168701 111:51. 26420. 17170. 0016. 9761. 16100, 8879. 5093. 5561. 22660. 19980. 9121. 7535. 23950. 31910. 14440. 10206. 22770. 19290. 12•100. 10936. 18250. 20290. 9074. 9052. 18800. 16220; 12250. 75f.l1. 27720. 18090. 16310. 102:54. 18940. 19800, 6881. 8136, 22870. 19240. 126<10. 10080. 21020. 16390. 8607. 8142. 28880, 20460. 10770. 9427. 23853. 21479. 13171. w I 00 J SUNSHINE STATION UPDATEll f'RE-PROJECT FLOWS OCT NOV IIEC 14003. 5639. 3611. 12226. 4712. 3804. 13713. 5702. 3782. 17394. 7199. '4080. 13227. 5092. 3977. 12188. 6340. 4313. 11011. 4367. 3161. 15252. 7029. 4907. . 18399, 9032. 6139. 11578. 5331. 3592. 15131. 6415. 4823. 16996. 6109. 5504. 14579. 6657. 4820. 13956. 6052. 4690. 18555 •. 5907. 3533. 15473. 7472. 4536. 18208. 5321. 3965. 11551 • 4295. 3856. 10706. 5413. 4563. 8593. 4048. 2650. 9<\16. 3978. 2848. 12264. 7o\67. 4930. 14313. 6745. 4.922. 13508. 6018. 4030. 11284. 4699. 3524. 12302. 4938. 3777. 15565. 4238. 2734. 10620. 5888. 5285, 17399. 7130. 5313. 11223. 5648. 4308. 13690. 5829. 4199. ' ' j " !!I JAN FEB HAR AF'R HAY 2748. 2276. 2033, 2311. 22418. 2930. 2435. 2144. 3563, 42196. 3470. 2511. 2282, 2357, 11258. 2818. 2343. 2317. 4292. 50302. 3667. 2889. 2423. 3204, 32595. 3927. 3189, 2577. 2658, 21758. 2612. 2286. 2-209, 2244. 33157. 4006. 3471. 2844. 2907. 34140. 4067. 2996. 2643. 3399; 27759, 3387. 3059. '2280, 2895. 29460. 4059. 3201. 2675. 2928. 34802, 4739. 3-4 78. 3480. 5109. 32438. 42.22. 3342. 2975. 3581. 24520. 4074. 3621. 2399. 2025, 35245. 2797. 2447. 2013. 2381. 8645. 3373. 2962. 2818. 3435,' 24597. 3404. 3009. 2875. 3598. 16479, 3698. 3294. 2793. 2639. 32912. 4181. 3986. 3898. 4359. 36961. 2218. 2082. 2077. 3458. 21509. 2600. 2448. 2382. 3150. 25687, 3325. 2514. 2351. 2640. 10652. 4257. 3801. 3335, 3210. 36180. 3312. 2984. 2646. 2821. 18215. 2882. 2519. 2220. 2916. 31486, 3546. 2990. 2810. 3160. 29380, 2507. 2355. 2281. 3294. 22875. 4231. 3640. 3171. 3537. 27292. 4213. 3227. 3002. 3542. 22707. '3674. -3206. 2963, 3704. 33876. 3498. 2952. 2631. l177. 27717. TABLE 3,3 Susitna River at Sunshine Pre-Project Monthly Flows ' ·~ -~ ~ -~. ' II ll ' J ' 1 JUN JUL AUG SEF' VR AVG 45613. 59179. 54849. 27734. 20201. 58872. 69474. ~18356. 51069, 25982. 68731:1, 64937. 5:3363. 32057. 22014. 64075, 54231, 49954. 33737. 24395. 54805, 53386. 57701. 28376. 21779. 69686. 70894. 77692. 35385. 25884. 73941. 80569, 69034. 44495. 27424. 79153, 62302. 53243. 48121. 26448. 60752. 59850, 56902. 20098. 22670 • 64286. 67521. 71948, 36915. 25188. 39311. 58224. 55315. 43086, 22498. 60886. 6,3640. 60616. 36071. 24922. 87537. 67756. 61181. 313711. 2665'7, 56629, 78219. 52938. 29182. 24086, 111073. 58836. 46374. 23267. 23819. 58488. 65042. 56375. 53703. 24 a:;;6. 695.69. 55243. 62007. 30156. 22820, 66162. 77125. 82747. 37379. 27371. 76770. 69735. 46730. 20885. 24016, 40404. 45267. 24656. 14268, 14269. 47602. 60'771. 54926. 27191. 20250, 76208. 64787. 74519. 32402. 24505. 6685.6. 62292. 51254. 341:)6, 24277. 59933, S1711. 51085. 25238. 20132, 43713. 51267. 43222. 29114. 19071. 72836. 75692. 51678. 35567. 2489(), 56366. 55506. 52155, 18502. 19865. 87773. 62194. 55157. 32719. 2512.1). 48044. 57930. 42118. 22742. 19781. 59849. 71774. 48897. 26790. 22993. 64198, 63178. 55900. 32304. ~. ~ I ~-l ) J I J •I w SUSITNA STATION UF'DATE[I f'RE F'I'<OJECT FLOWS· OCT NOV [IEC JAN FE II MAR 26869. 1136 7. 6197. 6072. 5256. 5377. 18026. 6933. 5991. 7074. 7295. 6392. 31053. 16364. 6989 •. 9274. 7036. 5853. 44952. 16289. 9746. 9069. 6775. 6350. 20169. 11829. 5272. 7202. 4993. 4980. 23896, 9168. 6193. 7255. 5845. 53.16. 19923. 10522. 7295. 6179. 6831. 63;!4. 41822. 21548. 14146. 10600. 8356. 7353. 52636. 19887. 10635. 7553. 6387. 6679. 305•13. 9529. 4763. 7795. 6564, 5666. 2575·~. 10165. 7005. 6716. 6310. 5651. 33782. 12914. 13768. 12669. 10034. 9193. 29029, 13043. 8977. 9050, 6183. 5951. 27716. 10755, 8865. 8671. 7854. 6058. 37846. 11702. 5626. 6351. 5762. 4910. 28747. . 10458, 6127. 6952. 6196 • 6170. 36553. 12313. 9159. 8031. 7489. 7091. 26396. 12963. El322. 8029. 7726. 6683. 37725. 15873. 15081. 11604. . 1153;:1,, 8772 • 15940. 6606, 4279. 503:3. 51~~7. 5172. 22683. 6799. 5016. 6074. 5581. 5732. 32817. 16607. 8.633. 6509. 6254. 5883. 32763. 14922. 8791. 9380. 8458, 6646. 26782. 14853, 8147. 7609. 7477. 6313. 20976. 10113. 6081. 7402. 6747. 6294. 19520. 10400, 9419. 8597. 7804. 7048. 31550. 9933. 6000. 6529. 5614. 5368. j, J Af'R 565i, 7354. 5985. 7993. 6306. 6412. 7182. 7705. 8099. 64691 5830. 9803. 6635. 5565. 5531. 7120. 8048. 7281. 8763. 6452. 5769. 5788. 6895, 7688, 6963. 6867. 7253, HAY 66294. 59273. 45294. 88840. 58516. 58164. 82486. 63204, 70321. 56601. 50062. 85457. 5•1554. 53903. 35536. 49485. 52311, 58107. 94143. 44317. 53036. 29809. 74062. 64534. 61458. 47540. 70460, JUN JUL 101616. 124890, 82255. 123164. 132547. 137322. 130561. 125949. 108881. 116732. 169045. 148877. 161346. 168815. 176219. 140319. 112897. 122280. 110602. 146217. 84134. 129403. 151715. 138969. 163049. 143441. 85648. 146420. 153126. 124806, 110075. 138407, 125183 .• 117607. 134881. 136306. 137867. 130514. 8322{,, 102121. 94612. 132985. 122258. 139183. tp6024. 142787. 122797. 123362. 67938, 102184. 128800. 135700t 107000. 115200. 30140. 18270. 13100. 10100. 8911. 6774. 6233. 56180. 165900. 143900. 38230. 12630. 7529. 36810. 15000. 9306, 30055, 12658. 8215. . 6974. 6771. 6590. 7033 • 48670. 90930. 117600. 8823. 7946. 7032. 8683. 81260, 119900. 142500. 7906. 7037. 6320. 6979. 60463. 123698. 131932. TABLE 3.4 Susitna River at Susitna Station Pre-Project Monthly Flows AUG SEP YH f1VG 106432. 39331. 42113. 100947. 73471. 41513. 116186. 82076. 49582. 97610. 44169. 48942. 128587. 66275. 44978. 120120. 53504. 51149. 131620. 104218. 59395. 124813, 87825. 58659. 99609. 53053. 47503. 138334, 67904, 11924'1. 113972. 81565. 43881. 116697. 62504. 54792. 121221. 74806. 52995. 106i'07. 70782, 44912. 92280. 46110. 114132. 111846, 89944. 117627. 11El729. 63887. 47200, 137318. 8952'7. 52795. 86875. 42385. 50094. 62369. 34085. 3122(), 117728. 80585, 44717. 133310. 69021. 48006, 107597. 60220. 54045. 107261. 45227. 45171. 90252, 56124. 36036. 91360, 77740. 45900. 996:;i0, 48910. 42789. 125500. 83810. 55735. 102100, 55500. 41713. 128200. 74340. 53317. 110841. 65963. 601.11 Of.T 77ll.o 691.7. 74A4o 10094, 7·)94. 7001.. 4A4:Jo 76911, lDIII4o 497:!. ll4:11. 9411<\o 7700. B4Uo Al4l, w 70A2o I 9097. 1-' 6B7Ao 0 7~119. 479.1, 717:!. 7141. 6900. 4610, 70AO, 4916. 94.11. 7194. 92:11. 7l41o 77118. J I a "'~---- , ·~I CRE£1( f'OST-tRUJECT FI.Oiolll Cf.ASE A) DF-1:, 2l II flU NOV 1.\EC 907:1. lU49o 71175. 9414. l06l:lo IHlllo liJilllo l :! 9:11)' 9991. 127:!\lo 10117-4. IJ;!74o 9791o 1~:12~· IOHI! Ul71o 1184:\o lH87o 71181., 10:!29. 111741. l:HJOo lD8'i'lo IH:!.Io 10:;91. lJJ29. I0491o ll:ll!9o I Ill 41 , l272J. 90/12o IH411o 119H9o l:!UAio 7599, 117:1:1. IO~H. IJ~84. 761.4. 9JII4o 90114o 9tll9o 7780o 89A7o 77tlflo II A79 o 99B7o l2494o 79=:t:!. 9:100. 777:1. 9lll4o 91lA4o l2ll0o 917:1i 97t7o 1141 ". lJOh'o 79:Slo 9lUo 94:12o li9JOi ' ~ JAN FEll liAR Af'R HAY .llltl Jilt AltO IOIII4o 119<\ II 7877. 7931. 111434. 111171.. il;l Ja I :177Jo 8l40o' . 61.14. 111.(14, Al:i:lo tOIIUo \IJ64Io i'A:IO, 4111 I lll8.So 917Jo 811:Jlo 7R:!Ao . Rlllllo j 31:12. i':i'll. llll:t:l .. lDIIH6, 8'192o 7971. 819:1. ll UD9 i l :!91 :lo iiiiUo 9 4:1:t. ll 087. 917:1. .79l<!o 811:11. l 3141. 121144• 81lllllo Yo\::Oifo l l :ill I • 9:17J, B:!:llo ·799Ro l0l79o hl1191 llH:iflo H:l!l4o 11171.6. 914.1o 809?.o '19'12o l:!i!ll7'. 132fWo 1:'i114l' I.AOO:io 11487. 947:1o n:1:12, )\'9lo I 11 :il, ll989o 847:1'o lO:I'U, II 7!'i 9. 9480. 11299 •. lllloli lor,llf; l07114o 71192. 'l:l~ii'' li2J4. 9480. H 1.11 • IHOlo Ll4f'llo l2D9:'io 1'-tlllo 141\1);.!, l16J:!o 91.~~. 8J4a. 79A7o illll:l'o '12:1'11 ll:l:'i9o A4llo 122:1'1' U:!Ao H9Aio 92:Ul hUi'o 1:17-tlo l07llto 12D:llo 11407. 9~7:1. 11:5:52. R2BI o · IIAJ:Zo u:1:u. 14A"'lo. U4.Uo liJA7, jA7:t, 815:2. 179:1. U:JIIli 1240/,·, 1:;n:~. 1471Jo IIIR.l:io 9lJ9o i'llHo 7fl7flo .. Al7Jo I Mi24, '47A7o 11482. 10747. 90J:t. 11051; 79411 9AOOo auo:•, YYIIUo IIIUAAo Ill 114, 947:t. 11452o R:J:iAo 11112'/o 141Ho AJ70o 7-417.. lllRAo 9573 ,· 8351 •. llo:'i6. lO:ill4o llAAAo 129:17, 17HOo 1171.11. i 0117:1 I PD:Il,. A19l I lll9;!9o i~V~:I, LhiCIDo H:t:!9, l05111o 8A94o 791o7o 0091. 9Jilo fl:l47o d.o:'llo :IIHo A420o 48111. 49/oflo 5A7:1o 67J7i l1:S52 o 9504o d.OJ4o fi:1:':Jo 7129. HAlo B41llo ll91Ao 128.141 OllllAo d.i'J:!o l20<16o 111<11) l. fl974o fi;!Yio l;t49?.o 1105'1• 14~iDIIo AOII211o 1119flloo un. fll:llo 7A:Ilo 11524• ll0611o 4:JA7o li:IHlo 7BH; 97981 7A7d.o 78:19'. , iii11A9.o 101144. . i':IAO i :14B2o ~~27. 4::il:lo 7:173, 8l7Ji j U:Ho l2710i 141190. VlHo i07AOo 9l2Jo lill:i I 1 IIO:SOi J12:11Jo 114\14. I &11:141 :'127lo 8Hlo suo. RA:'ili iJ:lAOo IUB4o J:tn91 UA17o 9AJ4o HBI:i. 9114io lf7tio\, 8211:1' 1129!11 HIIA:l1 7:SUo ':>'17'11 11124. A99R, BJ!'ilo IIOJUo ro74i 8870• l;tO\IIo 1111lo I0:174o RP4Jo aU7. ,,o, lodn. ·· l:!ild. 107.1-0o 9:1!'ilo TABLE 3,5 Susitna River at Gold Creek Post-Project Monthly Flows (Case A) ~ ' ·~ ~. ' " ·~ 3 ~ 'll 1 ~ ' 6F.P YR /1VO 1911Ao 8724. l2:11Ao Rl:l:i'o 6&\l:lo 9:5Uo 8l48o lOD:I:\o uov. iiiAIIo Ill 511. lllll:'io l411l7o llH2o 12789. llll4i'. 499:1, 97116. '1909o iOl04o ll !/!ill. 94\Ho 64Ad.o lDJ!'i9o 12t77o 11:1:12. ~IJlo 1099(1,· :u :'14. l11114'1lo I:ZlHo 9ABYo !'i:J!'i:lo V:'iAB. H90:'io 10912. SDJ2o IOI;!o\, -'9:171 '1772. :ll!'ilo 71.4:1. ti:?10. Allfllo :IAHo lD.Ul, 4\I:J:.Oo !5J(I, :141lo (119. 9:19Bt 9297i :11170i 8942o :iAAio 'l:Hlo tiD71o 90!'i7o :1024. 8:19Ao 77llo " t J. '1 ) j 1 ) j SUNRHINE STAo OCT NOV I :14114, 12129. I5H5o II ;!07, 15&06; 13:193. 19::!0~. 15090. 15119. 1:298], 13824· 13&54. l2903o 12250. 17144· 14920. 202911 141923. I J 719, 100111, l 70 71. I430o!-, IBAHR, 14001), w 1634\J. 145411. .1 I:IAUo IJ94Jo 1-' ::!0447, IJ79AI I-' U2A4o IJ7J:I. 20I00o U:!l?.o ·14~641 10294 0 IJJ9:S, Dl04o II :11111 IOOII<!o I 34114, 10767. 14120. 11810, I :S:JA/1, 11410. 1:1:19 :;>. ll7:S::"I 14,0,11. 11090. 15479. IIOIJ, 174:17o 12129. 1)940. 114JJ, 190:19. t:sou. 134:S7. lJOA~o I:J8J9, 12814. h ~ j j ') jj I ) j » ) j ~ ~ PII9T f'RIJ,I£C:T Ft.DII!I lr.ASF. At l1U;o'2Jr 19Ri DEC 1411411 l:Ulll, 15012. 15:1111. 1:120&. 1:1:54;!, 14JFO, UIJA, l7362o 12:100. 1&05:11 11\'l:t:t. 16049. 1:5919. IV•s:!• 'i:S74!5. 11'119!1. 1411911 I 5 792 '· 110 72. 11!101. 11627. 142911 15259. 11791'11 1147111 lJUJ; 12599, lll!f4:1. 1197Ao '143511. .tAN fEll HAR APR HAl' .Ill if .JilL AIJIJ U!IJ:S, 10449. 91A4o 937:lo 21JHI 34109, 44917; 4074:?. 10310, 821.9. 801)8, \flO l, Jlll?.:!o 414Ho lH5:14, H191, ll2:16o IOAh4, 943:"1. 9:i'93o 14.411. !IOI;>(I, 477511. 4011n: I:.!AO 4 I 10515. 94/oH, IIIR72i 4<11141· 41'670. 4167JI JR797o ll4:S4o 1104121 9:17:11 1ooon. 2A47ih 4:i'~2l. 410114\o Hn9. i3714• lll412o 917Ao 94!"141. 224\ tB. :11 F .l!t, :";21v:t. Ao\49.4. 1:1:1911. 104:19. 934111 9266. 277841 !t3R:'iAo 4!\110 •. AO:i09o u79lo 114\Ho . 9994\o 9700i JJ :i4J •. &OI'Alo 474414. 4294411 IJII/11, 111119. 97941 9980· :7:1:177 .• 4~7:14\o 44 911<!. 4:1&19. IJl'l:lo 112:1'2. 1'4:11. 97411. 2Afl'11fo ~:tolllo. 1111'20!. :W.t70o l J046 1 11374. 9H;o,\, 9~9!1. :n1H, :130401 43AOJ, ;UIIJA, 14:1:!.\. II oHiO, iOi\311 11690· . ;!4\J7:11 1n177, -t9711Ho ~11n47. 1400'1', U:'JI!So IOU71 IOIII:lo :!071121 . 404\?.0. I'IAII:!9, :S4119J, IJIIIIlo 11794' 9:1:Sio fi9DAI :007:1:11'11 .uo:t::;. 1'19:194· 4:19Aio 12:SA4, 1111120o 91114. 9::il4o 1~711 I 77017i :IOII7J, JA4UI lJ 1110. 1113:11 991\9, 10011\o :112(17; HJ70o · 47110. 44U:li IJ 1'10. Ill H?.o l001.7o jOI79o. 1691.1; l'lflll'iJo U75:1, 47~119. 1:141141 II 4117, 9944. '~~n. ~79:14. 411~311, 432A<!o 67JA71 ll9AII I 121:19. II 049, 111940 i 3i710i llffl47o • !t71 Hlo :171189, 12004. I0:.05:'1o . ·~~!H • aoo:iv. 1"17H, JJ•!lll :11'12'1.0. ',lU'HI1 11119.\o fHOio 81114. 7t41'1o :lloH, 401'121. 47617. ~09110. toto~. BlloA.· Afi/IJ, 99411 I:SA21'11 · :1&112. 409.:1:1. <ttJ-411' 14044. II 974 I 1041161 97\11• 277A<1o 46411:1. 1'140:111. 42:197.. IJOYii1 lli~~. d'70'1~ 9(,~:1. IR:I0/11 ollt91' .. ,. -t004fi, :111~76i ',. .-r • YII:SO!; 111:140. Vl72o 978:11 7.6 17!'11 .tSHBY, 400'-7· 3:2&84. 1112!"17. AOl4o n9oJ; 97401 2:1:1041 1'1323A• 6:Uo4\<!o. 4271:ti 12293. 10:12111 94:121 9971. 21!113o ~l41121' 4:1:;!0(1, J76<!Ai 11)!'19lo 1011121 IOll:lo aoiH1 71.2911; AJ:S32, 1'11141· 4S7:11o 1391'91 11400;. iOI:IJ1 1oi:d1 1901'12. :nn:;'1. 444211. lH.iO:I. 1040JI 99111. ill It-t. i 0:!114 •. :l'90Ui <140291 llli9II:So 39408. i:.OAifi IOA:S9,t U!'l:i1 9Ro0, . z4oU; 411331. 4'1:14:1. 43974 • TABLE 3.6 Susitna River at Sunshine Post-Project Monthly Flows (Case A) i J REP Yil AVO :14:1l9. :!09:!4. 4).;147. :;!:1072. :1-t<!AS',· l2014o ?.1141 u. :!U9~. :11 :SA!), · 21A4A. :192:14· :I':'IAI!'Io 407fl:lo 274:!4. ~iJJo~ ~644Bo 1,43. 2JO:Sl• :191'041 24804; :nn:t~, ~~4YR • . ;!'11167 •. 1.4'131 • :1499Ao · :I' AHA, 74Hlo 2411AIIo I 1111:12, :14047· -H-119 .... 246:::9. ;!:17" •• ?.2992. 31'141-to :niJ2o 1710io' ·;)4Jfflo HIHo loHAOo 2J:!:H. 20:l,O,Oo :!-J2J2; t!<!3ff0o :!7]91), :lJHOJo 210YIIo 20AIOo 2:.'!277• 1950A. ::n:sn!t. 7l'l':'i3o III.U I, 201190. 2:1940i :04319o l'i'?.OAo 20694\o ~t044o 721114· ~1toitH, 51l51THA &TAllON POfiJ PRCI.U:r. J FlOWB CCA6i AI Pt;r.,2Jilll'lll OCT HOV OEC .IAN FEB HIIR AFR HAY ,JIIH .I Ill AIIO !iH YR AVIl 28270. 17R57o 17427. l:ifi:ill'o 1Hl9, 12:5~8. l:i71Ho ' -6ti~~ 1ft I II':IIV~~. I 106;•11, 'l:!:t~~~ I :H1'i:l6, 4:1AA~i, 2114:1. U:illllo 142?5o 144:141. IJIIAII'o lllH1 1:109:11 :'1:1199. 71111~!7. I 1111::111 07Jf1Ro 64lH, 411AIIlo J2916. 24255. 11121111 UOhllo . 1:1209. U004o :~v;•11 <IlOilo lllY:.•t>, I~OI4lo I 11.1:.'9.1, 7421l0 • 49:\Hlo 4&1114. 21 IHO, ;!09161 171155. I 4i'11• ll~illlo I <I :17:1. Hl.l/'i, u .u:;.&. li,I.IYio H44!i:J, )104~. 411'141. 22114 I, 19720, U:llllo JAII'III'o I Jl66, l:!ll:o'o ll.IO:t; :iUS'7 • S'i\497. 11144:12. 11211Se :il/1~4. ol!"i04H. 25:"1:12. U41121' 174l2o 170421 140101 124471 1:12111. fj90:,• .. I l:"il:lt4. 1:11117:1. J.onv:H, 11:1n. :11079. 2101!1 1 11141J. 18:1?.4. l:I.U:i1 15004. U41~~ 14204. '771 u. 14llAI, I :"i:UA41 12:1M:i, IUII!'iO:"i, :19:19:1. 41714. 2?4:191 2:1l7:"io 20:JR7o IMI:!P, 14505. 144'/R, AOAil:S, 1:1110411. 125<1110. U4:11Ao 11111114. :"iiM:I9, :j4:12fl. 271711; 2111:lll. 17:147. 14:1.10, lJillO, l4AilO, · 6JV:1v. 'ilY<ll1 107J'I:.!. H6J'JAo :i049fl. 47URA, 32704. l:'.illo\41 JJ47IIo 17!1111. '147:J7o llllJ7, Ul<'l• :140]9, 911:177. 1:111~ Ill. J2J:tl'.6. I-1111\'J, 4Ril~o\, Z7o'.41o IIIO:IAo 111:.!:15. U:IO.I, l44Hlo 121102. 1:;!497. 11:1'111 7/llto:t. 114711•1· 'iA/9:11 ,,!:JIJ, 4.111111. J:l~14. 201lO:io 24'1971 224!11\, lll:!OAo Ul44• u;lfi41 79J94o ll60(1A, l:f:IJH, 11161\;.•H, ~\~t\UCh :i4HOI, lOfiJl, 209J4, 20206, 11111:17. 14l!l4o IJIOJ, u;.ou. :f079A, t:IAIJ:/ • IJ2.tl4,, IJ.IIll1 71119:1. :.:;o~·~~~. 29~09, 111641\ I 20094. lll4:illo 16027. llllll. I :l:i:Hlo 46lfll· 7:)Q:i4 I 1:1779:1. 977:\0o U!\9.1. 4491 ;!, :1?7:111. 19~93. 168:i:S1 IAIJA, l39l:i. l2041o U~H. :19~11:1. 11110711. IU64:t, ft4l22f otlo\9:\, HHO,_ w :!9:ilfto 16?211 17:1!16. ill7l9. l4H111 IJUI, Jl70 I, 460\'111 \'~?f1i' I 1:~o1l!'i1 lllJ:\941 11~'\IJJ. 47400. I JAH:i, 20204; 20:1119. 171111. l:iA~2. l424lo 14629. :127'13. Jll6.li\/1 loAil7, 101.111. ri749:!, 47l7Jo ,..., 29109. lll942o 111:1:17, Hlll:io 1:109\lo UIIH1 14170. :o;J Ill. 11;1;0:17. 1:.•Hu. l;lii'.!Bo fl;l!'l~:?. :i:!:I:IA. tv 23764. 2A:tto. 2llU1 111'70:1. 1:19llo t:'iH 4 ·, IIAII'I:l1 119244. 1111f'i4. :.oao:11. :lilA 0 I, !104~11. 40414. 18911. 1!1640. 1270 I , Hfil9o IJJIO, l2l2l1 uon. 4::!:1711. 7.&:?7JI 11:1074, :'iiiAlllo :1.1'149. :UU91 26 lll1 13:11111. IJ6691 ll670. 11414· II 11'24, IO:iHo 411HJ, li:?:iH. 1191131• 10:1111~. 7AU:'i, 4411:.!1\, 34fo7J, 20900. t:IJJO i ll21111'o 12J~6. 12:19:1. IJI09o 349&2. 111:11621 l:i':t:U9o ,IOfHJ:t, t;YHS I , 1:iiiHI, Jllll4. 19!\1171 111160. IYU7. · li.A:Il, 1:1:.0971 1:1416. 1156641 lei!i/l:iJ, .IH:i'J~~ 'iii'IJ:'io' :114:14. :5:1~172. 211:1114. 2~:581· 19376. 17U:I. 154411'. IJ4641 . 14:112. 6411ir.. H1606:11 Sllo\'111'1 v~·=-~~:? • "1 ou~ .. ..~.~491 2UO], IA!H:ZI IU47. 14l12· 147611. IJ4441 l:SII:Jil, :1~'147, 40014. '10944, 49714. 49:!1'17. :16114. 22691. 1647:1. 17120. I!IJ()fj, 1211111· ll:o':i'l1 13417. 4H44o Jll'i:!Oo. 12~·A70, 11:::194. 707:!11. 44'i'i\J, lH42, 1711:<'4. 17229, 16:11:1. ll707,' 1:1!\l'l· I JV:III, 690911, 94116o 11121194. H5H•I, 47097. 1:1~1:11 3]461), ;!J7?:1o 20414. 144~2. l:i4:1JI ll'l2!\l 12111:1. :S:"il66o 1414:'191 ll21147. IUO'i'4 I 77031. ~49:111. J90PO, 205211 1117:i9o 11.7611. 149441 &j74Jo I:IAI4o 4!'iOI:J, · HoH:i. 104011~. 914d7o :; 19/14' 4:!6:!11. :19044 •. 2041~. 169141 l:'i:i:l:lo IJA:illo IHIIJ. 1:'1:!1\Jo 71.4A4o 11140110. ...... , ... llll'IU· AH:'i'i-1. :1241111. J:!20J. 1116Uo IIIJ71o l:t021. l414:1o IJH:to IJIIOio :i7:14-\o llli'UI1 ll~o=Y'i'o YIIV I :1, 611~04, TABLE 3.7 Susitna River at Susitna Station Post-Project Monthly Flows (Case A) J 1 ~ J 1 ' ~ ~ ·~ 1 ~ '11 t ~ ~ ·~ ll 1 ' ' 1 l l '~ J i J J ~ I I j llDl D oCT 79:5J. 60:1:1, :1827. 8;!02. 76]0, 5711 I, 709io 7B4J, 842':1. 7 Jllll. 7637. 7990, 7524. w I 74118, I-' i'507, w ?777. 62:!9 .. :1664' 71:!6. 6932. :1494o 61:1:1. 6087. 11347. 6J44. :1Bl4o 6324. 6394. 62Bio 15871o 6901, j j B J I j ~ ] J J I ~ li j i .$ CREEK POST-PROJECT n.nua ! I:AsE .,, DF.C.2Jti9AI NOV IJEC • 7870. 90:131 678:1, no]; 6:122. 7J09o 1109 7. 91 !II o 787.i.. 9120. fo97!1o 9:'9lo 7698. f()69• 8149. 92lllo 9J77, 9727, 7A76o '11214o 1100],· 92P2o 80llo 94:18o. 7811Bo. 9112; 7654. 90l9. 782Bo 9071. 71101, 8916: 7B99o 9209'. 629fo 8123; 77,96. 9146. 774-4. 8969. 6963. 9:il9 0. AAHiio ;sos. 67Blo. 7629o 7219. ,8212o ~ono. BOJ:Jo 6521. 7J10o 6:1l6o 7l27t 7252. 81431 lo78 I o 1:149. 6:112. 7276i 7JROo 8:19:1o JAN f£1.1 HAR AF'R HAY .Ill~ JUL All II HOI16o . 6799. 690i'l !1821. 8016, 7497 • 1291\7. HillA 9, l .-UIOI. 15Jio01 !1221o :171:1. 77112o ~756o !;l744o 109110, . 720:11 6787 i 6(116. :1729, 6HIJ, JJCI:IIIo I :J:Offo JYIIlJo 8ll!loo 61109o lon:l-4 i 11820, 'IIJ:S:I; I o 19J, 11.11o6o' I '1110 I , 8103 •. 6B:IIo c\9112. 1:11'29o 10751t · I o li'V, 12'1'~ .... 1'01111. 11284. 69811. .· 69:'1lo' :1817, 77:11. r:t~8. IJOit7, 24674. 80~2. 11880, .· 7017. :IBBOo 9804, I 0:176, 2UUo 24:iJO, 81910 69J:io 6998o :111:18. 811Cto V272o 129:SOo ·2024:1. ll284o 6Bl:lo 6fl10o :1819, Bolio 7'i'4i'o UIMi'o , .. ~:14, 8~70. 7022 0, 7!):14, loOOIIo HD24o 9Hilo I :IJioll o ?,·~;··}.4. 11:29111 6922o '6942. !1817, 7fi:IAo Mi:l'i'o ···9'1'1• 192114 0 8407i 7(l?.ltl 7148o lt2J I; RROc\1 I098.H 19l7:1o 2:!11)1), 8142; ltA:I4 •. 6929o :s8:U. c\:17:1 i 14:11111 :I:IA:Ioo ?:t:'i:IO, Bl22o .... ,u. c\~ll; l'i.U:I; 884110 'lc\111 ?.:il'ti2o :!.lc\ 71 • 8116~, 6B22t 111190; !17112. ~llff:li hiHI'i; :i'ltv:lo IIIHOo 796:1. 6~24; 6Allo :IH:So 7i7li 8R9Vo ·l:s:J94o 20112:1; R:!lllo, 69:110 111:11, c\04~· 1A'I41 lt41 'lo 1:1074. H.11:"io IJJ20i h49o 7119Jo :19 7!Z. lllOffo 9214· HHIIo J:.OII:ln. . 112:111. c\'l4c\ i 70:1tli :19\!1 0 847c\i au;~ll21 7,1)24!c\o 17171 • lfiiH, 6RI-4o 69J7o !IS'24o . ~u9; :191l:lo 1:1199. RR79, 84J4, 7H4, 7:124o uo 4. . n.Jof A979o 13269. 191187, ?t6.1i 17Pl! 1990. All' 4;' , 701Po 111!'1:111. 127:'111. l9J:I4o A:'io/.. · 7o:so; 775:1, ll:ll:lo .. .. ,.. 1'1749 0 1;illli:lo iiUYA, 7041Jo :1711o ,15:14 7 I 44c\O, :1299, 4677• 1:11;•jj, IH:17~o loB79i MoHo :14~·· 4;178. c\9JAi '·. 7:12c\. !A!U.IIo U220o 6914o 744:1t ;.tM4, 647:!o t:!U j I n:1110 o IJ:!H?.o IIIG90o lo460i 71lo4, 7120; 61l79'. 89671 8909, 12U7o 182112o ABHlo. 5!160l :i4o2, 491 Oo· 94?,Ri UhVI 12879. I All;!¥, . 6H8i 6211Ri ~020 ,· II A 4ft, !IRlo • 611 :,>, 12A91o u:t90o ?Jill I ~881, 6R4A, 57:54. 6~:1:11 U7lo 11>914. :1041111 •. 7719• A1A:II ABU,· liBJO o tl07lo f:Yl:lo j ..,, .... llll124o TABLE 3.8 Susitna River at Gold Creek Post-Project Monthly Flows (Case D) ] J j i' llf.l' l'R AVR . SJOI, 8998, l:t:IH, 9~07, I :!:184!, 9044. ·~:!70. llllll:lo 121H, 9R71o, 14;!90, V\14 7, 111].10, 11412. lYHUOo IOJ47, 7~:10, 941 J. llo9?.1l. 10489. 161'1'7. 9<149, IJJ70' 107:10. l:iH911o u:s:u 0 l2.120. 10'1190. \1:'171. 979lo 1 v:l:illo 10117. 117:10. 040 •. lf>A711o 101107 •. . fiR I". 9Hio 5(19], 75J I, u:u. ?ISO, II 894, ¥1HII, ll~~:t. 7:-!24! 'i'll74o 8049. 11970o n:u1. 1:.~:!4~. ,.~87. ~nBI, , 11:12/., 11814. 90:19. lliill7 •. 7911:1. 1111711. R9:1Ro 11.371. 5UN1i1UN£ &TAo OCT NOV, I :1:1~ I , I O'i'i'4, IHJJ, 10197. I J9o\9, 9481lo I 7l9i • I 1799, l525lo JOAt.Ro 12:\9\lo I 0:1:15, 131:14. ICII55, 1nll9• ~~~~~n, IBHO, 1l4:!5o I 41 :l:lo 110!)7, 1421(1, II 569, 17192. II I 40. IAI87o 117115. 14Hio 109116. 191>1:1• 1140:!o 169:19. I 247 4, w 192J:!. II 122o I IJO:I:!o 0994. I-' "'" 129:12o IOB:J&, I I 70J, 10162. I I 781\, 9n4. lllllo J0748o 1455Jo 104J!j, 15109. 109114. IJA9:1o 102:;A, I 4:197, 97:19. l41:10o Q7RI o Jl I 40, 10490, 16109· IOlllo\o 12190o 962::1· 14fll1.o 107Uo J ~ • } , :~ 1' ll ,. ' ., f'OST f'RO.Jf.CT flOIIIi «CAIIIt it I llfr.o:Zl• ulii [lfC 1122:1. I0407o 9191. Jt5.1i, ll:'i97o 115Aio I 09J(I, 119AJ, 1260:1. llHlo I 191 :So 12268. It OJ2, 11729. 1 l1 u·, I 224lo I I 54lo 10479. I Jo\:14. 107371 11:1~11 IO:ZO:It I 01141, 10777. I052:1i 9:S64o H9ROo 111125. 1027:1. 990Jt Uo22o ~ ' .IAN fU liAR APR HAY .IIIN .llll AIJO 98117o 8277. 9:?14. 72A2o 19924. Jl:llllt 49:14.\o :ll7AB. ll:illllo A97:io 6o\2:1o 71\AII l:IAIIilo 448:lllo 59448. 57581\o 907:1. 8298, fl:?71lo 71114. l:l187o <47:196• ~182:1. 514Jloo ' 9Dl4 • 11.1:121 fll:'ilo 11497. 40:Jtl7o 41\HIIo 461\17, 4\IH:Io 10470o 1174(1, 8:14:\o 78'/'Ao O'o\(1611, 397J4t 4:19fl:i'o :ii:I0\11 10417. fl717o H4lllo 7JJ:Io 2019(), -t\':!:!4. ::io\4 :IJ • lo\o\IAo Po\94. 1119Ao ll::!Ro\o 7 I 74, 2:1381, :IH77o 71411. o\9(1J4o 111497, fl'i'clA, . llo\:12.' 7:11\:lo 21/ltHlt t;I1~!A~H :II 1/Ho !1~948, 1 OJ8o\, · 8:'124. 8J.l:lo 761l:lo 221190t 4:1\199. 498l7o 5o\4Uo lll"l09o U714o lll:l4o 74:1:1. 2H\14,. l10:11&. :i:IIHllo 6J09;!o l11:104o flo\ 7 I , fl4211o 74411. 24fl(j(l, JfiHOo 4112l:io :II009o 10774. 8750. 1111.111· flo\9(lo 2311114. 4:.041'i'o :IRH!Io 6P4Uo IO~Hi Ao\~6, A:'i04o 77117. IIIJII:Io :10774.· · A71:1Ao 6 I Ill I , 1115\'o\. 90Uo e:Ho. 6Q~fl. 2:101\ I, 40JIIoh o\96'111. :1:19J9. 91114. IIJOl1 01 no; 7J9IIo IM2Ji 7"4711o :17J79o 4o\J74o · I O~HIIo 1\ll:!o\o fl7!11t 7020, I117Rc\, 111\o\:lt :s11nu. :lo\011(1, IO~H 4 o 81\Mo H42Ao :18/0o 145:!11. 41111:111· 4tJ4!17. :'11:12~· IO:IIIlo 1194lt Bo\ilo\o 7444o A':l:l40o h8o\o\, 64.\71; o:1747• l04lo\o. 9052. 905Jo 8J70o 292:17. :1:1.22o dJ:i41. 467.11. 9:1JJ. 1117lo 9199, 78721 1739Ro 30009. 4JJU, 24A:Io\o I 0410, 90241 91]01 IIJ74t 71114:1t :179:1 I, :11379. :140JJ, il04o\o 9271i 9371 ~ H:182t ll7~&. :i;,lllo\1 :IJ:I'i'5o iiiUli A~i~4. flll2.1t 92A:Io no:•:s• 2:1164, 4417:'il 112 :l<!:lt M.lo\Q, 91:17. 74951 7193. 42!14. l:1279t . JHIIIOI 4:11189. <4\IJ47o 11807. 7:109; A9l7o 6J02o 2::!2i21 :u.t611i 4:1:.!:!7. u;!?.:!o P944o' 8964 •. 90141 BOJ9. 2J291 i :11190Ao o\12!14. fii47Ao 799lt 84091 . 11501. IIOOOo l9222o 41109:1• UCIOJo 5<14 17. 9;'8:1. 7:1821 707Jo 471\71 2~040•· 611972; :u2o:1, li4!1Ut . 11422. 7047. 114i7o 711118. 145671 J:llllo\o 49401. 42118· 96:181 11801t BAHt IIOOilo :.»Uo\i • 41JJ21. :19AOAo 411897. 982-t. 841111 fiJAilo 71>411, :·:u47i. bM:Io :'14J21. :'iU4:So TABLE 3.9 . Susitna River at Sunshine Post-Project Monthly Flows' (Case D~ ·~ , ~ ~ "' ~ ' ., 1 ·~ ' B i llf.P YR AVO :.077J4o 21228, <42lo\(l; 2:1427. :1111:19. 21542. ,137:17. 2U9:1. O':IIIH7o 2;'(1lf~. :l!jJ8!5, 251\27. 4449:1. 274:!4. ~11121. ;l.o\448o ;•1)098. 221\70, · :169 I :1, 2!11A8o :111/'J;f i 224~11. lll07 I ,• 249~2. :111711. :;!o\4:17 •. 291fl:!t :HOPo\o :!J2111o 2JIIl9o !iJ70:to 2411~6. JQI:I.So 2:11Ho 37379. :170'17. :l'(IRII:Io 24014. 1421\ilo Jo\2411. 27191t 218o\4o ;.t\'tl:!4t 2.177\1, J:l279. 2291\:5. :.o~:-:111. 20129. 2811Ho U7:IO, l1:102t ::uu. 111:111~. ;!07:14 •. JIQ9J, 240115. 20174:1. 19A2J, :lo\7t0. :12:124. JJSU41 • j .! -J J l --) SUR I lilA ur.T ~n:tn7. :!O:l'J:lo ]l:I09. 449:1:'. :!219~. 24:107. 2:!0~A. 4:111:19. 52047. JJI20o 2611:1:1. J397fl, :101\]7' 29401 I 31J904o w J02:1h I 37571o 1-' U1 271197. 399~1. 19050. 256!'5:1. :131\04. JJOO.I, 20:1o:1, 2J:'ill7o :!11\do JOI:l:lo .J21\I\O. J6Y4!lo J7777o llll6o Ji I j J J J I ) J ) ~ i I J i I • i J &lloTION PIIIH f'HO.JF.I:l Fl.0119 fC:ARE nl br.r.o?.loi9AI NOV 11tc .JAN ff.ll HAR APR HAY .lilH .Jill. Atln liEf' U~54. 1:11111. 1:11:11 • il257o IJ:I:'illo . tOI.QR. A~!IH!O, !J\':IIl. i 1:'12:17 • I 0:1.171, ;s~HI· t;!41 B, 1:!:184. 1:;>7:'4. IIB:l:lo ioo.u. 114:;2. :l:<'flfl:'io 411::!:11. IJ:IUR, 100177. 6-fi'A:!, 20142. l:!HQ, 1:1079. I :!R:!:I, 118.9, 10794. 41\:!i!:J. 111205. IH:!IO, 114:1~9;. HUI7R. :100119. 17197. s:son;. 1:!71>4. 12384· 'I :;>1911· 7119:l':'io h:14:14o llll:ll:lo u11oi.. 4HM1o 171\0:i, I ::!EI '2, HOO!'i, 101144· Ill o', ,IIOOOo :119B7o 9:181!1. 109:1211. 122:?7:1. A:l7111\o Ulfllo ll431. IH4!lo ll4:t:1o 1111\9. IIOH9, !IMIUo 148:1R:lo 1:14414. 1191)44, :'1:1504o IUIOo I:IOHo .-132~1. 12741. t240io 12112. 74710o I:IH:IR:lo I :19Mi7, IJII\:111. '1114:/IHo • l'illl t.4. l:l!i:t:ill iUY:JR, IH:ilH·' iiJII'l.:'io 21\647. :n?.n. 24JIOo 170911. l!i254t . 12464. 1:'1:118. 14097, 1794:1. 205J2. I Rl:ll, ll\9119· I!IAO'i'o 15904. 17200. ll209. 1541\0. Ull:l:!o 18114 I 167:17. 1761\2o 1494:io 21316. 2217:2. 12720. 12:1/oAo 12:147. 1:1/ofl9 I 19980. IJ90Bo IIIAUo .1.1910. 19BUo 141!94 I 15/o70o ~:~oilo; 1:1221. 1~2ii.So 1447&o 12246 I 2~R72• 10840 1 158111\o I24AS'o 111977. 14901. 171172. l!lo'J7o 171)91, 1:179lo IJI4lo 101:11\J • non.· 1191 :'lo I :1:171, J:'Jff:'j I 6:14:12. 1':1144. 11 ?.lt.7o 91':123. 14/ol7o 12279, 11740. I I :2 :i'/o, :111\:l:lo Ulo92, 1.14:177. 1294711. t :1 i lo I, 11780. 11:19&. IOJ-17, 4:o'l40o 7!'fl/o:lo I H414, I CIUA/o, 111704. 15:106. 14:1Jlo 1:1:1114. 1490:1. f:U:;>411o U3774o ll/oi\V7o 1529:;>, ll:il7o I t4RO I 107/olo 40JJ9 I 1 :t4206, IH44lo 121n1. 1519:1o 1:121\t. I IIO/o9 I I OJMio 4Hl9o /o9.1'l.3t 1:17110:1., IOHOIIo I J.lMio IUlllo II077o IO:i4Ho l71l4o ll47Jio 17JHt. 9:-!:?HCio IJ9:i:lo I;'OI\Ilo l:!lllJo ll:iOSo 4 Jlo/ollo fl:.!S1o l <1J96lo Ill ~:I c I 14041. 1:1140. 1::!94:!o 12:1;'0. 50:1/o(l, IO:Yio52o 11oo21, II 6:;o 4 4, . 14111'1· l:IJ7:i. l2:i7Ao I ~!llH/o, :;o7;t:;, 114:'iH:i, 12:1Utl2• U7:1ltlo j7H:Ifo llo:i9lli ll917i 1::!714. ffl\439. IIMlUo l24:14'0i IIMI76o t:!J4H, 112;1Ro 11.:>9:1. lOII/o6o 40:11)/oo 1JA:llo '9ono. lo:!.li\Oo IJIIR4o 121:17. 12480, 109\':lo 49194 I (1491\ I I I2J:I9Jo lloHil:lo l4UOo a:.ou, 12923· 11:1:10, J:108;J, U81lfto 1:17991. 1207:14. IJH:Io IJ4RO, t;~~1A, 117:.!1). 1\:11\46. lt'i.lHlo j J:!II:!C), •111/oiO;I, IH:i4o II'Pflfl, 101160o Jlt21o 61598. 101674. ll7!140o I o:'l:iU I l:J407o 11:137 I llllllo IOH9i !12~! 14. !174'14. '.96144· 110:!:1,2 I l:i'i'95o 1J77f!. !:!:?:!:<'. IIHAo 414:'ilo I Oo\070·, l:i'U6:1o 91 JAOo 1201:1. ltloAfl, IUfiO, 11759. 61\R07o Pl:129. I08/o97o 901 u. 15ltS4o. 12fl:l:lo' ldl\76t f41o:lo. !i~,.~.,. Jl90V9, 1;1:1V0'1o 124illl9o· IIJOJ I II 39lo I~005o 11179. H:i:IO, 779\':1 I 109:171. 1021(10. l4807o IJ541o , 1:!/oiiO, 129117. . 1404!io J 0 t:ld:l • t:!Oi'IH, 1282011, 142;12 •. t:!:!iiA, 120!17. HHio Sll:'i7o I0!11o:So UJ07:So IOY:i'R6o TABLE 3.10 Susitna River at Susitna Station Post-Project Monthly Flows (Case D) !IJO:i:lo 67904o 7J:1:12o 6:l':I04. 7~1106o 70782o 4&110o IIY,44o 6:Jf187o lt'l:i:!?o · 42:111:1. .J40R:io IIIJ:'iH:io t.64l:io :i9Hlo 4:14':;'7. ~:>RHo 7lA75o 48910. B7.904o 5~!';(10, 74340. 6!'11/o:Jo · 1 ) J l j l YR AVO 4:1140. 40'i':lllo .49109. 41194:!. 4:'i:UI\o :IOH9lo :1939:1. :'illl\l'i9o 47:1!1:1 • 49:?49. 4:1881, :14792. !i~Y'i':\o 44912. 44 t:l2. 471\27. 4754:'io ~2-tfrt), ~009:1. J:ll 90. HJJio 47:'80o :1:!7.14. 4:11.111. :11\., 1/o. 449~:1. u1n. 54.!,94 I 4J:I!'j/o I 521140o ... ,.-..<:r , ....... TABLE 3.11 RELATIV.E CONTRIBUTION OF FLOWS AT SUSITNA-CHULITNA-TALKEETNA CONFLUENCE (PRE-PROJECT) ,,.~ Flow Contribution b}!: Total Percent Flow b}!: -Flow D/S "'c Chulitna 1 1 s . 1 Talkeetna us1tna Talkeetna Chulitna Talkeetna Susitna ·~l ;wr· October 4859 2537 5639 13035 37% 20% 43% ~"""' November 1994 1187 2467 5648 35% 21% 44% December 1457 838 1773 4068 36% 21% 43% ~ ..... ~ January 1276 671 1454 3401 37% 20% 43% February 1095 565 1236 2896 38% 19% 43% fili'/Pfif" March 976 492 1114 2582 38% 19% 43% 11'1' 38% 18% 44% l!!"r· April 1158 557 1368 3083 May 8511 4176 13317 26004 33% 16% 51% "" """'. June 22540 11910 27928 62378 36% 19% 45% July 26330 10390 23853 60573 44% 17% 39% -· .. August 22190 9749 21479 53418 42% 18% 40% September 11740 5853 13171 30764 38% 19% 43% f/1/lifi?,t ~ -Annual 8748 4086 9567 22401 39% 18% 43% ~ 1 Discharge data from U.S.G.S. records. r31/c 3 -16 TABLE 3.12 RELATIVE CONTRIBUTION OF FLOWS AT SUSITNA-CHULITNA-TALKEETNA CONFLUENCE (POST-PROJECT, CASE A) _ Flow Contribution by Percent Flow by fh!:!!.itna 1 Talkeetna 1 Susitna2 Total Flow D/S Talkeetna Chulitna Talkeetna Susitr -- ,, October November December January February March April May June July August September Annual 4859 1994 1457 1276 1095 976 1158 8511 22540 2Ei330 2t~190 1"1740 8748 2537 1187 838 671 565 492 557 4176 11910 10390 9749 5853 4086 1 Discharge data from U.S.G.S. records. 7788 9452 11930 10574 8943 8137 7990 10418 12061 10220 9553 7711 9573 -' 2 Based on 30 years of simulated power operatioilts. r31 /c: 3 -17 15184 12633 14225 12521 10603 9605 9705 23105 46511 46940 41492 25304 22407 32% 16% 10% 10% 10% 10% 12% 37% 48% 56% 53% 46% 39% 17% 9% 6% 5% 5% 5% 6% 18% 26% 22% 24% 23% 18% 51% 75% 84% 85% 85% 85% 82% 45% 26% 22% 23% 31% 43~ TABLE 3.13 -RELATIVE CONTRIBUTION OF FLOWS AT SUSITNA-CHULITNA-TALKEETNA CONFLUENCE (POST-PROJECT, CASE D) ,,- Flow Contribution b:t Total 1$7 ~ Flow D/S Percent Flow b~ Chulitna 1 Talkeetna 1 Susitna2 Talkeetna Chulitna Talkeetna Susitna -.--.~ October 4859 2537 6901 14297 34% 18% 48% (llliW ~- November 1994 1187 7380 10561 19% 11% 70% December 1457 838 8595 10890 13% 8% 79% ~.,. January 1276 671 7779 9726 13% 7% 80% February 1095 565 6765 8425 13% 7% 80% ""' "'""' March 976 492 6851 8319 12% 6% 82% ""' ~ April 1158 557 5830 7545 15% 8% 77% May 8511 4176 8071 20758 41% 20% 39% _p -" June 22540 11910 9335 43785 52% 27% 21% 51% 20% 29% "" July 26330 10390 14996 51716 -· August 22190 9749 19924 51863 43% 19% 38% "' f!iJi?'~- September 11740 5853 12371 29964 39% 20% 41% -- Annual 8748 4086 9567 22401 39% 18% 43% """" 1 Discharge data from U.S.G.S. records. 2 Based on 30 years of simulated power operations. - r31/c 3 -18 r28/u1 -- - Recurrence Interval 2 5 10 25 Recurrence Interval 2 5 10 25 Recurrence Interval 2 5 10 25 Recurrence Interval 2 5 10 25 Recurrence Interval 2 5 10 25 TABLE 3.14 ESTIMATES OF PRE AND POST l'ROJECT DISCHARGE AND STAGE FREQUENCY ANALYSIS Devil Canyon Damsite Preproject Postproject Q (cfs) 47,000 61,000 71,000 84,000 Revised Q (cfs) 11,000 12,000 13,000 28,000 Susitna River at Gold Creek Preproject Postproject Q (cfs) 49,500 66,000 78,000 94,000 Stage (ft) 13.4 14.9 15.8 16.7 Q (cfs) 13;~500 17,000 20,000 38,000 Susitna River at Sunshine Station Stage (ft) 8.7 9.6 10.1 12.3 Preproject Postproject Q (cfs) 95,000 124,000 144,000 174,000 Stage (ft) 12.5 14.8 16.3 18.4 Q _j£fs) 59,000 75,000 85,000 118,000 Susitna River at Delta Islands, Stage (ft) 9:3 10.8 11.7 14.3 Preproject Postproject Q (cfs) 105,000 138,000 159,000 193,000 Stage (ft) 94.6 95.6 96.3 97.3 Q (c:fs) 69,000 89,000 101,000 137,000 Susitna River at Susitna Station Stage (ft) 92.7 94.0 95.0 96.0 Preproject Postproject Q (cfs) 157,000 206,000 239,000 289,000 Stage (ft) 16.7 19.3 20.9 23.0 3-19 Q ~fs) 121,000 157,000 181,000 233,000 Stage (ft) 14.8 16.7 18.0 20.5 Change In Stage (feet) -4.7 -5.3 -5.7 -4.4 Change In Stage (feet) -3.2 -4.0 -4.6 -4.1 Change In Stage (feet) -1.9 -1.6 -1.3 -1.3 Change In Stage (feet) -1.9 -2.6 -2.9 -2.5 r30/F1 TABLE 3.15 LOWER SUSITNA RIVER BASIN CHARACTERISTICS FOR MEAN ANNUAL FLOOD CALCULATIONS Drainage Area Glacial Area Forested Area Lake Area Mean Annual Mean Annual Mean Minimum Stream Precipitation Snowfall January Temp. Length D.~. G F LP M.A.P. M.A.S. J L (mi. ) (%) (%) (%) (in.) (in.) (Of •} (mi.) Susitna River at 19,400 12 23 2 43 167 -4 301 Susitna Station Local Area: Susitna Station 640 1 60 5 30 70 0 to Delta Islands x-section Skwentna River nr. 2,250 16 34 5 43 140 -5 98 Skwentna Yentna River nr. 3,930 20 12 4 50 150 -5 Susitna Station Delta Islands x-section 12,580 9 23 41 182 -3 281 Local Area: Delta Islands 1,080 60 x-section to Sunshine 5 ?O 70 0 Susitna River at 11,500 10 19 42 193 -4 224 Sunshine (.,.> Local Area: Sunshine 764 0 90 2 30 50 0 I to Talkeetna N 0 Chulitna River 2,570 27 22 1 55 250 -5 87 Talkeetna Talkeetna River nr. 2,006 7 25 0 . 70 150 -2 90 Talkeetna ' Susitna River at Gold 6,160 5 7 29 200 -4 189 Creek Local Area: Gold Creek 350 0 0 20 0 to Devils Canyon Devils Canyon 5,810 5 7 29 200 -4. .~ I 1 • t ~ ~ 1, ?l 'r: c~ ] <C<~ J I J i~ l ~ ~ ~ I 1i ] , ) J 1 i r30/g1 Susitna River at Gold Creek Chulitna River near Talkeetna w I N Talkeetna River I-' near Talkeetna Susitna River at Susitna Station Susitna River at Gold Greek Chulitna River near Talkeetna Talkeetna River near Talkeetna Susltna River at Susitna Station j ~ ! j j i .J 1 j lJ TABLE 3.16 MONTHLY AVERAGE RATIOS ) -J (1-DAY HIGH AND 1~DAY LOW FLOW)/(MONTHL Y FLOW) 1 ~Day High Flow Ratios Month!~ Average ~Standard Deviation) May June July Aug. 2.45 (1.33) 1.49 (0.27) 1.36 (0.18) 1.57 (0.33) 2.05 (0.38) 1.52 (0.29) 1.36 (0.22) 1.56 (0.28) 2.51 (0.76) 1.69 (0.27) 1.64 (0.49) 1.89 (0.62) 1.89 (0.44) 1.25 (0.05) 1.21 (0.07) 1.27 (0.06) 1-Day Low Flow Ratios Monthl~ Average (Standard Deviation) Ma~ June Jul)!: Aug. 0.26 (0.14) 0.68 (0.13) 0.78 (0.08) 0.65 (0 .13) 0.31 (0.15) 0.63 (0.14) 0.78 (0.07) 0.66 (0 .10) 0.24 (0.08) 0.61 (0.11) 0.72 (0.07) 0.59 (0.08) 0.25 (0.10) 0.74 (0.09) 0.82 (0.05) 0.64 (0.05) ) 1 j J Sept. Oct. 1.61 (0.32) 1.66 (0.39) 1.72 (0.39) 1.81 (0.38) 1. 91 (0. 51) 1.64 (0.26) 1. 58 (0. 18) 1.69 (0.27) Sept. Oct. 0.66 (0.11) 0.59 (0.13) 0.62 (0.13) 0.58 (0.10) 0.63 (0.12) 0.62 (0.11) 0. 70 (0. 12) 0.60 (0.11) r30/g2 Susitna River at Gold Creek Chulitna River near Talkeetna w Talkeetna River I N near Talkeetna N Susitna River at Susitna Station Susitna River at Gold Greek Chulitna River near Talkeetna Talkeetna River near Talkeetna Susitna River at Susitna Station 1 I 1 ' ·~ TABLE 3.17 MONTHLY AVERAGE RATIOS (3-DAY HIGH AND 3-DAY LOW FLOW)/(MONTHLY FLOW) 3-Day High Flow Ratios Monthly Average (Standard Deviation) May June Jul~ Aug. 2.24 (0.96) 1.42 (0.23) 1. 29 (0. 16) 1 . 49 ' ( 0 . 30) 1.91 (0.31) 1.40 (0.19) 1. 28 (0. 15) 1.47 (0.26) 2.33 (0.60) 1.51 (0.22) 1.44 (0.30) 1.69 (0.45) 1.89 (0.39) 1. 20 (0.05) 1.16 (0.05) 1.23 (0.07) 3-Day Low Flow Ratios Monthly Average (Standard Deviation) May June July Aug. 0.28 (0.14) 0.71 (0.13) 0.80 (0.08) 0.67 (0.12) 0.33 (0.13) 0.66 (0.13) 0.80 (0.06) 0.68 (0.09) 0.24 (0.09) 0.65 (0.11) 0.75 (0.07) 0.61 (0.09) 0. 30 (0. 16) 0.78 (0.08) 0.85 (0.05) 0.68 (0.05) 1! ., l ' ·~ ~ '!! ~ ~ 1 ' ' ~ I I J ) ) ~ Seet. Oct. 1.52 (0.27) 1.56 (0.31) 1.60 (0.29) 1.66 (0.28) 1.69 (0.37) 1.53 (0.19) 1.45 (0. 15) 1.52 (0.23) Sept. Oct. 0.68 (0.11) 0.61 (0.12) 0.64 (0.13) 0.59 (0.10) 0.64 (0.12) 0.64 (0.11) 0.71 (0.12) 0.63 (0.11) ! ) l .o. !J l t J!j h 1 J J ) ' i r30/g3 Susitna River at Gold Creek Chulitna River near Talkeetna Talkeetna River w near Talkeetna I N w Susitna River at Susitna Station Susitna River at Gold Greek Chulitna River near Talkeetna Talkeetna River near Talkeetna Susitna River at Susitna Station ~ i j : ·~ j j i J TABLE 3.18 MONTHLY AVERAGE RATIOS ) J ~ J (7-DAY HIGH AND 7-DAY LOW FLOW)/(MONTHLY FLOW) 7-Day High Flow Ratios Monthly Average (Standard Deviation) May June July Aug. 1.87 (0.46) 1.28 (0.15) 1.17 (0.10) 1.33 (0.20) 1.75 (0.23) 1. 29 (0. 14) 1.19 (0. 08) 1.34 (0.17) 2.00 (0.39) 1. 32 (0. 15) 1.25(0.15) 1.43 (0. 27) 1.62 (0.33) 1.14 (0.07) 1. 09 (0. 04) 1.17 (0. 06) 7-Day Low Flow Ratios Monthly Average (Standard Deviation) May June July Aug. 0. 34 (0.15) 0.77 (0. 11) 0.86 (0.07) 0.74 (0.11) 0.38 (0.12) 0.73 (0.12) 0.82 (0.05) 0.73 (0.09) 0.30 (0.12) 0. 72 (0. 10) 0.81 (0.07) 0.68 (0.09) 0.42 (0.26) 0.84 (0.07) 0.90 (0.05) 0.76 (0.04) J l i l l J j Sept. Oct. 1.37 (0.18) 1.43 (0.23) 1.41 (0.17) 1.54 (0.20) 1.45 (0.22) 1. 38 (0. 14) 1.31 (0.12) 1. 34 (0. 16) Sept. Oct. 0. 72 (0.10) 0.65 (0.11) 0.69 (0.12) 0.61 (0.10) 0.69 (o. 11) 0. 68 (0. 11) 0. 76 (0.11) 0.68 (0.13) r30/g4 Susitna River at Gold Creek Chulitna River near Talkeetna Talkeetna River w near Talkeetna I N .p. Susitna River at Susitna Station Susitna River at Gold Greek Chulitna River near Talkeetna Talkeetna River near Talkeetna Susitna River at Susitna Station .... J i I J I TABLE 3.19 MONTHLY AVERAGE RATIOS (15-DAY HIGH AND 14-DAY LOW FLOW)/(MONTHLY FLOW) 15-Day High Flow Ratios Monthly Average (Standard Deviation) May June July Aug. 1.51 (0.20) 1.13 (0.07) 1. 08 (0 .04) 1.16 (0.10) 1.48 (0.14) 1 .15 ( 0. 09) 1.11 (0.04) 1.17 (0.09) 1.53 (0.16) 1.15 (0.07) 1 . 11 (0.06) 1.19 (0.12) 1.38 (0.22) 1.06 (0.04) 1.05 (0. 03) 1.12 (0. 04) 14-Day Low Flow Ratios Monthly Average (Standard Deviation) May June July Aug. 0.48 (0.21) 0. 77 (0. 11) 0.92 (0.05) 0.83 (0.09) 0.50 (0.16) 0.84 (0.10) 0.89 (0.05) 0.83 (0.08) 0.45 (0.15) 0.85 (0.06) 0.90 (0.06) 0.81 (0.10) 0.61 (0.24) 0.92 (0.04) 0.95 (0.04) 0.87 (0.04) ' ' 1 ' -~ ' ~ ·~ ~ '!\ I Sept. Oct. 1.19 ( 0. 08) 1. 26 (0. 10) 1. 22 (0 .10) 1. 32 (0.11) 1. 22 (0. 10) 1.23 (0.08) 1.17 (0.07) 1. 23 ( 0.11) Sept. Oct. 0.82 (0. 10) 0. 73 ( 0.11) 0. 78 (0.10) 0.68 (0. 10) 0.79 (0.11) 0.76 (0.09) 0.86 (0. 10) 0. 78 (0.14) 1\ ] ' ~- ,-..-.,., TABLE 3.20 r- """ AVERAGE RATIOS OF ANNUAL DAILY LOW FLOWS TO ANNUAL MONTHLY LOW FLOWS ~ '"" (~ 1-Day 3-Day 7-Day 14-D~ 30-Day 60-Day 90-Day """ Susitna River near Cantwell 0.98 0.98 0.98 0.98 0.99 1.02 1.06 Susitna River at Gold Creek 0.97 0.97 0.97 0.98 0.99 1. 02 1. 08 ,_, Chulitna River near Talkeetna 0.96 0.96 0.96 0. ~}6 0.99 1. 03 1.10 ... """ Talkeetna River near Talkeetna 0.96 0.96 0.96 0.96 0.98 1. 02 1.07 -~ ,,_ Susitna River at Susitna Station 0.92 0.92 0.92 0.92 0.99 1.10 1.06 ·- !~ r31/c 3 -25 Oct Nov Dec !1&0 o.o o.o o.o o.o o.o (),O o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o J6·1 .2 o.o o.o o.·o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o w o.o .o. () o.o I o.o o.o o.o N o.o o.o o.o ()I o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o ·o.o o.o o.o o.o o.o 0;0 o.o o.o o.o o.o o.o o.-o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o J J J Jan Feb Mar Apr May Jun o.o o.o o.o o.o o.o o.o 1),0 o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o 0 ,C) o.o o.o o.o o.o o,o o.o (). () o.o .o.o o.o o.o 010 o.o o.o o.o o.o o.o o.o o.o o.o o.o O;O o.o o.o o.o o.o -o.o o.o .o.-o o.o o.o o.o o.o o.o (t,O OoO o.o o.o o.o o.o o.o-o.-o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o (I ,O o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o 010 o.o o.o 0•0 o.o o.o ().0 o.o o.o o.o o.o o.o o.o o.o (), 0 o.o. o.o o.o (),() ' o.o o.o o.o o.o o.o o.o _, o.o o.o o.o 1),0 o.o o.o o.o 0·0 o.o o.o o.o o.o Ch 0 o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o ·o. o o.o o.o o.o o.o o.o o.o ·o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o •. b o.o o.o o.o o.o b.o thO o.o o.o o.o TABLE 3.21 Average Monthly Spill Below Devil Canyon Dam J I I ~ ' -~ -,o;, ~ '11 ~- Jul Aug Se~ o.o o.~ (),. o.o o.o o.o o.o o.o (),() (),IJ o.o C) • () o.o o.o o.o (.1,() o.o o.o 0·0 J~t.6 o.o o.o o.o o.o o.o o.o (),0 o.o. o.o 0 ,.() o.o o.o 0 .!) o.o o.o o.o o.o D90 ,5 o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o o.o tl49. 0 o.o o.o o.o (). 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' : -, 17 --: _-. ·-. . . ---~, .-__ ---I -I' -H-::r-..::...:.1 ~ .... , .·· :z -13~ -12~ ' ll:r ~i£~ .· :;c: ' jc_c : c --; -----t=-~ r-:J-~ -! ,--·- j ~:c~l · i ' ~--~.-.-~-; -f=-:c: " I t "' "' "' %OFTIIII£015Ct1ARGE EOUALLEOOROCEf()[O ··~T·M-·1111 ~ I ---PRE-PROJECT FLOW ---CASE A (OPTIMAL POWER FLOW) ---CASED (MINIMAL FISHERIES IMPACT) Z CURVES GENERATED FROM 30 YEARS RECORD OF HISTORICAL, SYNTHESIZED AND SIMULATED AVERAGE MONTHLY FLOWS fiE VII~ "' 3 1=-1-1- ~ 2 0: o;~·····: ,-·==t '~ ~ ,·--~-. ! ~ T¥~===-·_ ·--~ _:.T-~ : : : ----+---+- 10 3 ! w w 4D ~ ~ ~ ao o/oOFTIIIIEDISCHAIIGE EQUALLEOORfXCE£()[0 MAY "~1§·~-± ·~ 9 ·O:~~.~~CC·CC~=-~~~~~~ ,.'-+-~-+-~--i-..,-...;--~-.---r-.,---' % 0~ TilliE DISCHARGE EOUIILLED 011 [XCEEOED acTa••~~~ FIGURE 3.8 ~ " " " " " G F E +- D c B [i] ~~~TSN~A" r:c:.~~~ c ~.~:~~o~J:c~ A MONTHLY AND ANNUAL .. LDW DUIItATIDN CUAv•• .U.ITNA lltiV.IIt AT .U.ITNA .TATIDN t 2 1-r~ ~--~-· 1-1 ~---·~---~· I I I I t I I I I I I I I I I I • I I G F E - D c B ,. l I ! 10 II ~ ,• ---;~.----,~ ~ f¥4f··=t= .___un --==1 ·j'-jllt~w~;:· 1- I~ ~: ~ :~ 10: . ' "' ro %Of TI .. E OISCMoUUit. EOU4LLEO OA HCE£[1[0 ..IANUAIIIY -~---:-::L::=: =+--t==1 =~== ~ ~-·· --· ·J· l~ --~_;-= j l :~ --- :---1- ___ =r-= 1o3 -+-=:. ro %Of TIME OISCMAitiiE EQUALLED OA EXCEEDED •o' ·~ !~ .I UN. -± I 1-----c--====f~ - ~ ::.L:..- -=---t-== ~-~ ~f-~ -~--j --=- " " " " 10: ~~r-c:~~ t=f\~ ·-""! _c_•tc •o't§:::::-' ' -. ~;·:"=:::--:~--:-"fcc. ,r+,+r~ :1_ - .. ~~~0!_-7-; •o'~ -:.::t.:::==c: ::r-- " g oo , . ' . -.:; :--:. -;----.-6 ~ j::_='f:~-- '--+~ :='=---.=:; ~·~- '-"+cf·c_c --,='-P'- %Of TIM£ DISCMAJIU EQUALLED 0A EXCEEDlD NaV•M-·11111 10 g t ----.-.......__._;.--...,,. 8 7 • I 10:-J--~----- "'+-~---'-~--'---_;.-~-,---=--~--' 'o/oOfTIM[OISCHi&RGE EOUALLEOORnCEEOEO .... -=-UAJIY -=-~-;~ _-=-! ---~ ": =-~ ; =~ ! --+~-=~~--\} ir~~~~·~·~· ~~~~~~~~~'~-~ f ~--= :_~ -- 1---~ . .... : ~ -' ' h '! ~4-~-c=c-F ~--~ " W=£ + • _'~J tl ~ T J:=: --]-:---:=-.-_-~- -- -·~---i _-i L-=-. ~-:--r - 103 I "t,OFTIIolfDISCt-IARGE EQUALLEOOREXCEEDlO .JULY l_ ~---r. · -~ r-Ta --- ~ -~=~t-,~-==-L=~d ~ •oi~--EP:itJJ:o --7 ~ 6 ~ ,: ~?~Et~r~-~ . ' !>+:S.. 103 t·~:~~- 8 3-32 ,-~='}~ •1.· !10 ro 10 110 "t,OFTIIIEDISCMAitGE EQUii,LLEOOitEXCEEOED a•c•M••R s -~i ;;:;: 7 ~ t ,,' j ' -.- ' - ' ' - ' 6 !5 ';~=--= •• ~;-~=----•. uc:~~~-~~ ~-u~·~g} 0:+---~---:---:--: '~ ~ ,'+----~-~-~~-~-,--~~ 0 10 20 30 40 !10 M 70 80 9Q 100 %0fTIIIEDISCMAitGE EQUALL[00"EXCEEDE0 MAIIIIICH ·; i---= ~~ --===---c_ • ·~~ -·-~ '+-----,-----!-----~--~-=!-·-=---=---­ ;---- --ct~~~-= i ~ --I:-==~ \1 ~__:_ ---,.._-:-:__= -' ~ 6 ~ -. . ,)==----, -,-ci ; . -=-~ ! :: l J --'- ~ . ~-:+---l-__ -l" ____ ~ __ -, ,,t .-:-_ ~- ~ 10 zo w 40 !10 ro ro ~ ~ ~ %Of TillE OISCMAitGE EQUAU.EOOitEXCfEOEO AUDU.T "l!~~==-~~-?ttj ,----r-----;------~-- •' ....... i ... ·~; :51+=···-c_Ti -. ' '§ '--= ~~ ,~=-: 3·C ---y::;;ey~ ,0 ,,'+-~~-~-~-;----;.-~-..;_~-~- "' %OFTIIoiEDISCMAitGE EQUolLLEOOR[XCEEDED ANNUAL 6 !5 ~ "' ~ ' 1= . =-E ',-; ~'" t --_ ~ :~ =' ~ . ro ~ ~ ~ w ro ~ ~ %DFT•OIEDISCH,tt.RGE EOUALLEOORDCEEOED A~IIIIL ... . . --·~ l~n ~~CT-C : -----------, -i - -__ ! ______ -.---- ' . 10:+----·-Cc:_cT =>o -r----=- ;---- •o'-t--~-~~-~-,--~~-r-~-,---' t •o ~ M ro 'f0 0fTIII[OISCHARGEEOUALLEDOREXCEfOEO ··~T·M-·1111 liQll.S.;_ I ---PRE-PROJECT FLOW ---CASE A (OPTIMAL POWER FLOW) --·-CASE 0 (MINIMAL FISHERIES IMPACT} 2 CURVES GENERATED FROM 30 YEARS RECORD OF SYNTHESIZED AND SIMULATED AVERAGE MO"'THLY FLOWS IU:\IISIONI. 4 3 J=-J-1- ~ 2 '!l ';1------=======-:~-~-~ =_ ~=1\1 '" ----..,__ ~ ·~ . -' r~ ~ ~ :l -: --':Str-=1-' 0 ' 10 ' ' lO W 40 ~ M ro ~ %OFTIIIEOISCMAitGE EQUALLEDO"EXCHCEO MAY ,, . ~ "~---.-~~ -.---~~, ---.... ·.---.--~ ' ---~~--------~- 8 -' --~.---- ~ . . I--- !> ·------------·----·------~ . -·--~ - 4 ----~-~-~ ~---- ------~---- ·:Ef~·.·~··· - -i ;-=----=-·-~ --, -, ~~ r- "' "t,OFTIII(OISCMAitGE [QUii,LLEDO"nCEE0£0 acTa••,. FIGURE 3.7 [i] ~~~,~~A"~~:~~ c ~.~:~~~~:c: MDNTHL.Y AND ANNUAL. "L.DW DURATION CUIIIV •• .U.ITNA IIIIV.III AT •uN.HIN. t 2 1-1~~ 1-·-~--· 1·-I ~--· r-r--· I G F E .... D c B A -• • • • • • • . • • '. • Q• , " • .: : . . . .. . -. -. . . ~-. .. . . ... . . r·, . . :, I 1\~ . ,, I I. I I I I •• I I I 1:· I I I I I .I 10!5 9 8 7 6 5 4 3 2 104 9 8 7 6 5 4 cri tJ.; 3 (..) z 2 w (,!) 0:: <! r:r XI (..) 9 (/) 8 0 7 6 5 4 ' ! . -· ('-J '"- 0 PREPARED BY t . :-.... " ' ; i l i . t . . • I • l • I . ' ··~I• I I . . . I • 1 • . ,. J 4 .k ' I :;:: = • :::.-·~. r:.:... ... ;: ... ;:., .... ,_ .. ·~~~ ~ - :: ''-"' .-1· l I k'Jo,-1!-)( ; " .,.. ;.;,--;-.,.. . , . I . ........ ,, i -.-. I -.... ' '.'\. l ' i i SliSJJfl\ a .Pn~ T-Pt-; .I;.;; r i --~ )..l\.1! TTT TTl T-l y ->L ,;.:. ·.;. ,: : ·~ r I -.... ; r i I "'C -N .. ~:["\.-1 I I I -ITT T /' -~11\\:>r:l. A/! i_ I j « I i_ -~ -,;: X --;:-;. l -.-• . ' l ' --' ' " _.._ 1 ' "'" ILl,.""' I ;oo... ......... ' . I 1'-i I ~ ~ ' I I 'II.. -. 'T'""+oo., ~ I I T I i i i I I 1 I ........... ,_,.._ I I ' T I T ' t r i 1 l i ; I .. ;, f"' ~ l ; --;- t • -. • l ' . _I . , I , j ; ; T ,T l ' I ' ,-. ~ . ~ ~ ; . ; I j -.-'j • I I i ' I i ' I t I I I I I . 10 20 30 40 50 60 70 80 90 iOO 0/o OF TIME DISCHARGE· EQUALLED OR EXCEEDED PREPARED FOR: ANNUAL FLOW DURATION CURVES AT . R&M CONSULTANTS, INC. SUSITNA-CHULITNA-TALKEETNA CONFLUENCE FIG. 3.8 _ 3-33 "----.. --·-.:.· •. l 1 -·- - 3 __ - .. 2 __ r-1-- - u) LL: - (.) I (/) 10~ 17 w g_ (!) 8_ 16 a:: .:> -<t 7_ :I: 15 ~ (.) -+-~ (/) 6_ -14 0 1-5_ --w ::!: .. -13 w ::::> -~ LL ~ 4_ I -X 12 w <t .(!) ::!: 3_ <t --1-.. II (/) .. -.. ---· ·- ·'--- 2- -10 -- ~g - ' ' 4 8 ' IQ'--'--L_ ---'-· --.. --.. --~-·-.. ---------·-· ... ---"---'=---... ----· --· ... 2 5 10 25 50 100 PREPARED BY• RETURN PERIOD YEARS ' PREPARED FOR: - i::)~ SUS ITNA RIVER AT GOLD CREEK I AP.nr~ I if,·B··· .. · .• -...... _,, .. -:.·:.->' PRE AND POST PROJECT RIM CONSULTANTS, INC. ' ---. ------------__ ....._ __ ...... --------- ~~~~--~~--~~~--~~~~-···· --------------~ l~~' ~ -"'"~ ----. [ .. 1 ,. .• I I I I I I I ·a I' I ..... I I I I I I I I .. 106 ' 3XI05 ' : I 2 XI05 I , u) lJ.: 0 I (/) w (.!) 0: <t 105 ::I: (.) - (/) -0 :E ::l ;.;E I== -X <( :; ~4 XI04 . . l . 4r 2Xl01 r r . ! I ~: lO ' . . ~' PREPARED BY• 't::l k~ ' .. :·· ~;-· M. '-r-":.: (S _.... . ~ R&M CONSULTANTS, INC. ~-. 0. ~ . "' . ·~ '.· m -- " . ' . ·n 11. . . ' ' . •• I ' . i ~!! 'H I li .H . ·H !.;o ~ ~ . t l "" .I ..... ~ I v i l . ' _l. '. . . '" '· '' . . ,, . '··· . . . """; ,._.;'I ~ ~ ' i; • 1·4 t ~ t " ' R ~ ; -ql l HJ• lH I !>t ;:H !U j .. -~ i t If 2 5 10 25 50 too "' RETURN PERIOD -YEARS . SUSITNA RIVER AT SUNSHINE PRE AND POST PROJECT . DISCHARGE ·-STAGE FREQUENCY CURVES 3-35 .. _ .. --.. " ... "'",.. ,. . .. , ·~··· ~" " . .,, .... «•· • .. ' ,.,_,...., - . . ' l I ' .'20 * . ! l 19 . • ~ ~18 t ; ._ f 1 f-i7 w l ~ 16 w . i LL.. ~15 I i t-14 H ._ 13 :I: (.!) 12 -w ll ::r.: w ,.._ tO (.!) . <! ~ ~ 9 (!) =;:;:;::::: '. •·; . . l\ .... . •· . ' • \_J. r: i ' t' -~ ·t .t i) ~ q f. II f ' f ~ n I l . J I t I I. PREPARED FO R: FlG. 3.10 All ~ .... •' . , .... ,,, ~ .. ~ ... ,~.. ... .. . ,., ..... - - r- 1 (/) Ll.: (,j I (/) w C!) 0: <t (/) Cl - 99 -97 ~~~~~~~~~~~~~~~~+H++~I/~~--H+HH~++~-++-*H+HH-~~95 ~ LLJ 94 LL. I I 93 w C.D <t 1- 92 (/) 1 Q'.llJ..UlUJ.l.L.l...Ll..L.Ll...Ll...LJ...LLLL~Lll.L..U..LL.JI..U...J...tJL.ll..L!..Wl..4-.L.LL....l..J-t--'--t.J..LL..J.+u..t...:L...Wi...-J....--L-L-.J:u.u:...u....L-I.-..I 2 5 10 25 50 100 RETURN PERIOD-YEARS SUS ITNA RIVER AT DELTA ISLANDS PRE AND POST PROJECT DISCHARGE-STAGE FREQUENCY CURVE 3-36 PREPARED FOR• FIG. 3.1;. -~ ··~ = -J-20 t-= LL.. en 19 I LL.: 18 t- ::::t: u : J-17 (!) -I -r-16 w (/) L[ 1-'H' II ::::t: w t-15 (!) w a:: 14 (!) <( <( ::::t: 5 13 (!) u 10-~ (/) E - Q ~ ~ • :::: ~ - X ~ <( § ::?! --E !"""' ' ~~~JttnmTIJTIITTIIITITll~IUlililUU~~illl~LU~~~~~LU~~~~~- 2 5 10 25 50 RETURN PERIOD -YEARS -PREPARED FOR• l II 1 1 2. 0 -__ -+-_+_ _+-_< ~-!--1+<~-+-1-i ·-· --.... ·--··--. -~ ·-.......... ; -. . -. :,.:;;t::.~~~= -.. : _,...r.~~~ .. .,...,... --p-~1-- --.• -1-------· --· ··-cRimt:~~i ---·· ---c---(/) ~= ~-¢pj~"f.ln~l . I . ~--· : . ~ J ( Q ~F (is l!f: ~/. ----. = I ~ I.O -. J........t.--1--+-++I.J.-H_ -+-~_. 1-~,_--:::1-:.::--1-_. ::---1-: _-+,, _-1-_ :.:-1-1: -,..J... __ 1-H+H+H.J+++H++H +J-..!:,O~f-t+J4+t+_H:_--I+~·H:H~H++-I-t+:.H_.I_-5,<_~:!f::,~!!,-,I:_F:!¥.:!_~'t!:~~~-'1'4-'fl"'~""fl'1'!"Ff-1f"+--l-c_f-__ -r--,:lll w > a:: :::J u --~ -f--·1-·· ·, .... ---- 1\ cc : : : -~ ·: z 0.9=:·;+··~. ~~~-~ ~-;~~:~~~±:~.~~~~~+:~+~:H;+HHHffil~H+~~~±HH.~-~--~--B···+,_H:+_B_IH_tffiffH+H~--~--~-+-~--'tffi~HH+_H_r_~ _____ + __ ~ __ _ 0 0. B .;;.:_~+~-.+. B. -t+H.::f+t+F. :·: :::+:· .· .:,:j_--::.1-:c-FEEI-:+l-l:B+f+HU~-M"t+Hl ++1-H+t++-1-1'-H--t+R--+ ... ···H--t:H+1+1+H-l-· .H-H-_ ::,J~ .:,::i __ · ~~~-+::-::;;·-_-_+H-l++l-+H-I-f-1f--=-t--F:-IH+HH-+:.,r- ~ ~7-~~~~~-~~uu··~:~~~?:~~-~-~~~~-~R:~B~~-~-~-~~~~HH~~~~+-~_H ... ~~~~H-~~~+:~~~0 ~~~ . _ ~:~z~. ___ _ :i: • -::-= ::::~:~ -·:. .... . -----. : .-::.-:~·---=: . . -. -_ -~-~-w~i ·~= -~~2. 0 0.6 .:;. ·._ -··. .. r:"'": .:.·p ~~~.: .: --1-+ .. -1-.f..t:t-:. 1-1-1·· :···. -. -H--:·+.l1~·~,~+~-~~~~H·':E· ·'"""·H···b;·l+l+lr-t+H;-H-t""c···t _·f'--'F~.E-··,-:'E:'~:-:tt-E::::.:.~.:'+; H+Hii .---~,.f·_-:: I:·_-~.-rl :_I :r--.... · : 0.5 ~~ -,. _I . ~-~-... :. ;~ :: . : .. :· .. -t-+1-H!~ . --: -. . • . .. . I+ ,.. IT • - ... 1.005 1.05 1.25 2 5 10 20 50 100 200 500 10,000 . -~--~ . . .r.l : .. : . I~~ -~~+-H~~. ~1-+--H • .. . . •. •• • . -~ t ~I~~ . f+ 1~· ~ ~--_· ·_ ---~-: 0.3 -:::~f:.:..+-.. H .. +1. 1+111 +++·_H _--~---+-__ --'~=f-::\-~--~---H __ +_~ ·1-t+lr++H+t. H-.+~ :H· -.. ~-~-_+_-!_ --~--_' H·H-H++++ . ·. · ... ,. ·: l-t~-1--l+l·,.ifH_ -1-+1-1-1-.· ... ::. :·.:::. :-:.::·: • . I .· . . . _l,. I :: ·-i RETURN PERIOD ( YRS.) l Pr ared for: R&M CONSULTANTS, INC. DESIGN DIMENSIONLESS REGIONAL FREQUENCY CURVE ANNUAL INSTANTANEOUS FLOOD PEAKS _FIGURE_3.13. - - 4 -SEDIMENT REGIME 4.1 -Suspended Sediment The concentration of suspended sediment in glacial meltwater streams in Alaska is 10-20 times the concentration in nearby non-glacial streams (Guymon, 1974). Most of the suspended sediment is transferred during the summer months. The Susitna River tr·ansfers over 98 percent of its annual sediment load during the months of May through October (Corps of Engineers, 1975). In general, there is no simple relationship between sediment transpor·t and water discharge in glacial meltwater streams (0strem, 1975). Suspended sediment concentration varies with time as well as with discharge over periods of one year (seasonal), one to twenty days (flood sequence), and one day (diurnal). A hysteresis effect has been observed by various authors (0strem, 1975; Everts, 1976) when the ratio of suspended concentration to water discharge was plotted by month or through a flood. Visual inspectkm of sediment discharge records for the Susitna River at Gold Cr·eek indicate a similar phenomena, with large variations in sediment concentrations with only minor increases rn streamflow. Despite the problems in reliably establishing a sediment discharge streamflow relationship, some estimate of annual suspended sediment discharge is necessary for engineering and environmental studies. Consequently, power curve equations were fit to available data for seven stations within the Susitna River basin. The equations for each station are given in Table 4. 1, together· with the coefficient of determination. The curves for each station are plotted on Figures 4.1 through 4.5. On the mainstem Susitna, the sediment concentration drops for a given flow when moving downstream, due to the larger particles settling out and the larger volume of water downstream. · The annual suspended sediment duration curves for all seven stations are plotted on Figure 4.6. These were estimated using the annual flow duration curves and the suspended sediment rating curve for each station. Despite the fact that sediment concentrations decrease while moving downstream, the total sediment discharge is increasing due to the Increased flow volume. 4. 2 -Bedload Bedload data from the Susitna River was nonexistent until summer of 1981.. Three bedload samples have been collected by the U.S. Geological Survey and R&M Consultants at Susitna River at Gold Creek, Chulitna River near Talkeetna River, Talkeetna River near Talkeetna, and Susitna River at Sunshine. Bedload transport rates fc:>r the three dates are shown in Table 4. 2. Estimates of bed material size distribution were made at numerous cross-sections r32/b 4 -1 between Talkeetna and Devil Canyon, using the grid sampling technique (Keflerhals and Bray, 1971). The bed material size distribution at these sites is tabulated in Table 4.3. The U.S. Geological Survey estimated total sediment load for ten samples taken at the Denal.i gage using the modified Einstein procedure. A bedload rating curve based on the USGS estimates was established in the Corps of Engineers 1975 report and is shown is Figure4.7. Using flow-duration curves, the_Corps report estimated the annual bedload at Denali to be 1,588,000 tons per year. However, Neill (1981) has commented that bedload computations for gravel rivers are not very reliable, with different procedures producing estimates varying by orders of magnitude. From the limited bedload .data collected in 1981, it can be inferred that the Susitna River has relatively little bedload below Devil Canyon until the confluence with the Chulitna River is reached. Most of the bedload is contributed by the glaciers in the Alaska Range, although some is contributed by downstream tributaries and bank erosion. All bedload entering the reservoirs will be trapped. In addition, post-project flows will be less than that measured on August 26, 1981, when only 380 tons/day of bedload transport were measured. Most of the river between Devil Canyon and the Chulitna confluence is well-armored. Under post-project conditions, bedload contribution from the Susitna River above the Chulitna confluence may be considered negligible except for extreme flood events. The Chulitna River is the major contributor of bedload at the confluence near Talkeetna, as shown on Table 4.2, and will thus have the major influence on sedimentation and river morphology at and downstream of the confluence. 4.3 -Reservoir Trap Efficiency The volumes of Watana and Devil Canyon reservoirs are so farge that is has been assumed in past studies that 100-percent entrapment would occur. This is believed to be a valid assumption for the larger sediment sizes, but it is possible that the very fine suspended sediment may remain in suspension and pass through the reservoirs. A literature search of sedimentation processes in glacial lakes indicated trap efficiencies on the order of 65 to 75%. (Zieler, 1973; 0strem, 1975). Kamloops Lake, a 3-miUion ac-ft glacial lake in British Columbia, trapped an estimated 67% of the incoming sediment, with median sediment size about 2 microns near the lake outlet (Pharo and Carmack, 1979). The suspended sediment size distribution analysis at Vee Canyon indicates that 85% of the incoming sediment is larger than 2 microns. Kamloops Lake has an annual bulk residence time of about 60 days. Watana Reservoir has an annual bulk residence time of about 660 days. r32/b 4 - 2 - ~·· ...., .. -· -· - ·- - The long bulk residence time in Watana Reservoir indicates that an ice cove1r will probably form on the reservoir before the sediment- laden river water can pass through the reservoir. Once on ice cover forms, essentially quiescent conditions should occur in the reservoir. A settling column study of a water sample from the Susitna River indicated that suspended sediment concentrations would decrease by about 95% in 3 days under quiescent conditions. This would tend to indicate that clarity of water in the upper portion 10f the reservoir should improve fairly rapidly once an ice cover forms. It is lik1:!ly that trap efficiencies greater than 70% will occur, based on suspended size distribution, annual bulk residence time, and the suspended sediment settling characteristics under quiescent conditions. For planning purposes, trap efficiencies of 70% and 100% were assumed as the limits for trap efficiency. AIJ bedload will be trapped by the reservoirs. The trapping of the bedload will have the most significant impact on the downstream river morphology. Reservoir sedimentation is discussed more completely in Reservoir Sedimentation (R&M, 1982). 4.4 -Bed Material Movement The stability of a particle resting on the bed or channel bank is a function of stream velocity, depth of flow, the angle of inclined surface on which it rests and its geometric and sedimentation ·characteristics (Stevens and Simons, 1971). However 1 the inter- action 01f the above factors is quite complex, and obtaining data for all parameters is often impractical under natural conditions. In order to determine at what flow rates the various reaches of the Susitna River above Talkeetna would be stable, an engineering approach for the design of stable alluvial channels was used. Two major variables affecting channel design are velocity and shear stress. Determining the shear stress is quite difficult. Consequently 1 velocity is often used as the most important factor in designing stable alluvial channels. Various techniques have been developed which estimate the maximum channel velocity so that no scouring occurs for values of velocity equal to or less than the maximum velocity. However, the maximum permissible veloc- ities varies with the sediment carrying characteristics of the chan- nel. Fortier and Scobey (1926) recognized this problem, and introduc:ed an increase in their listed values of maximum permis- sible velocities when water was transporting colloidal silt. Various engineering formulas for maximum permissible velocity were presented by Simons and Senturk (1976). The formula selected for anallysis was that derived by Neill (1967). Neill's formula uses r32/b 4 - 3 data readily available for the Susitna River, and gives results in the same range as Fortier and Scobey's. The formula as presented by Neill is: where: u f t's g D d = = = = = = {frsJ-1 gO = maximum permissible velocity 1 ft/sec density of water 1 lb/ft3 density of sedHnent, lb/ft3 (assumed to be 165 lb/ft3 ) gravitational constant,32 ft/sec 2 bed material diameter, ft average depth, ft The above stability criterion was developed for use on uniform bed material or. on the median (o50) size in mixed bed material with moderate size dispersion. Nein (1968) later indicated that the bed material mixture remained fairly stable until the 0 50 size became mobile, at which time general movement of the beef would occur. The stability criteria was designed to use vertically-averaged local velocities (mean column velocities) 1 thus identifying bed stability on only a short segment' of the river cross-sectional width. However 1 only average velocity across each cross-section is available. The results from the equation would thus indicate when bed movement across the entire cross-section is imminent. Bedload normally does not move uniformly across the width of a river, but is concentrated in a relatively narrow band. Therefore, the results of this analysis are not strictly accurate, but do provide an adequate indicator of bed movement occurence. In order to estimate the o50 size of bed material which would be at the point of movement at' a particular cross-section for a given flow rate, the above formula was re-arranged so that bed material diameter was the unknown value. The average velocity and average depth were obtained from runs of the HEC-2 model for different flow rates. The formula in its re-arranged version is: r32/b u2.5 D= 464. 43 d 0 · 25 4 - 4 -.: -·· ...... - .) Using the above formula and hydraulic parameters obtained from runs of HEC-2, estimates were made of the median material size at the point of movement at flow rates of 9, 700; 17 ,000; 34,500; and 52,000 cfs. The median bed material size at the point of movement is described on Figures 4.8 through 4.13, working downstream from Devil Canyon to Talkeetna. Included on the plots are the bed material size distribution in the reach described on the figures. To assist in classifying the size range of sediment which is being moved, a sediment grade scale is incJuded on the bed movement figures. The bed material movement curves are for given cross-sections in each river reach. Table 4.5 correlates the cross-sections with river miles. Table 4.4 gives average velocities at selected cross-sections at the same flow rates. By comparing th.e bed material movement curves to the bed material size distribution, predictions can be made of the effect of reducing the streamflow, i.e. reducing the mean annual flood from 52,000 cfs to 11,000 cfs. Once the median bed material size is moved, . general movement of the bed would occur. In general, bed material size ranges from coarse gravel to cobble throughout most of the river. Some movement of the median bed material size (from the grid samples) could occur above 35,000 cfs throughout much of the river, although these samples were primarily taken afong the upper shore. Lt is believed that an armor layer consisting of cobbles and boulders exists throughout most of the river. At 13,000 cfs, it appears that little bed material movement will occur in the main channel except in the region of river miles 124.5, 131.5 and 133 and near the confluence with the Chulitna River, where bed material size is in the coarse gravel range, somewhat smaller than in most of the rest of the river. 4.5 -Contribution of Sediment Downstream Contributions of sediment downstream of Devil Canyon are primarily from talus slopes, mass wasting, erosion of river banks, and sediment contributed by tributary streams. The locations and types of sediment sources between Devil Canyon and Talkeetna are summarized in Table 4.6. r32/b 4-5 ~1'. - 0 TABLE 4.1 SUSPENDED SEDIMENT DISCHARGE EQUATIONS SUSITNA RIVER BASIN ... Station Susitna River near Denali MacLaren River near Paxson Susitna River near Cantwell Susitna River at Gold Creek Chulitna River near Talkeetna Talkeetna River near Talkeetna Equation q = 1 43 (10-4) q2.122 s . q = 8.04 (10-6) q2.523 s q = 6.33 (10-8) q2.784 s qs = 2.39 (10-6) q2~354 q = 2.63 (10-5) q2~151 s ·. Susitna River at Susitna Station q = 3 09 (10-6 ) q 2 ·146 s . q = Streamflow, cfs q = Suspended sediment discharge, tons/day s r29/a 4-6 Number of Samples 51 32 37 286 20 63 22 •••• . . I I I . Coefficient of ' Determination ( r 2 ) 0.891 0.931 0.881 0 .. 735 0.948 0.832 0.885 " I •• J. .I I I I I ' I I I J I I ·-~ ·~ ·""" - TABLE 4o2 1981 BEDLOAD TRANSPORT DATA SUSITNA RIVER BASIN Water Total Bedload Discharge Transport Rate Station Date (cfs) (tons/day) Susitna R o at Gold Creek 7/22/81 37,200 2,180 Chulitna R 0 1 7/22/81 31,900 3,450 Talkeetna R o 7/21/81 16,800 1,940 Susitna Ro at Sunshine 7/22/81 89,000 3,520 Susitna R. at Gold Creek 8/26/81 25,900 380 Chulitna R. 8/25/81 22,500 5,000 Talkeetna R. 8/25/81 9,900 800 Susitna Ro at Sunshine 8/26/81 61,900 4,520 Susitna R .. at Gold Creek 9/28/81 8,540 1 Chulitna FL 9/29/81 6,000 3,820 Talkeetna R. 9/29/81 2,910 30 Susitna R .. at Sunshine 9/30/81 19,100 400 1 Bedload data gathered approximately 4 miles below Chulitna River gaging site on 7/22/Slo Data gathered at Chulitna gaging site on other dates. r32/b 4 -7 TABLE 4.3 ~.: '", SUSITNA: LOWER RIVER CROSS SECTIONS l""'l'' BED MATERIAL DISTRIBUTION ANALYSIS ~ LRX Number o16 (mm.) o50 (mm.) o84 (mm.) """'T 4 13 25 46 5 12 21 39 6 20 47 112 8 . 19 45 112 9 14 32 72 10 58 94 152 ..,.. 11 18 43 100 14 20 36 66 16 8 26 92 18 12 36 110 19 47 80 132 20 16 38 92 21 26 49 ss 22 8 21 58 23 22 48 108 26 25 54 113 """" 27 19 43 100 28 13 31 68 29 32 59 110 .-w. 30 33 64 122 31 28 49 84 32 19 43 100 40 20 46 110 42 15 38 94 43 19 44 94 44 14 35 88 """' 46 29 53 100 i. 48 21 56 155 49 26 53 112 ....,. 50 18 53 160 51 44 88 170 53 86 125 188 ..... 54 18 43 105 55 178 220 265 56 29 73 183 57 20 47 110 ~ 58 62 112 200 59 26 66 170 """" •" j .... r32/b 4 - 8 ~ I 1""' r;-#ll"t .,.!h .¢'~ •""" ..... TABLE 4.4 AVERAGE VELOCITIES AT SELECTED CROSS-SECTIONS Average Ve.ocities (ft/sec) Cross Given Flow Rates at Gold Creek Section RM 9,700 17,000 34,500 52,000 LRX-4 99.6 5.27 4.32 4.78 4.47 LRX-7 101.5 3.15 3.86 5;31 6.09 LRX-11 106.7 2.53 3.60 5.64 6.89 LRX-20 117.2 3.15 4.13 5.13 4.86 LRX-24 120.7 3.80 5.34 8.25 10.34 LRX-25 121.6 4.71 6.94 7.99* 10.12 LRX-29 126.1 3.71 5 .. 04 7.66* 9.50 LRX-·35 130.9 3.52 5.04 8.12 10.44 LRX-40 134.3 4.12 5.43 7.67 9.29 LRX-A1 134.7 5.71 7.63 5.95* 5.71 LRX-44 136.4 5.54 6.36 7.13* 7.99 LRX-A5 136.7 4.28 5.86 9.13 11.53 LRX-·50 138.5 3.17 4.37 6.87 8.63 LRX-53 140.2 3.83 5.01 7.62* 9.56 LRX-·54 140.8 4.53 5.72 6.93* 7.63 LRX··55 141.5 3.55 4.66 6.63* 7.77 LRX-61 148.7 4.25 5.67 8.64 10.45 LRX··68 150.2 3.24 4.54 7.21 8.89 * Sloughs and/or side channels are blocked off below 20,000 cfs by gravel berms at upstream end. r32/b 4 - 9 ------·-----------------------------------------=-------------------------------------- TABLE 4.5 SUSITNA RIVER PROFILE DATA SUMMARY CROSS RIVER THALWEG SECTION MILE ELEVATION LRX-3 98.59 332.6 4 99.58 344.4 5 100.36 352.6 6 100.96 357.1 7 101.52 359.4 8 102.38 364.1 9 103.22 366.6 10 104.75 386.2 11 106.68 401.0 12 108.41 414.4 13 110.36 426.5 14 110.89 437.2 15 111.83 446.1 16 112.34 449.7 17 112.69 453.4 18 113.02 452.9 19 116.44 481.7 20 117.19 483.3 21 119.15 500.9 22 119.32 503.4 23 120.26 515.5 24 120.66 507.6 25 121.63 526.2 26 122.57 532.1 27 123.31 533.8 28 124.41 549.8 r32/b 4 -10 .. \ ...,, -\ -·· -; ~- ~· -· ~I) """"' ""'"". - """' - ..::i, ~"">.., "'"" -, -I - r32/b '·~""~~ ~F CROSS SECTION LRX-29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 TABLE 4.5 (cont.) RIVER MILE 126.11 127.50 128.66 129.67 130.12 130.47 130.87 131.19 131.80 132.90 133.33 134.28 134.72 135.36 135.72 136.40 136.68 136.96 137.15 137.41 138.23 138.48 138.89 139.44 140.15 140.83 141.49 4 -11 THALWEG ELEVATION 563.3 578.4 586.8 597.2 607.0 608.9 605.5 614.0 618.8 634.7 641.5 650.0 655.3 663.9 657.6 674.6 673.5 681.4 681.9 685.3 694.2 693.5 701.9 707.2 717.2 726.3 735.2 r32/b CROSS SECTION LRX-56 57 58 59 60 61 62 63 64 65 66 67 68 TABLE 4.5 (cont.) RIVER MILE 142.13 142.34 143.18 144.83 147.56 148.73 148.94 149.15 149.35 149.46 149.51 149.81 150.19 4 -12 THALWEG ELEVATION 744.4 745.5 756.9 775.8 808.5 819.5 822.3 827.2 825.4 836.1 837.2 840.6 829.6 . I ~· - -- -~- - ·,;o.. - - - TABLE 4.6 SEDIMENT SOURCES DOWNSTREAM OF DEVIL CANYON Location Vicinity of RM 149.5 Island at RM 149.3 Downstrteam of Island Mouth of' Portage Creek Vicinity of RM 148 Island at RM 147 Downstr1eam of Island at RM 147 r32/b Sediment Source and Type Talus slopes delivering material at each steep narrow ravine. Valley walls controlled by bedrock outcrops. Cobble and gravel material on midchannel bar at river expansion. Island surface paved with cobbles and boulders, intermixed with sand and gravel. Bedrock controls both river banks. Bedrock controls both banks, but some talus slopes delivering material. Creek is delivering coarse gravels, cobbles, and a few boulders, developing an alluvial fan into the river. Fan is truncated where Susitna River flow becomes significant. Significant bedload delivered at high news. Local change in river gradient has caused formation of a mid-channel bar in the river expansion. Island is well vegetated above normal high water, with its banks paved with cobbles. Some sand deposition exists in the backwater zone on the downstream end of the island. Alluvial deposition exists on the right bank where the main channel is abutted against left bank. 4 -13 Location RM 145.3 Tributary on left bank at RM 144.8 RM 143 Near RM 142 Upstream of RM 141.5 RM 141 to RM 139 RM 138.9 r32/b Sediment Source and Type Some erosion along the main channel exists, along with mass slumping. A mid·channel gravel bar exists where the river has eroded laterally, widened, reduced its velocity and deposited bedload at high flows. The bar may continue to grow, forcing the channel into the right bank. 30-foot wide stream is very stable with vegetation leading down to a predominantly boulder/cobble bed. It does not deliver significant sediment to the river. Moderate erosion and scalloping of the right bank. Several mid-channel bars exist, but appear to be unstable, with young brush growing on them. River is trying to erode into the island on left bank ·downstream of LRX-56. Gravel is being deposited in the center channel and trying to create a split channel configuration. Acitve erosion of the island on the left bank of the main channel. The river is undercutting the bank, causing slumping into the river, with the sediment being only temporarily held by coarser material and vegetative roots. A mid-channel gravel bar is building. The river is meandering across the valley, eroding valley wall material and depositing it on mid-channel bars. Glacial/fluvial deposit of gravel and cobbles on the right bank appears erodible at high flows. Topsoil over the gravel alluvial deposits would erode at high flows, although it is stabilized with vegetation. 4 -14 -, - - ~ .. - fl-. - r Location Mouth of Indian River RM 138.3 RM 137.2 Mouth of Gold Creek Sediment Source and Type Indian River is a steep stream capable of contributing considerable bedload during high flows, although there is no glacial input. Material near its mouth is coarse gravel and cobbles, as smaller material is carried away by the Susitna River. The cobble material helps stabliize the right bank of the Susitna. An alluvial fan has been built out into the Susitna River, forcing it into the south valley wall. Moderate to active erosion along the left valley wall fc:ir approximately 1 ,000 feet, leaving a cobble paved bank. Moderate to active erosion on the right bank on an outside bend, extending for about 1,000 feet. Erosion occurs at high flows; at normal flow, cobble material armors the bank, resisting erosion. Gold Creek bed is paved with boulders. Downstream of Gold Creek bridge Moderate to active erosion of topsoil and gravelly material along the right bank. Primarily, though, the river is reasonably stable, with shallow sloughs and gently ·sloping gravel bars along the left bank. At high flows, there will be some scour and deposition in the high water channels. Between RM 135.4 and RM 134 The valley wall is being eroded by the left bank high water channel, contributing a moderate amount of sediment during high flows. r32/b 4 -15 ------~-------·---·-------------------------·------------------------------·----------------- Location RM 134.3 RM 132.5 Mouth of Fourth of July Creek Sherman RM 130 RM 128 RM 124 RM 123.5 Curry. r32/b Sediment Source and Type Active erosion and undercutting of the past alluvial deposit on the right bank to just downstream of LRX-40. There is also moderate erosion of the steep high bank on the left bank, with vegetative mat overhanging the bank. Erosion extends for about 1, 000 feet along the left bank. Erosion of sand and gravel on a mid-channel bar is causing short-term local transport of bed materials. Little sediment build-up at the creek mouth indicates that the creek does not carry much sediment. The creek slope is relatively gentle as it enters into the Susitna River. The channel is constricted by alluvial deposits on both banks, with the bank lines well armored with cobbles and boulders, resisting erosion. A few areas of instability are located along the intermediate gravel bar. The river broadens into a braided pattern, with the main channel meandering from the west to the east edge, causing unstable intermediate gravel bars. Moderate erosion and slumping of fine material for about 800 feet along the left bank. Active erosion a tong the right bank. Although the left bank is an alluvial deposit, it appears quite stable. 4 -16 Loc:ation Curry to RM 116.4 RM 116.4 to IRM 103.2 -RM 103.2 to RM 102.4 RM 102.4 to RM 101.5 - Mouth of Whiskers Creek - r32/b Sediment Source and Type A typical split-channel condition exists in this reach 1 with no unusual erosion or breaks in the river gradient. The river is very stable due to coarse bed material armoring the bed and due to well established vegetation above the normal high water mark. The river remains stable, flowing in a well-paved bed with well-established vegetation on the banks. Several large remnant boulders are in the channel, probably deposited from glacial processes. Erosion in this reach can occur only at high water levels 1 as a cobble paved bankline lies beneath two to three feet of soil. The left bank at LRX-8 is eroding at the outside of the meander 1 but only at high flows. Deposition is occurring upstream and downstream of LRX-8 along the right bank. The western floodplain elevation lowers at RM 102, becoming more erodible. The channel splits and start to meander in the braided/split .channel pattern. The shifting channels appear to be caused by a sudden decrease in gradient, deposition of bed material, and erodible banks. The banks at LRX-7 are moderately erodible at high flow. Bed material is cobble with a thin layer of fine sediments. The creek joins the west sub-channel on the outside of a meander, helping to keep Susitna sediments away from the mouth. The right bank materials in the west sub-channel have five to six feet of fine material overlaying easily erodible gravel. 4 -17 ..., .,....,....., Location Downstream of Whiskers Creek RM 101.0 RM 100.5 RM 100 RM 99.6 r32/b Sediment Source and Type Fine material overlaying gravels would erode at high water levels. A mid-channel bar covered with young vegetation appears to be well established, helping to keep the major sub-channel to the east. The main channel JOins the west sub-channel. A scallop in the right bank indicates turbulence during extreme flows. Numerous gravel bars appear with the river becoming wider and shallower. Seve raj examples of cross-channel flow reflect the instability of the bed through the lower reach. The floodplain elevation lowers, with bank material appearing easily erodible at moderate to 'high flows. Sank erosion in this reach is accelerated by undercutting of trees which fall into the river, creating sweepers, turbulence and niching of the bank. The west side of the channel is in a very unstable condition. Easily moved bed material creates numerous gravel bars which catch debris, forcing the river to create new channels which are constantly moving back and forth. Along east bank, erosion will probably occur only at high flows. An ice jam occurred here in 1981, and is believed to occur virtually every year. 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SUSPENDED SEDIMENT DISCHARGE (TONS I DAY) SUSPENDED SEDIMENT RATING CURVES SUSITNA RIVER NEAR DENALI AND MACLAREN RIVER NEAR PAXSON Prepared for: FIGURE4.1 • , ______ _.. .... -.. ----~. .... -- I 1,000 I 2 I 3 I I I I I I I I I I I I l I I I 4 5 6 7 8 9 10,000 2 3 4 5 6 . 7 8 9 100,000 f 2 I 3 I 7 SUSPENDED SEDIMENT DISCHARGE (TONS I DAY) SUSPENDED SEDIMENT RATING CURVE SUSlTNA .RIVER NEAR CANTWELL (VEE. CANYON) ________ .. _ . --------- I .. ! ~ h I I I 1,000 R&M CONSULTANTS • .lNC. I I 2 3 I I I I ~ I I • · • I l I I I l I I I 4 5 s 7 a 9 1 o,aao-. . 2 3 4 5 6 7 s 9 1oo,ooo SUSPENDED SEOIMEN.T DISCHAR~E (TO.NS /DAY) SUSPENDED SEO·I~1ENT RATING CURVES SUSITNA RIVER AT· GOLD CREEK I I • I I I 2 3 4 5 6 7 Pr ared for: ·. FIGURE 4.3 ----------.. --.. .. .. ---- l ~ . ' . !i_ ---~-I-!-· I- ! Tf t jq ,, J . i ; . ' . I : : .. ; . .: ; ... • li . 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IJI· <( .. 1·-1-:-1-1-1-!- :I: ,_ I·· I-1-1--,...._ I·· ~-!-!-.. ,_ 1--I~ • )i U\::' j (.) .. 1--f-I • i. r· 1-I-1-1- !i[!tL . 1-1--.. 1-I·• f· I· 1-1--1-!· I· (/) ~--f-i l f• [j' ·~ ; -,_ 1-1-1--i-1---1-1· a 1-t--I~ f.-1-i-I· -I~· 1-· 1·-I· ,_ i-1-I·· ' i. . II !f.: .. h· J t ·-1--. ~· l-,, , .. II !~~~~ -t,o6o I 1 I I ' I I I I I I ' I I I I I I I • I I . 1,000 2 3 4 5 6 7 8 9 10,000 2 . 3 4 5 6 7 8 9 100,000 2 3 4 5 6 7 -n --...1 by· . SUSPENDED SEDIMENT DISCHARGE {TONS./ DAY) . n. __ : .'1 ~~or· i L-.~u ... J::'J.. ·: i . - I . -' ~ i. " ~~J ~) ~ ~ l . t .~ SUSPENDE.D SEDIMENT RATING CURVES : ll ~-._ c.s .i. ' R&M CONSULTANTS, INC. CHULITNA AND TALKEETNA RIVERS 10 FlGURE 4 .. 4. ' ' _;_ ... ~.::.. . . .. .·.· . . ',. .J:> I N w -Cit -u - liJ (!) a:: 4: :r: 0 (/) -0 -· ----· ' : .. : --1-.... 2--· -· ---------. --------·· ---- --·--------------·· .... .. -------.. . I I 1,000 2 Prepared by: ~ -~ CJ~ .. :1.: c::s ,~:~! 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Lt~u. ~ lJtt~Il li!ItV1TlJ HtL.-1 ----: ···~•·· fl L 1 IILliiTJJriJ i_JIFI!l}U_ULUI 0 20 40 60 80 tOO 120 140 150 180 PREPARED BY, MI\XIMUM BED MATERIAL DIAMETER MOVED, MM PREPARED FOR: BED MATERIAL MOVEMENT CURVES R&M CONSULTANTS, INC. LRX -4, -7, -9, -12 FIGURE 4.13 ijJ -----------~~· ~-··-----..............-·-.. -- ;:j 5 -QUALITATIVE ANALYSIS 5.1 -Response Relationships Hydropower development in the upper· Susitna Basin will change the sediment and flow regimes downstr·eam of the project until the effects are either diluted by tributaries or until related dominant geomorphic processes override the pro>ject induced changes. Flow of water and sediment are the independent variables which determine river channel morphology, and for which the· project will establish a new regime for. The remaining channel dimensions, shapes 1 patterns and hydraulic parameters will be forced to respond and perhaps eventually establish a new balance. Morphologic parameters that are dependent on and would respond to alter·ed water discharge and sediment load include: d -mean depth, determined by dividing the area by top width w -surface width of channel w d -channel shape, width-depth ratio S -Slope, river gradient D -bed material size, o50 ML -meander wave length 1' -Sinuosity When considering a specific river reach there is a defined pattern that the river has developed or is striving to achieve. A pattern change could occur if the independent inflow variables of sediment load and water discharge were changed. However, certain constraints are imposed onto the system which could predominate and locally override both the independent and dependent variables. The potential constraints consist primarily of remnants from past geologic processes such as valley walls, bedrock outcrops, and glacial/fluvial processes. Based on research results of Lacey (1929-30), Blench (1937), Lane (1955L Leopold and Maddock (1953), Santos-Cayudo and Simons (1972) and Schumm (1971), the following general statements concerning a river's response to ajtered water discharge and sediment load can be made. r30/a Depth is discharge discharge. directly proportional to the cube root of and inversely related to the bed-material 5 - 1 (2) Channel width is directly proportional to the square root of discharge. (3) Channel width is directly related to sediment load. (4) Channel shape (width-depth ratio) is directly related to sediment load. (5) Meander wavelength is directly related to discharge and to sediment load. (6) Gradient is inversely related to discharge and directly related to sediment load and grain size. (7) Sinuosity is related to slope and inversely related to sediment load. These qualitative relationship~ are used as guidelines in determining potential changes to river morphology as a result of flow and sediment regulation. The base premise of these relationships is that the river has a full opportunity to form channel(s) within its own sediments. Limitations on the Susitna Rivers freedom of movement are discussed in ·the following sections. 5. 2 -River Pattern and Channel Characteristics Control Some 15,000 to 20,000 years ago, the Susitna River valley betweeen Devil Canyon and Talkeetna was the route of glacial ice flows. Recession of the glaciers formed some of the surficial features present within the valley. Several of these remnant forms and depositions impose controls on the river behavior and act as an independent variable along with flow and sediment. Presence of several terraces in the valley bottom indicate that as the ice receded, a larger quantity of water and sediment was available and the older river bed was at a higher elevation. The process of degradation through the periglacial deposits has been by a preferential sorting mechanism, in that the river has moved the small and medium sized particles down the system and either formed temporary alluvial deposits within the floodplain or flushed the material to and beyond Talkeetna. This process of downcutting and reworking of the glacial sediments has developed an armor layer of cobble sized material around the main channel perimeter. r30/a 5 - 2 .. - - - ...... The presence of the armor layer around and along the river channel is not verified by subsurface excavations. However, numerous observations were made during the hydrographic surveys conducted in the fall of 1980, when the water level was low and water clear. Exceptions assuredly do exist, but the armor layer is a definite control feature of the system that limits or retards channel movement. Bedrocik controls the river through Devil Canyon and intermittently downstream to Curry. Although no direct evidence exists that the channel bed is on bedrocik, it is believed to influence the river gradient in some locations upstream of Gold Creeik. The more obvious influence of bedrock on river behavior is along the valley walls where the channel flows impinge on it. At several locations, the bedrock limits movement on one side, thereby magnifying the influen1c:e of processes that may occur along the opposite valley wall. This situation exists at the confluence of several tributaries. These steep gradient streams have delivered a significant quantity of sediments to the Susitna mainstem and have formed conical shaped alluvial deposits. Due to the steep gradient of these streams, a portion of the material delivered by the tributaries is larger than that which the Susitna normally carries. Therefore, the progressive encroachment has narrowed and deepened the channel against the bedrock valley wall. These constrictions establish hydraulic control points that influence the flow of water, ice and sediment. Several small tributaries have pronounced alluvial fans which have formed on the valley bottoms. These depositional features are considered periglacial because of the established vegetation and the incised channel. During deglaciation, abundance of glacial debris and meltwaters provided large quantities of sediment to the valley. Subsequent stabilization of the basin resulted in a reduction of sediment, allowing the streams to develop a channel through the alluvial fan. Presently these fans are relatively stable and are not expected to grow significantly. During torrential events, reworking of the deposits and episodic delivery of sediments can be expected . Patterns Four 1river patterns are evident on the Susitna River: single channel, split channel, braided, and multi-channel. Characteristics of each are shown in Figures 5.1 through 5. 4. These characteristic patterns are used in Section 5.3 when describing the various river reaches. In general, the Susitna River has either a single channel or split channel configuration above the confluence with the Chulitna. Near the Chulitna confluence, the Susitna assumes a braided pattern for the remainder of its length. In the reach from RM 61 to 42, a combined pattern is evident, with a braided pattern on the western r30/a 5 - 3 floodplain and a multi-channel pattern an the eastern floodplain. The pattern of braided rivers contrasts sharply with the pattern of ather common river types. An explanation far this phenomenon has been offered by several investigators (Fahnestock, 1963; Leopold, et al., 1964; Leopold and Wolman, 1957; Mackin, 1948; Henderson, 1966; Church, 1972). Although each explained reasonably the cause of braiding with respect to the individual study, the resulting conclusions often conflicted with others. The cause of braiding has been variously attributed by different authors to abundant sediment load, large and sudden di.scharge variations, erodible banks, and high gradients. It appears that braiding results from all of these characteristics rather than being dependent on only one. Mallard (1973) developed a scheme to define the influencing factors an alluvial river patterns. This scheme expresses braiding as a result of high rates of bedload transport, low channel stability, high sediment supply, high gradients and law upstream flaw regulation. 5.3 Regime Analysis of Susitna River Reaches Project released flaws will vary considerably from the natural flow regime. Generally the Susitna River at Gold Creek exceeds its mean annual flaw of 9,650 cfs during the months of May through September and drops to 1,000 to 3,000 cfs during the winter months.· At Gold Creek the mean annual flood (recurrence interval of about 2 years) is 49,500 cfs, and far river reaches considered to be in regime corresponds to bankfull flow. Bankfull flaw is regarded as the dominant discharge that shapes the river channel to accomodate it. Far the purposes of qualitatively assessing the response of the river to regulated flaw and sediment conditions, bankfull flaw is often used as the baseline. Post project flaws and sediment loads will be reduced significiantly below this baseline and therefore will effect the dependent variables. For example, a stable single-channel reach of the Susitna upstream of the Chulitna confluence has a bankfull width of about 600 feet. Assuming a dominant discharge equal to the mean annual flood, 49,500 cfs, and applying a generalized farm of Lacey1 s regime width equation: 1 W = CQ~ yields a value far C of 2. 70, very close to Lacey 1s original value of 2. 67. Reversing the procedure far a past-project dominant discharge of 13,000 cfs yields a regime width of 310 feet. This relationship indicates that the project will result eventually in a substantial narrowing of the channel, nat only by abandonment of side channels in multi-channel reaches, but also in width reduction in the main channel. Due to reduction in suspended and bed sediment loads, this process will be very slaw, covering many decades or Ianger. r30/a 5 - 4 .. , - - . ~ I !'F' I I I I II -I 'i I Downstream of the Susitna and Chulitna River confluence a braided river pattern prevails. Dominant discharge in a briaded system is that which produces a stage that overtops the intermediate active gravel bars. When this occurs the bed material is set in motion, and changes in channel network configuration and shape normally result. Regulating Susitna flow will reduce the frequency of the threshold from a mean annual flood to a flood that would be expected to occur with a recurrence interval of 5 to 10 years or greater· (Table 3. 14). Under post-project conditions, the frequency of occurrence of dramatic changes in river morphology will decrease, resulting in a more stabilized floodplain, decreased number· of subchannels and increased vegetative cover . A summary of river patterns by reach is presented on Table 5. 1. Each reach was defined by distinguishable breaks in bed slope and observable changes in river pattern. A general decrease in slope is associated with the downstream progression of the river with the exception of the reach from RM 149 to RM 144. The gentle slope through this reach indicates that bedrock may control the bed gradient. The river profiles for the Susitna River and its major tributaries are shown in Figure 5.5 and 5.6. r30/a 5 - 5 RM 149 to RIVI 144 Pattern Through this reach 1 the Susitna flows in a predominately single channel confined by valley walls (Figures 5.7 and 5.8). At locations where the valley bottom widens 1 deposition of gravel/cobbjes has formed mid-channel or side-channel bars. Occasionally a vegetated island or fragmentary floodplain has formed to a top elevation above normal flood levels, and vegetation has become established. Control Features Frequent occurrence of bedrock outcrops along the valley wall indicates that the river slope may be controlled by bedrock. This hypothesis is further supported because the. average slope from the downstream end of Devil Canyon to RM 144 is less than the next downstream reach, and there appears to be no correlation between the bankfull stage and mean annual flood. Presence of cobbles and boulders in the bed material (Figure 5. 7) aids in stabilization of the channel geometry. Processes Portage Creek JOins the Susitna at RM 148.9 and has formed a gravel and cobble fan at the confluence. This steep-gradient, non-glacial stream delivers significant coarse grained sediment to the Susitna. The Portage Creek fan geometry is dependent on Susitna stages and transport capabilities. Summary of Potential Post-Project Morphological Changes 0 0 r30/a The channel is stable and little change in form is expected. Portage Creek fan will progress out into the Susitna until equilibrium with the regulated Susitna stage is established. Perching of the stream mouth is not expected. 5 - 6 ~· - :·i . ! RM 144 to RM 139 Pattern A broadening of the valley bottom has allowed the river through this reach to develop a split channel form with intermittent well-vegetated islands (Figures 5. 9 and 5.10) A correlation exists between bankfull discharge and mean-annual flood. Control Features Where the main channel impinges on valley walls or terraces, a cobble armour layer (Figure 5. 9) has developed with a top elevation at roughly bankfull flood stage. At RM 144, a periglacial alluvial fan of coarse sediments confines the river to a single channel. Processes Reworking of alluvial deposits is frequently evident through this reach. Erosion of islands is evident where a channel impinges against the alluvial deposits. Frequent mid-channel bars, composed of gravel, are mobile during moderate floods~ These active bed sediments reform along with subchannel pattern changes. Summa1ry of Potential Post-Project Morphological Changes 0 0 0 0 0 r30/a Erosion of valley walls and terraces will decrease dramatically due to the armour layer. Reworking of alluvial deposits in the main channel will continue but at a reduced rate. Main channel form will progress slowly to a more uniform sinuous pattern. Subchannels may become inactive. Tributary at RM 144 could become perched. It may not be able to regrade its coarse bed sediments to meet the regulated Susitna water level. 5 -7 RM 139 to RM 129.5 Pattern This river reach is characteristized by a well defined split channel configuration. Vegetated islands separate the main channel from the side channels. Side channels occur frequently in the alluvial floodplain (Figure 5.12) and are delivered Susitna water only at flows above 15,000 to 20,000 cfs. Often, valley bottom springs flow into sloughs. There is a good correlation between bankfull stage and the mean annual flood. Controls Where the main channel . impinges valley walls or terraces, a cobble armour layer (Figure 5.11) has developed with a top elevation at roughly bankfull flood stage. The main channel bed has been frequently observed to be well armoured. Primary tributaries include Indian River, Gold Creek and Fourth of July Creek. Each have built an alluvial fan into the valley bottom, constricting the Susitna to a single channel. Each constriction has establishes a hydraulic control point that regulates water surface profiles at varying discharges and associated hydraulic parameters. The railroad bridge location takes advantage of the Gold Creek fan constriction and further stablizes this constriction. One mile downstream of the bridge, the main channel impinges the bedrock valley wall and orients the river southward. Ice jams have been reported to commonly occur at this location, and backwater behind the jams causes water to spill into the east floodplain 1 contributing to the formation of the subchannels. Processes Indian River joins the Susitna at RM 138.5 and has formed a gravel fan at the confluence. This steep-gradient, non-glacial stream delivers significant coarse grained sediment to the Susitna. The fan extends several hundred feet upstream and downstream of the present mouth. The stream gradient is dependent on the Susitna stage and does not have difficulty in adjusting to a variable Susitna stage. The Gold Creek bed is composed of cobbles and boulders. The mouth is presently very steep. Be~ause the confluence is at the outside of a Susitna meander 1 Gold Creek bedload sediments are readily transported by the Susitna. This creek has difficulty adjusting to a variable Susitna stage. r30/a 5 - 8 .... - - - '""" r ! r I "F" ! 'F' 'f"" .! :! Fourth of July Creek has a relative gentle gradient as it flows into a Susitna subchannel. It is a non-glacial stream with a cobble bed. Comparison of 1951 and 1980 air photos indicates a few changes in bank lines and island planform, but generally the channel delineation is stable. Although visible evidence indicates that a majority of the main channel is well armoured with cobbles, there are several active gravel bars through this reach. A partial source of this sediment is from ei'"Osion of alluvial deposits. Currently, active erosion is occurring on the west bank between RM 134 and RM 135. At RM 132.5, several active gravel bars exhibit a braided river pattern. It has been observed that during moderate flows, these mid-channel gravel bars erode and reform. These processes indicate a long duration, small volume, but relative continuous movement of gravel bed material. A common fe.ature associated with the beds of side channels and sloughs at the bifuration point is a cobble berm. These berms act as control weirs, limiting delivery of main channel surface water to flows greater· than 15,000 to 20,000 cfs. Summary of Potential Post-Project Morphological Changes 0 0 0 0 0 0 r30/a Indian River will continue to extend its alluvial deposits into the Susitna. Indian River should easily grade its bed to meet the regulated Susitna Stage. Gold Creek gradient is presently very steep as it enters the Susitna. The cobble and boulder bed will resist regrading the bed to meet the regulated Susitna stage. Fourth of July Creek gradient is currently relatively flat and should easily adjust to the regulated Susitna stage. Erosion of valley walls, terrace deposits and alluvial banks will reduce dramatically due to the armour layer. Reworking of active gravel bed materials will continue at a reduced rate. Main channel form will slowly progress to a more uniform sinuous pattern. Several of the sloughs and subchannels could be blocked off from the Susitna main channel at the regulated stage. Where these channels rejoin the Susitna, gradual siltation and vegetation encroachment will occur. 5 -9 RJVI 129.5 to RM 119 Pattern River patterns through this reach are similar to those discussed in the previous reach. The most prominent characteristic between Sherman and Curry is that the main channel prefers to flow against the west valley wall and the east floodplain. has several sidechannels and sloughs (Figure 5.14). The alluvial fan at Curry (Figure 5.13) constricts the Susitna to a single channel and terminates the above described pattern. A fair correlation exists between bankfull stage and mean annual flood through this reach. Comparison of 1950 and 1980 airphotos reveals occasional local changes in banklines and island planform. Controls The west valley wall is generally nonerodible and occasionally has exposed. bedrock outcrops. The resistant boundary on one side of the main channel has generally forced a uniform channel configuration with a well armoured perimeter. The west valley wall is relatively straight and uniform except at RM 128 and 125.5. At these locations bedrock outcrops protrude out and deflect the main channel to the east side of the floodplain. Processes At RM 128 and RM 125.5, where the main channel crosses over to the east floodplain, a tendency to braid is exhibited. The river has an opportunity to increase its breadth, to decrease its depth and to deposit a portion of its bedload. The broadened channel flows against the resistive east bank, regains its shape and resumes its preferred western route. In comparing 1980 aerial photos with 1950 photos, it can be seen that similar processes have been ongoing throt.Jgh this era. Some erosion of the east channel alluvial deposits has occurred but no dramatic changes are evident. There is moderate erosion of fine material along the left bank near RM 124 (Figure 5.13). Cobble berms at the bifurcation of subchannels and sloughs are prevalent through this reach. A possible explanation for this phenomena may be as follows. Even when a river pattern appears straight, such as when the main channel flows against the west valley wall, streamlines will meander within the channel. This process develops secondary currents that flow in a helicoidal direction. The total sediment load is directed away from the hard surface toward the opposite bank. Depending upon flow, local hydraulics, and other controls, the sediment may either be re-entrained or deposited along the bank. As the flow increases and spills into the side channels, the coarser sediments are delivered to the sidechanne/s. When the coarse sediment r30/a 5 -10 -· ,.,..,, - ,...,, r I i r I 'F i I ,... i encounters a shallow channel with lower velocities, it will drop out and deposit. As flow recedes, the flow over the berm may channelize, developing a minor incised channel on the downstream side of the berm, and eroding a niche into it. This niche provid1es a temporary waterway at moderate flows. The minor tributaries along this river reach all appear to have fairly stable, but steep, basins. Contribution of sediment to the river will be episodic during extreme precipitation events. Of prime importance is that the tributaries and springs will deliver fresh water to the east subchannels and sloughs. Summary of Potential Post-Project Morphological Changes 0 0 0 0 r30/a Erosion of valley walls, terraces and alluvial deposits will reduce dramatically. At RM 128 and RM 125.5, reworking of gravel bed material will continue, but at a reduced rate. Main channel form will become more uniform. Cobble berms at the side channels and sloughs will control and perhaps bloclk main channel flow from entering them. The river should continue its preferred and stable route along the west valley wall. 5 -11 RM 119 to RM 104 Pattern Through this reach the · river is a very stable, predominantly incised single channel pattern (Figure 5.16) with a few islands. Control The channel banks are well armored with cobbles and boulders (Figure 5.15), and visual inspection indicates that the bed is also. Several large boulders occur intermittently along the main channel, and are believed to have been transported down the valley during glacial ice movement. They provide local obstruction to flow and navigation, but do not have a significant impact on channel morphology. · Processes The bankfull flow and the mean annual flood criteria do not appear to apply to this reach. Flow at 53,000 cfs is lower than the vegetated island and bank elevations. It appears that this reach is capable of transporting all sediment delivered to it. In addition, this broad low-relief valley delivers little or no sediment to the system. In effect, it appears that this reach acts as a conduit carrying the total sediment load through it. Erosional and depositional processes are almost indetectable. Comparison of 1951 and 1980 aerial photographs reveals no significant changes in channel morphology. Gravel bars above the 18,000 cfs flow level appear to have the same form, with only one exception at RM 114. There have been some changes in the alluvial gravel deposits, minor erosion of the islands, and some stabilization of the floodplain adjacent to the east bank. These processes are representative of the system. Summary of Post· Project Morphological Changes 0 r30/a No consequential changes in the channel morphology are expected. 5 -12 ~.· - ,_. ~', - ....... n- 1 ~ I I r r r t' I RM 104 to RM 95 Pattern At the confluence of Susitna, Chulitna and Talkeetna Rivers, there is a dramatic change in the Susitna pattern from a split channel to a braided pattern (Figures 5.17 and 5 .18). Emergence from mountainous confined upstream basins into the lowland unconfined basin has introduced the ability of the river systems to develop laterally. Ample bedload transport and a gradient decrease also assist in establishing conditions to support the braided pattern. The Chulitna River has a similar mean annual flow as the Susitna, yet its drainage basin is about 40 percent smaller. Its glacial tributaries are much closer to the confluence than the Susitna, and a majority of the Chulitna River•s length is confined by rock valley walls. As it emerges from the incised canyon 20 miles upstream of the confluence, the river transforms into a braided pattern with moderate vegetative growth on the intermediate gravel bars. At about a midpoint between the canyon and confluence, the Chulitna exhibits a highly braided pattern with no vegetation on intermediate gravel bars and evident recent lateral instability. This pattern continues beyond the confluence and the impression is given that the Susitna is tributary to the dominant Chulitna River. The split channel Talkeetna River is tributary to the dominant braided pattern. Control: Terract~s generally bound the broad floodplain but provide little control over channel morphology. General floodplain instability results from the three river system striving to balance out the combined flow and sediment regime. Processes Referencing Figure 5.19 it can be seen that considerable movement of channel boundaries has occured in the three rivers between 1951 and 1980. The background is 1980 aerial photography and the dark lines delineate 1951 channel boundaries as defined by vegetation limits. In the Susitna River, there has been some lateral movement of the vegetation lines, with both erosion and stabilization of alluvial deposits with vegetation. The river has maintained the basic braided river pattern. Since 1951, there has been a progressive movement of the Chulitna River main channel from the south edge of the floodplain towards the nt::>rth. As a result, a remarkable amount of vegetated floodplain on the north bank has eroded. Continued movement to r30/a 5 -13 the north is limited because the lateral migration is progressing up the valley slope. During a mid-summer flood in 1981, the Chulitna main channel relocated from the north side of the floodplain to near the central floodplain. Cause of this change is unknown but could be related to the limited northward movement, debris accumulation or some anomalie that occurred during the flood event. The broad fan-shaped active floodplain gives the impression that the Chulitna is currently aggrading. This concept is further evidenced by inundation of the established vegetation along the north floodplain that is killing the spruce trees. Although not supported by field data, it appears that a rise in the gravel floodplain bed has occurred recently. Glacier instability far upstream could be the source of flow and sediment regime changes that are influencing apparent instability near its mouth. Continued measurements of bedload transport rate, elevations and stage/discharge relationships will be required to determine with confidence the stability of the Chulitna. The Talkeetna River has had several channel changes upstream of the railroad, but the bridge and bank revetment have stabilized the river as it enters the Susitna River. In 1979, the bankline around the village of Talkeetna was stabilized with rock riprap. Preliminary bedload measurements indicate that the Chulitna is the main source of bed-material transport and provides roughly 4000 tons per day. Through the 90-day summer flow period this would produce 360,000 tons per year or a volume of 240,000 c.y. per year. Assuming that 50% of this were no longer transportable by the reduced flood regime downstream of the Susitna and was deposited over a length of 10 miles on an active floodplain width of 3000 feet, an aggradation rate of about ~ inch per year would result. This wouJd raise the average bed level 1-foot every 25 years. The above simplistic analysis indicates that continued monitoring of the sediment balance at the confluence is advisable. Summary of Potential Post Project Morphological Changes (a) Chulitna River will continue to expand and extend its alluvial deposits. Decreasing the summer flow magnitude in the Susitna River will allow the Chulitna to extend alluvial deposits to the east and south. This could induce erosion of the east bankline towards the railroad. (b) Increased deposition at the confluence will cause backwater up the Susitna River. Lateral instability will continue after the project. (c) The Talkeetna River will maintain the ability to create its channel into the Susitna system. No consequential interactions can be foreseen at this time. r30/a 5 -14 -: ., - ...., .. , . .._ """' '' I !"""' I - RM 95 to 61 Pattern Downstream of the three-river confluence, the Susitna continues its braided pattern, with multiple channels interlaced through a sparsely vegetated floodplain. The channel network consists of the main channel, usually one or two subchannels and a number of minor channels (Figure 5. 20). The main channel is easy to identify when viewing the river at low flows, as its surface water width is greater than that of other channels. Observations of cross-sections of the river floodplain indicates that the main channel thalweg is 5 to 10 feet deeper than in other channels. The main channel meanders irregularly through the wide gravel floodplain and intetmittently flows against the vegetated floodplain. It has the ability to easily migrate laterally within the active gravel floodplain, as the main channel is simply reworking the gravel that the system previously deposited (Figure 5.20). When the main channel flows against vegetated bank lines, erosion is retarded due to the vegetation and/or bank materials that are more resistant to erosion. Flow in the main channel should persist throughout the entire year. Subcha1nnels are usually positioned near or against the vegetated floodplain and are generally on the opposite side of the floodplain from the main channel. These channels normally bifurcate (split) from the main channel when it crosses over to the opposite side of the floodplain and then terminate when the main channel meanders back across the floodplain and intercepts them. These channels have smaller geometric dimensions than the main channel, and their thalweg is generally about 5 feet higher. Their flow regime is dependent on the main channel stage and on local behavior at the point of bifurcation. Flow may or may not 'persist throughout the year. Minor channels are considered to be those relatively shallow, wide channels that flow over the gravel floodplains and complete the interlaced braided pattern. These channels are very unstable and generally short-lived. Control The main channel is intermittently controlled laterally where it flows against terraces. Since the active floodplain is very wide, the presence of terraces has little significance except for determining the general orientation of the river system. An exception is where the terraces constrict the river to a single channel at the Parks Highway bridge!. Subchannels are directly dependent on main channel flow and sediment regime, and generally react to the same. Minor channels react to both of the larger channels behavior. r30/a 5 -15 Processes For braided rivers that have the ability to form channel networks within the river sediments, bankfull floods are considered to be the dominant discharge. Floods of greater magnitude do not significantly increase the river's stage because of a sudden increase in flow width. Flows above bankfull stage move gravel from bars into the channels and change the channels' shape and network. Dramatic changes in channel position and form occur whenever the river attains bankfull stage. At this stage, the active gravel floodplain is subject to movement, with considerable local scouring and filling. The main channel can change its lateral location dramatically, intercepting the other channels at different locations and therefore forcing them to readjust. Generally, it can be said that the geometric dimensions of the main channel will remain uniform. The minor channels react to other predominant processes such as main channel and major subchannel movements, debris accumulations and local sediment movement. When the flow recedes, the channels merely reflect the most recent governing processes. Through this reach of river, debris accumulations participate heavily in forming the gravel floodplain and channel network. Debris accumulations along the periphery of active gravel floodplain bars are common. Evidence indicates that the debris controls several of the minor channels and influences the meandering pattern of major subchannels and the main channel. Debris accumulations can grow, move, dissipate or emerge during floods greater than bankfull stage, and it is impossible to predict debris locations and local river response to this process. Summary of Potential Post-Project Morphological Changes 0 0 r30/a Under post-project conditions, the bankfull flood (mean annual flood under pre-project conditions) could be expected to have a recurrence interval of once every five to ten years. This wilt tend to decrease the frequency of occurrence of both bed· material movement and of changes in braided channel shape, form and network. Over a long period, a trend towards relative stabilization of the floodplain features should occur. The main channel and major subchannels could progress to a more uniform meandering pattern. The active gravel floodplain may develop a vegetative cover and the minor subchannels become relatively inactive. It must be recognized that an extreme flood generated by either the Chulitna River, Talkeetna River, or both, could mask this process and delay observable changes for several years. 5 -16 """'i """· ..... - ,~'·. -· """"· .,... I ·I .I 'i' I .I T I .Pf~ I I RM 61 to RM 42 Pattern Downstream of the Kashwitna River confluence, the Susitna River branches out into .multiple channels separated by islands with established vegetation (Figures 5.21 and 5.22). This reach of the river has been named Delta Islands because it resembles the distributary channel network common with large river deltas. The multiple channels are forced together by terraces just upstream of the Deshka River. Through this reach, the very broad floodplain and channel networl< can be divided into three categories: 1. Western braided channels 2. Eastern split channels 3. Intermediate meandering channels The western braided channel network is considered to be the main portion of this very complex river system. Although not substantiated by river surveys, it appears to constitute the largest flow area and lowest thalweg elevation. The primary morphologic parameter that has maintained the western side as the prime 1conveyor of water (and probably sediment) is the fact that the western braided channels is the shortest distance between the point of bifurcation to the confluence of the Delta Island channels. Therefore it has the steepest gradient and highest potential energy for conveyance of water and sediment. Controls Terracjas bound the very broad floodplain and only provide general orientation of the channel network. The floodplain appears to be filled with river deposited alluvial sediments which the river can readily massage. Vegetation retards channel changes, but should not be considered to control channel positions. Processes The basic processes described for the Sunshine Station reach would be applicable for the western braided channels. The active gravel floodplain is subject to majo1r changes during bankfull floods. A main channel prevails that has an irregular meandering pattern, the largest channel geometric dimensions, and conveys water throughout the year. The distributary channels branching off the western . channeJs collect along the east valley wall and form the eastern split channels. A split channel system differs from a braided system in r30/a 5 -17 that there is more relative stability and the channels are generally deeper with respect to width. A better defined and more uniform meandering pattern reduces the channel gradient, which aids in maintaining channel stability. Distribution of water and sediment from the west to east is dependent on the flow and sediment regime of the Susitna River as well as local behavior at each of the channel bifurcation points. Quantity of sediment and flow delivered eastward is expected to be highly variable from year to year. Several intermediate channels meander through the vegetated islands. These channels are expected to be deep with respect to width, and have a relative gentle gradient because of the pronounced meandering patterns. These channels react to the regime behavior of the western and eastern channels. Upon comparing the 1951 aerial photos with 1980 aerial photos, dramatic changes were revealed in the Delta Islands between the Little Willow Creek and Willow Creek confluence (RM 48 to RM 52). The western braided channels eroded away a considerable amount of the islands and opened up a major flow connection between the west and east. This major change could instigate long-term changes in the lower Delta Island channel network form for several years. In viewing this area during late summer, 1981, it appeared to be very unstable; again the governing control appears to be the steeper gradient in the western braided channels. Summary of Potential Post-Project Morphological Changes 0 0 The Delta Island reach is a very complex and unstable channel network. There exists a very broad floodplain filled with varying channel types. Project-induced changes in flow and sediment regime realized at this reach will be diluted by contribution from tributaries and by the Susitna satisfying its sediment load by reworking the wide floodplain alluvial deposits. Basic changes in the overall channel network are not expected. Local changes could occur in the main channel lateral position but basic channel geometry should remain relatively similar. To quantify post project morphology changes with respect to the natural system would be extremely difficult, if not impossible. r30/a 5 -18 -· !'¥"" . I q-,, ,, -I I '1- 1 ' RM 42 to RM 0 Pattern Downstream of the Delta Islands, the Susitna River gradient decreases as it approache~ the ocean. The river•s basic pattern tends toward a split channel configuration as it adjusts to the lower energy slope. There are short reaches where a tendency to braid emerges in the river pattern. Downstream of RM 20, the river branches out into delta distributar·y channels. Control Terrac1es constrict the floodplain near the Deshka River confluence and at Susitna Station. Further downstream the terraces have little o1r no influence on the river. The Yentna River joins the Susitna at RM 28 ·and is a major contributor of flow and sediment. Tides in the Cook Inlet rise above 30 feet and therefore will control the water surface profile and to some degree the sediment regime of the lower river. River elevation of 30 feet exists at about RM 20 and corresponds to wlhere the Susitna begins to branch out into its delta channels. Processes The v1egetated floodplain consists of alluvial deposits with surface features revealing old meander scrolls and filled-in channels. The well established vegetation helps to retard erosional processes and channel migrations, but these processes are definately on-going. In comparing 1951 and 1980 aerial photographs for the river reach at Deshka River confluence ( RM 40 to RM 42), there can be seen significant channel movements, bank erosion and deposition, with ban kline movement of several hundred feet (Figure 5.23). Several highwater channels and/or sloughs branch off the main channel into the wide floodplain. These channels appear to be very stable except for the occasion where the main channel migrat1es laterally and intercepts one: of the stems. Delivery of water and sediment to these subsystems is directly dependent on the main channel flow regime and associated stage. The Yentna River contributes about 40 percent of the mean annual flow to the Susitna River as measured at Susitna station. At the confluence, considerable changes in bank lines have occurred since 1951 as a result of each of these systems adjusting to each other (Figure 5.24). Because of the variable flow and sediment delivered by each of these systems during events, on an annual basis or even long-term, instability of channel morphology at the confluence is expected to continue. r30/a 5 -19 At RM 19 1 Alexander Slough branches off the main channel network. It also marks the beginning of the Susitna River distribution through the delta into Cook Inlet. Alexander Slough outlet has drawn attention recently because it is the prime navigation corridor downstream to Alexander Creek. Comparing aerial photos 1 there are no noticeable significant changes in the slough outlet configuration, gravel bars or banklines. The slough flow is directly related to the Susitna main channel flow and stage. Because Alexander Slough is a major distributary that feeds straight and direct to tidal waters 1 it is believed that an outlet will naturally' be maintained during normal summer flow regimes. Summary of Potential Post-Project Morphological Changes 0 Effects of the project on river morphology through this reach of river would be extremely difficult or impossible to quantify. The above qualitative discussion has simply brought out some of the natural processes and observable changes that have occurred over the last 30 years. · The dilution effect of major and minor tributaries as well as the balancing of changes by the Susitna River system should mask any measurable changes that could occur as a result of the project for several decades. r30/a 5 -20 - - - - - - - River Mile RM 149 to 144 RM 144 to 139 R M 1:39 to 129 . 5 -RM 129.5 to 119 RM 1'19 to 104 \~ RM 104 to 95 - RM 9S to 61 RM 61 to 42 - RM 4:2 to 0 - r30/a TABLE 5.1 SUSITNA RIVER REACH DEFINITIONS Average Slope 0.00195 0.00260 0.00210 0.00173 0.00153 0.00147 0.00105 0.00073 0.00030 Predominent Channel Pattern Single channel confined by valley walls. Frequent bedrock control points. Split channel confined by valley wall and terraces. Split channel confined occasionally by terraces and valley walls. Main channels 1 side channels sloughs occupy valley bottom. Split channel with occasional tendency to braid. Main channel frequently flows against west valley wall. Subchannels and sloughs occupy east floodplain. Single channel frequently incised and occasional islands. Transition from split channel to braided. Occasionally bounded by terraces. Braided through the confluence with Chulitna and Talkeetna Rivers. Braided with occasional confinement by terraces. Combined patterns: western floodplain braided 1 eastern floodplain split channel. Split channel with occasional tendency to braid. Deltaic distributary channels begin forming at about RM 20. 5 -21 -I ...... ...... RIVER MILE 103.2 Single Channel 0 0 0 0 PREtPARED BY I Stable Non-erodible banksi controlled by _valley walls, bedrock or armor layer consisting of gravel/cobbles . Channel may be either straight or meandering; in straight channels, thalweg often meanders across channel. Occasional fragmentary alluvial deposits in floodplain. PREPARED FO SINGLE-CHANNEL RIVER PATTERN R.!iM CONSULTANTS, INC. FIG~ 5.1 -;I r i , .... - .r '.I 'I :·1 RIVER MILE 124.4 Split Channel 0 0 0 0 0 0 Main channel behaves similar to single channel at low flow. Side channels provide flood relief at high flows (greater than 20, 000 cfs) . Islands well established with vegetation. Gravel/cobble bed material. Mean annual flood correlates with bankfull flow. Channels are moderately stable. PREPARED FOR SPLIT-CHANNEL RIVER PATTERN ~ R&M CONSULTANTS, INC. FIG.5.2. -- - - -:J CHULITNA RIVER NEAR CONFLUENCE WITH SUSITNA RIVER Braided Channel 0 0 0 0 PFIEPASEO BY 1 Floodplain is very wide and shallow even at flood flow. Multiple and interlacing channels in unvegetated gravel floodplain. Move large quantities of bed material during flows greater than ban kfu II . Results from combination of high rates of bedload transport, low channel stability, high sediment supply, high gradients and low upstream flow regulation. PREPARED FOR BRAIDED-CHANNEL RIVER PATTERN R&M CONSULTANTS, INC. FIG. 5.3 - ,.,... .) I DELTA ISLANDS Multi-Channel (Delta Islands) 0 0 0 0 0 PFtEPARED BY I Very broad floodplain with little lateral control. Multiple channels consist of a mix of braided, split channel and single channels within floodpla i n. Relatively unstable, subject to major local changes during single flood events. Large amount of fine suspended sediment helps stabilize banks; dense vegetation effective in trapping sediment. Bed material consists of gravel/sand with pockets of silt. PREPARED FOR MULTI-CHANNEL RIVER PATTERN FIG. 5.4 , I I I I I ·- 1 I I I I. I I I I I: I I I -....1 w > w ....1 <( w ClJ z <!: 1'300 11 100 w 80 ~ w > .o CD <( r-70 w w u. -z 0 t-60 <t > w ..J w 5 400 300 NOTES: t TALKEETNA a CHULITNA R \VER PROFILES- BASED ON U.S.G.S. CONTOUR MAPS. 2. SUSITNA RIVER PROF'lL.E-BA~lEO ON tHALWEG ELEVATtON. I I I I I I I I I I I 80 90 100 TALt<EETNA l~lVER I / I I I I I I CHULIT~A RIVER I I / I I I I I I I I I l..OW£R END DEVIl. CANYON PORTAGE CREEK I / GOLD CREEK I / CURRY U.S. G.S. C H UL lT NA GAGE SITE SHERMAN HO 120 1'30 140 150 ISO PREPARED BY : RIVER M1LES PREPARED RIVER PROFILE, SUSlTNA RIVER AND TR 1 BUT ARIES ABOVE SUNSHINE -26 --·-,, ..... -·---------- r.::':::;=::;;-r::-r·----"-·-----------------------------.;_--------------------, ., m ::0::0 fY1 --r << 0 fl'liTl :e· ::o:O (/) ]>"'0 c: z:O z 0 c.,. (J) -:c -lr--z ::om 1'11 _._. tom c:c -icn 01 )>-I ::0 -4. N -....a -Z fT'Il> en , -(i') c: :tJ 1'1'1 (J1 . m .. _,.·,.;- :n m ~· :n m 0 CD ~ .. 500 400 300 200 100 0 .,o :D m ., )I :n m t:J ., 0 ~ ~= -.J w > w _J <t 1.1.1 en z <t w ~ LLJ > 0 Ill <{ .... w w tJ... -z 0 ... <t > LLJ -' w SUSITNA-YENTNA R. CONFLUENCE lO 20 30 40 50 60 70 RIVER MILES PARKS tHGHWAY BRI OGE (SUNSHINE) SKWENTNA. R. CONF~UENCE 80 90 100 1\0 120 '"""' --.. ;._ ~ ". ~-~ - Looking Upstream at Portage Creek, River Mile 148.8 - Talus Slide PBEPARED BY: PREPARED FOF SUSITNA RIVER REACH RM 149 TO RM 144 R&M CONSULTANTS, INC. FIG. 5.7 00 I N ~ i . . ) PREPARED BY 1 z 0 -1- c( > ~ w RIM CONSULTANTS, INC. 1- 1- ~0 'b 1- 1- 1- 1- 'b ~0 1-. 1- -o 'b~ ' - - ~0 'b ~ .. 0 1 ... l SUSITNA HYDROELEC-rRIC PHOJECT CROSS-SECTION Number 61 • \ -~ ·----- • I ' I . I • 1 ScbROCK • I I . r • ~ -- .S lrOROt.IC I '"" I J ! I l .. J /" ..... -I / I \ ,, ,/ \ /' \ \ ,, ' / ' !--..... ----\-............ -::-----·--- '··· oO oO oo oo oo t>'oo oo ~ I I I 0 ' ~ ~ ~ q,' • • • • \ I I 0 ~ I I I \ t I 0 I I \ I I I I 0 0 '}. I I CROSS-SECTION RM 148.7. :STATION; FIGURE·5~8 PREPARED FOR• IIU -~ tl - PFIEPARED BY • R&M CONSULTANTS, INC. Split Channel, River Mile 141.5 Gravel/Cobble Bed Material·, River Mile 140.1 PREPARED FOR SUSITNA RIVER ~ REACH RM 144 TO RM 139 FIGo S. 9 • i I I I ! 1 --i 1 J ~ l 'I 1 CROSS-SECTION Number 55 SRNbf! ~~RV£L ---l~ --r.PJ'/I.Sinbl'l: So/ 7"0 S/IN~ • -7~1JNSI71~N .:!!4N.& Tb Co8SL"£-$i'8ouLb£.l!S ~ . SR,b,) BL&S f (#/fii~L-~'\0 ~--------I------+---~-+------~-----+~---~~-M----~-------4----------~ '1 I 7"/fiJ/'JSJ'TTC"-r: VEe;. T'O 1 coBBLE:S__.. -· cc:>,~ BLES f t]RPI'EI. wlrN SAN~ .J. Ar~~.Cs 01 I w ...... z 0 ;: c( > w _, w PREPARED BY • 1-Co88L£S 1-0 l [A~ ,, Q It 1---·-·-,llf-, --+-' . 1- 1 [ 77/!RA/Sir''pN Tl:l ' -v£11. l i ·~fi\;_'~_o ____ t.--lf---t--+----~---H--11-+--+--f--------~-HI-----· I , ;---~~-~~------ • --------,_I ) 0 \ ..,~.......... I~"" ~~ r . ~-' t------t-------t------i---. ...:-_;_\_ --I \ .... ·--------··-"" I------ ~0 ~ I \ a I o • STATION \ ... ___.. ..... -.... ... .,.- ~ ~,/ ' ..... . . O ~ LoliflT"u::W op-GRI..b PltCirO b,,_ :-178........... , b.s-0 • 2.20 ,... ..... . b 8 y = 211:.s- } PREPARED FOR• Rill CONSULTANTS, INC. CROSS-SECTION RM 141.5 · FIGURE 5.10 IMIU I .·('!~ Gold Creek Railroad Bridge, River Mile 136.7 - - Gravel/Cobble Bed Material and Sand Bar, River Mile 137.4 PREPARED BY : PREPARED FOF REACH RM 139 TO RM 129.5 IPD[f SUSJTNA RIVER • FIG. 5.11 ftUO[IJ ---,----~==~~======~===;~~~=============== R&M CONSULTANTS, INC. l U1 I w w PREPARED BY • z 0 -1- ~ .. ~· R&M CONSULTANTS, INC. , } r l SUSITi\JA HYDROELECTRIC PROJECT ----~-··--- CROSS-SECTION Number 41 STATION CROSS-SECTION RM 134.7 PREPARED FOR• 'FIGURE 5.12. - Curry, River Mile 120.7 - - - Sloughing Banks, River Mile 124 ;. __ PFIEPARED BY ' PREPARED FOR SUSITNA RIVER [ii REACH RM 129.5 TO RM 119 . . . MID ~-----·----~==::.: .. :_:.::::::::::~:==::::::,:.::.:.:.:.:,~==~34l·:=:=:=::::::::::::~:Gi::•:5::.1::3:::::::: R:&M CONSULTANTS, INC. .. -1 01 I w 01 PREPARED BY • z 0 ~ i:i ..J w. ... i . -J SUSIT~~A HYDROELECTRIC PROJECT . CROSS-SECTION Number 2 5 i,.t--TRRRS,7X>It/'t:CJ8 r'SRIVb n Vcy. (co7ToN" oob.Sf"RL.OCRS) -'TbP OF 81-Nk • WILl OW.$ . i-~RNSIT.'pl'l 7b (!a88l.E:S i A rE:t..J Sob.<~£~ ,. t -T'O£ OF' /Y.CJI=If nO ao, tl:)Etf:S RNb ~V C088L£S ~··-----+------.J..-..-------I-·-----l--------4·---·-----J~------ f.. 1 ~ r--.11tK or t;RRVE", SHRLl. cos. /INb SIIN/) I i ~cP oOO . ~00 oO oO \ I • • • • ! v ..... I 'C. . . . I. • • • ':>0 t t t • ''>~ I . . . STATION PREPARED FOR• R&M CONSULTANTS, INC. · CROSS-SECTION RM 121.6 FIGURE 5.14 . . ,_ . i -_,..... - - -- t'". River Mile 104 -. - Gravel/Cobble/Boulder Bed Material, River Mile 112.7 PREPARED BY I PREPARED FOI R&M CONSULTANTS, INC. SUSITNA RIVER [i REACH RM 119 TO RM 104 . MIR FIG. 5.15 j . -. J 1 U1 I w --..1 PREPARED BY • RIM CONSULTANTS, INC. z 0 ~ ~ w SUSIT.i'-JA HYDROELECTRiC PROJECT CROSS-SECTION Number 1 2 "' .· "£c;. rb -1--r~A#S• ~·CollsL.e £-ClllnVGL 8ED AN'o H~cw s n To SP 9..qsE t;RR.ss F $~6 ~ . • t.() ' BAA/X-V'£4. HIXTV~ 0~ I TbPOF t. ~Wit. .tow, 81RC:N, f CoVONWCc I I I ---1- 1-I ______ .,.,.,..- I. ' ----~ II ---------.... ~() , .. ,, ~ 1: f -f, ;t ,I-i ~ ~ !I i": t • • 1. ~ () ' • ~~ I 'I \ 1-\ I I ' ,J ~ \ ;----...._ "• ,o t. ·• 1- () . oo ()() ()() ()() ~() () ':>() 0 ~ '1-0 0 I I 0 I I 0 '1-~ . J. Ll I I I I 0 I ').' t I I I t t t ~. . . . .. I 0 0 STATION CROSS-SECTION RM 108.4 '1RI...L /J0~~-01£ ~ I / ;~bE"~ ;' ___ .. ;;;:;;o-" ' ()() ()() ' .':. fj I t t t I ~ ' • ':.~. I t I I t t t F l I PREPARED FOR' IIU Susitna-Chulitna Confluence, Looking Downstream - ...... ' Gravel/Small Cobble Bed Material, River Mile 101.5 P'REPARED BY I PREPARED FOI IUM CONSULTANTS, INC. REACH RM 104 To RM gs APnm SUSITNA RIVER [i FIG~ 5.17 ftUfi[IJ I ~ Ul I w t.D ---J PREPARED BY • . -J J -1 J J ) --J i J H\/QRQI=I E·r..T~IC 1J II L-.1-'-'llfl PROJECT CROSS-SECTION Number 7 _____ ..._..:_ -~~-·-·--·~---........ --..--... 1 .. _, _____ ....,... ____ .. __ _,... _______ ---.,----~~ T.tfA#SIT/Of'/t t:CIJ;4~AV. 7b, C08. MTI'f 60/>f~qltAI/11. f .4F£W !IHRLI. &Jtll.biRS- ~() ·y· tltAIJ$,rlcK• 'iR~>~i."rCI' COB8L~S f ffltlitlt!L- z 0 ;:: ~ w iif ~() ~ 1-... -..... ___ .. SHII~L SI.OVt;ll- .. / }' -1-T~A#/StTiol'/: C08·(J.tf/atl. 4Eb 7 p .SHNb ...--IIPS7tll£11M TIP ol' flli!!'QET/9 ""A/ oN ,,,lUll:> • Ml~tEb W.fL.t.ciA ; 11'-11'11/TqRE Ce>"l'r'Oilt/W CIQ6 ·-;·" ,.:;~·-~:.:_ A /' /' \ , v ~~() , \. ;' , ' '· I , ... ',, ... I ...... .... ..... , ... •· .. • • "" --··-···-·-... r'-' t,P ,'to I 0 0 I • 0 .., __ t_ ... o (,,o ,...,o (. o ,,o ,.. n'l/ n'\':.. ,.,_r;,-' o'\'-' '\• I 1. I I .,,· 1101111 .,,01111111 t';IOIII 1 r"l I IIIII STATION AIM CONSULTANTS, INC. CROSS-SECTION RM 101.5 ·fiGURE 5.18. -] ) PREPARED FOR= J -J I~ RIM CONSULTANTS, INC. ... -~ l l ..... ll l LEGEND ~.-·:..::::::~---·:: Indicates location of atreambanka 1951-1980 AERIAL PHOTO COMPARISON SUSITNA-CHULITNA-TALKEETNA CONFLUENCE' and_lalanda ln. 186.1. Baae'_ photo waa taken· In 1880. PREPARED FOR• Figure 5.19 [iii] I '' River Mile 79.5 -' Brush Pile-up on Gravel Bar PREPARED BY I PREPARED FOR: R&M CONSULTANTS, INC. SUSITNA RIVER liil REACH RM 95 TO RM 61 ~~~~[@ FIG. 5.20 ftU [d :~ Delta Islands r - ..... -Erosion of Sand and. Gravel Bar PREPARED BY' PREPARED FOR= R &M CONSULTANTS, INC. SUSITNA RIVER ~ REACH RM 61 TO RM 42 FIG. S. 21 • ------~----------------~-------------r--------~~-------------------------------- I '{ ~ j J J -. ) 1 ·-~ 1 1 ] l 1 1 1 1 J ,-, ----i--~~~~.~.~~~~~~~~~~~:!~[ ~.:l~l:.~. ~~~,~!~,-~~~~--~~1 ~~ l • • I I ' . i ' ' ' I' " \ I i ' . . . ' ' I . i ; . ! ' 1 1 ! : I i ! . i ' I ! I . ! ' ' ' : ; I! I: 95 I Q:): I I ssij .!3-:) ' '_ ~hn~ IH -i --;-----cf7 'I I ' ,~ IJn: ~ ' I I i ~ ..• ' ~~ ,!'-' L< f ::'!, ,:! ill, li:'L((,i> I u ,I~ I Lt'U'r-'i '~~---~~ u, I I ' i I ! I ! I! 'I: I . 'I \1 II.: : 'I' ! :I :! i I ! I': I ; I \ ' ' :I I I' ': i I I i ' i ! ' I ' i ' i 'I' ' ! 111 I t i ; ! : : I i ; I ) jl ' ' I 'I' i I I I ' ! I ! ' " : I ; : ' ;. ' ' ' : I ! I ! I ' I ; I I ' ! ~ J ; : : I I I : i I Jill I I I ' I : l : ; ! : I I i . ·._j' .·· .. · :' ,:_ ·. ·.· ' i .' .. ' : ·, ·.·. ', _: -· ... · I, ' I. ' l ' ' i ' ... !. ! : 1 ! : ' ~ f ~ I j ! : : t : : \ ! :1 I 1 ! ~ ' : : : i . :TL i -' I I ,. i! :,I· I i : i I': I: 't ',:I 1'1 l:: I ' '' : I'' : i; :! : '' i : I' ·I i ' ' . j' ~· I' ,. ' II' ' ; I i ' ' I ,. I I ' : ! : I ' I I I i II ; ' ,, il ::_•I' 'I I ' : I ' ':. :!! · ! , !, 1 · i ·· !i 1, #q.s~ . .s.;I..T'Ja~ :v,E.Jv•o ·1:, '1' 1 1 ~-:· t ,i :1 , , · , 1 .. ! I !.1 1 !!! oaK.'N6 .,t>aWl~r.qJJe.fM · · · I '' ! 1 i ! ''' '1 1 1 ! 'I . 1 ·: ! : i i . ; I' I ! I! I I f l I i '! . ; : I I j 'l. I I : I : : i I I I I i ' I ' ! ' i : ' : I : I I ! ' I i I i I I I : ! : ' I 40t-00 so reo 70-tOO 80+00 IOOt-00 1/0t'OO I:Z.Dt'OO 13otDO 140t00 150100 160+00 /01·00 201-00 NOTE:. • E:L£VAT/oN,$ SA.!J£C> ~N AS3UH£0 &>1TIJM • BANKFULL E:LE!VATit:>N IS q,s.oFT. • CJ!'033 SECTION ~E£C> e>N At::CONNAISSA~ 1'"/ELD SUP.Vi£1' ANO Ri>&IME: FrEl-ATION~UIPS, ALL E:L£',(4TION3 ANI:> STATioNS APPF'rO>fiMA1T • !L /NDICATIES ToP ICE£ I.. EYE I. ONMAFU'f, /981 CJ!'OSS :!.E:CTioNJ.o~nro eooo' &>OWN$~1£AM 01"' WILLOW &RIEEI< &c>f'JFILIE:NC.£. FIGUIIE! ll.l!:.!, ~~~(lj! ~~~~.s.~A "~?.~~~~c ~.~~~~.~I'T"~ .: 'BUSITNA RIVER ~! SYNTHESIZED CRDSS B&CTIDN DELTA ISLANDS ~-1 .r ~~ cp~~~.!:'!~J!~!~.E't'4AncH m ,1 --. J LEGEND --= L~catlon of vegetated rlverbanka and Iaiande tn 1951 ----= Loc:atlon of aandbara In 1961 . 8886 Photo taken In 1980 1951-1980 AERIAL: PHOTO COMPARISON. Figure 5.23 [iii] SUSITNA-DESHKA· CONFLUENCE RIM CONSULTANTS, INC. LEGEND --= Loclltlon of vegetated rlverbanka and ~~nda ~ t951 ----= Location of aandbara In 1861 Baa& photo taken tn 1aao PREPARED FOR• 1951-1980 AERIAL PHOTO COMPARISON SUSITNA-YENTNA· CONFLUENCE: Figure 5:24 ~~~~ I - -! - - - 6 -51 DE CHANNELS AND SLOUGHS 6.1 -Present and Projected Flow Regime Many of the side channels and sloughs between Devil Canyon and Talkeetna are overflow. channels, with water flowing into the channels only above certain flows (Figure 6.1). Several of the sidechannels are important as either main stem spawning grounds or. as access to spawning grounds. Often, the sloughs have gravel berms on the upstream end, effectively restricting open channel flow from the Susitna River through the side channels until the berm is overtopped. The critical flow rate for overtopping of the berm occurs between 15,000 and 20,000 cfs. The location of the upstream end of the side channels and sloughs which are either blocked or partially blocked are tabulated in Table 6.1. For modelling in the HEC-2 water surface profile model, it was assumed that flow into the side channels and sloughs was restricted below 20,000 cfs. Despite the fact that flow into the upstream end of the channels was often blocked, water was still found in the side channels and sloughs due to seepage through the riverbed gravels, backwater effects at the lower end of the the channel, and/or the occurrence of springs and small streams entering the channel. The water in the blocked side channels is usually relatively clear, especially when compared to the silt-laden water flowing in the main channel. Water surface elevations were modelled from Devil Canyon to Talkeetna, using the Corps of Engineers• HEC-2 model. Water surface elevations determined ·from the model studies are shown for selected cross-sections in Attachment C. A complete compilation at all cross-sections is included in the closeout report for 3.06 - Hydraulic Studies. The model assumes an uniform water surface elevation across any cross-section. However, this uniform water surface elevation does not· occur naturally, as demonstrated in Tables 6.2 and 6.3 by the differing water surface elevations of different channels on a cross-section. The disparity in water surface elevations is due to the differing hydraulic characteristics of the channels, to backwater effects, and to the inflow of springs. Consequently, the results of the HEC-2 model should be viewed as being somewhat uncertain in the side channels, especially at flows less than 20,000 cfs. The most valuable data on water surface elevations in the side channels would be actual observations at varying stages. Even then, it is probable that the relationship of the side channel stage to flow at Gold Creek will vary depending on whether data are gathered on a rising or falling limb of the hydrograph. r31/g 6 - 1 6. 2 -Expected Changes · Two oost-project flow options were discussed in Section 3. Case A, the optimal power operation~ has average monthly flows at Gold Creek varying between 5,000 -· 16,000 cfs (Table 3.5). These flows wHl not overtop the gravel berms at the upstream end t'f many side channels. Consequently 1 these berms should stabilize and b€-come essentially permanent features of the system. Howev~r, it_ is not expected thaf.; most of the sloughs will dewater 1 as water will continue to seep through the river gravels, and there win continue to be cnflow from springs and small streams. In channei.s where water seeps through the gravels, the water should be clear instead of silty, especially since much of the suspended sediment will be trapped in the reservoirs. The flows for Case D were constrained so as to have minimal impact .on the side channels. Consequently, average monthly flows in the summer are such that the upstream gravel berms will normally be overtopped, allowing water .to flow into the side channels and having minimal impact on existing fisheries habitat. r31/g 6 - 2 I 1 I I ) l I - - - -• 1. - - F i ~ - r- - .~ - TABLE 6.1 LOCATION OF BLOCKED AND PARTIALLY BLOCKED SIDE CHANNELS Blocked Side Channels Partially Blocked Side Channels RM 100.8 RM 99.8 RM 101.5 RM 100.6 RM 109.0 RM 115.8 RM 109.3 RM 121.6 RM 114.0 RM 121.8 RM 1.18.2 RM 123.0 RM 120.0 RM 125.9 RM 121.5 RM 126.1 RM 122.5 RIVI 126.9 RM 125.1 RM 129.7 RM 127.0 RM 129.8 RM 127.1 RM 131.6 RM 129.3 RM 131.8 RM 130.8 RM 132.6 RM 132.1 RM 136.5 RM 133.8 RM 141.0 RM 133.9 RM 134.7 RM 134.9 RM 135.1 RM 135.3 RM 136.4 RM 138.2 RM 139.3 RM 140.5 RM 141.4 RM 141.5 RM 141.7 RM 141.8 RM 142.2 RM 142.3 RM 143.6 RM 144.7 RM 145.9 r31/g 6 - 3 '=-,_......,. _ ___, ___________________ z __________ _ Station Number LRX-4 LRX-7 LRX-16 LRX-29 LRX-31 LRX-36 LRX-39 LRX-42 LRX-43 LRX-44 LRX-47 LRX-48 LRX-52 LRX-53 LRX-54 LRX-55 TABLE 6.2 ,. ~I ,I HEC-2 SUMMARY .. SUPPLEMENTAL INFORMATION Variation in Water Surface Elevation Between Channels I I I Date of Flow Survey (cfs) 10/4/80 9800 10/6/80 9380 10/10/80 9695 11/6/80 4950 11/18/80 2400 10/30/80 5525 10/28/80 5400 10/20/80 7230 10/17/80 7350 10/17/80 7350 10/20/80 7230 10/15/80 7440 10/14/80 7290 10/24/80 6420 10/24/80 6420 10/24/80 6420 10/23/80 6270 Water Surface Elevation (ft.) Main Channel Side Channel{s) Comments 350.4 364.6 455.2 568.4 594.1 619~0 645.6 668.7 670.9 679.9 688.5 691.7 713.8 722o2 731.8 .• 742.6 348.2, 350.9 365.7 455.5 ? 592.6, 593.7 618.5 644.7, 642.9 666.8 (slough) 667.8 673.7 680.8 689.7 (ponded) 716.3 724.0 733.5 739.9 Frazil ice accum.; · I 101 wide shore ice .. Shore ice[ ice floes .• Variation of 0.41 in water surface across main channel Frazil ice Ponded water in side channel Sm. side channel w /flowing water •• I I. I ·I I HEC-2 assumes a uniform water surface elevation across the entire X-sectlon. However, this is not the case in the field, due to the complexity of the river system. The variation in the water surface elevation is illustrated in the above table, which shows eievation differences of up to 2. 8 feet (LRX-43) in the natural system. Therefore, some care should be taken in assuming an absolute water ·I surface elevation in the sloughs for a given flow. 0 r31/g 6 - 4 I I I I Station Number LRX-3 LRX-4 LRX-7 LRX-9 LRX-16 -LRX-19 LRX-24 LRX-28 LRX-29 LRX-31 LRX-35 LRX-36 """" LRX-39 ! LRX-40 -LRX-42 LRX-43 -LRX-44 LRX-45 !'""'> LRX-47 LRX-48 LRX-51 -LRX-53 LRX-55 LRX-59 -LRX-62 LRX-68 - F ! TABLE 6.3 HEC-2 SUMMARY -SUPPLEMENTAL INFORMATION Variation in Water Surface Elevation Between Channels Date of Flow Water Surface Elevation (ft. Survey (cfs) Main Channel Side Channel s 8/31/81 22300 343.7(L) 8/31/81 22300 351.4(M) 351.5(L), 352.6(R) 8/31/81 22300 367.6(L) 368. O(R) 8/31/81 22300 381. O(M) 8/31/81 22300 457.4(L) 457 .6( R), 455. 9(ctr. SL) 457 .3(RSL) 8/31/81 22300 489. 7(M) 8/31/81 22300 523. 8(M) 8/31/81 22300 557. 7(M) 556.4(L), 557.2(R) 8/31/81 22300 572.4( R) 574.0(LSL) 8/31/81 22300 598.2(R) 594. 8(ctr .SL), 593. O( LSL) 8/31/81 22300 619.6(M) 9/1/81 21100 622.4(L) 621.6(R) 9/1/81 21100 648.5(R) 647. 0( L) I 646.1 (LSL) 9/1/81 21100 657. 4(M) 9/1/81 21100 672.2(R) 669.5(LSL) 9/1/81 21100 673.5(R) 673. 5(ctr SL) 1 674.8(LSL) 9/1/81 21100 683.8(R) 681.8(ctr,SL) 682.8(L.SL) 9/1/81 21100 686.4(M) 9/1/81 21100 693.7(M) 691.1(LSL 9/1/81 21100 695.3(R) 692. 7( LSL) 9/1/81 21100 709.6(M) 9/1/81 21100 725.4(R) 725.1 ( LSL) 9/1/81 21100 743.6@LB 743.1 (LSL) 744.9@RB 9/1/81 21100 788.3(M) 9/1/81 21100 838.3(M) 9/1/81 21100 853.8(M) r31/g 6 - 5 Comments L -left channel M -middle channel R -right channel SL -slough ponded water in left slough Flowing water in left slough --- - -~ .! ·- - - - PREPARED BY ' R&M CONSULTANTS, INC. Overflow Channel, River Mile 142.2 Bed Material, River Mile 141 .5 SUSITNA RIVER OVERFLOW CHANNELS AG. 6.1 PREPARED FOR: 7 -ICE PROCESSES 7.1 -Pre-Project Ice Conditions The river ice conditions observed through the winter of 1980-81 on the Susitna River are summarized Ice Observations -1980-81 (R&M, 1981a). The following section is a synopsis of that report. For more detailed information on conditions during freezeup and breakup, readers are referred to the Ice Observation report. The description and data in that report will provide input needed for modeling of the ice cover development for pre-and post-project conditions. Very limited records are available for the Susitna River basin relating to river ice regime, especially during the freezeup process. Personnel from the Alaska Railroad indicated that over the past twenty years there has been no serious flooding or ice jamming related to ice cover development on the Susitna. As a result, they have kept no records of dates for first occurrence of frazil ice in the river or dates for ice cover formation at key locations. However, the U .5. Geological Survey has freezeup dates for selected sites on the Susitna River. At Gold Creek, October 15-28 is the range of dates noted for first occurrence of frazil ice. It should be noted that this range of dates indicates only first occur- rence of frazil ice at the gaging station and may not truly reflect the ice regime within a particular river reach. During1 the winter of 1980-81, frazil ice was first observed on October 11 in the Susitna River below Devil Canyoo. From then until early December, when the ice cover began forming, the concentration and strength of ice floes varied depending on variations in climatic conditions in the basin. At several locations along the river between Talkeetna and Portage Creek, frazil slush tended to accumulate. These locations were related primarily to bedrock outcrops along the banks or to con- strictions in the channel 1 (both natural and those due to growth of shore ice). Table 7.1 lists the key river sections where heavy frazil ice accumulations were observed during freezeup in 1980. Many of these same locations were the site of ice jams during breakup the following spring. Though frazil slush accumulated to 100% coverage in places, the slush blanket did not consolidate and form ice bridges. The ice cover on the river from the Susitna-Chulitna confluence upstream appeared to form entirely by a process of juxtaposition. Depending on conditions at the leading edge of the ice cover 1 floes were either carried underneath the ice cover or added to the upstream r29/c 7 - 1 end. When velocity of flow was too high or the ratio of ice cover thickness to water depth too low, floes were dragged under the ice sheet, thus thickening the ice cover until equilibrium was reached and upstream progression .could occur. Formation of the ice cover was initiated in the Susitna just above the confluence with the Chulitna River. No severe changes in water level were observed during the formation process. On the average, water level rose 2 to 4 feet during ice cover formation. However, as the leading edge of the ice cover progressed upstream through certain reaches, levels rose enough to cause water to begin spilling into side channels which were previously dry or had formed an ice cover prior to freezeup in the main channel. Listed below are locations of the primary side channels carrying overflow due to rising water levels as the ice cover developed from the confluence to Gold Creek. 0 0 0 0 0 0 0 West channel between RM 112 & 113 East side channels between R&M 113.8 & 114.8 Far west channel below Curry between RM 119.2 & 120.4 Far east channel between RM 121.1 & 122.3 Slough on the east side of the floodplain between RM 122.4 & 123.0 East channels near Skull Creek confluence between RM 124.4 & 125.9 East channel between RM 132.5 & 133.4 Complete ice cover development from the Susitna-Chulitna con- fluence to Devil Canyon took approximately two weeks during 1980. By the end of February, the average river ice thickness at Gold Creek was 2. 9 feet, very close to the historical average for that site. Overall, there were no observable changes in river channel con- figuration due to ice cover formation. Water levels were low enough that Jess resistant alluvial banks ·and vegatation on the banks and mid-channel islands were not. adversely affected by movement of ice floes in the channel. or development of the ice cover. For the most part, flow was confined within the armored portion of the river bed. However, in the spring, ice jams and general breakup of the ice cover had a more noticeable effect on river banks and vegetation. Location of ice jams observed during the May of 1981 are listed in r29/c 7 - 2 ~·, -· -· -. - - - -; - - - -I I' - lj 'I . : i Table 7.2. Comparison of this table with Table 7.1 will verify that ice jam.s occurred in many of the same locations where accumulation of frazil ice was observed during freezeup. As described in Table 7 .2, the most significant changes in banks and vegetation occurred from the Susitna-Chulitna confluence upstream to RM 101. 5. Several new ice scars in the vicinity of Whiskers Creek confluence and new bank erosion were observed after the ice released. 7.2 -Post-Project Ice Conditions Ice growth simulation studies conducted by Acres American, Inc.,. are summarized in the report Hydraulic and Ice Studies (R&M, 1982a). The ice simulation studies, using reservoir water temper- atures from other studies, river hydraulic conditions determined from the HEC-2 Water Surface Profile studies and varying climatic conditions, have determined that once both dams are built, water temperatures downstream of Devil Canyon will not drop to 32°F until approximately 15 kilometers above the Susitna-Chulitna con- fluence.. Even though the water temperature drops to 32°F, ice cover formation will be insignificant above Talkeetna under post-project conditions. Under pre-project conditions, the Susitna River contributes 70-80% of the frazil ice appearing at the Chulitna-Susitna confluence, with most of the frazil ice being formed in the Devil Canyon reach. This frazil ice generation will be ess4~ntially eliminated once Devil Canyon Dam is cqnstructed, greatly diminishing the ice delivered to the lower Susitna River. This is likely to delay ice cover formation on the lower river, although this effect can not be quantified at this time. Under post-project conditions, ice processes should not play any signific,ant role in the shaping of the river morphology above Talkeetna. Little or no ice cover should form in the mainstem above the Chulitna-Susitna confluence. No ice jamming should occur in this reach, since little ice cover will form in it. The ice run from the upper river will be trapped in the reservoirs. Little dlata are available for ice conditions below Talkeetna. Post- project winter water levels will be 1 to 2 feet higher than pre- project levels, due to winter power releases 6,000 to 8,000 cfs greater than pre-project levels. However, the lower river has such a broad floodplain that, should staging or ice jams occur, there c:1re several flow relief channels. Consequently, ice proces- ses have some influence on channel processes in that they may redirect the main flow, but do not affect the overall pattern of the river . r29/c 7 -3 TABLE7.1 LOCATION OF ICE ACCUMULATIONS DURING FREEZEUP -1980 Location RM 105.3 -105.6 between LRX 10 & 11 RM 110.3-110.4 near LRX-13 RM 111.5.:. near LRX-14 RM 121 -just above Curry RM 122.6 RM 123.3-123.7 near LRX-27 rock. RM 126.0-126.5 -near LRX-29 RM 128.5 -near LRX-31 RM 131 -just above Sherman RM 135.7 -near LRX-43 r29/c Description Return to single channel from split channel with turbulent flow. Local change in gradient. Multiple channels join to form single channel at Curry. Rock wall on right bank. Shore ice growth from the left bank constricting the channel. Channel constricting, right bank bed- rock. Channel constricting, right bank bed- Channel constriction to single channel, prominent bedrock outcrop on the right bank at RM 126.5. Prominent bedrock point on right bank, wide shore ice on left bank constricting the channel . Split channels join to form single channel at Sherman. Channel constricted by shore ice growth. Prominent rock point on the right bank. 7 - 4 lllllli': ""')!-· ..... - IFJ~ :! • I I - ~. - i ; i TABLE 7.2 ICE JAM LOCATIONS DURING BREAKUP MAY I 1981 L()cation Description Susitna-Chulitna to LRX-7 (RM 101.5) RM 112.6 to 113.4 RM 115. 1 to 115. S RM 119. 1 to 119. 9 RM 120. 8 to 121 . 0 RM 126.0 to 127. 0 r29/c Largest ice jam observed during breakup. Water and ice observed well up into vegetation on both sides of the floodplain. New ice scars on trees on mid-channel islands near LRX-7 after release of ice jam. Increased bank scour above LRX-3 and in the vicinity of LRX-8 along the left bank. Key of the jam near LRX-17 extending upstream through single channel to Lane Creek confluence. Heavy overflow into below LRX-17. No new ice scars or signs of bank scour apparent after release of the jam. Ice jam initiated by rock point on the right bank. Heavy overflow through channel between the islands at RM 115.3. Ice jams of varying magnitude occur nearly every year through this reach. Overflow in all side channels to the west of the main 'channel. No signs of bank scour or effects on vegatation after release of the jam. Small ice jam formed above Curry where mulitple channels join. Channel confined by bedrock wall on the right bank and Deadhorse Creek floodplain deposits on the left bank. Ice jam through the constricted reach at LRX-29. ·Bedrock outcrops along right bank hindered ice movement. Overflow in far east channel beginning at RM 126.7. 7 -5 Location RM 129.6 to 130.5 RM 135.7 to 136.1 RM 139.0 to 139.8 RM 142.1 to 143.1 r29/c Description Ice jam caused by local breaks in gradients near LRX-32. Bedrock walls and outcrops in the channel bed may have influenced formation of the jam. Little change in water level upstream, due to overflow relief in east channel below Sherman. Jam initiated by rock outcrop on the right bank at LRX-43. Overflow in side channel at LRX-44. Jam in the main channel above prominent rock point on the left bank. Overflow through the east channel. Ice jam initiated at channel constriction. 7 - 6 - . ' -· - -·· - - - - - l""t' I I ! . I 1 I BIBLIOGRAPHY 1 . Alaska, University, Arctic Environmental Information and Data Center. 1974. Alaska regional profiles; southcentral region. Alaska Office of the Governor Juneau, AK. 253 pp. 2. Baxter, R.M. and Glaude, P. 1980. Environmental Effects of Dams of Impoundments in Canada, Experience and Prospects. D1epartment of Fisheries and Oceans, Bulletin 205, Ottawa. 3. 4. Blench, T. 1969. Mobile-Bed Fluviology. University of Alberta Press, Edmonton, Alberta. Bray, D.l. 1972. Generalized Regime-Type Analysis of Allberta Rivers. Ph. D. Thesis, presented to the University of Alberta, Edmonton, Canada, 232 p. 5. B1rune, G. M. 1953. Trap Efficiency of Reservoirs. Trans. Am. Geophys. Union, June. U.S. Dept. Agr. Misc. Publ. 970, p. 884. 6. Church, M.A. 1972. Baffin Island sandurs. A study of ar·ctic fluvial processes. Geological Survey Canada Bulletin 216, Information Canada, Ottawa, 208 p. 7. 8. D«)lan, R., Howard, A. and Gallenson, A. 1974. Man's Impact on the Colorado River in the Grand Canyon, American Scientist, 62(4), pp. 392-401. Everts, C.H. 1976. Sediment discharge by glacier-fed rivers in Alaska. Pages 907-923 in Rivers '76. Vol. 2, Symposium of Inland Waterways for Navigation, Flood Control and Water Diversions. 3rd Annual Symposium, Colorado State University, Fort Collins, Colorado. Waterways, Harbors and Coastal Engineering Div., American Society of Civil Engineers, New York, NY. 9. Fahnestock, R.K. 1963. Morphology and hydrology of a glacial stream, U.S. Geol. Surv. Prof. Paper 422-A. 10. Fortier, S. and Scobey, F.C. 1926. Permissible canal VE!Iocities, Trans. ASCE. Vol. 89, pp. 940-956. 11. Freethey, G.W. and Scully, D.R. 1980. the· Cook Inlet Basin, Alaska, U.S. HA-620, 4 sheets. Water Resources of Geol. Surv., Atlas 12. Gottschalk, L.C. 1964. Reservoir Sedimentation, in Chow, V .. T. (Ed.) Handbook of Applied Hydrology. McGraw-Hill, New York. r29/d - 1 - 13. Guymon, G. L. 1974. Regional sediment yield analysis of Alaskan streams, ASCE Proc., Vol. 100, n. HY1, p. 41-51. 14. Henderson, F.M. 1966. Open channel flow, MacMillan, New York, 522 p. 15. Kellerhals, for coarse August. R. and Bray, D. I. fluvial sediments, 1971. Sampling procedures J. Hydraulics Div., ASCE, 16. Kellerhals, R., Church, M., and Davies, L.B. 1977. Morphological Effects of lnterbasin River Diversions, in Third National Hydroelectrical Conference, Quebec, 30-31, May 1977, Canadian Society for Civil Engineering, pp. 833-851. 17. Kellerhals, R. and Gill, D. 1973. Observed and Potential Downstream Effects of Large Storage Projects in Norhtern Canada. Proceedings, 11th International Congress on Large Dams Madrid, pp. 731-754. 18. King, N.J. 1961. An Example of Channel Aggradation Induced by Flood Control. U.S. Geological Survey Prof. Papers 424B, 15, pp. 29-32. 19. Lacey, G. 1929-30. Stable Channels in Alluvium, Proceedings, Institute of Civil Engineers, England. 20. Lane, E. W. 1955. The importance of fluvial morphology in hydraulic engineering: Am. Soc. Civil Eng. Proc., v. 81, No. 745, 17 pp. 21. Leopold, L.B. and Maddock, Thomas Jr. 1953. The 22. hydraulic geometry of stream channels and some physiographic implications: U.S. Geol. Surv. Prof. Paper 242, 57 pp. Leopold, L.B. and Wolman, M.G. patterns: braided, meandering and Surv. Prof. Paper 282-B. 1957. River channel straight, U.S. Geol. 23. Leopold, L.B., Wolman M.G. and Miller, J.P. 1964. Fluvial processes in geomorphology. W. H. Freeman and Company, San Francisco, 522 pp. 24. Mackin, J.H. 1948. Concept of the graded river. Geological Society America Bulletin. Vol. 59, No. 5, pp. 463-511. 25. Mallard, J.D. 1973. Airphoto interpretation of fluvial features. In Fluvial processes and sedimentation, Proc., Hydrology Symposium held at Univ. Alberta, Edmonton. Thorn Press Limited, Ottawa, Canada, 38 p. r29/d - 2 - ' - - - - r I I . -ro ' !'I M"' '' f"''"' i I 26. Moore, C.M. 1969. Flow, In Moore, C.M. Watershed Changes on Austin, pp. 101-117. Effects of Small Structures on Peak and Morgan, C. W. ( Eds. ) , Effects of Streamflow, University Texas Press, 27. Neill, C.R. 1968. A re-Examination of Beginning of Move- ment for Coarse Granular Bed Materials. Hydro. Res. Stn., Wallingford, England, Internal Report. 28. Neill, C. R. 1981. Letter Review of Susitna River Morphoi- OI;;lY Studies, December 16. 29. Neill, C. R. 1967. Mean velocity criterion for scour of coarse uniform bed material, IAHR, 12th Congress, Fort Coltins, Colorado. 30. 0strem, G. 1975. Sediment transport in glacial meltwater streams. Pages 101-122 in A.V. Jopling and B.C. McDonald, eds. Glaciofluvial and glaciolacustrine sedimentation. Society of Economic Paleontologists and Mineralogists, Tulsa, Oklahoma, Special Publication 23. 31. Petts, G.E. 1977. Channel Response to Flow Regulation: the Case of the River Derwent, Derbyshire, in Gregory, K.J. (Ed.), River Channel Changes, John Wiley & Sons, New York, pp. 145-164 . 32. Pharo, C.H. and Carmack, E.O. 1979. Sedimentation Processes in a Short Residence-Time Intermontane Lake, Kamloops Lake, British Columbia. Sedimentology. 216:523-541 . 33. R&M Consultants, Inc. 1981a. Susitna Hydroelectric Project, Ice Observations -1980-81, prepared for Acres American Incorporated and Alaska Power Authority 1 August. 34. R&M Consultants, Inc. 1981b. Susitna Hydroelectric Project, Regional Flood Studies, prepared for Acres American Incor- porated and Alaska Power Authority 1 December. 35. 36. R&M Consultants, Inc. 1982a. Susitna Hydroelectric Project, Hydraulic and Ice Studies 1 prepared with Acres American Incorporated for Alaska Power Authority, March. R&M Consultants, Inc. 1982b. Susitna Hydroelectric Project, Reservoir Sedimentation, prepared for Acres American I ncor- porated and Alaska Power Authority, January. 37. Santos -Cayudo, J., and Simons, D. B. 1972. River res- ponse, Chap. 1 in H. W. Shen, ed., Environmental impacts on rivers, Water Resources Publ., Fort Colllns, Colorado. r29/d - 3 - 38. Schumm, S.A. 1971. Fluvial geomorphology -the historical perspective, in Chap. 4, Vol. I, H.W. Shen, ed., River mechanics, Water Resources Publ., Fort Collins, Colorado. 39. Shulits, S. 1934. Dams on European pp. 838-839. Experience with Bed Degradation below Rivers, Engineering News Rec., June, 40. Simons, D.B. and Senturk, F. 1977. Sediment transport technology, Water Resources Publications, Fort Coli ins, Colorado, p. 465. 41. Stabler, H. 1925. Does Desilting Affect Cutting Power of Stream? Engineering News Record, December 95, 24, p. 960. 42. Stanley, J.W. 1951. Retrogression of the Lower Colorado River after 1935. Discussion: T. Bienek; E.W. Lane; J.W. Stanley, Transactions, American Society of Civif Engineers, Vol. 116, Paper No. 2453. 43. Stevens, M.A. and Simons, D.B. 1971. Stability analyses for coarse granular material on slopes, Chap. A in H. W. Shen, ed., River Hydraulics, Vol. 1, Fort Collins, Colorado. 44. Taylor, K. V. 1978. Erosion Downstream of Dams, in Environmental Effects of Large Dams, Report by the Committee on Environmental Effects of the United States Committee on Large Dams, American Society of Civil Engineers, New York, New York, pp. 165-186. 45. Trihey, E.W. 1981. Utilization of Time Series Streamflow Data in the Determination of Project Effects on Physical Habitat for Spawning and Incubating Pink Salmon. Presented at the Western Division of the American Fisheries Society Symposium, Acquisition and Utilization of Aquatic Habitat Inventory Information, October 28-30, Portland, Oregon. 46. Tutt, D.B. 1979. Kootenay River Diversion Project River Regime and Morphology Studies, in Fourth National Hydroelectrical Conference, River Basin Management, Vancouver, B.C., May 7-8, 1979, Canadian Society for Civil Engineering, pp. 530-554. - 47. U.S. Army Corps of Engineers, Alaska District . 1975. Hydroelectric power development, upper Susitna River basin, southcentrat railbelt area, Alaska. Draft environmental impact statement. Anchorage, AK. 998 pp. 48. Woodward-Clyde Consultants. 1980. Interim report on seismic studies for Susitna hydroelectric project. Subtasks 4.01 through 4.08. Acres American Inc., Buffalo, NY. Report for Alaska Power Authority. 1 vol. r29/d - 4 - -· - - ·- - , .... , - 49. Ziegler 1 T. 1973. Material Transportundersokelser i norske bre-elver 1971: Rept. No. 41/73 1 Hydrologisk avdeling, Norges, vassdrags -og elecktrisitetsvesen, 91 p. (English summary). r29/d - 5 .. -===============~~~================~-=-==--~·-·--~-------------------------------------- ·- - r29/g1 ATTACHMENT A SUSITNA RIVER STAGE-DISCHARGE RATING CURVES AND TABLES -~ ------} } ) J 1 , J 1 -) l -l f J "----111 1 ~ ' ' !5-- 40- 30- 20 IU g_ 8 7 ~ ._; 6_ lL ~ 5. 1- :X: (!) 4 -ILl :X: ILl 3_ (!) <( (!) 2 II IIIII I X 102 5 I ~ I X 103 -XI04 6 7 ) PREPARED'-BYi DISCHARGE (C.F.S.) . PREPARED FOR• IR~ RATING CURVE FOR SUSITNA RIVER AT GOLD CREEK AJiil RIM CONSULTANTS, INC. --'\ ' FIG.: ~l="l"l~liWIII l="~nu ll~r.~ nl~rl-lliRr.l=" TliR I I=" l\ln 1n i c~1 'j ~ -) . ;._. 1 ) ) ] ... ~ .. J J I ,_uo UNITED STATES DEPARTMENT ·oF THE INTERIOR ,llu. a-6l) GEOLOGICAL SURVEY (WATER RESOURCES DIVISION) Sta. Ho. L ~ g 2?.. Q. Q Q Table tlo. L Q Begin --------~tin g tabk for _____ Su."'r.·&zK __ /G:v.~::r.:.._a/.._i1.Q/d' _ tL ____ L2/a;:d:a _________________________________ _ VI. 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It is based on /4 discharge measurements made during .. /..'?..ft.Z.::/.2.Z;?.. ____ ... · ............................... -......... ~---------------···---•nd is··---·----------·-well defined bct~P.·een .. :'1,-?.?.J?.. •• cfs and .6.5,9.!2.9.. ••. cfs. Comp. by :U!!-. date .S::.!!.:Z Z.::; .. c?..!:~;.? .. tr.?.:i .. £:~,P.C9.Z2'h'.~e:'.frea?.-_f.~.6,{ ... .c~c;:;o..cd. ... r:P.ct.'qj'. ... ,e.<;;c.($?_e:..!.?.~Z:::L7.Z..g·_._, . Ckd. by ........ _ due .......... . .. T./.: :. ... oc. 9lt:..' 2/.. .I.':;_ .•• /?.'.S /.: .................... ------·---_ ··-· .................................................... ··-· ... ······---· .. U.S. GOYUINNlMl P•I"TI•Ci OrriC( Ill) Ol-111•111 z. ... .. ... . .. _ ... 9-liO (Rev. 2-67) UNITED STATES DEPARTMENT. OF THE INTERIOR GEOLOGICAL 5URVIY (WATER RESOURCES DIVISION) Rating table for _________________________ ... _ .. ___________ --.. ---___ -------------------------------------------------------------------------------------------· Table No. t:J. L Begin YR. NO. D. HR. from-------------------------to ________________ ---------------, fr0111 _________________________ to _____ --------------------------,. from _____ ---------------_____ to ______________________________ . ______ _ Gage o· h height uc arge Differ· ence Fut Cfi Cfi /5" 00 I; ?A (j" ,.., •. • k-':1 •• ,'aw;' tf/_Q_t;_ .10 1 'Z~.aao .. J ___ _ .20 : t:.'2.7fH.2. f .3o l_f.?..laa .10 .20 .30 .40 .60 .70 .80 .90 Gage height Fttt .00 .10 .20 .30 .40 .60 .70 .80 .90· .00 .10 .20 .30 .40 .60 .70 .80 .90 Discharge Cfi Differ- ence Cft Gage height Fttl .00 .10 .20 .30 .40 .60 .70 .80 .90 .00 .10 .20 .30 .40 .60 .70 .80 .90 Cfi Differ· ence Cft Gage height Fttt .00 .10 .20 .30 .40 .60 .70 .80 .90 .00 .10 .20 .30 .40 .~0 .60 .70 .80 .90 Discharge Cfi Differ- ence Cfi Gage height l'tll .00 .10 .20 .30 .40 .60 .70 .80 .90 .oo .10 .20 .30 .40 .60 .70 .80 .90 Discharge C/1 -----~------ Differ· ence Gage height Fttl .00 .10 .20 .30 .40 -~0 .60 .70 .80 .90 .00 .10 .20 .30 .40 .60 .70 .80 .90 Discharge Cfi This table is applicable for open-channel conditions. It is based on ____ discharge measurements made during----------------------------------- ------.. ----------------------------------------------------·-----------and is--------------··-·----well defined between --------------cfs and ·---------------. cfs. -.I. .I j Differ- ence Cfi Gage height Fttt .oo .10 .20 .30 .40 .60 .70 .80 .90 .00 .10 .20 .30 .40 .60 .70 .80 .90 Disc huge Differ· ence C[l Cfi Comp. by-------date------··-- Ckd. by---------date---------- ~~.: ..... ~: l~IG Of><' .-' .: OP-ii.. ~ ---.. -------au ---- ---' ~ ' : . s __ ~. 4-- 30- 20 ,.,.. v . ' -""" IO I Q A -o-: 7_ 1.1.. ~ 1-s ::r i (.!) ~' I -!JJ i :z: 4 w c;.t <( 3 (!) 2 • I ' f . 9 l X 103 3 I B ~ I X I 0 4 : 5 . 5 7 :l X 105 . :t 5 f: 7 a 4 5 6 7 .: j ... -·--·=> ? -· PREPARED BY• 0 I SC HARGE (CF.S.) PREPARED FOR• l>l~J ~~~~.~ RIVER AT SUNSHINE B~fl ~ I-~7:,.' _· RATING CURVE FOR SUSITNA . R&M CONSUlTANTS, INC. A .. 2 . ' . FIG~ I nr-,...n/1\ •U I""MI"''~ I I f" I"> .,... -""Tf'.j'•t..fl\_~f">C". ·T_I\.01 r-.. ·,...r . Ll· I I 9-UO (!lev. l-67) J ~] l UNITED STATES DEPARTMENt OF tHE INTERIOR GEOLOGICAL SUIVEY (WATEI IESOUICIS DIVISION) Sla. No. L. S: ~ _}_ -~ L ~ Q.. Tobie No. ,.1 L. . ' ' --. / Rating tabfe for ...... :;,.~_r.t::...L!..NB. .... )/J.Y.f.IJ:. .. L~~----~·-t..IJ.\L·~~t_-~Jji£..r .. J./t..n.:.. .. :r:.£·1................................................... Begin ~~:--r.~;,--o-:--; 11 ;:- from .......................... to ............................... , from ......................... to ............................... ,.from .......................... to ..................................... . Gage Discharge height Fttt Cft . 00 ••••••••••• .10 .......... . .20 ••••••••••• .30 .......... . .40 ......... .. • )0 ••••••••••• . 60 ••••••••••• .70 .......... . .80 .......... . . 90 .......... . .00 .......... . • 10 .......... . .20 ••••••••••• . }0 ••••••••••• .40 ......... .. ,,0 .•••••••••• .60 • 70 .......... . .80 .......... . .90 ......... .. Differ- ence Cft Gage Discharge height Fttl Cft Differ- ence Cft 3 .00 •• :7.k.4::.1 ' ,-f' ... ........... .. .10 {JJ.J.Q.Q. /(' . ' .20 •••• ~.(.Q. ·;'"···' ~.i •.•.• . 3o k'!.L:.:.~. " . , u: __ ~,: __ .40 i.(t...7.t.~Q. l/..-1 , .. , ' .90 .~./..•c!L • 4 .00 /.G.~9.~: •••• L ... .10 .~{;:,~JQ.(1 ... ..l ... .20 t~r;. .• ;..c.~: I .. • .! .... .Jo L7 • .L l:l.o. . 'I I} ~ (' .40 :..t-t.! •• t. . . r __ ,_.:. ........ ···y--· .60 ~x .... :"~~-1 .70 :.u:~·,.l:~. ---"1---- . 80 ~:~~~~:~/~--L~·- . .• J. .•• • .,.., '?1.)(1 .90 .... J.:-.~~---· J..~.!~. Gage Discharge height p,, Cft .1o ~Ca.a.ca .10 ~ .. L.<.:c.? Differ- ence Cft ..~:.. .. :L Gage height Fttl Discharge Cft Differ· ence Cft 1 ·.; .1.:.2. c· n .oo lo-< • ·--~-.9C~'2 . ..:r ·,. o .10 r:----····-·· .. 9.Ci. •• • 20 .;~[~.LJ2. .,o 1:f.z{.?.r.. .so J.r:l:2.rd:.. .90 1f...~.9..f~. 8 .oo 1~.LC.~Q. . 80 :.;. • .J.d} . 90 :.·~l t ') (• . • •• c •• -···· //•(; J ·""'··'-· Gage hdght Discharge Fttl Cft ,40 S.-i.:t~~o.. .)0 ~.9-.~.?.:..Q . .60 ;_j,_.[{-:.£.: • / ..... ,.. ~ . . 70 ~-"·--~---~- Differ- ence Cft .8o .~;..:t_:;_c_ 1 . .. s.r •• :. -.~ r1 9c~ () .9o --•·····--·· !.tL?. . I I D.oo ~·-·:.>.,.Q.·"'~Q . to .;_ j_, }.-;._ J.' . .2o 16l;L;;'.0.Q .30 6.~l.3P-J2. . 4o ZY...~lQ.f.L .50 1/~.::.~~Q- .70 73.1P..Q .• 90 ,.-~.· ~C1r1 . .£ ... l ......... ·L2: .. . Gage height Fttl Discharge Cft .2o 7.9.ZJ~.9. ,..-, J A (' .40 \::1t~~.t7 •• :. .90 s..~ .... i.[QQ Differ- ence Cft -::o c .. , ()QC·'" I c;..OO ·~~a .. <U I I (}u .1o lc1.1~c~ ~.~~~~~~ • 20 ~:c;, .:..(~- . 50 ?.3 •. l2CJ .10 ~t??.3.:a:.~ .80 '{J.,[Qi~ . --------"'~ '{ c: .9o rl-'·•· . · ... L--:?:.12.~~ This table is applicable for open-channel conditions. It is based on r discharge measurements made during . .!.!l.FJ...~ ....................... . Gage D' h height uc arge Fttl · Cft ,10 ,·'_Q}.J.fJ..P. . .4o · Q!J~_c.:~c,_ Differ- rnce Cft .9o 11 Lc .. ~'ZLW 1 ~-: • .- ;4.oo Vf.f.90D. ~~~;~~~::~ .loi![L~C . .20 II J.·1,5.C.l:. .3o 'LSJ.I':.::u.. ,.4o 1/J.Z.l!:.:.¥ .. .5o li~~2:1C.-." . ......................................... ~7 -;,.7 ..................... -and is ... j':1l!.IJ~-~i/····-well defined between /.'.l.C;,-;;L~'. .. cfs and .. l·~-?..~~L~~~--cfs. ········ .. Q.:: .. !.7.?; -~. _(6, :. Q 1 .. ~ ~-.. -. ·-.......... ····· ....... ····· ......................... -............................... -............ --............. -... Comp. by .!:U.·_ date~~:-.-.~:::..: F J til( 11-1\l · ~I Ckd. by ......... date ......... . ------------------- 5 __ 30_ IQ_ 9_ a_ -7_ ...,: u.. -6_ r- :X: 5_ (!) -UJ :r: 4_ w (!) <t 3_ (!) l X 103 PREPARED . BYi . I 2 ll-i-H11mtt1 ttf . . . . t 1 lt!l 4 I I 5 6 7 8 9 t X 10 2. 3 0 l S C H A R G f5. .. ( C. F. S.) I 3 ~ATING CURVE FOR SUSITNA RIVER AT SUSlT.NA STATION . · .. B~ll FIG .. AM3 _ __,._..,,.,· -~ REDRAWN FROM U,S.G.S. DISCHARGE. -TABLE N9 •. 02. I 1 I 9-JIO (~ev.l-67) . JUNii~~}STAic::t beP"'"';:lENI urJTH~ ~~~.\Rit.,,.-:J GEOLOGICAL SURVEY (WATER RESOURCES DIVISION) :l ~-} .• .. ). -) Sta. No. L ~ g 2 £. ...l. .2' e T Table N.o. !2 Z Rating table for __ ${t'.s_~/aa...RLV.ec...rl'LS(,!.si/.aa.. .. S-k.b"..a-.. -----------------------------------------------------------Begin - - -____ _ YR. MO. D, HR. from .. Qt;;..tc 4 .l9.Z8 ..• to -------------------------------~ .from ________________________ to---·-------------------------,. from-----------------------to---------------------------------·-- Gage Diachorgc Differ- heighr encc F~tt Cfi Cfi .00 ·---------- .10 ...................... .20 ................ ____ .30 ......................... .40 ···----.. -- .50 ---------- .60 ------ .70 ................. ---..: --·.·--- . 80 ilk,.4CJ2 .a.QQ .90 z:z_gQq 7-00 .10 .lO .)0 .40 .! ... Z.QQ .8..QQ _,o tz._,.Q.OO -~U:?.9. "'-~;2QQ ··t-· .:t£L.· ----...... .4~_7QQ G~ge Discharge heoghr · F~tt Cfi Differ· ence Cfi Gage Discharge heighl Fttr Cfi Differ· ence Cfi Gage heighr Fm Gage h heighr Disc arge Differ· Discharge ence Cfi Cfi F~tl Cfi Differ· ence Cfi Gage heighr Fttt a.oo .3.b._,. --·-.9.QQ_ /o.oo ~,..7.! -LLQQ 12 .oo at_,.ZOQ !..3..9!2 ;Q .oo /Lf?l.tl..O.. ~.0.12 l/,.oo .10 7,.4.((). .10 .7,J.L .. !.L?!P. .to 2,.~9.2 !.3..Qr1 .1o l.t.!-rZtXl-.1o .2o 3B7 _EiQQ .30 3.9.:?..Q2 .40 1lf4J.QQ_ .20.Q .50 !IJ,_Q_QQ. /{2_Q.Q .60 4ZJ.X:O. 1 .70 4~_Q[._.>Q_ .80 4.4,0.QQ .90 #.S,OJ2<.'?. q.oo tf.Gl;OO.Q. .10 4.4-lXlQ ···r·· .20 .l3,202 /./.QQ .20 .,.B.02 1.4t!r2 .20 .JO ~(J.CK& !2..t?J2 .30 B~Z.... .30 .40 .I;"ZQQ Ao ..to t!.£?.,..5!2£ · .4o .50 ti-..~4.... .50 .50 .lf3.,..{QQ_ .60 .60 .70 .70 .8o gz,zm . .10 .60 tL9..,.1e2 .70 .i?L,.3.QQ .80 .20 4.8/).QQ /.f2QQ .20 .20 9 i3,Jl!2Q. .3o 9.9,.S:O.Q .10 28,.9. -- .. 2o -:::Z.9.,..6Q;; ~t_,..3.QQ .3o 4..t;raa LtaQ .3o .40 54/.00 .60 .70 .80 7.8_,.bQ2 .90 ?:~_0-QQ !J.Q_Q .9o Z9}~QQ l.J.QO .70 .:3.871QQ .ao • .3.~_ea J.ZQQ .9o .4/,.St!?. tB..c;Q Discharge Cfi 1.4....~3.Q .!I.S,.i£2C. This table is applicable for open-channel conditions. It is based on 10 discharge measurements made during .!.9..22::].8 ____________ _ ····--------···-------·····-------··---------------·-------------·--and is ___ f'a..t:t:f-----well defined between .£8r002cfs and .2£.?0r~cfs. ----.......... --........ -----... -... -.... -........ -----.. -............................. ---...... --..... -----..... ------·-· ... --------.......... -~------............ ----....................... ---.. -....... ---.. ---· --..................... _ .......... ---................ 4 Differ-Gage Discharge Dilfer- encc heighr cncc Cfi Fttt Cfi Cfi .!Be; /£3.00 .10 .20 .30 .40 .10 ----------- .20 ----------- .30 ----------- .40 ----------- .50 ----------- .60 • 70 ----------- .80 ----------- .90 ----------- Comp. by~.(-date ~.-:llr.:.79 Ckd. by _________ date--~----·- ·-------------------... ·-----------·----·~------.. --... ·---------·----... --------·--------------------··----.---· .. --.. -----------.... --........................ -........................ _ ......... . U.l. GOVIINIIIIIT PIINTUIG OniCII IIU OI-J41-Jtl 9-2!0 (Rev. 2-67) UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY (WATER RESOURCES DIVISION) Rnting table for _f..f~i!.._!_~_l}_ __ !f_(_t::_!!_!j_ __ d!:.. .. £J!.f..([_~!_-~~ 1':4 !:!..~_"Y_ _______________ ......................................... . Sta. No. j_ £2-CJ. il-3 !7 q Table No. C> 2- Begin Yll. 1.10, D. HR. from Qf~:_!./1 _ _( l2Jl_ to ________________ " ______________ , .from.------------------_ to __ ---------___________ -------, . from_------------------------to _____ -------------------------------- Gage Discharg~ height l'fll Cft Differ· ence Cft J9 .00 7.f?.4t9..0.. l 1.(10 ;z. OJ )a:; -·-·- .lo ··-·-------)._211 " zo5SC'O ------- .20 -----------!!!:~E. 207~ -~0 ·----·--·---~!~. .40 1:.C:..?..f..'?f! ll~e. ,)0 .60 ~ .70 lIZ. "ZcC ---------.?lP~~ "2.1 1/)'(10 -----------2.1 (10 Yf&:?.. . ?.l.~ .ao 'Z:_t!.tE!?. -~1£'! . . 90 J.'/:!Jt£/2 .l1DO ) o .00 fJJ.7P.E ;1~~~ 7., ~'"1'(/i .10 kk-.b.-: • .:-~ }J.~~ 2283oo ;20 ---------·· J.1"o 01\ 2 "f ~(.CO ··-····· '"" ····-······ l} DO .40 '?}_~_1._'(Q _f.}q_~ .,o u~-~~-?- .60 .70 .80 .90 1------------ Gage Discharge height flfl Cft .00 .ao .20 .30 .40 .)0 .60 .70 .80 .90 .00 .10 .20 .30 .40 .)0 .60 .70 .80 .90 Differ· ence Cft 1------- ------- Gage Discharge height F111 Cft .00 f-·---------- .10 .20 .30 1------------ .40 .• )0 .60 .70 .80 .90 .00 .10 .20 --------- .30 --------- .40 .)0 .60 .70 .80 --------- .90 1-··--------- Differ· ence Cfs 1------- Gage h~ight fill .00 .10 .20 .30 .40 .)0 .60 .10 .80 .90 .00 .10 Discharge Cft .20 --------- .30 .40 .)0 .60 .70 .80 ~ .90 Differ· ence Cft ------- ------- ------- Gage . height Ducharge 1'111 Cfs .00 .10 .20 .10 .40 .60 .70 .80 .90 .00 .10 ----------~- .20 .30 .40 Dilfc:r· ~nee Cft 1-·-·---- ------- -------- .60 r-------------------- .70 .80 .90 Gage height Discharge Ptll Cft ,00 .10 1------------ .20 .30 .40 .)0 .60 .70 .80 .90 f..----------- .00 .10 .20 .30 .40 .)0 .60 ---------- .70 --------- .80 .90 1----------- This table is applicable for open-channel conditions. It is based on ____ discharge measurements made during -------------------····------- -----··-·-------····················-··---------------------··-·--·-and is •• ·-······---------well defined between __________ cfs and --~-~-----·····rfs. Differ· ~nee Cft -----·-·· Gage height I'll I .oo .10 .20 .30 .40 .)0 Discharge Cft .60 ~---------- .70 .80 .90 .00 .10 1------------· .20 .30 .40 .)0 .60 .70 .80 .90 1------------ Cft Comp. b.;J.!Jc'L date .ff..'!f_JP.) Ckd. by········-date---------· ... 1. liOVIIM1111M1' PIUITUI~ OffiCI1 1117 OP-141 .. 711 .. t _c__j l . - ATTACHMENT B FLOW VARIABILITY RATIOS - - r29/g2 I . ~l l jl } ) ·~ } '{, l 1 ----~ y susi8/b1 Comparison of Peak Flows to Average Monthly Flow Susitna River at Gold Creek ~ No. 15292000 I May I Mean Monthly 1 Da~ Peak Flow 3-Da)! Peak Flow 7-Da)! Peak Flow 15-Day Peak Flow Flow ·QM Q1 o17oM 03 Q3/QM Q7 Q7/QM Q15 Q15/QM 1 ~ (cfs) 1950 11510 21900 1.90 20200 1. 75 16700 1. 45 16200 . 1.41 1951 14090 24700 1. 75 23900 1. 70 22500 1.60 17800 1.26 1952 5419 28000 5.17 26700 4.93 17000 3.14 9570 1.77 1953 19270 31000 1.61 30100 1.56 26400 1.37 22400 1.16 1954 17280 23000 1.33 23000 1.33 22800 1.32 21600 1.25 1955 9319 19500 2.09 18300 1.96 17900 1.92 14500 1.56 1956 17660 39400 2.23 -36200 2.05 32400 1.83 26200 1.48 1957 13750 31000 2.25 30500 2.22 28800 2.09 21800 1.59 1958 12900 25000 1.94 23700 1.84 21700 1. 68 18500 1. 43 1959 15990 39600 2.48 37200 2.33 30700 1.92 27300 1. 71 1960 15780 40000 2.53 35800 2.27 27900 1. 77 23700 1.50 .1961 17360 29400 1.69 26100 1.50 22300 1.28 21700 1.25 1962 12590 36000 2.86 29600 2.35 23000 1.83 20300 1.61 1963 19030 45000 2.36 42900 2.25 37100 1. 95 33900 1. 78 1 1964 4307 37100 8.61 26400 6.13 14200 3.30 7740 1.80 1965 12900 37900 2.94 37300 2.89 30400 2.36 21200 1.64 1966 9645 23300 2.42 22600 2.34 20400 2.12 15300 1.59 1967 15480 31200 2.02 30200 1.95 29700 1.92 24600 1.59 1968 16177 39700 2.45 37000 2.29 33800 2.09 29100 1.80 1969 11045 26500 2.'40 24400 2.21 20500 1.86 16200 1. 47 1970 11380 21600 1.90 19500 1. 71 18100 1.59 16300 1.43 1971 3745 9500 2.54 8830 2.36 7640 2.04 5680 1.52 1972 21890 55500 2.54 43600 1.99 37000 1.69 29800 1.36 1973 8235 17000 2.06 16400 1. 99 15400 1.87 13500 1.64 1974 16180 33600 2.08 33200 2.05 32400 2.00 26400 1.63 1975 15350 31000 2.02 30400 1.98 28300 1.84 24100 1.57 1976 12620 17000 1.35 16000 1.35 15100 1.20 14000 1.11 1977 12680 33100 2.61 30400 2.40 24500 1.93 21500 1. 70 1978 11950 20500 1. 72 19400 1.62 17700 1.48 14900 1.25 1979 13870 34400 2.48 33900 2.44 29400 2.12 22700 1.64 1980 12060 21000 1. 74 20800 1. 72 17900 1.48 15100 1.25 # of Val. 31 Average 13270 2.45 2.24 1.87 1.51 Standard 4240 1.33 0.96 0.46 0.20 Oev. susi8/b2 Comparison of Peak Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000 June Mean Monthly 1 Da~ Peak Flow 3~oa~ Peak Flow 7-Day Peak Flow 15-Da~ Peak Flow Year Flow -QM o, o17oM Q3 Q3/QM Q7 Q77QM Q15 Q15/QM (cfs) 1950 19600 34000 1.73 32100 1.64 27000 1.38 22400 1.14 1951 20790 35800 1. 72 32100 1.54 29800 1.43 25200 1.21 1952 32370 43300 1.34 42300 1.31 39500 1.22 37000 1.14 1953 27320 37700 1.38 37200 1.36 35500 1.30 31000 1.13 1954 25250 30100 1.19 29500 • 1.17 28500 1.13 25800 1.02 1955 29860 38000 1. 27 37300 1. 25 36000 1.20 34600 1.16 1956 33340 51500 1.54 49900 1.50 46800 1.40 40300 1.21 1957 30160 40600 1.35 39900 1.32 38400 1.27 35400 1.17 1958 25700 28000 1.09 28000 1.09 28000 1.09 28000 1.09 1959 23320 29300 1.26 . 27900 1.20 26000 1.11 24300 1.04 1960 15530 18700 1.20 17100 1.10 16900 1.09 16000 1.03 1961 29450 54000 1.83 52000 1. 77 42700 1.45 36800 1.25 1962 43270 79900 1.85 75200 1. 74 64700 1.50 53200 1.23 1963 26000 26000 1. 00 26000 1.00 26000 1.00 26000 1.00 1964 50580 85900 1. 70 81900 1.62 75000 1.48 63500 1. 26 1965 25720 39900 1.55 37200 1.45 33000 1.28 27200 1.06 1966 32953 58400 1.77 56600 1.72 49200 1.49 39800 1.21 1967 29513 36800 1. 31 37400 1. 27 34600 1.18 31500 1.07 1968 31550 39500 1.25 38900 1.23 38100 1.21 36500 1.17 1969 15503 21900 1.41 2o9oo 1.35 18700 1.21 17500 1.13 1970 18630 30800 1.65 30100 1.62 26100 1. 40 20400 1.10 1971 32930 66300 2.01 59000 1. 79 48300 1.47 38200 1.16 1972 34430 70700 2.05 65600 1. 91 53500 1. 55 39800 1.16 1973 27800 52800 1. 90 45300 1.63 40900 1.47 34600 1.24 1974 17870 29800 1. 67 27000 1. 51 22700 1.27 19700 1.10 1975 32310 44000 1.36 42200 1. 31 37100 1.15 32600 1.01 1976 24380 33300 1.37 32100 1.32 29800 1.22 28600 1.17 1977 37970 52600 1. 39 52200 1.37 48300 1.27 41500 1.09 1978 19050 24300 1.28 23800 1.25 23100 1.21 20600 1.08 1979 24690 32500 1. 32 31200 1.26 29400 1.19 26400 1.07 1980 29080 43200 1.49 40300 1.39 34700 1.19 31300 1.08 # of Val. 31 Average 27970 1.49 1.42 1.28 1.13 Standard 7740 0.27 0.23 0.15 0.07 Dev. ~ ·' 1 l j I. J ----J .. ---J . . ~~-=~.::::} .·· . ---~ -"t . ~--~ -=; J ---J ----1 ·j-~ B 1 susi8/b3 Comparison of Peak Flows· to Average Monthly Flow Susitna River at Gold Creek No. 15292000 July Mean Monthly 1 Da~ Peak Flow 3-Da~ Peak F=low 7-Da~ Peak Flow 15-Da~ Peak Flow Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q15 Q15/QM Year (cfs) 1950 22600 32500 1. 44 29600 1.31 26300 1.16 24500 1.08 1951 22570 ~5000 1.11 24800 1.10 24600 1.09 23800 1.05 1952 26390 41700 1.58 40400 1.53 33900 1.28 29100 1.10 1953 20200 26200 1.30 24300 1. 20 22800 1.13 21000 1.04 1954 20360 28700 1. 41 26600 1. 31 24500 1. 20 21800 1.07 1955 27560 39000 1.42 38300 1.39 34200 1.24 ' 30900 1.12 1956 31090 32000 1.03 32000 1.03 32000 1.03 32000 1. 03 1957 23310 34500 1.48 31300 1.34 26300 1.13 24900 1.07 1958 22880 32400 1.42 32100 1.40 25900 1.13 23800 1. 04 1959 25000 32000 1.28 30700 1.23 29500 1.18 26500 1.06 1960 22980 37500 1.63 36100 1.57 32900 1.43 26100 1.14 1961 24570 30300 1.23 27100 1.10 26100 1.06 25500 1. 04 1962 25850 32700 1.26 28600 1.11 27700 1.07 . 26600 1.03 1963 34400 49000 1.42 46300 1.35 42900 1. 25 39200 1.14 1964 22950 33200 1.45 29100 1.27 27100 1.18 25800 1.12 1965 27840 37700 1.35 34900 1.25 32000 1.15 30500 1.10 1966 19864 31800 1.60 29800 1.50 25100 1.26 21800 1.10 1967 26800 50000 1. 87 46300 1. 73 38900 1. 45 32500 1.21 1968 26922 32000 1.21 31600 1.20 29400 1.11 28400 1.07 1969 16103 20900 1.30 20200 1.25 19100 1.19 17700 1.10 1970 22660 29100 1.28 27700 1.22 25000 1.10 23000 1.02 1971 23950 38300 1.60 35800 1.49 31800 1.33 26500 1 . 11 1972 22770 27200 1.19 26400 1.16 25500 1.12 25500 1.12 1973 18250 22900 1.25 22400 1.23 22200 1.22 20300 1. 11 1974 18800 26300 1.40 25000 1.33 21900 1.16 20300 1.08 1975 27720 33900 1.22 32500 1.17 30700 1 .11 29200 1.05 1976 18940 22800 1.11 21600 1.14 19700 1.04 19300 1. 02 1977 22870 30000 1. 31 29700 1.30 27900 1.22 25100 1.10 1978 21020 24100 1.15 23300 1.11 22500 1.07 21600 1.03 1979 28880 39300 1.36 34800 1. 20 32600 1.13 31700 1.10 1980 32660 49700 1.52 45100 1.38 36800 1.13 33700 1.03 # OfVal. 31 Average 24150 1.36 1.29 1.17 1. 08 Standard 4240 0.18 0.16 0.10 0.04 Dev. susi8/b4 Comparison of Peak Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000 August Mean Monthly 1 Da~ Peak Flow 3-Da~ Peak Flow 7-Da~ Peak Flow 15-Da~ Peak Flow Year Flow -QM Q1 0 1/QM Q3 Q3/QM Q7 Q77QM Q15 Q15/QM (cfs) 1949 24250 35000 1. 44 34000 1.40 31900 1.32 30900 1.27 1950 19880 27600 1.39 26200 1.32 24800 1.25 23600 1.19 1951 19670 30600 1.56 26900 1.37 24200 1. 23 21100 1. 07 1952 20920 41900 2.00 37400 1.79 30100 1.44 26800 1. 28 1953 20610 28100 1.36 26600 1.29 ?5400 1.23 22100 1.07 1954 26100 41000 1.59 40300 1.54 33300 1.28 28300 1.08 1955 25750 56900 2.21 54000 2.10 43100 1. 67 29900 1.16 1956 24530 31000 1.26 31000 1.26 30900 1.26 28600 1.17 1957 20540 . 26600 1.30 24900 1.21 21400 1.04 20900 1.02 1958 22540 47800 2.12 45900 2.04 38300 1. 70 30200 1.34 1959 31180 59700 1. 91 56700 1. 82 49100 1.57 41700 1.34 1960 23590 33300 1.41 30500 1.29 27700 1.17 25600 1.09 1961 22100 26000 1.18 26000 1.18 26000 1.18 26000 1.18 1962 23550 30600 1.30 28700 1.22 25500 1.08 24100 1. 02 1963 23670 35000 1. 48 32700 1.38 30300 1.28 25400 1.07 1964 16440 21600 1.31 21500 1. 31 20200 1.23 18100 1.10 1965 21120 33600 1.59 33000 1.56 30600 1.45 26000 1.23 1966 21825 33500 1.53 31400 1.44 26900 1.23 23200 1.06 1967 32622 76000 2.33 69300 2.12 55400 1. 70 42200 1.29 1968 17167 21800 1.27 21600 1.26 20500 1.19 19900 1.16 1969 8879 16800 1.89 15800 1.78 14300 1.61 12100 1.36 1970 19980 31600 1.58 29500 1.48 26100 1. 31 22900 1.15 1971 31910 77700 2.40 72700 2.28 57900 1.81 41900 1. 31 1972 19290 26400 1.37 24900 1.29 22200 1.15 21000 '1.09 1973 20290 30500 1.50 29900 1.47 27800 1.37 21300 1.05 1974 16220 22300 1.37 21300 1. 31 18900 1.17 17600 1.09 1975 18090 24800 1. 37 23400 1.29 21600 1.19 19900 1.10 1976 19800 ' 32000 1. 62 30000 1.52 28600 1.44 24900 1.26 1977 19240 26200 1.36 24600 1.28 23400 1.22 21500 1.12 1978 16390 20900 1.28 20800 1.27 20500 1.25 19500 1.19 1979 20460 28400 1.39 27600 1.35 25800 1.26 24000 1.17 1980 20960 31100 1.48 27700 1.32 24500 1.17 24100 1.15 # of Val. 32 Average 21550 1.57 1.49 1.33 1.16 Standard 4725 0.33 0.30 0.20 0.10 n';Jv. ' t ·"'' I i ] ) "'J I j I .J ; ' -. .) 1 . ...::.:.---=J :· . __ _:_..'} .. -=~_j --l ,. •· .. --l ·:_--1 -~~ -l t l ] t £ susi8/b5 Comparison of Peak Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000 September Mean Monthly 1 Day: Peak Flow 3-Day Peak Flow 7-Day: Peak Flow 15-Day Peak Flow Flow -QM Q1 Q1/QM 03 Q3/QM Q7 Q7/QM Q15 Q15/QM Year (cfs) 1949 15650 25400 1.62 24600 1.57 21300 1. 36 18100 1.16 1950 8301 12000 1.45 11300 1.36 10700 1.29 9940 1.20 1951 21240 31800 1.50 31500 1. 48 30600 1.44 24800 1.17 1952 14480 30000 2.07 27700 1. 91 21500 1.48 16800 1.16 1953 15270 20000 1. 31 19400 1.27 18900 1.24 18100 1.19 1954 12920 17000 1. 32 17000 1. 32 16700 1.29 15300 1.18 1955 14290 23300 1.63 22900 1.60 20600 1. 44 17700 1.24 1956 18330 25000 1.36 25000 1.36 25000 1.36 22000 1.20 1957 19800 27000 1.36 24400 1.23 22100 1.12 20600 1.04 1958 7550 8500 1.13 8500 1.13 8500 1.13 8500 1.13 1959 16920 41000 2.42 38000 2.25 31500 1.86 23000 1.36 1960 20510 40100 1.96 36200 1.76 30500 1.49 24700 1.21 1961 13370 16200 1. 21 15800 1.18 14500 1.08 14400 1.08 1962 15890 31000 1. 95 28700 1. 81 24900 1.57 19700 1.24 1963 12320 16100 1. 31 15800 1.28 15400 1.25 14500 1.18 1964 9511 14100 1.47 12900 1.35 12000 1.25 10600 1.11 1965 19350 30100 1.56 27800 1.44 24700 1.28 21000 1.09 1966 11753 17300 1. 47 16000 1.36 14300 1.22 12900 1.10 1967 16867 31800 1. 89 31500 1.87 29100 1.73 22900 1.36 1968 8815 13400 1.52 13100 1. 49 12200 1.38 11300 1.28 1969 5093 6780 1.33 6640 1.30 6300 1.24 5860 1.15 1970 9121 13600 1.49 12900 1.41 12400 1.36 10900 1.20 1971 14440 27000 1.87 25900 1.79 22900 1.59 18600 1.29 1972 12400 26400 2.13 23300 1.88 19600 1.58 16300 1.31 1973 9074 18000 1.98 16100 1. 77 13800 1.52 11400 1.26 1974 12250 20900 1. 71 20500 1.67 18000 1. 47 13500 1.10 1975 16310 28600 1.75 25400 1.56 20900 1.28 19600 1.20 1976 6881 9280 1.35 9040 1. 31 8150 1.18 7170 1.04 1977 12640 16900 1.34 16800 1.33 15700 1. 24 14500 1.15 1978 8607 12400 1.44 12000 1.39 11200 1. 30 10600 1. 23 1979 10770 15000 1.39 14500 1.35 13600 1.26 12300 1.14 1980 13280 28000 2.10 24900 1.88 20100 1.51 16200 1.22 # of Val. 32 Average 13250 1.61 1. 52 1.37 1.19 Standard 4190 0.32 0.27 0.18 0.08 Dev. susi8/b6 Comparison of Peak Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000· October Mean Monthly 1 Da~ Peak Flow 3-Da~ Peak Flow 7-Da~ Peak Flow 15-Da~ Peak Flow Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q15 Q15/QM (cfs) 1949 6334 20100 3.17 16300 2.57 12900 2.04 8960 1.41 1950 3848 5aoo· 1.51 5530 1.44 5260 1.37 4950 1.29 1951 5571 11000 1.97 10200 1.83 9230 1.66 7520 1.35 1952 8202 12500 1.52 11700 1.43 11100 1.35 10700 1.30' 1953 5604 8700 1.55 8480 1.51 8120 1.45 7330 1.31 1954 5370 6500 1. 21 6500 1.21 . 6500 1.21 6190 1.15 1955 4951 8600 1. 74 8260 1. 67 7240 1.46 6160 1.24 1956 5806 7200 1. 24 7200 1.24 7200 1.24 7200 1.24 1957 8212 12600 1.53 11300 1.38 10300 1.25 9400 1.14 1958 4811 6600 1.37 6400 1.33 5990 1.25 5610 1.17 1959 6558 11900 1. 81 11100 1.69 10700 1.63 8770 1.34 1960 7794 14500 1.86 13600 1.74 12500 1.60 10600 1.36 1961 5916 12500 2.11 12000 2.03 10400 1. 76 7320 1.24 1962 6723 10100 1.50 9830 1.46 9150 1.36 7970 1.19 1963 6449 9310 1. 44 9130 1.42 8900 1.19 8070 1. 25 1964 6291 9620 1.53 9520 1.51 8890 1. 41 8050 1.30 1965 7205 18200 2.53 17300 2.40 15100 2.10 11300 1.57 1966 4162 7530 1.81 7280 1. 75 6990 1.68 5770 1.39 1967 4900 8010 L63 7660 1.56 6850 1.40 6210 1.27 1968 3822 5400 1. 41 5270 1.38 5060 1.32 4670 1.22 1969 3124 4220 1. 35 4160 1.33 4000 1.28 3810 1.22 1970 5288 9000 1. 70 8040 1.52 7020 1. 33 6340 1.20 1971 5847 8260 1. 42 8230 1. 41" 7740 1. 33 7190 1.23 1972 4826 7000 1. 45 6630 1.17 6210 1.29 5430 1.12 1973 3733 6000 1.61 5940 1.59 5640 1.51 5000 1.34 1974 3739 7530 2.01 6210 1.66 5720 1.53 5370 1. 43 1975 7739 13000 1.68 12000 1.55 10300 1.33 9700 1.25 1976 3674 5400 1. 39 5040 1.30 4830 1.25 4340 1.12 1977 7571 11000 1. 45 9820 1.29 9020 1.19 8890 1.17 1976 4907 6570 1.34 6480 1.32 6120 1.25 5700 1.16 1979 7311 12200 1.67 11200 1.53 10100 1.38 8930 1.22 # of Val. 31 Average 5690 1.66 1.56 1.43 1.26· Standard 1450 0.39 0.31 0.23 0.10 Dev. .I t ! ) ' t J • J c] -", J I ······~ ··. ········j .· ---} susi8/b7 Mean Monthly Year Flow -QM (cfs) 1958 10460 1959 7413 1960 13890 1961 10100 1962 7743 1963 11060 1964 2355 1965 7452 1966 3971 1967 12400 1968 10940 1969 6001 1970 9643 1971 4468 1972 9765 # OfVal. 15 Average 8510 Standard 3270 D~v. .. -i -. J ---J -~] -1 ··-... ... i -. c Comparison of Peak Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 May -ll ~ .... 1 Da~ Peak Flow o17oM 3-Da¥ Peak Flow 7-Da~ Peak Flow Q1 Q3 Q3/QM Q7 Q7/QM 16000 1.53 16000 1.53 16000 1.53 13000 1. 75 13000 1.75 12700 1. 71 35700 2.57 33300 2.40 29600 2.13 16000 1.58 . 15000 1.50 13100 1.30 16500 2.13 16000 2.07 14900 1. 92 28500 2.58 26600 2.41 22600 2.04 4000 1. 70 4000 1.70 4000 1. 70 12000 1.61 12000 1.61 12000 1.61 9110 2.29 6700 1.68 6020 1.52 22000 1.77 21000 1.69 20700 1.67 25400 2.32 23900 2.18 22200 2.03 12300 2.05 11700 1. 95 10100 1.68 19000 1. 97 17700 1.83 16100 1.67 11000 2.46 10300 2.31 8860 1.98 23800 2.44 20000 2.05 16700 1. 71 2.05 1.91 1.75 0.38 0.31 0.23 ) J j ' f 15-Da¥ Peak Flow Q15 Q15/QM 14200 1.36 11300 1.52 21500 1.55 12700 1.26 12200 1. 58 19600 1.77 3330 1.41 12000 1.61 5740 1. 45 18100 1.46 18400 1.68 8160 1.36 13900 1. 44 6710 1. 50 12800 1.31 1.48 0.14 susi8/b8 Mean Monthly Year Flow -QM (cfs) 1958 23170 1959 23660 1960 17~90 1961 20490 1962 20620 1963 17750 1964 40330 1965 20070 1966 21740 1967 25520 1968 29000 1969 18560 1970 19670 1971 22180 1972 17900 '1980 22490 #ofVal. 16 Average 22530 Standard 5650 Dev. Comparison of Peak Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 June 1 Da~ Peak Flow 3-Da~ Peak Flow 7-Da~ Peak Flow Q77QM Q1 Q1/QM Q3 Q3/QM Q7 29000 1.25 28300 1.22 27300 1.18 33400 1.41 33100 1.40 32300 1.37 22000 1.27 21700 1.25 21200 1.22 .29200 1.43 27600 1.35 25900 1.26 38000 1.84 34100 1.65 29700 1.35 27700 1.56 24300 1.37 23000 1.30 45000 1.12 45000 1.12 45000 1.12 30000 1.49 28000 1.40 24900 1.24 29000 1. 33 27700 1.27 26100 1.20 56000 2.19 40800 1.60 34300 1.34 38800 1. 34 37900 1.31 35900 1.24 28100 1. 51 26300 1.42 24800 1. 34 33000 1.68 29700 1. 51 25400 1.29 44500 2.01 41600 1.88 38300 1. 73 28000 1.56 25800 1.44 23300 1.30 30200 1.34 27400 ·1.22 25000 1.11 1.52 1.40 1.29 0.29 0.19 0.14 I .. J 15-Da~ Peak Flow Q15 0 15/QM 23900 1.03 29500 1.25 19100 1.10 24900 1.22 25300 1.23 18900 1.06 43000 1.07 21900 1.09 24100 1.11 30200 1.18 33600 1.16 24500 1.32 21600 1.10 28400 1.28 20300 1.13 23700 1.05 1.15 0.09 .J --) . ---=1 susi8/b9 Mean Monthly ~ Flow -QM (cfs) 1958 25010 1959 25650 1960 23650 1961 27420 1962 27720 1963 28950 1964 24930 1965 23230 1966 23750 1967 35570 1968 30140 1969 20820 1970 26100 1971 27280 1972 25770 1980 34950 # of Val. 16 Average 26930 Standard 3980 Oev. .. -... ; . -l Comparison of Peak Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 July 1 Da~ Peak Flow 3-Day Peak Flow 7-0a~ Peak Flow o 1 o 17oM Q3 Q3/QM Q7 Q7(QM 31700 1. 27 30700 1.22 27700 1.11 36400 1. 42 31500 1.22 30200 1.18 33400 1.41 31500 1. 33 29300 1.29 38900 1. 42 36500 1.33 32800 1.20 36800 1.35 32900 1. 21 31000 1.14 34000 1.17 34000 1.17 34000 1.17 27000 1.08 27000 1.08 27000 1.08 27400 1.18 27100 1.17 26400 1.14 30500 1.28 29900 1.26 28700 1. 21 71200 2.00 61400 1. 73 47300 1.33 35400 1.17 35000 1.16 33600 1.11 26000 1.25 24700 1.19 24000 1.15 34800 1.33 33200 1.27 30200 1.16 42600 1.56 40100 1.47 35900 1.32 34100 1.32 33600 1.30 33100 1.28 55800 1.60 47900 1.37 40800 1.17 1.36 1.28 1.19 0.22 0.15 0.08 15-Da~ Peak Flow Q15 015/QM 26100 1. 04 29100 1.13 25700 1. 09 30200 1.10 29600 1.09 34000 1.17 26000 1.04 24800 1.07 27100 1.14 40900 1.15 31700 1.05 23800 1.14 28200 1.08 31800 1.17 29700 1.15 38500 1.10 1.11 0.04 susi8/b10 Mean Monthly ~ Flow -QM (cfs) 1958 20760 1959 22100 1960 19320 1961 24580 1962 21980 1963 18390 1964 20250 1965 22550 1966 27720 1967 33670 1968 20710 1969 11300 1970 24660 1971 23810 1972 20970 1980 20780 # of Val. 16 Average 22100 Standard 4690 Dev. Comparison of Peak Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 August 1 Day Peak Flow 3-0a~ Peak Flow Q3/QM 7~Da~ Peak Flow Q7 Q7/QM Q1 Q1/QM Q3 33800 1.63 31900 1.54 29100 1.40 34000 1.54 29100 1.32 28000 1.27 25000 1.29 25000 1.29 25000 1.29 40000 1.63 37700 1. 53 33600 1.37 36700 1.67 32700 1.49 26600 1.21 20000 1.09 20000 1.09 20000 1.09 28000 1.38 25800 1. 27 23100 1.14 34400 1.53 34000 1.51 31700 1.41 37600 1.36 36700 1.33 34800 1.26 73000 2.17 71000 2.11 56300 1.67 29800 1.44 29000 1.40 26800 1.29 22500 1.99 21400 1.89 18800 1.66 35600 1.44 33700 1.37 31500 1.40 45000 -1.89 40900 1.72 36100 1.52 27200 1.30 25800 1.23 24400 1.16 32500 1.56 28100 1.35 26500 1.28 1.56 1.47 1.34 0.28 0.26 0.17 _) ... I 15-Da}! Peak Flow Q15 Q15/QM 25900 1.25 25300 1.14 25000 1.29 27600 1.12 23200 1.06 19700 1.07 21300 1.05 27700 1.23 29300 1.06 42200 1.25 24600 1.19 15100 1.34 27600 1.12 29400 1.23 22700 1.08 25200 1.21 1.17 0.09 ~ · . cl • -] •.. . ) ! susi8/b11 Mean Monthly Year flow -QM (cfs) 1958 8000 1959 9957 1960 12420 1961 16030 1962 13490 1963 11330 1964 9235 1965 22260 1966 12200 1967 12510 1968 7375 1969 6704 1970 11330 1971 11080 1972 12120 1980 3240 # of Val. 16 Average 11520 Standard 3770 Dev. Comparison of Peak Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 September 1 Oa~ Peak Flaw 3-Day: Peak Flow 7-Day: Peak Flow Q1 0/QM Q3 Q3/QM Q7 Q7/QM 9200 1.15 9200 1.15 9200 1.15 20200 2.03 18600 1.87 15700 1.58 23000 1.85 21000 1.69 18000 1.45 30700 1. 92 28200 1. 76 23200 1. 45 35500 2.63 30500 2.26 24400 1.81 14000 1.24 14000 1.24 14000 1.24 15000 1.62 14000 1.52 13000 1. 42 41100 1. 85 34800 1.56 30800 1.38 18000 1.48 17000 1.39 14600 1.19 21700 1.73 20600 1.65 17500 1.40 10500 1.42 10300 1.40 9810 1.33 9680 1.44 9390 1.40 8760 1. 31 19300 1.70 19000 1.68 17900 1.58 16900 ' 1.53 16600 1.50 16000 1.44 29100 2.40 25300 2.09 19300 1.59 12900 1.57 12000 1.46 10400 1. 26 1.72 1.60 1.41 0.39 0.29 0.17 15-Day Peak Flow Q15 Q15/QM 9200 1.15 12400 1. 25 15600 1.26 19300 1.20 18000 1.33 12700 1.12 11000 1.19 23900 1.07 13700 1.12 16100 1.28 9330 1.27 7980 1.19 15400 1.36 14500 1. 31 16400 1. 35 8830 1.07 1.22 0.10 susi8/b12 Mean Monthly Year Flow -QM (cfs) 1958 4195 1959 4723 1960 5135 1961 5777 1962 3506 1963 8062 1964 5642 1965 6071 1966 4682 1967 3483 1968 2898 1969 4578 1970 3826 1971 5439 # of Val. 14 Average 4858 Standard 1324 Dev. ) 3 Comparison of Peak Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 October 1 Da~ Peak Flow 3·Da}:: Peak· Flow 7-Da}:: Peak Flow Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM 6200 1. 48 6000 1.43 5600 1.33 7800 1.65 7400 1.57 -7070 1.50 10900 2.12 9750 1. 90 8800 1. 71 12500 2.16 11600 2.01 10100 1. 75 7820 2.23 7190 1.82 6380 1.82 12000 1.49 12000 1.49 12000 1.49 15300 2.71 12700 2.25 10000 1. 77 9400 1.55 9400 1.55 9400 1.55 8500 1.81 8170 1.74 8000 1. 71 5800 1.67 5600 1. 50 5180 1.49 4400 1.52 4150 1. 43 3820 1.32 7700 1.68 6960 1.31 6010 1.25 5000 1. 31 4930 1.29 4770 1.25 11000 2.02 10300 1.89 8830 1.62 1.81 1.66 1.54 0.38 0.28 0.20 ' I 15-0a~ Peak Flow Q15 Q15/QM 5030 1.20 6030 1.28 7140 1.39 7750 1.34 5050 1.44 10300 1.28 7580 1.34 9400 1.55 6630 1.42 4520 1.30 3480 1.20 5740 1.25 4450 1.16 7050 1.30 1.32 0.11 j ~-'"_,, I : j ,J ~ . 1 ' susi8/b13 Mean Monthly .Y!.ru:: Flow -QM · {cfs~ 1965 3474 1966 2410 1967 4112 1968 8840 1969 3869 1970 3950 1971 2145 1972 3516 1973 3860 1974 5678 1975 4084 1976 3439 1977 4244 1978 2950 1979 7790 1980 4820 # of Val. 16 Average 4324 Standard 1782 Dev. l . . l . . l ---) Comparison of Peak Flows to Average Monthly Flow Talkeetna River near Talkeetna No. 15292700 May .. 1. ····j 1 Da}! Peak Flow 3-Da}! Peak Flow 7-0a}! Peak Flow Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM 14300 4.12 12100 3.48 9060 2.61 5890 2.44 5750 2.39 5020 2.08 7500 1.82 7430 1. 81 7360 1.79 19000 2.15 17500 1. 98 16600 1.88 13500 3.49 11100 1. 87 8430 2.18 7900 2.00 7520 1.90 6690 1. 69 4980 2.32 4940 2.30 4420 2.06 12600 3.58 10400 2.96 8520 2.42 6920 1. 79 6770 1. 75 6640 1. 72 15000 2.64 14400 2.54 13000 2.29 12200 2.99 11900 2.91 10100 2.47 5000 1.45 4500 1.31 4110 1.20 12800 3.02 12500 2.95 9530 2.25 4750 1.61 4670 1.58 4340 1.47 20700 2.66 20200 2.59 16700 2.14 10000 2.07 9670 2.01 8170 1. 70 2.51 2.33 2.00 0.76 0.60 0.39 15-Da}! Peak Flow Q15 Q15/QM 5890 1.70 3700 1.54 6140 1.49 14600 1.65 6000 1.55 5630 1.43 3360 1.57 5790 1.65 5840 1. 51 9340 1.64 7210 1. 77 3880 1.13 7090 1.67 3870 1. 31 11800 1.51 6650 1.38 1.53 0.16 susl8/b14 Mean Monthly ~ Flow -QM {cfs) 1964 17080 1965 11090 1966 12970 1967 9286 1968 14100 1969 5207 1970 7979 1971 19040 1972 12700 1973 12210 1974 8030 1975 13180 1976 10580 1977 18280 1978 7429 1979 12010 1980 11380 # of Val. 17 Average 11910 Standard 3800 Dev. Comparison of Peak Flows to Average Monthly Flow Talkeetna River near Talkeetna No. 15292700 June 1 Da~ Peak Flow 3-Da~ Peak Flow 7-Da~ Peak Flow Q1 o1JoM Q3 Q3/QM Q7 Q7/QM 27000 1.58 25000 1.46 23000 1. 35 16700 1. 51 15200 1.37 l3600 1.23 24000 1. 85 23400 1.80 21200 1.63 15400 1.66 13400 1.44 11500 1.24 22000 1.56 20500 1.45 18200 1.29 7120 1.37 6800 1.31 6060 1.16 17900 2.24 16500 2.07 11700 1. 47 33700 1.77 30200 1.59 26500 1.39 27500 2.17 22400 1.76 17000 1. 34 25000 2.05 21200 1.74 19200 1.57 14100 1.76 11200 1.39 9420 1.17 . 18600 1.41 15900 1.21 14300 1.08 17200 1.63 16200 1.53 15000 1.42 27100 1.48 24700 1.35 23500 1.29 12900 1. 74 9900 1.33 8920 1.20 20500 1.71 19200 1.60 17000 1.42 15000 1.32 14700 1.29 12900 1.13 1.69 1.51 1.32 0.27 0.22 0.15 .J .J ..• J .I ' 15-Day Peak Flow Q15 o,siOM 20400 1.19 12300 1.11 16400 1. 26 11100 1.20 16300 1.16 5880 1.13 9060 1.14 22900 1.20 14200 1.12 15600 1.28 8670 1.08 14100 1.07 12900 1.22 20900 1.14 7870 1.06 14000 1.17 11800 1.04 1.15 0.07 J I .I ) ·" 1 I - --~-) . ---} --~ ( . ---~ susi8/b15 Mean Monthly Year Flow -QM (cfs) 1964 9810 1965 12180 1966 10100 1967 12000 1968 11230 1969 7080 1970 10320 1971 11760 1972 12030 1973 7676 1974 7755 1975 12070 1976 9026 1977 9344 1978 10790 1979 14440 1980 13900 # of Val. 17 Average 10710 Standard 2120 Dev. : __ ] Comparison of Peak Flows to Average Monthly Flow Talkeetna River near Talkeetna No. 15292700 July 1 Da~ Peak Flow 3-Da~ Peak Fiow 7-Da~ Peak Flow 15-Day Peak Flow Q1 Q1/QM Q3 Q3/QM Q7 Q77QM Q15 Q15/QM 12800 1.30 11900 1. 21 10500 1.07 10100 1. 03 19500 1.60 19200 1.58 16300 1.34 14200 1.17 20200 2.00 19300 1. 91 15200 1.50 11500 1.14 40000 3.17 28300 2.25 20700 1. 64 16000 1.27 15000 1.34 14300 1.27 13300 1.18 12700 1.13 9100 1.29 8510 1.20 8170 1.15 7520 1.06 16500 1.60 13700 1. 33 12300 1.19 11100 1.08 18600 1. 58 17300 1. 47 15100 1. 28 13200 1.12 13500 1.12 13100 1.09 12900 1. 07 12500 1. 04 9920 1. 29 9610 1.25 9210 1.20 8380 1.09 9680 1.25 9200 1.19 8590 1.11 8270 1.07 17800 1.47 17300 1. 43 15000 1. 24 13600 1.13 14400 1.60 12500 1.38 11000 1.22 9990 1. 11 16800 1.80 13500 1.44 11700 1. 25 10400 1. 11 14800 1.37 13000 1.20 12300 1.14 11300 1.05 28000 1.c94 25100 1.74 19700 1.36 16900 1.17 29500 2.12 22100 1. 59 16700 1.20 14400 1. 04 1.64 1.44 1. 25 1. 11 0.49 0.30 0.15 0.06 susi8/b16 Mean Monthly Year Flow -QM (cfs} 1964 8396 1965 11150 1966 10730 1967 14160 1968 7546 1969 3787 1970 8752 1971 16770 1972 9576 1973 9927 1974 7704 1975 8487 1976 8088 1977 8005 1978 7001 1979 8274 1980 7220 # of Val. 17 Average 9151 Standard 2922 Dev. -~-~ 0 •• Comparison of Peak Flows to Average Monthly Flow Talkeetna River near Talkeetna No. 15292700 August 1 Da~ Peak Flow 3-Da:t Peak Flow 7-Da:t Peak Flow Q1 o11oM Q3 Q3/QM Q7 Q7/QM 11900 1. 42 11100 1.32 11000 1.31 21400 1. 92 20900 1.87 17900 1.61 19800 1.85 19100 1. 78 15100 1. 41 34700 2.45 27600 1.95 23600 1.67 9900 1.31 9200 1.22 8290 1.10 7900 2.09 7450 1. 97 6810 1.80 12700 1.45 11600 1.33 11100 1.27 63000 3.76 50400 3.01 35800 2.13 14000 1.46 13700 1. 43 12900 1.35 24000 2.42 21300 2.15 16400 1.65 18800 2.44 14300 1.86 9330 1.21 12900 1.52 12100 1. 43 10200 1.20 11700 1.45 10500 1. 30 10200 1. 26 11300 1. 41 9990 1.25 9390 1.17 10500 1.50 10200 1.46 9440 1.35 15800 1.91 15000 1. 81 12600 1.52 12700 1.76 11100 1.54 9630 1.33 1.89 1.69 1. 43 ° 0.62 0.45 0.27 . .~ 15-Da:t Peak Flow Q15 01s/OM 9650 1.15 14600 1. 31 12400 1.16 18500 1. 31 8020 1.06 5400 1.43 9790 1.12 24300 1.45 10600 1.11 11600 1.17 7760 1.01 9770 1.15 9420 1.16 8550 1.07 8740 1.25 10200 1.23 8500 1.18 1.19 0.12 ----~ ----J -----l r- susi8/b17 Mean Monthly Year Flow -QM (cfs) 1964 3815 1965 10610 1966 5370 1967 6971 1968 4120 1969 2070 1970 5993 1971 5990 1972 8709 1973 3861 1974 4763 1975 7960 1976 3205 1977 5826 1978 3513 1979 4039 1980 5400 # otVai. 17 Average 5428 Standard 2192 Dev. Comparison of Peak Flows to Average Monthly Flow Talkeetna River near Talkeetna No. 15292700 September 1 Da~ Peak Fiow 3·Da~ Peak Flow 7-0a~ Peak Fiow Q1 o1/oM 03 Q3/QM 07 Q7/QM 5100 1.34 5000 1.31 4690 1. 23 23400 2.21 19000 1.79 16600 1. 56 8900 1.66 7400 1.38 6410 1.19 13300 1. 91 13100 1.88 12100 1. 74 6640 1. 61 6380 1.55 5730 1. 39 3220 1. 56 2970 1.43 2660 1. 29 14700 2.45 12600 2.10 9910 1.65 12000 2.00 11000 1.84 9640 1.61 19800 2.27 16200 1.86 13300 1.53 7500 1. 94 6830 1. 77 5860 1.52 9200 1.93 8540 1. 79 7120 1.49 14900 1.87 13600 1. 71 10700 1.34 4010 1.25 3790 1.18 3410 1. 06 8450 1.45 8030 1.38 7260 1.25 6400 1.82 5450 1.55 4770 1. 36 6760 1,67 6080 1.51 5860 1.45 18600 3.44 14900 2.76 10400 1. 93 1. 91 1.69 1.45 0.51 0.37 0.22 15-Da~ Peak Flow 0 15 015/QM 4180 1.10 13200 1.24 6050 1.13 9630 1. 38 5290 1.28 2400 1.16 7310 1.22 7830 1.31 11400 1. 31 4830 1.25 5390 1.13 9970 1. 25 3280 1.02 6840 1.17 4350 1.24 4560 1.13 7440 1.38 1.22 0.10 susi8/b18 Mean Monthly Year Flow -QM (cfs} 1964 3115 1965 4438 1966 2388 1967 2029 1968 1637 1969 1450 1970 2817 1971 2632 1972 3630 1973 1807 1974 1987 1975 2884 1976 1857 1977 3268 1978 1660 1979 3370 # of Val. 16 Av~rage 2559 Standard 854 Dev. . I Comparison of Peak Flows to Average Monthly Flow Talkeetna River near Talkeetna No. 15292700 October 1 Da~ Peak Flow I 3·Da~ Peak Flow 7-Da~ Peak Flow Q1 0 1/QM Q3 Q3/QM Q7 Q7/QM 4820 1.55 4610 1.48 4180 1.34 10200 2.30 9050 2.04 .7610 1. 71 4170 1.75 3970 1.66 3610 1.51 2940 1.45 2860 1. 41 2660 1.31 2280 1. 39 2200 1.34 2080 1.27 2100 1.45 2070 1.43 1910 1.32 5200 1.85 4570 1.62 3870 1.37 3600 1.37 3530 1.34 3170 1.20 6120 1.69 5510 1.52 4750 1.31 3000 1.66 2760 1. 53 2560 1.42 3260 1.64 3110 1.57 2810 1.41 5100 1. 77 4830 1.67 4480 1.55 2400 1.29 2270 1.22 2200 1.18 5400 1.65 5020 1. 54 4520 1. 38 2380 1.43 2310 1.39 2090 1.26 6700 1.99 5870 1.74 5120 1.52 1.64 1.53 1.38 0.26 0.19 0.14 15•Da¥ Peak Flow Q15 Q15/QM 3840 1.23 6080 1.37 3200 1.34 2440 1.20 1920 1.17 1730 1.19 3430 1.22 3090 1.17 4090 1.13 2240 1.24 2480 1. 25 3950 1.37 2040 1.10 4080 1.25 1830 1.18 4270 1.27 1.23 0.08 . J. . ---1 ... ----l susiB/b19 Year Mean Monthly Flow -QM (cfs) 1975 47540 1976 70460 1977 56180 1978 48670 1979 81260 1980 66580 , # of Val. 6 Average 61780 Standard 13295 Dev. -- -. . j Comparison of Peak Flows to Average Monthly Flow Susitna River at Susitna Statton No . 15294350 May 1 Day Peak Flow Q1 Q1/QM 3-Daz: Peak Flow 7-Da~ Peak Flow Q3 Q3/QM Q7 Q7/QM 121000 2.55 114000 .2.40 103000 2.17 115000 1.63 113000 1.60 101000 1.43 128000 2.28 121000 2.15 105000 1.87 66000 1.36 65300 1.34 62800 1.29 136000 1.67 134000 1.65 121000 1.49 124000 1.86 116000 1. 74 99200 1.49 1.89 1. 81 1.62 0.44 0.39 0.33 15-Day: Peak Flow Q15 Q15/QM 81000 1. 70 83100 1.18 91000 1.62 58800 1. 21 105000 1.29 85100 1.28 1.38 0.22 susi8/b20 Mean Monthly Year Flow -QM (cfs) 1975 128800 1976 107000 1977 165900 1978 90930 1979 119900 1980 142900 # of Val. 6 Average 125900 Standard 26510 Oev. Comparison of Peak Flows to Average Monthly Flow Susitna River at Susitna Station No. 15294350 June 1 Oa~ Peak Flow 3-Da~ Peak Flow 7-Da~ Peak Flow Q7 Q7/QM Q1 Q1/QM Q3 Q3/QM 161000 1.25 152000 1.18 141000 1.09 131000 1.22 13000 1. 21 128000 1.20 195000 1.18 191000 1.15 186000 1.12 118000 1. 30 114000 1.25 . 113000 1.24 158000 1.32 150000 1. 25 133000 1.11 173000 1.21 164000 1.15 152000 1.06 1.25 1.20 1.14 0.05 0.05 0.07 15-Da~ Peak Flow Q15 Q15/QM 137000 1.06 116000 1.08 175000 1.05 103000 1.13 122000 1.02 149000 1.04 1.06 0.04 l -~ --J '. ---~ susi8/b21 -] ' -1 -11 ----" Comparison of Peak Flows to Average Monthly Flow Susitna River at Susitna Station No. 15294350 July Mean Monthly 1 Day Peak Flow 3-Day Peak Fiow 7-Da~ Peak Flow Year Flow -QM (cfs) Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM 1975 135700 171000 1.26 159000 1.17 155000 1.14 1976 115200 146000 1.27 139000 1.21 126000 1.09 1977 143900 166000 1.15 161000 1.12 152000 1.06 1978 117600 130000 1.11 126000 1.07 120000 1.02 1979 142500 175000 1.23 169000 1.19 155000 1.09 1980 181400 226000 1.25 215000 1.19 203000 1.12 # of Val. 6 Average 139380 1.21 1.16 1.09 Standard 23950 0.07 0.05 0.04 Oev. 15-Da~ Peak Flow Q15 Q15/QM 148000 1. 09 123000 1. 07 146000 1.01 119000 1. 01 153000 1. 07 189000 1.04 1.05 0.03 susi8/b22 Mean Monthly Year Flow -QM (cfs) 1975 91360 1976 99650 1977 125500 1978 102100 1979 128200 1980 126400 # of Val. 6 Average 112200 Standard 16300 Dev. Comparison of Peak Flows to Average Monthly Flow Susitna River at Susitna Station No. 15294350 August 1 Da~ Peak Flow 3-Da~ Peak Flow 7-Da~ Peak Flow Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM 113000 1.24 109000 1.19 105000 1.15 138000 1.38 134000 1. 34 125000 1.25 151000 1.20 144000 1.15 141000 1.12 130000 1.27 130000 1.27 126000 1.23 160000 1.25 157000 1.22 146000 1.14 163000 1.29 153000 1.21 142000 1.12 1.27 1.23 1.17 0.06 0.07 0.06 15-Da~ Peak Flow Q15 Q15/QM 99800 1.09 115000 1.15 135000 1.08 120000 1.17 141000 1.10 141000 1.12 1.12 0.04 1 ' . -] susi8/b23 Mean Monthly Year Flow -QM (cfs) 1975 77740 1976 48910 1977 83810 1978 55500 1979 74340 1980 91200 # of Val. 6 Average 71910 Standard 16440 Oev. ] ] Comparison of Peak Flows to Average Monthly Flow Susitna River at Susitna Station No. 15294350 September 1 Da}!: Peak Flow 3-Da}!: Peak Flow 7-Da~ Peak Flow o, Q1/QM 03 Q3/0M Q7 07/QM 122000 1.57 110000 1. 41 100000 1.28 93800 1.92 84100 1. 72 69700 1. 43 119000 1.42 109000 1.30 99600 1.19 83400 1.50 77900 1.40 72100 1.30 118000 1.59 113000 1.52 108000 1.45 135000 1. 48 122000 1.34 108000 1.18 1.58 1.45 1.31 0.18 0.15 0.12 15-Da~ Peak Fiow Q15 015/QM 93800 1.21 56400 1.15 92000 1.10 69200 1.25 90900 1. 22 98600 1.08 1.17 0.07 susi8/b24 Mean Monthly Year Flow -QM (cfs) 1974 19520 1975 31550 1976 30140 1977 38230 1978 36810 1979 58640 # OtVal. 6 Average 35815 Standard 12990 Dev. J . Comparison of Peak Flows to .H.verage Monthly Flow Susitna River at Susitna Station No. 15294350 October 1 Da~ Peak Flow 3-0a~ Peak Flow 7-Da~ Peak Flow Q1 o11oM Q3 Q3/QM Q7 Q7/QM 35000 1. 79 30000 1.54 26300 1.35 61000 1.93 54600 1.73 45400 1.44 43000 1.43 36000 1.19 33000 1.09 77400 2.02 68400 1. 79 56700 1.48 50000 1.36 48000 1.30 45400 1.23 93300 1.59 90600 1.55 86000 1.47 1.69 1.52 1.34 0.27 0.23 0.16 . J ..·~·J 15-Da~ Peak Flow Q15 Q15/QM 25200 1.29 39400 1.25 31000 1.03 51000 1.33 43500 1.18 74800 1.28 1. 23 0.11 f ' ---=J '----J ~"_~~-ll ,. l --J --J -: J l -J 'a -~ . --------' . -~ .l! susi8/b25 Comparison of low Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000 May Mean Monthly 1 Da~ Peak Flow 3-Da~ Peak Flow 7-Da~ Peak Flow 14-Da~ Peak Flow Flow -o, .. Q1 Q1/QM Q3 Q3/QM Q7 OlQM Q14 Q14/QM ~ (cfs) VI 195'1 14090 5200 0.37 6070 0.43 8600 0.61 12200 0.87 1952 5419 1100 0.20 1200 0.22 1390 0.26 1460 0.27 1953 14270 10700 0.56 12000 0.62 13200 0.69 16100 0.84 1954 19280 8800 0.51 8800 0.51 8800 0.51 12300 0.71 1955 9319 4500 0.48 4500 0.48 4500 0.48 4500 0.48 1956 17660 1500 0.08 1970 0.11 4930 0.28 8820 0.50 1957 13750 4300 0.31 4300 0.31 4300 0.31 5760 0.42 1958 12900 3420 0.27 3880 0.30 4840 0.38 7130 0.55 1959 15990 3400 0.21 3400 0.21 3400 0.21 4540 0.28 1960 15780 7600 0.48 7600 0.48 7600 0.48 7600 0.48 1961 17360 9000 0.52 9000 0.52 9000 0.52 12700 0.73 1962 12590 4500 0.36 4500 0.36 4500 0.36 4500 0.36 1963 19030 3400 0.18 3400 0.18 3400 0.18 3400 0.18 1964 4307 900 0.21 900 0.21 900 0.21 1040 0.27 1965 12900 2200 0.17 2200 0.17 2870 0.22 4690 0.36 1966 9645 3400 0.35 3400 0.35 3400 0.35 3990 0.41 1967 15480 1700 0.11 1800 0.12 2140 0.14 5010 0.32 1968 16177 2200 0.14 2230 0.14 2340 0.14 3160 0.20 1969 11045 3200 0.29 3400 0.31 3890 0.35 5730 0.52 1970 11380 1800 0.16 1900 0.17 2240 0.20 5330 0.47 1971 3745 1400 0.37 1470 0.39 1570 0.42 1820 0.49 1972 21890 2500 0.11 3030 0.14 5930 0.27 14000 0.64 1973 8235 1400 0.17 1400 0.17 1600 0.19 2540 0.31 1974 16180 2200 0.14 2470 0.15 3260 0.20 5880 0.36 1975 15350 2500 0.16 2770 0.18 3540 0.23 6170 0.40 1976 12620 3800 0.30 4600 0.36 7190 0.57 11100 0.88 1977 12680 1900 0.15 1930 0.15 2100 0.17 3440 0.27 1978 11950 2500 0.21 3300 0.28 5610 0.47 10300 0.86 1979 13870 2500 0.18 2700 0.19 3260 0.24 4840 0.35 1980 12060 3700 0.31 4100 0.34 5260 0.44 8520 0.71 # of Val. 31 Average 13270 0.26 ' 0.28 0.34 0.48 Standard 4240 0.14 0.14 0.15 0. 21 Dev. ] ' J l~ j . 1 susi8/b27 ] ] ) J J 1 Comparison of Low Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000 I July Mean Monthly 1 Oa~ Low Flow 3-0a~ Low Flow 7-Da~ Low Flow 14-Da~ Low Flow Year Flow -OM Q1 Q1/QM Q3 Q3/QM 07 07/0M Q14 Q14/0M (cfs) 1950 22600 18000 0.80 18700 0.83 20000 0.88 20600 0.91 1951 22570 18200 0.81 19000 0.84 20700 0.92 22200 0.98 1952 26390 17200 0.65 17900 0.68 19500 0.74 22200 0.84 1953 20200 17200 0.85. 17500 0.87 18100 0.90 19000 0.94 1954 20360 19000 0.93 19000 0.93 19000 0.93 19000 0.93 1955 27560 20200 0.73 20500 0.74 21500 0.78 23700 0.86 1956 31090 26600 0.86 28200 0.91 29100 0.94 30400 0.98 1957 23310 18900 0.81 19600 0.84 21200 0.91 22100 0.95 1958 22880 19000 0.83 20300 0.89 21300 0.93 21600 0.94 1959 25000 19900 0.80 21000 0.84 21500 0.86 23500 0.94 1960 22980 14900 0.65 15100 0.66 16700 0.73 18200 0.79 1961 24570 23000 0.94 23000 0.94 23000 0.94 23600 0.96 1962 25850 20900 0.81 21700 0.84 22900 0.89 24800 0.96 ] 1963 34400 23600 0.69 23900 0.69 29100 0.85 31400 0.91 1 1964 22950 14800 0.64 15400 0.67 16900 0.74 19600 0.85 1965 27840 20700 0.74 21200 0.76 22100 0.79 24700 0.89 1966 19864 16200 0.82 16400 0.83 16900 0.85 17600 0.89 1967 26800 19400 0.72 20100. 0.75 21000 0.78 21200 0.79 1968 26922 21400 0.}9 23200 0.86 24000 0.89 24300 0.90 1969 16103 11800 0.73 12500 0.78 13900 0.86 15600 0.97 1970 22660 16500 0.73 17200 0.76 '18600 0.82 21300 0.94 1971 23950 14500 0.61 15800 0.66 18700 0.78 20700 0.86 1972 22770 17400 0.76 17700 0.78 18200 0.80 19500 0.86 1973 18250 14200 0.78 14500 0.79 14900 0.82 15800 0.87 1974 18800 14900 0.79 15100 0.80 16900 0.90 18800 1.00 1975 27720 23400 0.84 24100 0.87 25500 0.92 26300 0.95 1976 18940 15100 ' 0.80 16100 0.85 17900 0.95 18500 0.98 1977 22870 18000 0.79 ' 18000 0.79 19300 0.84 21600 0.94 1978 21020 19400 0.92 19800 0.94 20200 0.96 20300 0.97 1979 28880 21800 0.75 21900 0.76 25800 0.89 26200 0.91 1980 32660 24800 0.76 25300 0.77 27500 0.84 30700 0.94 # of Val. 31 Average 24150 0.78 0.80 0.86 0.92 Standard 4240 0.08 0.08 0.07 0.05 Dev. susi8/b28 Comparison of Low Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000 August Mean Monthly 1 Da~ Low Flow 3-Da~ Low Flow 7-Da~ Low Flow 14-Da~ ·Low Flow Year Flow ·QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 Q14/QM (cfs) 1949 24250 15200 0.63 16100 0.66 17100 0.71 17700 0.73 1950 19880 11000 0.55 11300 0.57 14200 0.71 15900 0.80 1951 19670 15600 .0. 79 16300 0.83 17400 0.88 17900 0.91 1952 20920 13500 0.65 13800 0.66 14500 0.69 14900 0.71 1953 20610 16400 0.80 16600 0. 81 16900 0.82 17700 0.86 1954 26100 24000 0.92 24000 0.92 24000 0.92 24000 0.92 1955 25750 13600 0.53 14400 0.56 17200 0.67 20800 0.81 1956 24530 18000 0.73 18000 0.73 18000 0.73 19900 0.81 1957 20540 16700 0.81 16900 0.82 '18300 0.89 19000 0.93 1958 22540 11000 0.49 11300 0.50 12300 0.55 14700 0.65 1959 31180 16700 0.54 17100 0.55 18400 0.59 20800 0.67 1960 23590 19000 0.81 19300 0.82 20700 0.88 21700 0.92 1961 22100 13800 0.62 14200 0.64 17300 0.78 18700 0.85 1962 23550 23000 0.98 23000 0.98 23000 0.98 23000 0.98 1963 23670 16500 0.70 17700 0.75 20300 0.86 21900 0.93 1964 16440 12000 0.73 12300 0.75 13700 . 0.83 15000 0.91 1965 21120 10000 0.47 10100 0.48 12300 0.58 17500 0.83 1966 21825 16400 0.75 16900 0.77 18800 0.86 20100 0.92 1967 32622 18900 0.58 19300 0.59 21600 0.66 27400 0.84 1968 17167 12600 0.73 12900 0.75 14000 0.82 14400 0.84 1969 8879 5280 0.59 5400 0. 61 . 5620 0.63 5810 0.65 1970 19980 12700 0.64 12900 0.65 14500 0.73 17200 0.86 1971 31910 16700 0.52 17500 o.ss 20200 0.63 22400 0.70 1972 19290 12900 0.67 13200 0.68 14700 0.76 17900 0.93 1973 20290 11100 0.55 11200 0.55 13100 . 0.65 17600 0.87 1974 16220 8100 0.50 8550 0.53 10500 0.65 13300 0.82 1975 18090 11800 0.65 12700 0.70 14600 0.81 15900 0.88 1976 19800 9340 0.47 10100 0.51 11900 0.60 14300 0.72 1977 19240 10000 0.52 11100 0.58 13700 0.71 16700 0.87 1978 16390 10400 0.63 10500 0.64 10900 0.67 13100 0.80 1979 20460 14000 0.68 14500 0.71 15700 0.77 16700 0.82 1980 20960 13900 0.66 14500 0.69 15000 0.72 17700 0.84 # of Val. 31 Average 21550 0.65 0.67 0.74 0.83 Standard 4725 0.13 0.12 0.11 0.09 Dev. ' ~-,_cc'·J ~e:,,~_, __ J ,_ ",,J __ J · ... J .J .... -t· J_ l __ J_ 'J. .L . -.::-l ' -l . ........ J ; j l J j 1 i l ·~ 1 l l -, susi8/b29 Comparison of Low Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292000 September Mean Monthly 1 DaY: Low Flow 3-DaY: Low Flow 7-Da~ Low Flow 14-Da~ Low Flow Year Flow -OM 01 01/QM Q3 0/0M Q7 Q7/QM Q14 o147oM (cfs) 1949 15650 9160 0.59 9400 0.60 10500 0.67 11600 0.74 1950 8301 6000 0.72 6100 0.73 6240 0.75 6600 0.80 1951 21240 11700 0.55 12900 0.61 15700 0.74 17700 0.83 1952 14480 9500 0.66 9830 0.68 10300 0.71 11600 0.80 1953 15270 8880 0.58 9430 0.62 10600 0.69 12300 0.81 1954 12920 7400 0.57 7560 0.59 8210 0.64 10300 0.80 1955 14290 8600 0.60 8960 0.63 9610 0.67 10600 0.74 1956 18330 14000 0.76 14000 0.76 14000 0.76 17100 0.93 1957 19800 14200 0.72 15000 0.76 18000 0.91 19400 0.98 1958 7550 6600 0.87 6600 0.87 6600 . 0.87 6600 0.87 1959 16920 9650 0.57 10200 0.60 10400 0.61 10700 0.63 1960 20510 13900 0.68 14100 0.69 15100 0.74 17000 0.83 1961 13370 11500 0.86 11600 0.87 12100 0.91 13200 0.99 1962 15890 10700 0.67 11300 0.71 11900 0.75 12100 0.76 1963 12320 9340 0.76 9430 0.77 9570 0.78 10100 0.82 1964 9511 7440 0.78 7600 0.80 7860 0.83 8490 0.89 1965 19350 9280 0.48 9380 0.48 13900 0.72 18300 0.95 1966 11753 8160 0.69 8560 0.73 8830 0.75 10300 0.88 1967 16867 8440 0.50 8830 0.52 9320 0.55 10700 0.63 1968 8815 5400 0.61 5430 0.62 5460 0.62 6150 0.70 1969 5093 3710 0.73 3760 0. 74 3920 . 0.77 4260 0.84 1970 9121 5000 0.55 5170 0.57 '5290 0.58 7070 0.78 1971 14440 8160 0.57 8260 0.57 9250 0.64 10100 0.70 1972 12400 5500 0.44 5670 0.46 5790 0.47 8710 0.70 1973 9074 5500 0.61 5670 0.62 6030 0.66 6720 0.74 1974 12250 8310 0.68 8470 0.69 9080 0.74 9320 0.76 1975 16310 10900 0.67 11100 0.68 11600 0.71 15400 0.94 1976 6881 5620 0.82 5800 0.84 5930 0.86 6220 0.90 1977 12640 9520 0.75 9750 0.77 10200 0.81 12200 0.97 1978 8607 4900 0.57 5100 0.59 5530 0.64. 6460 0.75 1979 10770 8220 0.76 8510 0.79 8720 0.81 9330 0.87 1980 13280 8890 0.67 8980 0.68 9160 0.69 10300 0.78 # OfVal. 32 Average 13250 0.66 0.68 0. 72 0.82 Standard 4190 0.11 0.11 0.10 0.10 Oev. -1 l J ~~ 1 . -~ -1 E J susi8/b31 Comparison of Low Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 1 May Mean Monthly 1 Day: Low Flow 3-Day: low Flow 7-Day: Low Flow 14-Da~ Low Flow i Flow -QM Q1 0 1/QM Q3 Q3/QM Q7 Q7/QM . Q14 Q14/QM ~ (cfs) - 1958 10460 3000 0.29 3370 0.32 4250 0.41 6560 0.63 1959 7413 3400 0.46 3400 0.46 3400 0.46 3400 0.46 1960 13890 2300 0.17 2870 0.21 3770 0.27 5940 0.43 1961 10100 2100 0.21 2630 0.26 4360 0.43 7040 0.70 1962 7743 3200 0.41 3200 0.41 3200 0.41 3200 0.41 1963 11060 2100 0.19 2100 0.19 2100 0.19 2100 0.19 1964 2355 1400 0.59 1400 0.59 1400 0.59 1430 0.61 1965 7452 2600 0.35 2600 0.35 2600 0.35 2600 0.35 1966 3971 2100 0.53 2100 0.53 2100 0.53 2100 0.53 1967 12400 1700 0.14 1970 0.16 2670 0.22 5530 0.45 1968 10940 2000 0.18 2130 0.19 2440 0.22 3470 0.32 1969 6001 2600 0.43 2770 0.46 3030 0.50 3840 0.64 1970 9643 2400 0.25 2600 0.27 3090 0.32' 5130 0.53 1971 4468 1200 0.27 1300 0.29 1540 0.34 2170 0.49 1972 9765 1700 0.17 2170 0.22 4070 0.42 7820 0.80 # of Val. 15 Average 8511 0.31 0.33 0.38 0.50 Standard 3270 0._15 0.13 0.12 0.16 Dev. susi8/b32 Comparison of Low Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 June Mean Monthly 1 Da~ Low Flow 3·Da~ low Flow 7-Da~ Low Flow 14-Da~ Low Flow Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 Q147QM (cfs) -- 1958 23170 18000 0.78 18000 0.78 18600 0.80 20900 0.90 1959 23660 11000 0.46 13700 0.58 16400 0.69 17700 0.75 1960 17390 13000 0.75 13700 0.79 14500 0.83 15500 0.89 1961 20490 10800 0.53 10800 0.53 11700 0.57 15500 0.76 1962 20620 12500 0.61 12700 0.62 13200 0.64 16100 0.78 1963 17750 12200 0.69 12400 0.70 13700 0.77 13900 0.78 1964 40330 37000 0.92 37000 0.92 37000 0.92 37600 0.93 1965 20070 12000 0.60 14000 0.70 16300 0.81 17200 0.86 1966 21740 9200 0.42 10900 0.50 17600 0.81 21200 0.98 1967 25520 16000 0.63 17700 0.69 18600 0.73 20700 0.81 1968 29000 20600 0.71 21200 0.73 22200 0.77 26500 0.91 1969 18560 8580 0.46 8990 0.48 9650 0.52 12000 0.65 1970 19670 14000 0.71 14300 0.73 15100 0.77 19100 0.97 1971 22180 10000 0.45 10000 0.45 11900 0.54 . 15600 0.70 1972 17900 11200 0.63 11700 0.65 12500 0.70 15400 0.86 1980 22490 15000 0.67 15800 0.70 19700 0.88 21700 0.96 # of Val. 16 Average 22530 0.63 0.66 0.73 0.84 Standa.rd 5650 0.14 0.13 0.12 0.10 Oev. J .· ... I J ' D } '_2:_-J susi8/b33 J -~ i 1 ] 1 Comparison of Low Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 July Mean Monthly 1 · Da~ Low Flow 3-Da~ Low Flow 7-Da~ Low Flow 14-Da~ Low Flow Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 01ioM (cfs) - 1958 25010 19000 0.76 20200 0.81 21000 -0.84 22900 0.92 1959 25650 20300 0.79 20800 0. 81 21600 0.84 22100 0.86 1960 23650 17000 0.72 17300 0.73 19000 0.80 20600 0.87 1961 27420 22100 0.81 22300 0.81 23400 0.85 23900 0.87 1962 27220 25000 0.92 25000 0.92 25000 0.92 25000 0.92 1963 28950 23000 0.79 23000 0.79 23000 0.79 25400 0.88 1964 24430 21000 0.86 21000 0.86 21000 0.86 23500 0.96 1965 23230 19800 0.85 19900 0.86 20000 0.86 22800 0.98 1966 23750 17200 0.72 17400 0.73 17600 0.74 20000 0.84 1967 35570 27600 0.78 28000 0.79 29100 0.82 30300 0.85 1968 30140 23600 0.78 24900 0.83 26600 0.88 28800 0,96 1969 20820 14400 0.69 15500 0.74 16200 0.78 17600 0.85 1970 26100 21000 0.80 21300 0.32 22000 0.84 23800 0.91 1971 27280 17000 ·o.62 18000 0.66 19000 0.70 21900 0.80 1972 25770 19600 0.76 20200 0.78 21400 0.83 22300 0.87 1980 34948 26600 0.76 27200 0.78 28500 0.82 31300 0.90 #of Val. 16 Average 26930 0.78 0.80 0.82 0.89 Standard 3980 0.07 0.06 0.05 0.05 susi8/b34 Comparison of Low Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 August Mean Monthly 1 Day Low Flow 3-Day Low Flow 7-Day Low Flow 14-Day Low Flow .. Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 Q14/QM (cfs) 1958 20760 12000 0.58 12500 0.60 13600 0.66 15500 0.75 1959 22100 16000 0.72 16400 0.74 17400 0.79 18900 0.86 1960 19320 14000 0.72 14000 0.72 14000 0.72 14000 0.72 1961 24580 16100 0.66 16800 0.68 18500 0.75 22000 0.90 1962 21980 15800 0.72 16200 0.74 17000 0.77 18200 0.83 1963 18390 16000 0.87 16000 0.87 16000 0.87 16900 0.92 1964 20250 15000 0.74 15000 0.74 17100 0.84 19400 0.96 1965 22550 11000 0.49 11300 0.50 12500 0.55 17300 0.77 1966 27720 20000 0.72 20700 0.75 23600 o.8S 25100 0.91 1967 33670 20200 0.60 20500 0.61 22100 0.66 28700 0.85 1968 20710 11200 0.54 12600 0.61 14000 0.70 16800 0.81 1969 11300 7500 0.66 7500 0.66 7570 0.67 7650 0.68 1970 24660 17700 0.72 17900 0.73 18800 0.76 21900 0.89 1971 23810 14000 0.59 14700 0.62 16400 0.69 18200 0.76 1972 20970 12600 0.60 13200 0.63 14600 0.70 19000 0.91 1980 20784 12300 0.59 12800 0.62 13500 0.65 16300 0.78 # of Val. 16 Average 22100 0.66 0.68 0.73 0.83 Standard 4690 0.10 0.09 0.09 0.08 I --' _] I J ) J ,I I ] ~J ·"+c··:+"l -cil __ . \ ' J ,_ ----1 ~-~_:l l! J ~~~~~~~ -~, 1 1 t ~~~ ~ ~~ -l . -l J 1 -J • susi8/b35 Comparison of Low Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 September Mean Monthly 1 Oa~ Low Flow 3-Da~ Low Flow 7·Day Low Flow 14-Da~ Low Flow Year Flow -QM Q1 Q1/QM Q3 Q37QM Q7 QlQM Q14 Q147QM (cfs) ' 1958 8000 6800 0.85 6800 0.85 6800 0.85 6800 0.85 1959 9957 6800 0.68 7000 0.70 7210 0.72 7460 0.75 1960 12420 7400 0.60 7470 0.60 7780 0.63 10700 0.86 1961 16030 9680 0.60 9990 0.62 11300 0.70 12900 0.80 1962 13490 8130 0.60 8170 0.61 8440 0.63 8990 0.67 1963 11330 10000 0.88 10000 0.88 10000 0.88 10000 0.88 1964 9235 6220 0.67 6850 0.74 7120 0.77 7380 0.80 1965 22260 10700 0.48 10700 0.48 17600 0.79 19900 0.89 1966 12200 8480 0.70 8660 0.71 9000 0.74 . 10500 0.86 1967 12510 6000 0.48 6400 0.51 7300 0.58 8760 0.70 1968 7375 4150 0.56 4260 0.58 4570 0.62 5360 0.73 1969 6704 4320 0.64 4410 0.66 4800 0.72 5350 0.80 1970 11330 5000 0.44 5000 0.44 5290 0.47 7040 0.62 1971 11080 6000 0.54 6170 0.50 6470 0.58. 7540 0.68 1972 12120 6000 0.50 6090 0.50 6330 0.52 7470 0.62 1980 8240 6080 0.74 6270 0.76 6540 0.79 7690 0.93 #of Val. 16 Average 11520 0.62 0.64 0.69 0.78 Standard 3770 0.13 0.13 0.12 0.10 Dev. susi8/b30 Comparison of Low Flows to Average Monthly Flow Susitna River at Gold Creek No. 15292400 October Mean Monthly 1· Da~ Low Flow 3-Da~ Low Flow 7""Da~ Low Flow 14-Da~ Low Flow Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 Q147QM -(cfs) 1949 6334 3300 0.52 3400 0.54 3640 0.57 3830 0.60 1950 3848 1500 0.39 1570 0.41 1810 0.47 2600 0.68 1951 5571 2900 0.52 3000 0.54 3170 0.57 3610 0.65 1952 8202 5100 0.62 5170 0.63 5260 0.64 5490 0.67 1953 5604 2400 0.43 2540 0.45 3200 0.57 3780 0.67 1954 5370 4600 0.86 4600 0.86 4600 0.86 4600 0.86 1955 4951 2800 0.57 3000 '0.61 3350 0.68 3730 0.75 1956 5806 4500 0.78 4500 0.78 4500 0.78 4500 0.78 1957 8212 5400 0.66 5800 0.71 6230 0.76 7140 0.87 1958 4811 3500 0.73 3500 0.73 3500 0.73 3890 0.81 1959 6558 3700 0.56 3770 0.57 4030 0.61 4520 0.69 1960 7794 3800 0.49 3970 0.51 4230 0.54 4920 0.63 1961 5916 4600 0.78 4600 0.78 4600 0.78 4600 0.78 1962 6723 4800 0.71 4900 0.73 5200 0.77 5460 0.81 1963 6449 3100 0.48 3270 0.51 3800 0.59 4690 0.73 1964 6291 3000 0.48 3490 0.55 3910 0.62 4400 0.70· 1965 7205 2800 0.39 2930 0.41 3090 0.43 3240 0.45 1966 4162 1800 0.43 1900 0.46 2100 0.50 2470 0.59 1967 4900 2900 0.59 3000 0.61 3140 0.64 3510 0.72 1968 3822 2600 0.68 2670 0.70 2820 0.74 2940 0.77 1969 3124 1700 0.54 1700 0.54 1810 0.58 2360 0.76 1970 5288 4000 0.76 4000 0.76 4000 0.76 4210 0.80 1971 5847 3600 0.62 3730 0.64 3970 0.68 4470 0.76 1972 4826 3200 0.66 3400 0.70 3830 0.79 4610 0.96 1973 3733 2000 0.54 2000 0.54 2140 0.57 2440 0.65 1974 3739 1700 0.45 1700 0.45 1800 0.48 2050 0.55 1975 7739 3600 0.47 3800 0.49 4200 0.54 5420 0.70 1976 3874 3000 0.77 3000 0.77 3090 0.80 3400 0.88 1977 7571 4600 0.61 4670 0.62 5160 0.68 6040 0.80 1978 4906 2870 0.58 3190 0.65 3560 0.73 4100 0.84 1979 7311 5050 0.69 5090 0.70 5200 0.71 5510 0.75 # of Val. 31 Average 5690 0.59 0.61 0.65 0.73 Standard 1450 0.13 0.12 0.11 0.11 Dev. I I 1 ~ J .I J j J l J I,. I I; j '· . ' susi8/b36 Comparison of Low Flows to Average Monthly Flow Chulitna River near Talkeetna No. 15292400 October Mean Monthly 1 Da~ Low Flow 3-Da~ Low Flow 7-Da~ Low Flow 14-Da~ Low Flow Year Flow -QM Q1 Ql/QM Q3 Q3/QM Q7 Q7/QM 0 14 Q14/QM (cfs) 1958 4197 2910 0.69 2940 0.70 3060 0.73 3290 0.78 1959 4723 3000 0.64 3070 0.65 3230 0.68 3500 0.74 1960 5135 2500 0.49 2600 0.51 2760 0.54 3130 0.62 1961 5777 3100 0.54 3270 0.57 ,3400 0.59 3850 0.67 1962 3506 1700 0.48 1800 0.51 1870 0.53 1940 0.55 1963 8062 4800 0.60 4800 0.60 4800 0.60 5590 0.69 1964 5642 3300 0.58 3330 0.59 3410 0.60 3690 0.65 1965 6071 2950 0.49 2950 0.49 2950 0.49 2950 0.49 1966 4682 2000 0.43 2000 0.43 2170 0.46 2630 0.56 1967 3483 1900 0.55 1930 0.55 2040 0.59 2390 0.69 1968 2898 1900 0.66 2000 0.69 2190 0.76 2330 0.80 1969 4578 3000 0.66 3000 0.66 3030 0.66 3170 0.75 1970 3826 3000 0.78 3000 0.78 3030 0.79 3170 0.83 1971 5439 2900 0.53 3000 0.55 3170 0.58 3700 0.68 # of Val. 14 Average 4858 0.58 0.59 0. 61 0.68 Standard 1324 0.10 0.10 0.10 0.10 Dev. J .I J . .J ·' > -1 ~J l -l - susi8/b37 Mean Monthly Year Flow -QM (cfs) 1965 3474 1966 2410 1967 4112 1968 8840 1969 3869 1970 3950 1971 2145 1972 . 3516 1973 3860 1974 5678 1975 4084 1976 3439 1977 4244 1978 2950 1979 7790 1980 4820 n OfVal. 16 Average 4324 Standard 1732 Dev. Comparison of Low Flows to Average Monthly Flows Talkeetna River near Talkeetna No. 15292700 May 1 Da~ Low Flow 3-Day: Low Flow 7-Dav Low Flow Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM 960 0.28 960 0.28 960 0.28 540 0.22 577 0.24 687 0.29 550 0.13 617 0.15 900 0.22 1650 0.19 1750 0.20 2050 0.23 1000 0.26 1100 0.28 1300 0.34 800 0.20 850 0.22 1010 0.26 650 0.30 683 0.32 743 0.35 800 0.23 850 0.24 971 0.28 850 0.22 900 0.23 1010 0.26 900 0.16 1000 0.18 1240 0.22 600 0.15 633 0.15 693 0.17 1300 0.38 1500 0.44 2200 0.64 660 0.16 673 0.16 739 0.17 700 0.24 .723 0.25 813 0.28 1800 0.23 2070 0.27 2760 0.35 2100 0.44 2200 0.46 2410 0.50 0.24 0.25 0.30 0.08 0.09 0.12 14-Dav Low Flow Q14 Q14/QM 1100 0.32 1060 0.44 1860 0.45 3000 0.34 1750 0.45 2030 0.51 932 0.43 1290 0.37 1500 0.39 2010 0.35 936 0.23 3030 0.88 1340 0.32 1810 0.61 3790 0.49 2900 0.60 0.45 0.15 susi8/b38 Comparison of Low Flows to Average Monthly Flows Talkeetna River near Talkeetna No. 15292700 June Mean Monthly 1 Da~ Low Flow .. 3-Da~ low Flow 7-Day: Low Flow ' 14-Da~ Low Flow Flow ·QM Q1 o,;oM Q3 Q3/QM Q7 Q7/QM Q14 Q14/QM Year (cfs) - 1964 17080 11000 0.64 . 11300 0.66 12300 0.72 13500 0.79 1965 11090 7120 0.64 7460 0.67 8700 0.78 9560 0.86 1966 12970 6420 0.49 7990 . 0.62 9130 0.70 9940 0.77 1967 9286 6200 0.67 6370 0.69 6660 0.72 7400 0.80 1968 14100 9500 0.67 9830 0.70 10600 0.75 12600 0.89 1969 5207 3440 0.66 3540 0.68 3730 0.72 4400 0.85 1970 7979 4700 0.59 5040 0.63 5700 0.71 6830 0.86 1971 19040 4750 0.25 4880 0.26 8450 0.44 16300 0.86 1972 12700 8560 0.67 8730 0.69 9030 0.71 10900 0.86 1973 12210 6260 0.51 6720 0.55 7630 0.62 9260 0.76 1974 8030 5200 0.65 5810 0.72 6470 0.81 7330 0.91 1975 13180 8810 0.67 9500 0.72 10500 0.80 11700 o.8g 1976 10580 6040 0.57 7480 0.71 7640 0.72 8820 0.83 1977 18280 13300 0.73 13900 0.76 14200 0.78 15700 0.86 1978 7429 4540 0.61 4800 0.65 5660 0.76 7080 0.95 1979 12010 7090 0.59 7390 0.62 7710 0.64 9300 0.77 1980 11380 8000 0.70 8330 0.73 10400 0.91 10900 0.96 # of Val. 17 Average 11910 0.61 0.65 0.72 0.85 Standard 3800 0.11 0.11 0.10 0.06 Dev. 1 . J . . ~] ~ I ~ j ··-•···· i 1 l -1 1 • ---•. 1 ] -} II susi8/b39 Comparison of Low Flows to Average Monthly Flows Talkeetna River near Talkeetna No. 15292700 July Mean Monthly 1 Da~ Low Flow 3-Da~ Low Flow 7-Da~ Low Flow 14-Day Low Flow Year Flow --QM Q1 Q,IQM Q3 Q3/QM Q7 Q7/QM 014 Q14/QM (cfsJ 1964 9820 7810 0.80 8190 0.83 8420 0.86 9310 0.95 1965 12180 8400 0.69 8490 0.70 9050 0.74 10600 0.87 1966 10100 5870 0.58 6220 0.62 6510 0.64 8640 0.86 1967 12600 8600 0.68 8800 0.70 8980 0.71 9370 0.74 1968 11230 9000 0.80 9000 0.80 9410 0.84 9770 0.87 1969 7080 5300 0.75 5680 0.80 6050 0.85 6840 0.97 1970 10320 7300 0.71 7690 0.75 8150 0.79 9110 0.88 1971 11760 7000. 0.60 7670 0.65 8710 0.74 9750 0.83 1972 12030 9800 0.81 9880 0.82 10400 0.86 11300 0.94 1973 7676 5800 0.76 5870 0.76 6140 0.80 6700 0.87 1974 7755 6440 0.83 6560 0.85 6960 0.90 7220 0.93 1975 12070 8690 0.72 8940 0.74 9560 0.79 10600 0.88 1976 9026 6310 0.70 6620 0.73 7380 0.82 8440 0.94 1977 9344 7310 0.78 7350 0.79 7630 0.82 8580 0.92 1978 10790 8110 0.75 8610 0.80 10200 0.95 10200 0.95 1979 14440 9180 0.64 9550 0.66 11900 0.82 12300 0.85 1980 13900 10000 0.72 10100 0.73 10800 0.78 13000 0.97 # of Val. 17 Average 10710 0.72 0.75 0.81 0.90 Standard 2120 0.07 0.07 0.07 0.06 Dev. susi8/b40 Comparison of low Flows to Average Monthly Flows Talkeetna River near Talkeetna No. 15292700 August Mean Monthly 1 Da~ law Flow 3-Da~ low Flow 7-Da~ low Flaw 14-Da~ low Flow Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 Q14/QM (cfs) 1964 8396 5300 0.63 5430 0.65 6140 0.73 7100 0.85 1965 11150 5300 0.48 5570 0.50 6560 0.59 9280 0.83 1966 10730 7520 0.70 7650 0.71 8070 0.75 9010 0.84 1967 14160 8550 0.60 8720 0.62 $750 0.69 13000 0.92 1968 7546 5720 0.76 5960 0.79 6530 0.87 7110 0.94 1969 3787 2100 0.55 2110 0.56 2170 0.57 2230 0.59 1970 8752 6000 0.69 6220 0.71 6870 0.78 7800 0.89 1971 16770 7500 0.45 7670 0.46 8430 0.50 9570 0.57 1972 9576 6400 0.67 6500 0.68 6970 0.73 8380 0.88 1973 9927 5220 0.53 5330 0.54 5910 0.60 7680 0.77 1974 7704 3680 0.48 3940 0.51 4760 0.62 6200 0.80 1975 8487 4920 0.58 5130 0.60 5980 0.70 7020 0.83 1976 8088 4190 0.52 4370 0.54 5170 0.64 6480 0.80 1977 8005 4780 0.60 4840 0.60 5560 0.69 7360 0.92 1978 7001 3890 0.56 4100 0.59 4390 0.63 5160 0.74 1979 8274 4580 0.55 5180 0.63 6140 0.74 6530 0.79 1980 7220 4320 0.60 4530 0.'63 4780 0.66 5960 0.83 # of Val. 17 Average 9151 0.59 0.61 0.68 0.81 Standard 2922 0.08 0.09 0.09 0.10 Dev. 1. J ] J I J I .. ,_I ,) ,, ; .-.. • ' I J : J -) --J ~ ] ] } l l J _]-. susi8/b41 I Comparison of Low Flows to Average Monthly Flows Talkeetna River near Talkeetna I No. 15292700 September Mean Monthly 1 Da~ Low Flow 3-Da~ Low Flow 7-Da~ Low Flow 14-Da~ Low Flow Flow -QAJI Q1 0/QM Q3 Q3/QM Q7 Q7/QM Q14 Q14/QM Year (cfs) ' 1964 3815 3080 0.81 3160 0.83 3230 0.85 3410 0.89 1965 10670 5100 0.48 5130 0.48 6560 0.62 8170 0.77 1966 5370 3500 0.65 3600 0.67 3980 0.74 4600 0.86 1967 6971 3140 0.45 3280 0.47 3540 0. 51 4200 0.60 1968 4120 2500 0.61 2530 0.61 2610 0.63 2890 0.70 1969 2070 1700 0.82 1700 0.82 1700 0.82 1730 0.84 1970 5993 3530 0.59' 3600 0.60 3680 0.61 4750 0.79 1971 5990 3400 0.57 3470 0.58 3770 0.63 4090 0.68 1972 8709 4600 0.53 4700 0.54 5110 0.59 6210 0.71 1973 3861 2420 0.63 ·2480 0.64 2610 0.68 2860 0.74 1974 4763 . 2860 0.60 2930 0.62 3280 0.69 3570 0.75 1975 7960 4720 0.59 4830 0.61 5700 0.72 7740 0.97 1976 3205 2600 0.81 2700 0.84 2910 0. 91 3100 0.97 1977 5826 3820 0.66 4030 0.69 4200 0.72 4960 0.85 1978 3513 2200 0.63 2300 0.65 2500 0.71 2760 0.78 1979 4039 3220 0.80 3230 0.80 3280 0.81 3400 0.84 1980 5400 2700 0.50 2730 0.51 2900 0.54 3470 0.64 # of Val. 17 Average 5428 0.63 0.64 0.69 0.79 Standard 2192 0.12 0.12 0.11 0.11 Dev. susi8/b42 Comparison of Low Flows to Average Monthly Flows Talkeetna River near Talkeetna No. 15292700 October Mean Monthly 1 Da~ Low Flow 3-Da~ Low Flow 7-Da~ Low Flow 14-Da~ Low Flow Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM 014 Q14/QM (cfs) 1964 3115 1910 0.61 2030 0.65 2170 0.70 2340 0.75 1965 ·4438 2150 0.48 2220 0.50 2410 0.54 2770 0.62 1966 2388 1100 0.46 1170 . 0.49 1270 0.53 1510 0.63 1967 2029 1500 0.74 1500 0.74 '1540 0.76 1610 0.79 1968 1637 1200 0.73 1200 0.73 1240 0.76 1340 0.82 1969 1450 1100 0.76 1100 0.76 1100 0.76 1150 0.77 1970 2817 2000 0.71 2000 0.71 2000 0.71 2170 0.77 1971 2632 . 1800 0.68 1830 0.69 1910 0.73 2130 0.81 1972 3630 2000 0.55 2130 0.59 2400 0.66 3020 0.83 1973 1807 1200 0.66 1200 0.66 1260 0.67 1360 0.75 1974 1967 1200 0.61 1200 0.61 1390 0.71 1450 0.74 1975 2884 1200 0.42 1230 0.43 1330 0.46 1710 0.59 1976 1857 1400 0.75 1470 0.79 1530 0.82 1680 0.90 1977 3268 1600 0.49 1700 0.52 1900 0.58 2360 0.72 1978 1660 1120 0.67 1280 0.77 1380 0.83 1450 0.87 1979 3370 2200 0.65 2250 0.67 2300 0.68 2430 0.72 tt of Val. 16 .Average 2559 0.62 0.64 0.68 0.76 Standard 854 0.11 0.11 0.11 0.09 Dev. cC~J J -j _1 I I I J .I I .I ) _c__] . .. J ] .. I ! --~.:; .. - l ':'''-" J· } ----- susi8/b43 Mean Monthly Year Flow -QM (cfs) 1975 47540 1976 70460 1977 56180 1978 48670 1979 81260 1980 66580 # of Val. 6 Average 61780 Standard 13295 Oev. ] J 1 ) --) r -~---- Comparison of Low Flows to Average Monthly Flows Susitna River at Susitna Station No. 15294350 May l ] 1 Oa~ Low Flow o 1 o17oM 3-Da~ Low Flow 7-0a~ Low Flow Q3 Q3/QM Q7 Q7/QM 9000 0.19 9330 0.20 10100 0.21 30000 0.43 41300 0.59 62700 0.89 7500 0.13 8000 0.14 . 9500 0.17 11000 0.23 12300 0.25 17600 0.36 18000 0.22 21000 0.26 32600 0.40 20000 0.30 22700 0.34 31300 0.47 0.25 0.30 0.42 0.10 0.16 0.26 1 ] : 14-0ay_ Low Flow Q14 Q14/QM 14100 0.30 63000 0.89 19000 0.34 36700 0.75 55000 0.68 46600 0.70 0.61 0.24 susi8/b44 Mean Monthly Year - Flow -QM (cfs) 1975 128800 1976 107000 1977 165900 1978 90930 1979 119900 1980 142900 :jf of Val. 6 Average 125900 Standard 26510 Dev. . J Comparison of Low Flows to Average Monthly Flows Susitna River at Susitna Station No. 15294350 June 1 Da~ Low Flow 3-Da~ Low Flow 7-Day Low Flow Q7/QM Q1 Q1/QM Q3 Q3/QM Q7 102000 0.79 106000 0.82 110000 0.85 61800 0.58 69300 0.65 84500 0.79 130000 0.78 143000 0.86 155000 0.93 62800 0.69 65700 0.72 66300 0.73 99000 0.83 101000 0.84 103000 0.86 110000 0.77 113000 0.79 126000 0.88 0.74 0.78 0.84 0.09 0.08 0.07 J -1 . 14-Day Low Flow Q14 Q14/QM 118000 0.92 97900 0,91 158000 0.95 76900 0.85 111000 0.93 138000 0.97 0.92 0.04 .I ·.··. -1 ~-,~ I ... 1 -· J I J -·· ··~ -] ·-1 susi8/b45 Comparison of Low Flows to Average Monthly Flows Susitna River at Susitna Station No. 15294350 July t Mean Monthly 1 Day low Flow 3-Da~ Low Flow 7-Dav Low Flow 14-Day Low Flow I Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 Q14/QM (cfs) 1975 135700 108000 0.80 113000 0.83 114000 0.84 121000 0.89 1976 115200 93400 0.81 95400 0.83 100000 0.87 107000 0.93 1977 143900 124000 0.86 127000 0.88 134000 0.93 141000 0.98 1978 117600 106000 0.90 109000 0.93 115000 0.98 117000 0.99 1979 142500 110000 0.77 111000 0.78 129000 0.91 133000 0.93 1980 181400 145000 0.80 148000 0.82 160000 0.88 176000 0.97 # of Val. 6 Average 139380 0.82 0.85 0.90 0.95 Standard 23950 . 0.05 0.05 0.05 0.04 Oev. susi8/b46 Year 1975 1976 1977 1978 1979 1980 # of Val. Average Standard Dev. I ' Mean Monthly Flow -QM (cfs) 91360 99650 125500 102100 128200 126400 6 112200 16300 Comparison of Low Flows to Average Monthly Flows Susitna River at Susitna Station No. 15294350 August 1 Day Low Flow 3-Day Low Flow 7-Day Low Flow 57600 0.63 63600 0.70 71200 0.78 56800 0.57 61700 0.62 71900 0.72 76200 0.61 80900 . 0.64 96600 0.77 66400 0.65 68400 0.67 7'2500 0. 71 . 78900 0.62 88800 0.69 99900 0.78 92000 0.73 95300 0.75 103000 0.81 0.64 0.68 0.76 0.05 0.05 0.04 J J t .. 1. ., ___ . __ ,_ I •·• . .: .. ! .. .J 14-Day Low Flow " 80000 0.88 82800 0.83 116000 0.92 83600 0.82 . 116000 0,90 111000 0.88 0.87 0.04 I ~ --J . ] J • --~ 1 ) . susi8/b47 Comparison of Low Flows to Average Monthly Flows Susitna River at Susitna Station No. 15294350 September Mean Monthly 1 Da~ Low Flow 3-Da~ Low Flow 7-Da~ Low Flow 14-Da~ Low Flow Year Flow -QM Q1 01/0M Q3 0/0M Q7 07/0M 014 01/0M (cfs) 1975 77740 47800 0.61 48000 0.62 57700 0.74 73700 0.95 1976 48910 37000 0.76 37300 0.76 38600 0.79 39200 0,80 1977 83810 59200 0.71 64000 0.76 69400 0.83 81200 0.97 1978 55500 29000 0.52 30000 0.54 32100 0.58 40100 0.72 1979 74340 51800 0.70 52200 0.70 53100 0.71 56900 0.77 1980 91200 80000 0.88 80700 0.88 81100 0.89 83700 0.92 # of Val. 6 Average 71910 0.70 0. 71 0.76 0.86 Standard 16440 0.12 0.12 0.11 0.10 Dev. susi8/b48 Comparison of Low Flow and Average Monthly Flows Susitna River at Susitna Station No. 15294350 October Mean Monthly 1 Da~ Low Flow 3-Da~ Low Flow 7-Da:l Low Flow 14-Da~ Low Flow Year Flow -QM Q1 Q1/QM Q3 Q3/QM Q7 Q7/QM Q14 Q14/QM II . (cfs) 1974 19520 11000 0.56 11300 0.58 12100 0.62 13600 0.70 1975 31550 16000 0.51 17300 0.55 18900 0.60 22700 0.72 1976 30140 23000 0.76 24000 0.80 26400 0.88 29300 0.97 1977 38230 19000 0.50 19700 0.52 21300 0.56 24800 0.65 1978 36810 26000 o. 71 26700 0.73 30000 0.81 35100 0.95 1979 58640 33800 0.58 34200 0.58 36100 0.62 . 41400 0.71 # of Val. 6 Average 35815 0.60 0.63 0.68 0.78 Standard 12990 0.11 0.11 0.13 0.14 Dev. J ' . . --· ~·~-.-'j 'j susi8/f1 Comparison of Annual Low Daily Flows to Annual low Monthly Flow Susitna River near Cantwell Station Number 15291500 1-Day low Flow 3-Da~ Low Flow 7-Day low Flow 14-Day Low Flow 30-Day low Flow 60-Day low Flow 90-Day low Flow Year Q1 o 11om Q3 0 310m Q7 0 11Qm 0 14 01iOm Q30 Q3o 10m 05o Q6o10m 09o 0 9o 10m 1962 940 1.00 940 1.00 940 1.00 940 1.00 940 1.00 972 1.03 1050 1.12 1963 720 1.00 720 1.00 720 1.00 720 1.00 740 1.00 740 1.03 777 1.08 1964 400 0.93 400 0.93 400 0.93 400 0.93 419 0.98 446 1.04 488 1.14 1965 680 1.00 680 1.00 680 1.00 680 1.00 681 1.00 694 1.02 718 1.06 1966 650 1.00 650 1.00 650 1.00 650 1.00 650 1.00 651 1.00 667 1.03 1967 500 0.97 500 0.97 500 0.97 500 0.97 510 0.99 536 1.04 571 1.11 1968 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1969 480 0.99 480 0.99 480 0.99 480 0.99 484 1.00 492 1.01 511 1.05 1970 420 0.99 420 0.99 42(~ 0.99 420 0.99 420 0.99 428 1.00 442 1.04 1971 460 0.98 460 0.98 460 0.98 460 0.98 465 0.99 474 1.01 500 1.06 1972 850 0.97 850 0.97 850 0.97 850 0.97 850 0.97 873 1.00 892 1.02 Aver· age 0.98 0.98 0.98 0.98 0.99 1.02 1.06 Standard 0.02 0.02 0.02 0.02 0.01 0.02 . 0.04 Dev. susi8/f2 Comparison of Annual low Daily Flows to Annual Low Monthly Flow Susitna River at Gold Creek Station Number 1529200 1-Da't Low Flow 3-Da't Low Flow 7-Da't low Flow 14-Da't Low Flow 30-Da't low Flow 60-Da't low Flow 90-Da't Low Flow Year 01· 0/0m 03 0/0m 07 0/0m 014 0 1/0m 030 03o10m 05o 06o/Om 09o 090/Qm 1950 600 0.76 600 0.76 614 0.78 648 0.82 674 0.93 716 0.99 797 1.10 1951 740 1.00 740 1.00 740 1.00 740 1.00 740 1.00 772 1.04 823 1 . 11 1952 880 1.00 880 1.00 880 1.00 880 1.00 880 1.00 899 1.02 932 1.06 1953 820 1.00 820 1.00 . 820 1.00 820 1.00 820 1.00 822 1.00 888 1.08 1954 780 1.00 780 1.00 780 1.00 780 1.00 780 1.00 854 1.09 956 1.23 1955 1100 1.00 1100 1.00 .1100 1.00 1100 1.00 1100 1.00 1150 1.05 1230 1.12 1956 940 1.00 940 1.00 940 1.00 940 1.00 940 1.00 945 1. 01 953 1.01 1957 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1300 1.08 1958 1100 0.96 1100 0.96 1100 0.96 1100 0.96 1140 0.99 1200 1.05 1280 1.11 1959 980 1.00 980 1.00 980 1.00 980 1.00 980 1.00 1040 1.06 1160 1.18 1960 1100 0.92 1100 0.92 1100 0.92 1100 0.92 1100 0.92 1220 1.02 1310 1.09 1961 1500 0.83 1500 0.83 1500 0.83 1500 0.83 1610 0.92 1800 1.03 2010 1.15 1962 1400 1.00 1400 1.00 1400 1.00 1400 1.00 1400 1.00 1450 1.04 1540 1.10 1963 830 1.00 830 1.00 830 1.00 830 1.00 830 1.00 915 1.10 1110 1.34 1964 660 0.93 660 0.93 660 0.93 660 0.93 683 0.96 728 1.02 794 1.11 1965 860 1.00 860 1.00 860 1.00 860 1.00 863 1.00 882 1.03 908 1.06 1966 1300 1.00 1300 1.00 1300 1.00 1300 1.00 1300 1.00 1300 1.00 1330 1.02 1967 1100 0.94 1100 0.94 1100 0.94 1100 0.94 1130 0.97 1180 1.01 1250 1.07 1968 1800 0.94 1800 0.94 1800 0.94 1830 0.96 1870 0.98 1880 0.99 1890 0.99 1969 700 0.97 700 0.97 700 0.97 700 0.97 700 0.97 723 1.00 750 1.04 1970 750 0.98 750 0.98 750 0.98 750 0.98 750 0.98 773 1. 01 790 1.03 1971 950 1.00 950 1.00 950 1.00 950 1.00 950 1.00 970 1.02 1020 1.07 1972 1600 0.94 1600 0.94 1600 0.94 1640 0.96 1680 0.98 1760 1.03 1850 1.08 1973 1000 1.00 1000 1.00 1000 1.00 1000 1.00 1000 1.00 1010 1.01 1070 1.07 197·1 700 0.97 700 0.97 700 0.97 700 0.97 707 0.97 730 1.01 762 1.05 1975 "1400 1.00 1400 1.00 1400 1.00 1400 1:00 1400 1.00 1410 1.01 1440 1.03 1976 900 1.00 900 1.00 900 1.00 900 1.00 900 1.00 916 1.02 928 1.03 1977 1500 1.00 1500 1.00 1500 1.00 1500 1.00 1500 1.00 1550 1.03 1590 1.06 1978 1600 1.00 1600 1.00 1600 1.00 1600 1.00 1600 1.00 1620 1.01 1650 1.03 1979 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1200 1.00 1230 1.03 1260 1.05 1980 1400 1.00 1400 1.00 1400 1.00 1400 1.00 1400 1.00 1400 1.00 1450 1.04 Average 0.97 0.97 0,97 0.98 0.99 1.02 1.08 Standard 0.05 0.05. 0.05 0.05 0.02 ·o.o3 0.07 Dev . !'·-·--·· . J .J ... J .J J .,.J .J c ... J .I .I ... J ·" ------------------- susi8/f3 Comparison of Annual Low Daily Flows to Annual Low Monthly Flow Chulitna River near lalkeetna Station Number 15292400 J -Oa~ Low Flow 3-Day: Low Flow 7 .. Qay: Low Flow 14-Da}!_ Low Flow 30-Day: Low F!ow GO-Day: Low Flow 90-Day: tt..~· .f!~ Year Q Q1/Qm Q3 Q3/Qm Q7 Q7/Qm Q14 01iQm Q30 Q3o10m 05o Oso/Qm 0 9o ~$0/Qm 1 , -- 1959 690 0.93 690 0.93 690 0.93 690 0.93 732 0.99 808 'L09 888 ~ .. 20 1960 880 0.94 880 0.94 880 0.94 880 . 0~94 889 0.95 941 1.01 1010 t;()S 1961 950 0.88 -350 0.88 950 0.88 950 0.88 1030 0.95 1100 1.02 1210 '. 12 1962 930 1.00 930 1.00 930 1.00 930 1.00 930 1.00 949 1.02 1020 1.1() 1963 650 0.93 650 0.93 650 0.93 650 0.93 690 0.99 771 1.10 947 l .. 35 . 1964 770 1.00 77Q 1.00 770 1.00 770 1.00 770 1.00 794 1.03 842 l-.09 1965 1300 1.00 1300 1.00 1300 1.00 1300 1.0CJ '1300 1.00 1350 1.04 1370 '\,05 1966 1100 1.00 1100 1.00 1100 1.00 1100 1.00 1100 1.00 1100 1 .. 00 11;\0 1 .. 03 1967 900 0.93 900 0.93 • 900 0.93 900 0.93 928 0.95 999 1.03 1090 1.12· 1968 1100 0.96 1100 0.96 1100 0.96 1100 0.96 1140 0.99 1170 1.02 1180 l .. OS 1969 800 0.97 800 0.97 800 0.97 800 0.97 823 1.00 857 1.04 885 1~07 1970 '1100 1.00 1100 1.00 1100 1.00 110} 1.00 1100 1.00 1120 1.02 1150 t .. OS 1971. 900 0.96 900 0.96 900 0.96 B14 0.$8 933 1.00 942 1.01 953. 1;02 1972 850 0.95 850 0.95 850 0.95 850 0.95 868 0.97 908 L02 954 1 .. 07 AVerage , 0.96 0.96 0.96 0.96 0.99 1.03 1 .. 10 Standard 0.04 0.04 0.04 0.04 0.02 0.03 \},09 Dev, 1_/ susi8/f4 Comparison of Annual Low Daily flows to Annual Low Monthly Flow Talkeetna River near Talkeetna Station Number 15292700 1-Da~ Low Flow 3-Da~ Low flow 7-Da~ Low flow 14-Da)l: Low flow 30-Da~ Low Flow 60-Da~ Low flow 90-Da~ Low flow Year Ql o,;om Q3 Q/Om Q7 Q/Om 0 14 Q14/Qm 0 30 Q3o 10m 05o 0 6o 10m -q90 Q90/Qm 1965 540 1.00 540 1.00 540 1.00 540 1.00 540 1.00 559 1.04 580 1.07 1966 390 0.99 390 0.99 390 0.99 390 0.99 393 0.99 405 1.03 446 1.13 1967 420 0.98 420 0.98 420 0.98 420 0.98 425 1.00 448 1.05 481 1.13 1968 740 1.00 740 1.00 740 1.00 740 1.00 741 1.00 754 1.01 774 1.04 1969 380 1.00 380 1.00 380 1.00 380 1.00 380 1.00 384 1.01 398 1.05 1970 440 1.00 440 1.00 440 1.00 440 1.00 440 1.00 444 1.01 456 1.04 1971 400 1.00 400 1.00 400 1.00 400 1.00 400 1.00 420 1.04 448 1.11 1972 400 0.77 400 0.77 400 0. 77 411 0. 79 434 0.84 481 1.00 539 1.12 1973 500 0.87 500 0.87 500 0.87 514 0.89 533 0.92 566 0.99 599 1.04 1974 450 0.93 450 0.93 450 0.93 450 0.93 458 0.95 485 1.01 516 1.07 1975 500 0.98 500 0.98 ·500 0.98 500 0.98 500 0.98 512 1.01 538 1.06 1976 460 0.98 460 0.98 460 0.98 460 0.98 463 0.99 471 1.00 479 1.02 1977 500 0.99 500 0.99 500 0.99 500 0.99 505 1.00 516 1.02 534 1.06 1~78 460 0.95 460 0.95 461 0.95 466 0.96 473 0.98 497 1.02 531 1.09. 1979 540 0.94 540. 0.94 540 0.94 541 0.94 548 0.~5 576 1.00 611 1.06 1980 700 1.00 700 1.00 700 1.00 700 1.00 700 1.00 713 1.02 742 1.06 Average 0.96 0.96 0.96 0.96 0.~8 1.02 1.07 Slandard 0.06 0.06 0.06 0.06 0.04 0.02 0.03 Dev. 1 '-"------' J I ) .. J .. --~ J ] ~-·-·--j J .. 1 J 'y ___ j J J I susi8/f5 1-Day low Flow 3-Day Low Flow Year Q1 Q1/Qm Q3 Q3/Qm 1975 6500 0.95 6500 0.95 1976 5200 0.97 5200 0.97 1977 6000 0.96 6000 0.96 1978 6400 0.91 6400 0.91 1979 6500 0.75 6500 0.75 1980 8600 0.97 8630 0.97 Average 0.92 0.92 Slandard 0.09 0.09 Comparison of Annual Low Daily Flows to Annual Low Monthly Flow Susitna River at Susitna Station Station Number 15294350 7-Day·.Low Flow 07 Q7/Qm 6500 0.95 5200 . 0.97 6000 0.96 6400 0.91 6500 0.75 8700 0.98 0.92 0.09 14-Day low Flow Q14 Q14/Qm 6500 0.95 5200 0.97 6000 0.96 6430 0.91 6640 0.76 8800 0.99 0.92 0.08 30-Day Low Flow Q30 Q30/Qm 6720 0.98 5310 0.99 6180 0.99 6520 0.99 6830 0.97 8870 1.00 0.99 0.01 --] 1 60-Day low Flow 06o 06o10m 6920 1.01 5370 1.00 6490 1.04 6590 1.00 7100 1.01 8960 1.01 1.10 0.01 90-Day Low Flow 090 09o/Om 7230 1.05 5580 1.04 7220 1.16 6680 1. 01 7500 1.07 9210 1.03 1.06 0.05 r· : ;~ - r : ·- - ATTACHMENT C WATER SURFACE ELEVATIONS r29/g3 ) ---1 I ~~~ ------------------------------------------------~ I C"'l 1r1Tt-.1,.. 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