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AEA Bradley Lake Hydro. Project FERC P-8221-AK May 2013
«= ALASKA @@_ ENERGY AUTHORITY ALASKA ENERGY AUTHORITY BRADLEY LAKE HYDROELECTRIC PROJECT FERC P-8221-AK BATTLE CREEK DIVERSION HYDROLOGY REPORT Prepared For: Prepared by: Alaska Energy Authority R&M Consultants, Inc. 813 West Northern Lights Boulevard 9101 Vanguard Drive Anchorage, Alaska 99503 Anchorage, Alaska 99507 May 2013 ESP REM CONSULTANTS, INC. LIST OF TABLES LIST OF FIGURES LIST OF APPENDICES... 1 ALASKA ENERGY AUTHORITY BRADLEY LAKE HYDROELECTRIC PROJECT FERC P-8221-AK BATTLE CREEK DIVERSION HYDROLOGY REPORT TABLE OF CONTENTS INTRODUCTION 1.1 Project Overview 1.2 Scope of Hydrologic Analyses .. 1.3 Background Review......... 1.4 Organization of Report... 2 METEOROLOGIC AND HYDROLOGIC DATA. 2.1 Meteorologic Data.... 2.2 Hydrologic Data........ 3. HYDROLOGIC ANALYSES... 3.1 Battle Creek Basin Overview .... 3.2 Battle Creek Gage Data and Hydrographs.. . 3.3 Duration Flow and Volumetric Yield Analyses .......... - 16 3.3.1 Comparison of Battle Creek Below Glacier Gage and Diversion Project Basins. 16 3.3.2. Comparison of Battle Creek Below Glacier and Middle Fork Bradley River 3.3.3. Record Extension of the Battle Creek Below Glacier Gage Data. 3.3.4 Flow Duration Curves for the Project Basin... 3.3.5 Post-Construction Hydrology 3.4 Peak Flow Analyses..........ssssssssees 3.4.1. Canal Peak Flow Analyse: 3.4.2 Extreme Flood Analyses 4 SEDIMENT ANALYSEG......... cee ecseseeeeeeeseeeeeeseseseeseeeees 4.1 Main Channel of Battle Creek Sediment Observations .. 4.2 South Fork of Battle Creek Sediment Observations....... 4.3 Diversion Structure and Canal Sediments .. 5 REFERENCES Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. i May 2013 LIST OF TABLES Table 1 — Meteorological and Hydrological Data Summary ..........c:cccsssesesseseseeeseeeseseeseseseeseseeneneaeeeneseenenes 8 Table 2 — Historical Average Monthly Flows for the Battle Creek Below Glacier and Battle Creek Above Mouth Gages, and the Basin Between the Gages .........ccccsssessseseeseseseseseseseseseseseseenenenenenenenenes 15 Table 3 — Basin Comparison for the Battle Creek Below Glacier Gage and Diversion Project Basins...... 18 Table 4 — Calculated Volumetric Yield for May through October for the Battle Creek Below Glacier Gage and Diversion Project Basin) ..........ccccccccssesesesseseseseseseeseseseseesesesesecseseseescsesescesesesescseseeenscseseeeees 18 Table 5 — Basin Comparison for Diversion Project Basin, Battle Creek Below Glacier Gage, and Middle Fork Bradley River Gage Table 6 — Battle Creek Diversion Flood Frequency Analysis Basin Parameters. Table 7 — Battle Creek Diversion Flood Frequency Analysis Results LIST OF FIGURES Figure | - Location and Vicinity Map .... Figure 2 - Project Area Figure 3 - Project Components Figure 4 - Meteorological Station and Stream Gage Locations Figure 5A - Battle Creek Below Glacier Gage Data Figure 5B - Battle Creek Above Mouth Gage Data Figure 6 - Battle Creek Diversion and South Fork Battle Creek Gage Data . Figure 7 - Normalized Battle Creek Gage Data Figure 8A - Normalized Average Daily Flow — Middle Fork Bradley River vs. Battle Creek (August 1991-Octobér 1993) sccscssessonssarscosseacnsneconsverivennvsnansennrnansienrsr eaves rane cea TUTTI TERETE 20 Figure 8B - Normalized Average Daily Flow — Middle Fork Bradley River vs. Battle Creek (August 2010-September 2012) Figure 9 - Battle Creek Below Glacier and Middle Fork Bradley River Gage Data Figure 10 - Battle Creek Below Glacier and Middle Fork Bradley River Normalized Gage Data.... Figure 11 - Linear Regression: Middle Fork Bradley River vs. Battle Creek Below Glacier .... Figure 12 - Project Basin Yield for Extended Record Figure 13 - Battle Creek Project Basin Flow Duration Curve — Annual... Figure 14 - Battle Creek Project Basin Flow Duration Curve — Operational Period.... Figure 15 - Battle Creek Diversion Canal System Basins LIST OF APPENDICES APPENDIX A June 29 and July 17, 2012 Site Visit Memorandums APPENDIX B Flood Frequency Analysis Documentation APPENDIX C HEC-HMS Extreme Flood Analyses Documentation Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. ii May 2013 ALASKA ENERGY AUTHORITY BRADLEY LAKE HYDROELECTRIC PROJECT FERC P-8221-AK BATTLE CREEK DIVERSION HYDROLOGY REPORT 1 INTRODUCTION 1.1 Project Overview The Alaska Energy Authority (AEA) intends to construct improvements to the Bradley Lake Hydroelectric project that will divert flows from the upper portion of the Battle Creek watershed into Bradley Lake. The purpose of the diversion project is to increase the energy potential of the Bradley Lake Project and thereby increase the annual energy output from the project with no increase in generation capacity. Construction of the facilities was completed in 1991 and consists of a 610-foot long, 125-foot high, concrete-faced, rock-filled dam, a 3.5-mile long power tunnel, and a steel-lined penstock. The project is located on the Kenai Peninsula in Southcentral Alaska, approximately 25 miles northeast of Homer (see Figure 1). AEA has tasked R&M Consultants, Inc. (R&M) with the performance of hydrologic analyses to assist with the design of the diversion project. Bradley Lake lies at an elevation of approximately 1,100 feet in the Bradley River watershed in the Kenai Mountains above Kachemak Bay. The lake has a watershed of 62 square miles, and collects flows from the Upper Bradley River and Kachemak Creek, as well as flows diverted from the Nuka River, Middle Fork Bradley River, and Battle Creek watersheds. The proposed project would divert flows from an 8.2-square mile area within the West and Middle Forks of Upper Battle Creek, and route the diverted flows to the location of an existing diversion of the East Fork of Upper Battle Creek into Bradley Lake (see Figure 2). The project will increase the area of the Bradley Lake watershed by approximately 13 percent. The diversion project consists of several individual components. A concrete diversion structure located at an elevation of approximately 1,700 feet within the canyon of the West Fork of Upper Battle Creek will divert flow into an approximately 3,300-foot long upper canal. At the downstream end of the upper canal, flow will enter an 1,800-foot long canal transition that will drop 180 vertical feet using a series of 45 4-foot high steps separated by flat, 40-foot long aprons. The flow of the West Branch of the Middle Fork of Upper Battle Creek will be captured within the upper canal transition. Water in the upper canal transition will be discharged to an approximately 4,400-foot long lower canal. The flow of the East Branch of the Middle Fork of Upper Battle Creek will be captured at the upper end of the lower canal. At the downstream end of the lower canal, flow will enter an approximately 1,500-foot long lower canal transition that will drop roughly 160 vertical feet using a series of 40 4-foot high steps separated flat, 40-foot long aprons. The lower canal transition will begin near the existing cascade on the East Fork of Upper Battle Creek above the existing diversion structure, capturing the flow of the East Fork near the upper end of the transition. The combined flows of the West, Middle, and East Forks of Upper Battle Creek will then follow the existing diversion flow path to Bradley Lake. Also associated with the project are an approximately 15,060-foot long main access road, 2,230-foot long outlet access road, and 3,390-foot long basin access road (see Figures 2 and 3). Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 1 May 2013 ef AIRBANKS PROJECT LOCATION * ANCHORAGE PROJECT - VICINITY,, Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\ Hydrology And Hydraulics\ACAD\1158.27 — Location & Vicinity Map 1 Of 3.dwg SCALE IN MILES E> ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT LOCATION & VICINITY MAPS APRIL 2013 FIGURE 1 DEVELOPED BY: RaM CONSULT, Plotted 4/12/2013 11:29 AM by Kim Anderson MAIN ACCESS ROAD Uj Creek Watershed-iT.dwg OUTLET ACCESS ROAD MAIN ACCESS ROAD EXISTING DIVERSION FLOW PATH BEGIN LOWER CANAL TRANSITION LOWER CANAL a BASIN ACCESS ROAD 4 CANAL TRANSITION . ax a . = ALASKA i BATTLE CREEK DIVERSION HYDROLOGY REPORT O BEGIN UPPER bs CANAL TRANSITION Aa a i ; aes A a PROJECT COMPONENTS a 10 SST - G 3 DIVERSION STRUCTURE : FIGURE " SCALE IN FEET ‘ DEVELOPED BY: : REM CONSULTAN 1.2 Scope of Hydrologic Analyses Hydrologic analyses were performed in support of the design of the Battle Creek Diversion project. Project-related background materials, including previous hydrologic and hydraulic analysis documentation, were reviewed. Available meteorologic and hydrologic data were collected, reviewed, and analyzed. The contributory areas above relevant stream gages and key project components were delineated. The delineation efforts included thorough reviews of available topographic mapping, aerial photography, and satellite imagery, helicopter and fixed wing flight simulator exercises using recently acquired imagery, and helicopter overflights during site visits. Peak flow analyses were performed for use in the design of the diversion structure, canal segments, and associated hydraulic structures. Duration flow analyses were performed for estimating the amount of water that the project will capture for power generation. Qualitative analyses of sediment production, storage, and transport were performed in order to develop an estimate of sediment-related maintenance requirements at the diversion structure and along the canal segments. Two hydrology site visits were performed in support of the hydrologic and sediment analyses. Site visit memorandums are provided in Appendix A. 1.3 Background Review A thorough hydrologic background review was performed. Reviewed materials included hydrologic analysis and design documentation produced for the original Bradley Lake Hydroelectric project by the U.S. Army Corps of Engineers (USACE) and the Stone & Webster Engineering Corporation (Stone & Webster). Documentation of previous Battle Creek diversion hydrologic and engineering analyses performed by Stone and Webster, R&M, and HDR Alaska, Inc. (HDR) was also reviewed, along with glacial and regional hydrology background materials. A list of references is included at the back of the report. 1.4 Organization of Report Section 2 summarizes available meteorologic and hydrologic data. Hydrologic analyses are discussed in Section 3. Section 4 provides a discussion of sediment analyses. References are presented in Section 5. A first draft of this Hydrology Report was submitted to the AEA for review on August 9, 2012. That report included discussions of both hydrologic and hydraulic analyses preformed for the project. Review comments from the AEA were received on August 15. A final draft report addressing the AEA’s comments was submitted on August 28. This final report presents updated hydrologic analyses performed using provisional stream gage data for the 2012 water year, and hydrologic analysis updates addressing design changes that have occurred since the submittal of the August 2012 final draft report. Hydraulic analysis efforts will be presented in a separate document. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 3 May 2013 2 METEOROLOGIC AND HYDROLOGIC DATA A good deal of meteorologic and hydrologic data is available for the Bradley Lake area. Much of these data have been collected since the initiation of the Bradley Lake Hydroelectric project from stations located within the watersheds of the Bradley River and Battle Creek. Available meteorologic and hydrologic data were collected and reviewed. Individual datasets were assessed for completeness, length of record, coincidence with other datasets, and usefulness for the hydrologic analyses. Available data are summarized below. 2.1 Meteorologic Data Precipitation and temperature data are available for three Natural Resources Conservation Service (NRCS) snow course / snowpack telemetry (SNOTEL) sites. Two of these — Middle Fork Bradley River and Nuka Glacier - have more than 20 years of records available, while another — Kachemak Creek — has about 8 years of available records. The quality and completeness of the NRCS data are good, and the data are available on the NRCS website. Precipitation and temperature data are also available for three National Weather Service (NWS) meteorological stations — Middle Fork Bradley River, Bradley River, and Upper Nuka Glacier — which have periods of record ranging from 7 to 10 years. The quality and completeness of the data varies from fair to poor, with numerous data gaps and poor correlation to the NRCS data. These data are available through the Hydrometeorological Automated Data System (HADS). Table 1 summarizes pertinent information on the six meteorological stations, and their locations are shown in Figure 4. 2.2. Hydrologic Data Hydrologic data are available for six U.S. Geological Survey (USGS) stream gaging stations in the Battle Creek watershed. Of these six gaging stations, four have continuous flow records available, and two of those stations are currently in operation. Stream gaging was conducted in the Battle Creek watershed for about two years in the early 1990s, presumably in support of earlier efforts on the Battle Creek Diversion project. These gages included the following: e 15238985 - Battle Creek Near Tidewater Near Homer, Alaska (Battle Creek Near Tidewater) e 15238984 — South Fork Battle Creek Near Homer, Alaska (South Fork Battle Creek) e 15238982 - Battle Creek Below Glacier Near Homer, Alaska (Battle Creek Below Glacier) Gaging was restarted in 2010 at two locations - 15238986 - Battle Creek 1.0 Mile Above Mouth Near Homer, Alaska (Battle Creek Above Mouth) and at the Battle Creek Below Glacier gage site. The Battle Creek Above Mouth gage is located in the lower watershed near Kachemak Bay. The elevation of the gage is 63 feet. The contributory watershed of the gage has been measured to be 21.3 square miles (the USGS lists the contributory area as 22.8 square miles). The location of the Battle Creek Near Tidewater gage that was operated in the 1990s was 0.5 stream miles upstream of the Battle Creek Above Mouth gage site, and was not reoccupied when gaging was resumed in 2010. The elevation of the Battle Creek Near Tidewater gage was 90 feet. The contributory watershed of the gage has been measured to be 19.1 square miles (the USGS lists Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 6 May 2013 the contributory area as 21 square miles). The locations of the Battle Creek Above Mouth and Battle Creek Above Tidewater gages are relatively close together, and the difference in the contributory drainage basins of the two gages is approximately 12 %. No major tributaries join the stream between the two gage sites. Due to the scarcity of gage data on lower Battle Creek and the importance of these gage data in understanding the hydrology of Battle Creek, the two gages are considered to be roughly equivalent, and their data have been combined and analyzed as a single dataset for the Battle Creek Above Mouth gage. The second gaging site that was restarted in 2010 - Battle Creek Below Glacier - is located within the upper portion of the watershed, a relatively short distance downstream of the proposed diversion site. The elevation of the gage is 780 feet. The contributory watershed of the gage has been measured to be 10.8 square miles (the USGS lists the contributory area as 11.8 square miles). The watershed above the gage contains the (informally named) Battle Glacier. A gage was operated on the South Fork of Battle Creek in the early 1990s, but was not restarted in 2010. That gage was located in the lower watershed near the confluence of the South Fork and main stem of Battle Creek. The elevation of the gage was 100 feet. The contributory watershed of the gage has been measured to be 6.1 square miles (the USGS lists the contributory area as 6.5 square miles). USGS topographic mapping shows glaciers present in the headwaters of the basin, but analyses of aerial imagery and observations from helicopter overflights have shown that no glaciers are present (see Appendix A). Other important USGS gage sites include station 15239050 — Middle Fork Bradley River Near Homer, Alaska (Middle Fork Bradley River) and station 15238978 - Battle Creek Diversion Above Bradley Lake Near Homer, Alaska (Battle Creek Diversion). Both of these gage sites are located near diversions that direct the flow of the streams to Bradley Lake. The elevation of the Middle Fork Bradley River gage site is 2,300 feet. The contributory basin of the gage is 9.2 square miles. The period of record for this gage is 33 years and it is still under operation. The Battle Creek Diversion gage records flows from the East Fork of Upper Battle Creek, which is now tributary to Bradley Lake and the Bradley River rather than Battle Creek. The elevation of the gage is 1,350 feet. The contributory watershed of the gage is 1.0 square miles. The gage has a period of record of 20 years and is still under operation. Under the current plan, the flow of the East Fork of Battle Creek will be captured in the new canal system near the top of the lower canal transition, and will no longer flow past the existing gage site. To address this, a new gage that records the combined diverted flows of the West, Middle, and East Forks of Upper Battle Creek will be installed near the downstream end of the lower canal transition, and will replace the existing Battle Creek Diversion gage. It is possible that an additional gage will be installed that allows the measurement of the flow of the East Fork of Battle Creek where is joins the new canal. However, at the time of completion of this final H&H Report, a post-construction gaging plan was still under development. Table 1 summarizes pertinent information on the various USGS stream gages, and their locations are shown in Figure 4. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 7 May 2013 im un o a 3 2 e co S0KO7 S0KOS 17DC8798 DEOB45F4 DEOBS682 594329150513700 15238982 594444150510700 15238978 15238985 15238986 15239001 15239000 15239050 15238984 15238990 15238648 Z:\project\\1158.27 AEA Bradley Lake Hydro Preliminary Design\\Civil\DESIGN\ Hydrology And Hydraulics\ACAD\1158.27 - Figs & Tables.dwg er Station Name Type Precipitation/ Kachemak Creek Temperature Precipitation/ Temperature Middle Fork Bradley Precipitation/ Nuka Glacier Temperature Precipitation/ Temperature Bradley River Below Dam Near Homer Precipitation/ Temperature Middle Fork Bradley River Near Homer Upper Nuka River Near Park Boundary Near Homer Precipitation/ Temperature Battle C at Glacier Nr Homer AK Flow - Points Battle C BI Glacier Nr Homer AK Flow - Continuous Battle C BI Proposed Minor Diversion Nr Homer AK Battle C Div Ab Bradley Lk Nr Homer AK Flow - Points Flow - Continuous Battle C Nr Tidewater Nr Homer AK Flow - Continuous Battle C 1.0 Mi Ab Mouth Nr Homer AK Flow - Continuous Period of Record NRCS NRCS 8/04/2004 - Present 10/01/1990 - Present 10/01/1990 - Present 10/31/2005 - Present 4/29/2003 - Present 11/02/2002 - Present 8/01/2011 7/23/1991 - 10/13/1993, 8/01/2010 - Present 5/30/1991 - 2/06/1992 6/03/1992 - Present 7/24/1991 - 9/30/1993 7/01/2010 - Present 10/01/1989 - Present USGS 8/13/1958 - 9/21/1990 USGS 10/01/1979 - Present USGS USGS 7/24/1991 - 10/13/1993 10/01/1979 - Present 9/01/1984 - Present Qual Good Good Fair Good KA = / ORITY ME ENERGY AUTH BATTLE CREEK DIVERSION HYDROLOGY REPORT METEOROLOGICAL AND STREAM GAGE STATION SUMMARY APRIL 2013 TABLE 1 DEVELOPED BY: RaM CONSULTAN’ Inc. Plotted 4/12/2013 4:26 PM by Kim Anderson rs Lar SS ass w PMT 7 BRADLEY LAKE BC-2 15238982 BATTLE CREEK BELOW GLACIER BC-3 15238984 SOUTH FORK BATTLE CREEK BC—4 15238985 BATTLE CREEK NEAR TIDEWATER Bc-5 15238986 BATTLE CREEK 1.0 MILES ABOVE MOUTH BC-6 | 59444150511000 |BATTLE CREEK BELOW MINOR DIVERSION BC-—7 |594329150514000|BATTLE CREEK AT GLACIER BR-1 15239000 BRADLEY RIVER BR-2 15239001 BRADLEY RIVER BELOW DAM BR-3 170C8798 BRADLEY RIVER BELOW DAM MF-1 15239050 MIDDLE FORK BRADLEY RIVER MF—2 DEOB45F4 MIDDLE FORK BRADLEY RIVER MF-3 1064 MIDDLE FORK BRADLEY RIVER UPPER BRADLEY RIVER NEAR NUKA NG-1 15238990 GLACIER UPPER NUKA RIVER NEAR PARK NG-2 15238648 BOUNDARY NG—3 DEOBS682 UPPER NUKA NG—4 1037 NUKA GLACIER KACHEMAK CREEK | KEY NUMBER NAME i] A BC-1 15238978 BATTLE CREEK DIVERSION ABOVE i @ USGS STREAM GAGE ®@ NWS MET STATION @ NRCS MET STATION ; — GAGE WATERSHED F% nc-3 aN BOUNDARY a BATTLE CREEK DIVERSION HYDROLOGY REPORT METEOROLOGICAL STATION AND STREAM GAGE LOCATIONS APRIL 2013 FIGURE 4 DEVELOPED BY: Z\project\ 1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\1158.27 — NEW Battle Creek Watershed-iT.dwg REM CONSULTAN 3 HYDROLOGIC ANALYSES 3.1 Battle Creek Basin Overview The Battle Creek Diversion project is located in the Kenai Mountains near the southern end of the Kenai Peninsula. This area experiences a maritime climate strongly influenced by the Gulf of Alaska to the south and, to a lesser extent, Cook Inlet to the west. As a result, temperature variations are relatively small throughout the year. Summers are relatively cool and winters are relatively warm. Precipitation is high and is strongly influenced by elevation. Orographic effects cause storms in the Gulf of Alaska to drop large amounts of precipitation as they move across and over the rugged Kenai Mountains. Values of mean annual precipitation in the Bradley Lake watershed range from 40 inches near tidewater to more than 120 inches in the high peaks. A good deal of the annual precipitation falls as snow in the upper elevations of the mountains, and glaciers are common in the region. The maritime influence can also produce winter warming periods resulting in rain at higher elevations and short-term increases in streamflow. The Battle Creek watershed covers an area of 21.6 square miles. Elevations in the watershed range from sea level to just under 5,200 feet. The axis of the watershed trends from the southeast to the northwest between the headwaters and the mouth, and a large proportion of the basin has a generally north-facing aspect (see Figures 2 and 4). The Battle Glacier occupies the upper reaches of the Battle Creek watershed. A comparison of topographic mapping, recent imagery, and field observations show that most glaciers in the project area have receded over the past 60 years. Between 1951 and 2011, the terminus of the Battle Glacier has receded approximately 3,500 feet, and the area of the glacier has decreased by 0.5 square miles (based on a comparison of 2011 project imagery and USGS topographic mapping developed from 1951 aerial photography). The current area of the Battle Glacier is 3.2 square miles. The percentage of the Battle Creek watershed covered by the Battle Glacier has decreased from 17 percent to 15 percent over the past 60 years. The channel of Battle Creek extends approximately 8.3 miles from the terminus of the Battle Glacier to tidewater. From the terminus of the glacier at stream mile (SM) 8.3 to approximately SM 6.6, Battle Creek flows through the outwash plain of the glacier, which is composed primarily of silt to gravel and cobble-sized material. The channel pattern through this section varies from braided to split-channel. Between SM 6.6 and SM 5.5, the stream flows within a deep canyon with a boulder and bedrock bed. Below SM 5.5, the channel gradient is typically very steep all the way to SM 1.8, with a relatively straight channel pattern, numerous canyon sections, several waterfalls, and a typically coarse boulder and bedrock streambed. There are a few short sections within this 3.7-mile stretch of the stream where Battle Creek flows over structural benches, the longitudinal gradient drops, gravel bars are formed, and the channel develops a meandering and split-channel form. Between SM 1.8 and 1.2, the channel begins to gradually transition to a lower gradient form, but boulder-sized substrate is still common, and the channel pattern in essentially straight. Between SM 1.2 and 0.5, the stream has a meandering, split channel pattern, with sand and gravel-sized streambed sediments. The lower 0.5 miles of the stream lie within the Battle Creek estuary, and the deltaic distributary channel network and fine-grained streambed sediments in that reach are characteristic of a tidally-dominated system. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 10 May 2013 The portion of Battle Creek above SM 5.4 is referred to as Upper Battle Creek. The West Fork of Upper Battle Creek is the largest tributary to Upper Battle Creek, and its headwaters include the Battle Glacier. The Middle Fork of Upper Battle Creek has a West and East Branch, and is much smaller than the West Fork of Upper Battle Creek. The East Fork of Upper Battle Creek has been diverted to Bradley Lake and is no longer within the Battle Creek watershed. Battle Creek has one major tributary — the South Fork of Battle Creek — which joins the main stem of the stream between SM 1.7 and 1.8. This 6.1-square mile basin ranges in elevation from about 100 feet at the confluence with Battle Creek to 4,800 feet in its headwaters. Recent aerial observations within the basin confirm that there are no glaciers present within the drainage, although glaciers are shown as being present on USGS topographic mapping. The channel of the South Fork of Battle Creek extends approximately 6.4 miles from its headwaters in a high cirque bowl to the confluence with Battle Creek. The upper branches of the stream cascade from glacially-carved basins, and coalesce on a broad, low-gradient section of the valley that extends between SM 3.9 (measured upstream from the confluence with the main channel of Battle Creek) and SM 2.5. The channel pattern in this area varies from braided to split-channel and appears to be strongly influenced by past beaver activity in the valley. Below SM 2.5, a short canyon section with a waterfall is followed by a 0.5-mile section of lower gradient stream with a gently meandering pattern. From SM 2.0 to the confluence with Battle Creek, the channel is typically very steep, with a number of deep canyon sections, a relatively straight channel pattern, and a boulder and bedrock streambed. 32 Battle Creek Gage Data and Hydrographs Gage data for three Battle Creek stream gages — Battle Creek Above Mouth, Battle Creek Below Glacier, and South Fork Battle Creek — have been plotted in Figures 5A, 5B, and 6, along with data for the diverted East Fork of Upper Battle Creek (Battle Creek Diversion). Average, minimum, and maximum daily flow values have been plotted along with mean monthly flow values for the period of record of each gage. The Battle Creek Below Glacier and Battle Creek Above Mouth gage data are shown in Figures 5A and 5B, respectively. The Battle Creek Diversion and South Fork Battle Creek gage data are shown in Figure 6. Some hydrologic characteristics are common among the four sites. Flows are low during the winter period of November through March when average basin temperatures are below freezing. In April, flows begin to increase as basin temperatures begin to rise above freezing. The majority of flow at all gage sites occurs during the period of May through October. At the higher elevation gage sites — Battle Creek Below Glacier (with a mean basin elevation of 2,950 feet) and Battle Creek Diversion (with a mean basin elevation of 2,920 feet) — more than 90 percent of average annual flows occur during the May through October period. Because of this, the period of May 1 through October 31 has been selected as the targeted operational period for the Battle Creek Diversion project. The actual operational period will vary slightly from year to year depending on the depth and distribution of the snowpack, as well as the timing of breakup in the spring and freeze-up in the fall. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 11 May 2013 Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\1158.27 - Figs & Tables.dwg Plotted 4/16/2013 11:00 AM by Irene Turletes 15238982 Battle Creek Below Glacier —— Maximum Daily Flow —— Minimum Daily Flow Average Daily Flow —— Monthly Average Flow 3 Discharge [cfs] 0 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep NOTES: PERIOD OF RECORD SHOWN IS 7/23/1991 - 10/13/1993, 8/1/2010 - 9/30/2012. GAGE ELEVATION IS 780 FT. 1-Nov 1-Dec /= ALASKA MED ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT BATTLE CREEK BELOW GLACIER GAGE DATA APRIL 2013 FIGURE SA DEVELOPED BY: RaM CONSULT, Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\1158.27 - Figs & Tables.dwg Plotted 4/16/2013 11:01 AM by Irene Turletes 15238986 Battle Creek Above Mouth Maximum Daily Flow —— Minimum Daily Flow Average Daily Flow —— Monthly Average Flow ¢ & e © 1200 5 £ 5 2 a 0 + } | } } t 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct NOTES: PERIOD OF RECORD SHOWN IS 7/24/1991 - 9/30/1993 FROM DISCONTINUED USGS GAGE 15238985 BATTLE CREEK AT TIDEWATER, AND 7/1/2010 - 9/30/2012 FOR USGS GAGE 15238986 BATTLE CREEK 1 MILE ABOVE MOUTH. ELEVATION OF THE BATTLE CREEK ABOVE MOUTH GAGE IS 63 FT. = E> ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT BATTLE CREEK ABOVE MOUTH GAGE DATA APRIL 2013 FIGURE 5B DEVELOPED BY: RAM CONBULTAN’ Inc. 15238978 Battle Creek Diversion —— Maximum Daily Flow —— Minimum Daily Flow Average Daily Flow Average Monthly Flow Discharge [cfs] 8 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct 1-Nov 1-Dec NOTES: PERIOD OF RECORD SHOWN IS 6/3/1992 - 9/30/2012. GAGE ELEVATION IS 1,350 FT. 15238984 South Fork Battle Creek —— Maximum Daily Flow —— Minimum Daily Flow Average Daily Flow Average Monthly Flow Discharge [cfs] 0 Z:\project\\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\1158.27 - Figs & Tables.dwg 1-Jan 1-Feb 1-Mar 1-Apr 1-Jun 1-Jul NOTES: PERIOD OF RECORD SHOWN IS 7/24/1991 - 10/13/1993. GAGE ELEVATION IS 100 FT. = = (MED ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT BATTLE CREEK DIVERSION AND SOUTH FORK GAGE DATA APRIL 2013 FIGURE 6 DEVELOPED BY: RaM CONSULTAN’ Inc. Plotted 4/17/2013 2:52 PM by Kim Anderson Peak flows typically occur within a 2-month period between early August and early October when Gulf of Alaska storms are common and rainfall is heaviest. However, some early winter rainfall-induced peaks have been recorded in November and December, reflecting the influence of the warm maritime climate. Glaciers exert a strong influence on basin hydrology. The hydrograph of a typical glacial stream shows a sudden and strong rise in flow in the spring as winter snow melts, followed by a continual rise into the middle of the summer, and then a gradual decline throughout the fall. The hydrographs of both the Battle Creek Above Mouth and Battle Creek Below Glacier gages follow this general pattern. The presence of glaciers within a basin tends to decrease annual and monthly variations in runoff. Glaciers tend to compensate for year-to-year variations in runoff by producing more meltwater in a warm and dry year than in a wet and cool one, thereby balancing lower rainfall runoff volumes with higher meltwater volumes. Glaciers also tend to produce a delay of the maximum seasonal flow by storing spring meltwater and producing peak meltwater volumes in late summer. The most important comparison to be made between the Battle Creek Above Mouth and Battle Creek Below Glacier gage data is with respect to the magnitude of the average monthly flows for the period of June through October. For that period, the average monthly flow rate for the Battle Creek Below Glacier gage data constitutes a significant majority of the average monthly flow rate seen at the Battle Creek Above Mouth gage (see Figures 5A and 5B, and Table 2). This is especially important since the contributory basin above the Battle Creek Below Glacier gage (10.8 square miles) is only half the size of the basin above the Battle Creek Above Mouth gage (21.3 square miles), yet it produces a majority of the water seen near the mouth of the stream in terms of average monthly flows for the June to October period. Also shown in Table 2 is the difference in average monthly flows of the two gages, which represents the flows generated in the 10.5-square mile portion of the Battle Creek basin between the two gages. Average Monthly Flows [cfs] Gage Jan _| Feb | Mar | Apr | May | Jun Jul Aug | Sep Oct | Nov | Dec Below Glacier* | 8.3 5.7 5-1 11.3 54.0 145.1 | 187.8 | 209.9 | 159.4 | 66.7 23.1 14 Above Mouth 19.4 | 14.8 11.1 38.8 120.0 | 229.4 | 277.5 | 284.3 | 238.6 | 108.8 | 49.0 36.6 Between Gages | 11.1 9.1 6.0 27.5 66.0 84.3 89.7 74.4 79.2 42.1 25.9 22.6 *The elevation of the Below Glacier gage is 780 feet, which is approximately 920 vertical feet below the proposed point of diversion of the West Fork of Upper Battle Creek. Table 2 — Historical Average Monthly Flows for the Battle Creek Below Glacier and Battle Creek Above Mouth Gages, and the Basin Between the Gages The high hydrologic productivity of the basin above the Battle Creek Below Glacier gage can be clearly seen when average monthly discharge data are normalized by dividing discharge values by the area of the contributory basin above each gage. Figure 7 shows normalized average monthly discharge data for the four Battle Creek stream gages. For the period of June through August, normalized average monthly discharge values are by far the highest for the Battle Creek Below Glacier gage data. These high normalized discharge values reflect the effects of higher precipitation rates at higher elevations. The high rates also reflect the effects of water produced Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 15 May 2013 from the melting of snow and ice during the warm summer months, which help to sustain flows after the spring snowmelt peak has passed, but before the heavy rains of late summer and fall have begun. The correlation of higher precipitation with higher elevation can also be seen in the normalized data for the Existing Diversion gage data. The mean elevation of the basin above that gage is 2,920 feet, and it shows high normalized discharge rates during the spring from snowmelt. However, because of the lack of glaciers in the basin above the gage, average monthly flows drop off steeply after the passing of the spring snowmelt peak. The lower normalized discharge values recorded at the South Fork Battle Creek gage probably reflect significantly lower annual precipitation totals for that basin than for the basin above the Battle Creek Below Glacier gage. This difference in precipitation is due to differences in both elevation and geographic location. The mean elevation of the basin above the South Fork Battle Creek gage is 2,100 feet, which is significantly lower than the mean basin elevation of 2,950 feet for the Battle Creek Below Glacier gage. Additionally, although meteorologic data are not available for the South Fork of Battle Creek basin, regional contours of mean annual precipitation show values for the South Fork of Battle Creek basin that are approximately 75 percent of the values for the basin of the Battle Creek Below Glacier gage. The geology of the area in which the diversion and canals are to be constructed is characterized by bedrock with thin layers of overburden. Groundwater is assumed to provide a minimal component of streamflow in the project basin, and effects on the groundwater table below the project are expected to be minor. 3.3. Duration Flow and Volumetric Yield Analyses The economic viability of the Battle Creek Diversion project is centered on how much water the project will divert to Bradley Lake in an average year. It is therefore critical to estimate the average annual volumetric yield for the project basin during the targeted operational period of May through October. It is also important to develop a flow-duration curve (a cumulative frequency curve that shows the percent of time specified discharges were equaled or exceeded during a particular period) in order to understand the distribution of flows throughout an average year. 3.3.1. Comparison of Battle Creek Below Glacier Gage and Diversion Project Basins There are no continuous stream gage data available for the diversion project basin. However, the Battle Creek Below Glacier gage has essentially complete gage records for the targeted May through October time period for three years — 1992, 1993, and 2011, and provisional gage data are also available for the 2012 water year, which extends through September 2012. If the hydrologic characteristics of the basin above the Battle Creek Below Glacier gage can be considered similar to those of the project basin, then the gage data can be applied to the project basin after accounting for differences in drainage areas. This technique is known as the drainage area ratio method. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 16 May 2013 Battle Creek Watershed Normalized Discharge Comparison 7 — —— Below Glacier South Fork Above Mouth Existing Diversion t e a e °o Discharge [cfs/mi*] Normalized Discharge [cfs/mi?] Basin Area [mi?] Below Glacier 10.8 i is F ; 5.0 | 13.5 | 17.4 South Fork 6.1 i < F i 6.9 8.9 V2 Above Mouth 21.3. i 7 A sl 5.6 | 10.8 Exist. Diversion 1.0 i F E 3 3.0 12:5 Gage Name May | Jun Jul Aug = ALASKA < {= ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT NORMALIZED BATTLE CREEK GAGE DATA APRIL 2013 FIGURE 7 DEVELOPED BY: RaM CONSULTAN A comparison of the project basin and the basin above the Battle Creek Below Glacier gage is presented in Table 3. The project basin is similar to the basin above the gage, but is somewhat smaller in area, has a higher mean basin elevation, and a higher percentage of glacier coverage. Because it has a higher mean basin elevation, the project basin is expected to receive slightly higher amounts of precipitation than the gage basin. Therefore, hydrologic estimates made using the drainage area ratio method should produce conservative estimates of flow for the project basin. Aves Range of Mean Basin Area of Glacier Basin Elev. Elev. Glaciers Coverage [mi] [ft] [ft] [mi] [%] Diversion Project Basin 8.2 1,400 - 5,200 3,285 3.2 39 Battle Creek Below 10.8 | 780-5,200 2,950 3.2 30 Glacier Gage Table 3 — Basin Comparison for the Battle Creek Below Glacier Gage and Diversion Project Basins Using the four years of data for the Battle Creek Below Glacier gage, the volumetric yield during the proposed May through October operating period was calculated, and then extrapolated to the project basin using the drainage area ratio method. The results, presented in Table 4, show a calculated average yield of 36,900 acre-feet for the project basin for the brief period of record. Battle Creek Below Glacier Gage | _, Diversion. (10.8 mi?) Project Basin Year (8.2 mi‘) Raw Volume | Norm. Volume Volume [acre-ft] [acre-ft/mi’] [acre-ft] 1992 34,600 3,200 26,400 1993 61,600 5,700 47,000 2011 47,200 4,400 36,000 2012 50,000* 4,600* 38,200* Average 48,400 4,500 36,900 *Volumes for 2012 do not include October 2012 gage data, which were not available prior to completion of the final H&H report. Table 4 — Calculated Volumetric Yield for May through October for the Battle Creek Below Glacier Gage and Diversion Project Basin 3.3.2. Comparison of Battle Creek Below Glacier and Middle Fork Bradley River Because the period of record for the Battle Creek Below Glacier gage is relatively short and there is a 17-year gap between the data collected in the 1990s and the data collected since the gage was restarted, it is unknown if the data provide a good representation of the long term variability of the basin. This uncertainty makes it difficult to know how much confidence to place in the estimate of average annual volumetric yield presented above. HDR, in a May 15, 2012 draft memorandum titled Flow Correlation Between Battle Creek and Middle Fork Bradley River, and Long Term Variation of Middle Fork Bradley River Flows, suggested that the longer term record Bradley Lake Hydro — Battle Creek Diversion May 2013 Final Hydrology Report R&M Consultants, Inc. 18 of the Middle Fork Bradley River gage can be used as a proxy for runoff in the diversion project basin. To test this suggestion, the Middle Fork Bradley River gage data have been examined in detail. The upper portion of the Middle Fork Bradley River has been diverted into the channel of Marmot Creek and now flows into Bradley Lake over the Marmot Creek Falls rather than to the lower Bradley River. The Middle Fork Bradley River gage and the adjacent NRCS SNOTEL site are located between 1,000 and 2,000 feet upstream of the diversion point. Characteristics of the basin above the Middle Fork Bradley River gage are presented in Table 5 and compared with the characteristics of the Battle Creek Below Glacier gage and project basins. The basin is intermediate in size between the project basin and the basin of the Battle Creek Below Glacier gage. The percentage of coverage by glaciers in the Middle Fork Bradley River basin (based on aerial observations made in July 2012; see Appendix A) is approximately half of that of the basin of the Battle Creek Below Glacier gage. The mean elevation of the basin above the Middle Fork Bradley River gage is higher than either of the other two basins, which might lead to the expectation of higher rates of precipitation. However, meteorological station data in the Middle Fork Bradley River basin show a value of 54 inches for mean annual precipitation near the gage site, which is significantly less than the regional estimates of 80 inches for the Battle Creek Below Glacier gage basin and 85 inches for the project basin. AG Range of Mean Basin Area of Glacier Basin ea Elev. Elev. Glaciers Coverage [m7] [ft] [ft] [mi] [%] Diversion Project Basin 8.2 1,400 - 5,200 3,285 3.2 39 eee 10.8 | 780- 5.200 2.950 3.2 30 Glacier Gage Eos Fors Braiiley 9.2 | 2,300-5,500| 3,855 13 14 River Gage Table 5 — Basin Comparison for Diversion Project Basin, Battle Creek Below Glacier Gage, and Middle Fork Bradley River Gage Normalized average daily flow data for the Battle Creek Below Glacier and Middle Fork Bradley River gages (discharge values divided by basin area) are presented for the period of coincident record in Figures 8A and 8B. Figure 9 presents maximum, minimum, and average daily flows, and average monthly flows for the full period of record for each gage. Normalized average monthly flow data for both gages are presented in Figure 10. Mean monthly flow values for both the full period of record and coincident period of record are presented for the Middle Fork Bradley River gage data in Figure 10. Final Hydrology Report R&M Consultants, Inc. 19 Bradley Lake Hydro — Battle Creek Diversion May 2013 Normalized Average Daily Flow: Middle Fork Bradley River vs. Battle Creek Below Glacier (August 1991 - October 1993) —— Middle Fork Bradley River Battle Creek Below Glacier vil\DESIGN\ Hydrology And Hydraulics\ACAD\1158.27 - Figs & Tobles.dwg Discharge [cfs/mi] il oy a OS SX oY om ov oy ov om S ” PP DP PP SP DP PP SP 5 SL NOS x ee ak) ee we FX FW KF FE Ww SF yw vv 8 KF FX SF VF Fy Sa 158.27 AEA Bradley Lake Hydro Preliminary Des NOTES: THE ELEVATION OF THE MIDDLE FORK BRADLEY RIVER GAGE IS 2,300 FT. THE ELEVATION OF THE BATTLE CREEK BELOW GLACIER GAGE IS 780 FT. Z:\project\1 BATTLE CREEK DIVERSION HYDROLOGY REPORT NORMALIZED AVERAGE DAILY FLOW: MIDDLE FORK BRADLEY RIVER VS BATTLE CREEK APRIL 2013 ; FIGURE 8A DEVELOPED BY: RAM CONSULT) Inc. Plotted 4/11/2013 5:47 PM by Kim Anderson Normalized Average Daily Flow: Middle Fork Bradley River vs. Battle Creek Below Glacier (August 2010 - September 2012) —— Middle Fork Bradley River —— Battle Creek Below Glacier 00 o a So £ E ry z @ = c | S 2 a S 2S © © © NY NY AY NY LIN’ i ed ; ; gee ; SI SSID cell Sel: Sy Ryerss ; 5 bs sy) yw” ZB eX s xe ¥ < ww sy ON RS Cea Sau, we FF Ww & | | | L 3 = NOTES: THE ELEVATION OF THE MIDDLE FORK BRADLEY RIVER GAGE IS 2,300 FT. THE ELEVATION OF THE BATTLE CREEK BELOW GLACIER GAGE IS 780 FT. f= ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT NORMALIZED AVERAGE DAILY FLOW: MIDDLE FORK BRADLEY RIVER VS BATTLE CREEK APRIL 2013 FIGURE 8B DEVELOPED BY: RaM CONSULTAN inc. 15238982 Battle Creek Below Glacier —— Maximum Daily Flow —— Minimum Daily Flow Average Daily Flow —— Monthly Average Flow Discharge [cfs] - Figs & Tables.dwg 0 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep NOTE: PERIOD OF RECORD SHOWN IS 7/23/1991 - 10/13/1993, 8/1/2010 - 9/30/2012. GAGE ELEVATION IS 780 FT. 15239050 Middle Fork Bradley River —— Maximum Daily Flow — Minimum Daily Flow —— Average Daily Flow ——Monthy Average Flow Discharge [cfs] Z:\project\1158.27 AEA Bradley Loke Hydro Preliminary Design\Civii\DESIGN\Hydrology And Hydraulics\ACAD\ 1158.27 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct NOTE: PERIOD OF RECORD SHOWN IS 10/01/1979 - 9/30/2012. GAGE ELEVATION IS 2,300 FT. /= ALASKA (MED ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT BATTLE CREEK BELOW GLACIER AND MIDDLE FORK BRADLEY RIVER GAGE DATA APRIL 2013 : FIGURE 9 DEVELOPED BY: RAM CONSULT: Plotted 4/11/2013 5:48 PM by Kim Anderson Battle Creek Below Glacier & Middle Fork Bradley River Watersheds Normalized Mean Monthly Flow Comparison —— Below Glacier —— Middle Fork (Full Period of Record) ——— Middle Fork (Coincident Period of Record) e a Figs & Tables.dwg Discharge [cfs/mi?] b o Normalized Discharge [cfs/mi?] | Gage Name aie Below Glacier | 10.8 5 | 0.5 0 14.8 24 Middle Fork (Full Period) ° ‘ ehrettetettt Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\ 1158.27 ME ENERGY AUTHORITY [= ALASKA BATTLE CREEK DIVERSION HYDROLOGY REPORT BATTLE CREEK BELOW GLACIER AND MIDDLE FORK BRADLEY RIVER NORMALIZED GAGE DATA APRIL 2013 FIGURE 10 DEVELOPED BY: RaM CONSULTAN' Inc. Plotted 4/15/2013 3:36 PM by Kim Anderson Normalized flow values for the two gages presented in Figure 8 show a moderate correlation between the datasets for the coincident period of record. Flows on the Middle Fork Bradley River typically lag behind those in the upper Battle Creek basin in the spring. This probably reflects differences in the mean elevation of the two basins and the consequent differences in the timing of the initiation of spring snowmelt. In general, normalized flows in the Middle Fork Bradley River basin are lower than the coincident flows in the Battle Creek basin. Peak flows are generally coincident in time, but not in all cases, and not all peak flows recorded at one gage are paired with a peak flow at the other gage. These differences in normalized flow values and peak flow characteristics reflect differences in the elevation, orientation, and geographic location of the two basins, and especially differences in the amount of precipitation and the weather patterns that the two basins are subject to. The average daily and monthly flow data for the two gages presented in Figure 9 show moderate correlation between the datasets for the full period of record for each gage. The highest maximum daily flows (reflective of peak flow events) occur in September and October in the Middle Fork Bradley River basin, while the highest mean monthly flows occur in July. In contrast, the highest maximum daily flows in the upper Battle Creek basin occur earlier (in August and September) than in the Middle Fork basin, and highest mean monthly flows occur later (in August). Some of the differences seen between the two datasets in Figure 9 may be the result of variability related to the much longer period of record for the Middle Fork Bradley River gage, rather than differences in hydrologic characteristics. Normalized mean monthly flow values for the two basins presented in Figure 10 show values within the coincident period of record that are greater in all cases for the Battle Creek Below Glacier gage than those for the Middle Fork Bradley River gage. This same trend is noted when comparing the Battle Creek Below Glacier gage data to those for the full period of record of the Middle Fork Bradley River gage, with the exception of the month of July. The maximum mean monthly flow occurs in August for the upper Battle Creek basin, and in July for the Middle Fork Bradley River basin. The two periods of Middle Fork Bradley River gage data appear to be relatively similar. This suggests that the hydrologic conditions during the coincident period of record were not significantly different from the long term record. The comparisons of gage data discussed above suggest a moderate degree of correlation between the Battle Creek Below Glacier and Middle Fork Bradley River gages. A linear regression was performed of average daily flow data for the two datasets for the coincident period of record. The results of the regression analysis are shown in Figure 11. The coefficient of determination of the regression (R’) is 0.80. This means that 80 percent of the variation in the Battle Creek Below Glacier gage data can be explained by the computed linear relationship (Y = 1.187X + 12.97), while 20 percent of the variation remains unexplained. This result confirms that there is a moderate degree of correlation between the two datasets. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 24 May 2013 Z:\project\\1158.27 AEA Bradley Loke Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\1158.27 - Figs & Tobles.dwg Plotted 4/11/2013 5:50 PM by Kim Anderson Battle Creek Below Glacier Discharge [cfs] 3 Linear Regression Plot: Middle Fork Bradley River vs Battle Creek Below Glacier y = 1.1866x + 12.968 R? = 0.7961 400 500 Middle Fork Bradley River Discharge [cfs] NOTE: REGRESSION IS FOR THE PERIOD OF COINCIDENT RECORD FOR THE TWO GAGES (7/23/1991-10/13/1993, 8/1/2010 - 9/30/2012). APRIL 2013 FIGURE 11 @ Middle Fork Bradley River vs Battle Creek Below Glacier —— Linear (Middle Fork Bradley River vs Battle Creek Below Glacier) BATTLE CREEK DIVERSION HYDROLOGY REPORT LINEAR REGRESSION: MIDDLE FORK BRADLEY RIVER VS BATTLE CREEK BELOW GACIER DEVELOPED BY: RAM CONSULT, Inc. 3.3.3 Record Extension of the Battle Creek Below Glacier Gage Data The record of the Battle Creek Below Glacier gage was extended using the long-term, 33-year record of the Middle Fork Bradley River gage as an index station. This was done by applying the computed linear relationship from the regression analysis to the long-term Middle Fork Bradley River average daily flow data to produce a synthesized long-term record for the Battle Creek Below Glacier gage. This method is sensitive to outliers and tends to over-predict the highest peak flows, but otherwise provides a reasonable estimate of average daily flows. Using the synthesized long-term record for the Battle Creek Below Glacier gage data, the volumetric yield for the operational period of May through October was computed for each of the 33 years. Using the drainage area ratio method, the computed annual yield estimates for the gage data were converted to the yield expected for the 8.2-square mile diversion project basin (see Figure 12). The computed yields for 1992, 1993, 2011, and 2012 from the original gage data (refer to Table 4) were substituted for the estimates from the extended record for those three years. The average annual volumetric yield for the operational period of the synthesized 33-year record was then computed to be 35,400 acre-feet. 3.3.4 Flow Duration Curves for the Project Basin Flow duration curves were developed from the synthesized long-term record for the project basin using the U.S. Army Corps of Engineers HEC-SSP Statistical Software Package. Curves were developed for both the full year and for the operational period of May through October. For the full year, the average flow is computed to be 58 cubic feet per second. For the operational period, the average flow is computed to be 99 cubic feet per second. The two flow duration curves are shown in Figures 13 and 14. The flow duration curves show the percent of time that specified discharges are equaled or exceeded during a given period. For example, for the entire year, the project basin is expected to have a discharge of at least 110 cubic feet per second for 20 percent of the time (see Figure 13). In contrast, for the operational period, the project basin is expected to have a flow of at least 150 cubic feet per second for 20 percent of the time (see Figure 14). 3.3.5 Post-Construction Hydrology Post-construction effects on basin hydrology are discussed in R&M’s May 2013 Technical Memorandum titled Battle Creek Diversion — Supplemental Hydrologic Analyses of Post- Construction Flows on Battle Creek. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 26 May 2013 Mean = 35,400 acre-ft —— Project Basin Yield (May-Oct) —— Mean Basin Yield (May - Oct) Volume [acre-ft] * Yield from Battle Creek Below Glacier Gage 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 Notes: 1. Long-term record based on record extension using a linear regression between Middle Fork Bradley River and Battle Creek Below Glacier gage data. /= Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\1158.27 - Figs & Tobles.dwg 2. Long-term mean basin yield incorporates 1992, 1993, 2011, and 2012 estimates based on Battle Creek Below Glacier gage data, and is for the operational period of May through October, with the exception of 2012 for which October data were not available. E> ENERGY AUTHORITY BATTLE CREEK DIVERSION HYDROLOGY REPORT DIVERSION PROJECT BASIN YIELD FOR EXTENDED RECORD APRIL 2013 FIGURE 12 DEVELOPED BY: Ram CONSULT, ING. Plotted 4/15/2013 8:10 AM by Kim Anderson Project Basin - Annual (January - December) Discharge [cfs] > So o Figs & Tobles.dwg es won Average flow =58 cfs 0 | 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent Exceedance Percent Discharge Exceedance [cfs] IGN\Hydrology And Hydraulics\ACAD\ 1158.27 99% 3 95% 11 90% 12 85% 13 80% 14 75% 14 70% 14 65% 15 60% 16 55% 18 50% 21 45% 27 Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\ 40% 37 35% 52 30% 70 25% 91 = i [= ALASKA 15%6 BATTLE CREEK DIVERSION 10% HYDROLOGY REPORT 5% BATTLE CREEK PROJECT BASIN 2% FLOW DURATION CURVE — 1% ANNUAL 0.10% APRIL 2013 FIGURE 13 DEVELOPED BY: Ram CONSULTAN' Inc. Plotted 4/11/2013 5:51 PM by Kim Anderson Project Basin - Operational Period (May - October) Discharge [cfs] So o Figs & Tables.dwg Average Flow = 99 cfs eee eee ee ee ene ee ee 158.27 4+} — + 4 4 + + + 4 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent Exceedance Percent Discharge Exceedance [cfs] 99% 11 95% 14 90% 20 85% 26 80% 33 75% 39 70% 48 65% 57 60% 67 55% 77 50% 88 45% 98 Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\\Civil\DESIGN\Hydrology And Hydraulics\ACAD\ 1 40% 35% 30% 25% 20% [= ALASKA E> ENERGY AUTHORITY 13% BATTLE CREEK DIVERSION 10% HYDROLOGY REPORT 5% BATTLE CREEK PROJECT BASIN 2% FLOW DURATION CURVE — 1% OPERATIONAL PERIOD 0.10% APRIL 2013 ___ FIGURE 14 DEVELOPED BY: RaM CONSULTAN Inc. Plotted 4/11/2013 5:52 PM by Kim Anderson 3.4 Peak Flow Analyses The proposed Battle Creek Diversion will capture flows from the West Fork of Battle Creek, the West and East Branches of the Middle Fork of Upper Battle Creek, and the hillsides above the canal system. The diversion project will also intercept the flow of the East Fork of Upper Battle Creek above the existing diversion structure. The combined flows of the West, Middle, and East Forks of Upper Battle Creek will be routed down the lower portion of the canal system and join the existing diversion flow path to Bradley Lake a short distance downstream of the existing diversion structure. For the purposes of design and hydraulic analyses, peak flow estimates are needed for five key locations — the diversion structure, and the outlets of the upper canal, upper canal transition, lower canal, and lower canal transition. The areas contributing flows at these five locations include the following: 1. Diversion structure: The upper 7.4 square miles of the West Fork of Upper Battle Creek. 2. Upper canal: The area above the diversion structure and 0.2 square miles of hillside above the upper canal. 3. Upper canal transition: The area above the outfall of the upper canal, and 0.2 square miles of hillside slopes above the upper canal transition, which includes the upper portion of the West Branch of the Middle Fork of Upper Battle Creek. 4. Lower canal: The area above the outfall of the upper canal transition, and 0.4 square miles of hillside slopes above the lower canal, which includes the upper portion of the East Branch of the Middle Fork of Upper Battle Creek. 5. Lower canal transition: The area above the outfall of the lower canal, and a 1.0-square mile basin that includes the East Fork of Upper Battle Creek and the hillside slopes above the lower canal transition. These five key project basins are shown in Figure 16. Two different kinds of peak flow analyses are required for the design of the Battle Creek Diversion. The project is being designed to capture the 2-year recurrence interval flood, and convey that flow within a system of canals, providing for 2 feet of freeboard above the elevation of the 2-year flood water surface. Therefore, higher frequency peak flow estimates are needed for the geometric design of the canal and canal transition segments. For the design of the diversion structure and spillway, however, estimates of extremely low frequency, high magnitude peak flows are needed in order to assure that there will not be a catastrophic failure of the structure during an extreme flood event. These two analysis efforts are described below. 3.4.1 Canal Peak Flow Analyses Methods exist for performing flood frequency analyses on long-term stream gage data, and extrapolating those results to ungaged sites elsewhere in the watershed. Because the period of record at the Battle Creek Below Glacier gage is so short, this technique cannot be used to develop peak flow estimates for the diversion site. Furthermore, the synthesized extended record that has been developed for the project basin provides reasonable estimates of average flows, but tends to over-predict peak flows, which makes the synthesized record unsuitable for flood frequency analyses. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 30 May 2013 radley Laie EXISTING UPPER BATTLE CREEK & DIVERSION STRUCTURE gm \, LOWER CANAL TRANSITION BASIN S AREA = 1.0 SQ MI 3 i 2 a» N - \ 5 Yl OE FP g 2 F Wa h , ae Ss cS A =r A b , a w S \ = Ls7 ‘ RA Vy - f e- go? EAST FORK UPPER 7 “ “ \ ? BATTLE CREEK i eZ KS ] t .\ CS \ J : SS) ne . . RSION STRUCTL BATTLE CREEK DIVERSION HYDROLOGY REPORT BATTLE CREEK DIVERSION CANAL SYSTEM BASINS APRIL 2013 FIGURE 15 DEVELOPED BY: REM CONBULTAN Inc. Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\1158.27 — NEW Battle Creek Watershed-IT.dwg Methods presented in the USGS publication Estimating the Magnitude and Frequency of Peak Streamflows for Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada, Water-Resources Investigations Report 03-4188 (Curran, Meyer, and Tasker, 2003) were used to develop peak flow estimates for the project. The methods outlined in the document produce flood flow estimates based on regression equations developed from peak flow data and generalized least-squares regression models. The peak flow data used in developing the regression equations were produced from log-Pearson Type III analyses of a number of regional index stream gaging stations with long-term records. The Middle Fork Bradley River stream gage is one of these index stations. The Battle Creek Diversion project lies within Curran, Meyer, and Tasker’s Region 3, for which the applicable independent variables are basin area, storage in lakes and ponds, mean annual precipitation, and mean minimum January temperature. The basin area (A) for the outlet of the lower canal transition was delineated using a combination of available topographic mapping, stereoscopic analyses of aerial photography, and satellite imagery. Initial delineation efforts were modified and refined after performing helicopter and fixed wing flight simulator exercises at the E-Terra offices using 2011 aerial imagery, and helicopter overflights performed during site visits to the project area in the summer of 2012. The area of the basin providing storage in lakes and ponds (ST) was developed by measuring areas denoted as ponds on USGS 1:63,360-scale topographic mapping. Mean annual precipitation (P) was estimated by overlaying regional mean annual precipitation contours presented in Plate 2 of the USGS publication Magnitude and Frequency of Floods in Alaska and Conterminous Basins of Canada, Water Resources Investigations Report 93-4179 (Jones and Fahl, 1994) on project mapping. The mean annual precipitation contours showed a range from approximately 65 inches at the lowest elevation of the basin to 95 inches at the highest elevation. The estimate of mean annual precipitation for the project basin was selected based on a combination of extrapolation of the precipitation contours to the mean elevation of the basin, a comparison to mean annual precipitation values for nearby meteorological stations, and engineering judgment. The value for mean minimum January temperature (J) was taken from Plate 1 from Jones and Fahl. Parameters used in flood frequency regression analysis are presented in Table 6. Drainage Area, Sees Mean Annual Precipitation, | Mean Minimum January " Area, ST : si A [mi’] 1%] P [in] Temperature, J [°F] oO 9.2 0.5 85 16 Table 6 — Battle Creek Diversion Flood Frequency Analysis Basin Parameters Flood frequency analysis results for the full project watershed at the outlet of the lower canal transition were normalized by dividing the analysis results by the area of the watershed above the lower canal transition. The resulting normalized flood frequency values were then applied to the contributory areas for the diversion structure and the other canal system segments. The results are presented in Table 7. Analysis documentation is provided in Appendix B. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 32 May 2013 Lower Canal Lower | Upper Canal Diversion Flood Transition Canal Transition Upper k peat Structure Recurrence 32) +2 2 (7.6 mi’) 2 Taal (9.2 mi‘) . (8.2 mi) (7.8 mi) (7.4 mi) [cfs] [efs/mi‘] [cfs] [cfs] [cfs] [cfs] 2-year 720 79 650 610 600 580 5-year 1,030 113 930 880 850 840 10-year 1,250 136 1,110 1,060 1,030 1,010 25-year 1,530 166 1,360 1,290 1,250 1,230 50-year 1,740 190 1,560 1,470 1,430 1,410 100-year 1,950 213 1,740 1,650 1,610 1,580 Table 7 — Battle Creek Diversion Flood Frequency Analysis Results A comparison was made between the results presented in Table 7 and annual peak flows recorded at the Battle Creek Below Glacier gage. Annual peak flows occurring in 1992, 1993, 2011, and 2012 were measured to be 450, 880, 1,030, and 1,660 cubic feet per second, respectively. When these flows are normalized, the resulting values are 42, 82, 96, and 154 cubic feet per second per square mile. A comparison of these values to the normalized flood frequency values in Table 7 for the lower canal transition shows that the 1992 peak flow was less than a 2- year flood, and the 1993 peak flow was approximately a 2-year flood. The 2011 peak flow was somewhere between a 2-year and 5-year flood, and the 2012 peak flow. which is the flood of record for the Battle Creek Below Glacier gage, was somewhere between a 10-year and 25-year flood. 3.4.2. Extreme Flood Analyses For diversion dam and spillway design, estimates of extreme floods are needed to assure that structures do not suffer catastrophic failures. Two extreme floods have been analyzed for the Battle Creek Diversion project — the Probable Maximum Flood and the Spillway Design Flood. The Probable Maximum Flood is defined as the flood discharge that would result from the most severe combination of critical meteorological and hydrologic conditions that are reasonably possible in a region. This flood is the direct result of the Probable Maximum Precipitation. This flood does not have a defined recurrence interval, but is understood to be much greater than the 1,000-year flood. The Spillway Design Flood is defined as the largest flow that a given project is designed to pass safely. The Spillway Design Flood, depending on the hazard level of the structure, is typically assumed to be 40 to 60 percent of the Probable Maximum Flood. The U.S. Army Corps of Engineers HEC-HMS computer program was used to compute the Probable Maximum Flood and Spillway Design Flood for the 7.4-square mile drainage basin above the diversion structure. Rainfall data used in the analyses were taken from National Oceanic and Atmospheric Administration (NOAA) Atlas 14 — Precipitation-Frequency Atlas of the United States, Volume 7, Version 2.0: Alaska. The estimate for the 1,000-year, 12-hour duration rainfall event of 12.6 inches was selected to define the Probable Maximum Precipitation for the Probable Maximum Flood analysis. The 100-year, 12-hour duration rainfall event of 7.6 inches was selected for use Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 33 May 2013 in the Spillway Design Flood analysis. Each storm event was assumed to have an NRCS Type 1A rainfall distribution. Basin soils, ground cover type, and the hydrologic conditions of the ground cover were estimated from soils mapping, helicopter overflights, and on-the-ground observations. Based on the estimated basin characteristics, a curve number (CN) of 77 was selected. The lag time was computed from the Soil Conservation Service Lag Time Equation. An estimate was computed for the travel time for rainfall landing in the most hydraulically distant point in the West Fork of Upper Battle Creek watershed to traverse the length of the Battle Glacier before being channeled through Battle Creek to the diversion structure site. Lag time was estimated to be 315 minutes. The results of the HEC-HMS extreme flood analyses were 4,000 cubic feet per second for the Probable Maximum Flood and 1,800 cubic feet per second for the Spillway Design Flood. Extreme flood analysis documentation is provided in Appendix C. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 34 May 2013 4 SEDIMENT ANALYSES General analyses have been made of the production, storage, and transport of sediment in Battle Creek above the diversion structure, and in the greater Battle Creek basin. Sediment is an important issue for the Battle Creek project for two reasons. First, sediment generated in the West Fork of Upper Battle Creek will be deposited in the basin above the diversion structure (the headwater pool), which will require periodic maintenance to assure proper functioning of the diversion and associated hydraulic components. Second, the diversion will change the hydrology of Battle Creek below the diversion, which will affect the timing and character of the movement of sediment through the system. Two site visits were performed in support of this analysis effort, and are documented in Appendix A. Included in the site visit documentation are detailed descriptions of the main channel of Battle Creek and of the channel of the South Fork of Battle Creek with respect to sediment production, storage, and transport. These descriptions are summarized below. 4.1 Main Channel of Battle Creek Sediment Observations Between the Battle Glacier terminus at stream mile (SM) 8.3 (see Figure 2) and SM 6.6 the stream flows in a braided channel across the outwash plain of the glacier. Sediment in the outwash plain ranges in size from silt to boulders, but is typically silt to gravel sized on exposed surfaces. The stream probably carries a high suspended sediment load through this reach at all flow stages, except during the late fall through early spring period. During high flows, it is likely that the stream also carries a significant bed load in this reach. Bed load material is expected to come from both subglacial and supraglacial sources (such as landslide and rock fall debris on the glacier surface), and from mobilization of the bed of the stream within the outwash plain. Sediment will also be introduced to the stream from eroding banks during high flows. The glacier and the stream reach between SM 8.3 and 6.6 probably produce a large proportion of the total bed load of the stream and almost all the suspended load. Between SM 6.6 and 5.5, the stream flows within a deep, steep-walled canyon. The diversion structure for the Battle Creek Diversion project will be located in this canyon near SM 6.0. Landslides in the canyon will periodically introduce sediment to the system. Occasional rock fall associated with normal weathering processes on canyon walls will also shed debris into the stream. The rate at which this debris is produced will depend on the geology, elevation, and aspect of the canyon walls. Landslide debris fans are probably the only form of unconsolidated sediment stored within canyon sections in significant volumes, except for boulders. The swift, turbulent character of flow in steep canyon reaches of the stream likely moves material that is cobble-sized or smaller through the system during average flow conditions. The slope of Battle Creek is relatively steep between SM 5.5 and 5.0, with a boulder and bedrock bed, and little to no storage of sediment in bars, with the exception of a few areas where there appear to be short sections of medial bars composed of boulders. A waterfall is present near SM 5.3. Numerous landslide debris fans are present along the base of the right (south) canyon wall near SM 5.0, and are introducing sediment to the system. Between SM 5.0 and 4.3, the stream flows across a broad structural bench and the gradient drops significantly. The channel pattern becomes gently meandering, and the stream develops gravel bars and a floodplain before flowing into a steep canyon between SM 4.2 to 4.0. Waterfalls are present at either end of this short canyon section. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 35 May 2013 Between SM 4.0 and 3.3, the stream flows swiftly through a steep section with a boulder and bedrock bed, and there is no visible storage of sediment in or along the channel. The stream again flows in a steep canyon between SM 3.1 and 3.3, and a waterfall is present at SM 3.2. At SM 3.1, the stream once again flows across a broad structural bench, causing the gradient of the stream to drop significantly over the course of 0.6 stream miles. The channel pattern becomes gently to tightly meandering, and a system of large, well-formed point bars and medial bars is formed. Sediment stored in bars in this reach of the stream appears to be sand and gravel sized material. The gradient begins to steadily steepen downstream between SM 2.5 and 2.2. Downstream from SM 2.2 to the confluence with the South Fork of Battle Creek at SM 1.75, the gradient is steep and the bed is dominated by boulders and bedrock. Little to no storage of sediment occurs in this section. From the confluence with the South Fork of Battle Creek downstream to approximately SM 1.2, the gradient of the channel gradually drops. The channel pattern is still relatively straight, and although the stream bed substrate is still dominated by boulders, a wider range of sediment sizes is visible. Downstream of SM 1.2, the channel begins to meander within a broad floodplain. Large well-formed point bars and medial bars composed of sand and gravel are present. A split- channel form is occasionally present. Downstream of SM 0.5, the stream enters the intertidal zone, and the channel pattern changes to a deltaic distributary system, and sediments are very fine-grained. 4.2 South Fork of Battle Creek Sediment Observations The main channel of the South Fork of Battle Creek begins high in a cirque basin and flows approximately 6.4 miles to its confluence with the main channel of Battle Creek (SM 0.0 for the South Fork of Battle Creek is located at the confluence with the main branch of Battle Creek, at SM 1.75 of the main branch). At SM 4.5, the stream enters a steep gorge and drops almost 1,000 vertical feet before entering a broad, flat, structural bench near SM 4.1. The western branch of the upper stream joins the main branch near SM 3.8, and the stream gently meanders through this broad valley to SM 2.5. The stream has an anastomosing pattern in this reach, with a number of smaller branches breaking off from, and then rejoining, the main branch of the stream. This pattern may be the result of past beaver activity in the valley, although no signs of recent activity such as ponds or beaver lodges were noted. Stable, thickly vegetated stream banks are common in this reach, and sand and gravels bars are rare. Between SM 2.5 and 2.4, the stream drops through a narrow canyon with a waterfall. Below the canyon, the stream flows in a meandering pattern across a second structural bench for approximately 0.5 miles. Sand and gravels bars and a floodplain are evident along this reach. The stream drops off of this bench into a steep canyon, and remains in this canyon all the way to the confluence with Battle Creek. The lower 2 miles of the stream are characterized by a steep boulder and bedrock bed. Sediment from landslides and rock fall will be introduced to the stream in this lower reach, and will quickly move through the system except for boulder-sized material. 43 Diversion Structure and Canal Sediments Sediment will need to be periodically removed from the headwater pool immediately upstream of the diversion structure. Relatively high suspended sediment concentrations can be expected during most flow conditions for the operational period between May and October. The majority Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 36 May 2013 of suspended sediments are expected to pass through the diversion and canal system without being detained, and therefore will not present a significant maintenance issue. In contrast, bed load is expected to accumulate in the headwater pool upstream of the diversion structure. The sediment will accumulate in an alluvial fan at the transition between the upper canyon of Battle Creek and the diversion structure basin. As sediments accumulate, the fan will advance into the basin towards the diversion structure, and these sediments will need to be removed before they affect the function and integrity of the diversion structure. For the most part, sediment will only accumulate in the headwater pool of the diversion structure when flow rates are high enough to mobilize bed load in the outwash plain of the Battle Glacier, and wash the bed load into the upper canyon. However, debris from landslides within the upper canyon will also be washed into the headwater pool, and the frequency with which this will occur is difficult to predict. Hydraulic modeling of sediment transport in the outwash plain is outside the scope of the current hydrologic and hydraulic analysis effort. However, it is likely that at least one flood event each year will be large enough to mobilize sediment in the outwash plain. The amount of sediment transported in each flood will vary, and would be difficult to estimate even with a hydraulic model. For maintenance planning purposes, it would be prudent to assume that sediment maintenance will be required in the diversion structure headwater pool and canal headworks at least once a year. Maintenance can be most effectively done by means of a sluice gate, which will allow sediment accumulated within the basin to be eroded and transported through the gate into the channel of Battle Creek. It may be that mechanical equipment such as an excavator will be needed to assist with this operation on occasion. Downstream of the diversion, rock fall from the rock cuts above the canal system will fall into the channel and accumulate. The amount of rock fall will depend on the geology of the bedrock and the time of year (rock fall is expected to be at a maximum during freeze-thaw cycles), but this volume is expected to be relatively minor. An excavator working from the canal maintenance road will be required to remove these deposits of material if they grow substantial enough to impede the hydraulic function of the canal system. The reduction of flow in Battle Creek downstream of the diversion will affect the sediment dynamics of the stream. The suspended sediment load and turbidity of the stream will be dramatically reduced. If all of the bed load that accumulates above the diversion dam is sluiced into the Battle Creek channel, the net volume of bed load in the lower part of Battle Creek will not change. However, the frequency with which bed load is transported through the system can be expected to change, since the magnitude of peak flows will be reduced. It is likely that it will be necessary to periodically divert peak flows down the Battle Creek channel in order to move bed load into the lower reaches of the stream. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 37 May 2013 5 REFERENCES Curran, J. H., & Wiley, J. B. (2003). WRIR 03-4114: Estimating Annual High-Flow Statistics and Monthly and Seasonal Low-Flow Statistics for Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada. Anchorage, AK: USGS. Curran, J. H., Meyer, D. F., & Tasker, G. D. (2003). WRIR 03-4188: Estimating the Magnitude and Frequency of Peak Streamflows for Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada. Anchorage, Alaska: USGS & AKDOT&PF. Emerson, D. G., Vecchia, A. V., & Dahl, A. L. (2005). Scientific Investigations Report 2005- 5017: Evaluation of Drainage-Area Ratio Method Used to Estimate Streamflow for the Red River of the North Basin, North Dakota and Minnesota. Reston, VA: USGS. Fountain, A. G. (1993). Geometry and flow conditions of subglacial water at South Cascade Glacier, Washington State, U.S.A.; an analysis of tracer injections. Journal of Glaciology, 39 (131), 143-156. Fountain, A. G., & Tangborn, W. V. (1985). The Effect of Glaciers on Streamflow Variations. In Water Resources Research (Vol. 21, pp. 579-586). American Geophysical Union. Granato, G. E. (2008). Appendix 3. Stream Record Extension Facilitator. In Computer Programs for Obtaining and Analyzing Daily Mean Streamflow Data from the U.S. Geological Survey National Water Information System Web Site: USGS Open-File Report 2008- 1362. Reston, VA: USGS. HDR Alaska, Inc. (2012). Draft Memo: Flow Correlation Between Battle Creek and Middle Fork Bradley River, and Long Term Variation of Middle Fork Bradley River Flows. Anchorage, AK. HDR Alaska, Inc. (2012). Battle Creek Aquatic Resources Investigation, 2010 and 2011. Anchorage, AK. Interagency Advisory Committee on Water Data. (1981). Bulletin #17B: Guidelines for Determining Flood Flow Frequency. Reston, Virginia: USGS. Jones, S. H., & Fahl, C. B. (1994). WRIR 93-4179: Magnitude and Frequency of Floods in Alaska and Conterminous Basins of Canada. Anchorage: USGS. Miller, J. F. (1965). Technical Paper No. 52: Two- to Ten-Day Precipitation for Return Periods of 2 to 100 Years in Alaska. Washington, D.C.: U.S. Weather Bureau. NOAA. (2012). Meta Data: 17DC8798. Retrieved July 2012, from DCP Meta Data - Hydrometeorological Automated Data System - National Weather Service: Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 38 May 2013 http://amazon.nws.noaa.gov/cgi- bin/hads/interactiveDisplays/displayMetaData.p|?table=dcp&nwsli=BRRA2 NOAA. (2012). Metadata: DEOB45F4. Retrieved July 2012, from DCP metadata - Hydrometeorological Automated Data System - National Weather Service: http://amazon.nws.noaa.gov/cgi- bin/hads/interactiveDisplays/display MetaData.p|?table=dcep&nwsli=- BRMA2 NOAA. (2012). Metadata: DEOB5682. Retrieved July 2012, from DCP Metadata - Hydrometeorological Automated Data System - National Weather Service: http://amazon.nws.noaa.gov/cgi- bin/hads/interactiveDisplays/display MetaData.pl?table=dep&nwsli= UNRA2 R&M Consultants, Inc., & Hatch Associates Consultants, Inc. (2012). Alaska Energy Authority Bradley Lake Hydroelectric Project FERC P-8221-AK Battle Creek Diversion: Preliminary Design Report. Anchorage, AK: R&M Consultants, Inc. R&M Consultants, Inc. (1983). Bradley Lake Hydroelectric Power Project: Phase I - Feasibility Study Final Report. Anchorage, AK. R&M Consultants, Inc. and Hatch Associates Consultants, Inc. (2012). Summary Level Supplement to Preliminary Design Report. Anchorage, AK. Searcy, J. K. (1959). USGS Water-Supply Paper 1542-A: Flow Duration Curves. In USGS, Manual of Hydrology: Part 2. Low Flow Techniques. Washington, D.C.: United States Government Printing Office. SNW. (2010). Hydroelectric Project Risk Analysis & the Bradley Lake Funding Model: Summary Report. Seattle, WA: SNW. Stone & Webster Engineering Corporation. (1990). Additional Drainage Area Studies Upper Battle Creek Drainage Basin Bradley Lake Hydroelectric Project. Englewood, CO. U.S. Army Corps of Engineers, Alaska District. (1979). Information Brochure: Bradley Lake Hydroelectric Project. Anchorage, AK: USACE. U.S. Army Corps of Engineers, Alaska District. (1981). Bradley Lake Project: Design Memorandum No.1: Hydrology. Anchorage, AK. US Army Corps of Engineers, Alaska District. (1982). Bradley Lake Hydroelectric Project Design Memorandum No. 2 February 1982: General Design Memorandum (Vol. 1 & 2). Anchorage, AK. Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 39 May 2013 USGS. (2012, April). USGS 15238978 Battle C Div Ab Bradley Lk Nr Homer Ak. Retrieved July 2012, from National Water Information System: Web Interface: http://waterdata.usgs.gov/ak/nwis/inventory/?site_no=15238978&agency_cd=USGS& USGS. (2012, April). USGS 15238982 Battle C Bl Glacier Nr Homer AK. Retrieved 2012 July, from National Water Information System: Web Interface: http://waterdata.usgs.gov/ak/nwis/inventory/?site_no=15238982&agency_cd=USGS& USGS. (2012, April). USGS 15238984 Sf Battle C Nr Homer AK. Retrieved 2012 July, from USGS National Water Information System: Web Interface: http://waterdata.usgs.gov/nwis/nwisman/?site_no=15238984&agency_cd=USGS USGS. (2012, April). USGS 15238985 Battle C Nr Tidewater Nr Homer AK. Retrieved 2012 July, from USGS National Water Information System: Web Interface: http://waterdata.usgs.gov/ak/nwis/inventory/?site_no=15238985&agency_cd=USGS& USGS. (2012, April). USGS 15238986 Battle C 1.0 Mi Ab Mouth Nr Homer AK. Retrieved 2012 July, from USGS National Water Information System: Web Interface: http://waterdata.usgs.gov/ak/nwis/inventory/?site_no=15238986&agency_cd=USGS& USGS. (2012, April). USGS 15238990 Upper Bradley R Nr Nuka Glacier Nr Homer AK. Retrieved 2012 July, from USGS National Water Information System: Web Interface: http://waterdata.usgs.gov/nwis/nwisman/?site_no=15238990&agency_cd=USGS USGS. (2012, April). USGS 15239000 Bradley R Nr Homer AK. Retrieved 2012 July, from USGS National Water Information System: Web Interface: http://waterdata.usgs.gov/ak/nwis/inventory/?site_no=15239000&agency_cd=USGS& USGS. (2012, April). USGS 15239001 Bradley R Bl Dam Nr Homer AK. Retrieved 2012 July, from USGS National Water Information System: Web Interface: http://waterdata.usgs.gov/ak/nwis/inventory/?site_no=15239001&agency_cd=USGS& USGS. (2012, April). USGS 15239050 MF Bradley R Nr Homer AK. Retrieved 2012 July, from USGS National Water Information System: Web Interface: http://waterdata.usgs.gov/nwis/nwisman/?site_no=15239050&agency_cd=USGS Final Hydrology Report Bradley Lake Hydro — Battle Creek Diversion R&M Consultants, Inc. 40 May 2013 ( mx WO | SAS 7 ( SS ff Wx : Ws por | . ! i NG q| SS . BT CEC NEAR Sy ox ale ts CNL WY Urey os J a : BN UN CREEK GAGE EUS AL Ney) 3) if Vs YEN |) 59°45.000' N MIDDLE FORK UPP EAST BRANCH OF 6 BATTLE CREEK MIDDLE FORK UPPER Soe Ee ~ E BATTLE 59°44.000' N 59°43.000' N Z:\project\\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\ Hydrology And Hydraulics\ACAD\ 1158.27 — NEW Battle Creck Watershed-lT.dwg 59°42.000' N BATTLE CREEK DIVERSION HYDROLOGY REPORT PROJECT AREA MB APRIL 2013 FIGURE 2 ts - a “te be La : ~ ; ‘ DEVELOPED BY: eS PNA AS a4 ABM CONSULTANTS, INC. Plotted 4/12/2013 4:00 PM by Kim Anderson APPENDIX A JUNE 29 AND JULY 17, 2012 SITE VISIT MEMORANDUMS 331M] R&M CONSULTANTS, INC. (997) 522-1707, FAX (907) 522-3403, www.rmconsult.com 9101 Vanguard Drive, Anchorage, Alaska S9507 Site Visit Memorandum To: file From: Hans Arnett, Senior Hydrologist Subject: Battle Creek Diversion — June 29, 2012 Site Visit Summary Date: July 05, 2012 Project #: 1158.27 | traveled to Homer early on the morning of June 29, 2012 for a site visit to the Battle Creek Diversion project site with R&M Consultants, Inc. (R&M) project manager John Magee and design lead David Pyeatt. The primary goals for my portion of the site visit included: 1. View the Battle Creek basin 2. View the route of the proposed diversion 3. Make observations along the main channel of Battle Creek and its major tributaries regarding the production, transport, and storage of sediment 4. View the Middle Fork Bradley River basin In addition to my efforts on the site visit, David Pyeatt and John Magee made detailed observations of the proposed diversion alignment, especially with respect to a recent realignment of the Lower Canal, and John Magee inspected the Upper Bradley River and Middle Fork Bradley River diversion structures with Bradley Lake Power Plant Superintendent Larry Jorgensen. The weather during the site visit was partly cloudy. Winds were light to calm, and temperatures were in the 40s and 50s. The R&M team arrived in Homer at about 7:00 a.m. and then proceeded to the Maritime Helicopters hangar. We took off from Homer at about 7:30 a.m. and flew up to the project site in the Upper Battle Creek basin. We took a number of passes over the proposed diversion alignment, and then flew up to the Battle Glacier in the uppermost basin. We then followed Battle Creek from the toe of the glacier to tidewater, and then flew up the South Fork Battle Creek valley (David captured video footage of these two legs of the flight). After flying up the South Fork Battle Creek valley, we landed on the outwash plain of the Battle Glacier. | made 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 2 Date: July 05, 2012 observations of the outwash plain, stream, and sediment sizes. After completing observations on the outwash plain, we again flew the proposed canal alignment, with special attention paid to the area between the tie-in to the existing Upper Battle Creek diversion and its mouth at Bradley Lake. An attempt was made to fly into the Middle Fork Bradley River valley, but we were turned back by fog before getting very far up the valley. We then flew up Bradley Lake to the site of the Upper Bradley River diversion near the base of the Nuka Glacier, and then returned to the power house by following the dam access road. After about an hour at the power house, John Magee, Larry Jorgensen and | flew up to the Upper Bradley River diversion, spending about half an hour on the ground inspecting the structure. We then flew to the site of the Middle Fork Bradley River diversion, but did not land. It was not possible to fly further up into the basin due to fuel concerns. After turning back, we returned to the power house. The R&M team left the power house shortly after that, and returned to the Maritime Helicopters base in Homer, arriving a little before 1:00 p.m. Our return flight to Anchorage arrived at about 4:00 p.m. Specific observations made during the course of the site visit are summarized below. Existing Upper Battle Creek Diversion Snow cover along the upper portion of the existing Upper Battle Creek diversion was still extensive, and limited the ability to see the diversion structure, which was mostly covered by snow. Thick vegetation (probably alders) could be seen growing on the top of the diversion structure, suggesting that it does not receive regular maintenance. The action of plant roots penetrating the surface of the diversion structure may be contributing to the permeability of the structure noted on previous site visits by R&M personnel. Flows in the Upper Diversion follow a complex path from the base of the cascade to Bradley Lake. The stream stair steps through a series of three lakes before plunging steeply to Bradley Lake. Immediately below the diversion, flow enters a small lake (see Photo 1). Quiet water was observed against the base of the diversion. It is not known if this condition persists once water levels drop, but ponded water against the base of the diversion could be another factor in the previously noted leakage of water through the diversion structure. Water flows from the outlet of the upper lake through a relatively well-defined channel that drops steeply to the middle lake in the system. The USGS gage (15238978 — Battle Creek above 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 3 Date: July 05, 2012 Bradley Lake near Homer, Alaska) was visible, and is located on the right bank below the outlet of the upper lake. A delta is present where the stream enters the middle lake in the system, which suggests significant sediment transport along the channel connecting the upper and lower lakes. This is to be expected since this flow path probably carried far less flow prior to the construction of the diversion, and would be expected to erode its bed in order to adjust to the higher flows. Flow drops steeply between the middle and lower lakes. It appears that the stream splits into two channels after entering a small pond a short distance downstream of the outlet (see Photo 2). The steepness of the two channels suggests that they are composed of bedrock. A broad low area is located to the east of the lower lake, and another small lake is located further east that flows into the lower lake (see Photo 3). From the outlet of the lower lake, the stream flows in a very steep, well-defined channel that has carved a small canyon where it enters the lake (see Photo 3). Aerial observations suggest that much of the length of this channel is composed of bedrock. There have been internal design team discussions about the need to enlarge the existing channel as part of the proposed Battle Creek Diversion project in order to limit the amount of erosion occurring along the channel, and to limit the amount of vegetation and debris washed into the lake. The following observations should be taken into account when designing any improvements to the existing channel. e The profile of the path of the existing Upper Battle Creek diversion consists of a series of three major steps. e Much of the flow within this system passes through a system of lakes. Probably as much as a third of the flow path between the diversion structure and Bradley Lake occurs within lakes, which will be expected to have a strong moderating effect on changes in water surface elevations and the magnitude of peak flows passing through the system. e Channels connecting lakes within the system are relatively short and steep. e The channels between the middle and lower lakes, and between the lower lake and Bradley Lake appear to be composed mainly of bedrock, which will lower their erosion potential. Only the segment of channel between the upper and middle lakes appears to have a gravel bed, and therefore subject to a significant increase in erosion potential. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 4 Date: July 05, 2012 e The presence of lakes within this system will make it difficult to produce a reliable water surface profile model, which would require the collection of bathymetric data to properly model flow through the lakes. Battle Glacier Outwash Plain At the time of the site visit, snow still covered the majority of the outwash plain of the Battle Glacier. The helicopter landed on the left side of the stream in an area located about midway between the terminus of the glacier and the top of the first canyon downstream. Flow in the stream was highly turbid. Discharge in the stream was probably somewhere between 50-100 cubic feet per second (cfs) at this location. At that time, the flow at the USGS’s gage 15238982 — Battle Creek below Glacier near Homer, Alaska was about 150 cfs. There was abundant evidence on exposed, snow-free surfaces that the outwash plain is becoming vegetated and stabilizing (see Photo 4). Exposed sediments on the floodplain surface at this location ranged from coarse gravel and cobbles (see Photo 5) to coarse sand and medium gravel (see Photo 6). Sediments exposed in adjacent low terraces were considerably finer, consisting of sand and silt sized material interlayered with coarser sand and gravels (see Photo 7). There was still a considerable amount of snow where the stream enters the top of the first canyon, but active gravel bars were visible in snow-free areas (see Photo 8). General thoughts and observations about sediments in the outwash plain of the Battle Glacier include the following: e The outwash plain will be the primary source of sediment to the proposed diversion and canal system, although rock fall in the upper canyon and in rock cuts will also produce material. It is assumed that the volume of material falling from rock cuts will be far less than the volume of glacially-derived sediments, but this will depend on the character of the rock in cut sections, especially its fracture pattern and susceptibility to weathering. e The outwash plain forms a regularly replenished sediment source of considerable size between the glacier and the upper canyon. However, there is considerable evidence that the outwash plain is stabilizing. e Asstabilizing outwash plain may suggest a decrease in peak flow magnitudes, a decrease in the frequency of peak flows, or a decrease in sediment availability. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 5 Date: July 05, 2012 e Although there is clearly a high suspended sediment load in the stream, it is unknown what sort of bed load it is carrying. Bed load is more likely to be an issue for sedimentation at the diversion structure than suspended load. e There appears to be a bedrock sill or lip at the top of the upper canyon, which may limit the amount of bed load that washes down the canyon. Main Battle Creek Channel A flight was made from the toe of the Battle Glacier to tidewater at Kachemak Bay. | was sitting in the back of the helicopter and did not always get a clear view of the channel, and the helicopter did not precisely follow the path of the channel, so video taken from the front seat of the helicopter does not provide a continuous view of the full length of the channel. Furthermore, the upper canyon still had a significant amount of snow in the bottom, and the channel could not be seen. Nonetheless, a number of observations can be made relative to the channel and its sediment transport characteristics. e Sediment that washes into the upper canyon probably flushes through relatively quickly. Although the bottom of the upper canyon was not visible for the most part, there was little evidence noted of sediment storage (i.e., sand and gravel bars) within canyons lower in the system. e There was some evidence of rock fall in the upper canyon, which could be expected to add minor amounts of sediment to the system. This sort of rock fall is probably most commonly the result of freeze-thaw cycles, and would be expected to be most common in the spring and fall, and on north-facing aspects. e Much of the length of Battle Creek is very steep, with high canyon walls, straight channel sections, absent floodplains, and bedrock and boulder beds (see Photo 9). e« Anumber of landslides were observed along the base of canyon walls in the middle portion of the basin, which could be significant sediment sources to the lower stream. e A few areas exist in the middle portion of the basin where gradients flatten, sediment is stored in bars, and meander bends and floodplains develop (see Photo 10), but these areas are uncommon. e Downstream of the confluence with the South Fork of Battle Creek, the gradient of the stream decreases and bar formation is common. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 6 Date: July 05, 2012 South Fork Battle Creek A flight was taken up the South Fork Battle Creek after the main channel had been flown to tidewater. Again, my observations were hampered by being in the back seat of the helicopter. Video footage of the South Fork does not start until about half way up the basin, so observations are limited. A few observations can be made regarding the channel and sediment transport characteristics of the South Fork of Battle Creek: e Flow in the stream was clear. The contrast was especially noticeable at the confluence with the main Battle Creek channel. e The lower portion of the channel flows within a canyon. The channel is very steep and commonly straight, with little to no bar and floodplain development. The channel appears to have a bedrock and boulder bed. e Inthe middle portion of the basin, the gradient flattens somewhat and the channel begins to develop some very slight meanders, but for the most part, bar and floodplain formation is rare to absent (see Photo 11). e The upper portion of the basin is distinct in character from the lower and middle portions (see Photo 12). The stream flows within a broad, flat valley. Floodplains are present and are thickly vegetated. Stream banks are also thickly vegetated. Sand and gravel bars are uncommon. There is evidence of past beaver activity, but there appears to be little activity currently. There appears to be little generation of sediment in the upper basin, and sediment transport is probably limited as well. Middle Fork Bradley River Two attempts were made to view the upper Middle Fork Bradley River drainage. The first attempt was aborted due to fog. The second attempt was aborted due to concerns about fuel levels. Flow from the drainage was noted to be relatively clear, which was surprising given the presence of glaciers in the basin (see Photo 13). 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 7 Date: July 05, 2012 Photo 2 — Middle and lower lakes in the existing Upper Battle Creek diversion system. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 8 Date: July 05, 2012 Photo 3 — Lower end of existing Upper Battle Creek diversion channel system where it enters Bradley Lake. Photo 4 — Battle Creek flowing through the Battle Glacier outwash plain. Note presence of vegetation on outwash plain surfaces. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 9 Date: July 05, 2012 Photo 6 — Battle Glacier outwash plain sediments. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 10 Date: July 05, 2012 Photo 7 — Exposed sediments in low terrace on Battle Glacier outwash plain. Photo 8 — Point at which upper Battle Creek enters the upper canyon. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 11 Date: July 05, 2012 Photo 10 — Gravel bars and meander bends in the middle portion of the Battle Creek basin. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 12 Date: July 05, 2012 Photo 11 —South Fork of Battle Creek in the middle portion of the basin. Photo 12 — Upper basin of the South Fork of Battle Creek. 1158.27 — Battle Creek Diversion June 29, 2012 Site Visit Summary Page 13 Date: July 05, 2012 Photo 13 — Middle Fork Bradley River. Note USGS gage to the right of center of the photo, and clear flow in stream. [36M R&M CONSULTANTS, INC. (907) 522-1707, FAX (907) 522-3403, www.rmconsult.com 9101 Vanguard Drive, Anchorage, Alaska S9507 Site Visit Memorandum To: file From: Hans Arnett, Senior Hydrologist Subject: Battle Creek Diversion — July 17, 2012 Site Visit Summary Date: August 03, 2012 Project #: 1158.27 | traveled to Homer on the morning of July 17, 2012 for a site visit to the Battle Creek Diversion project site with R&M Consultants, Inc. (R&M) water resources engineer Irene Turletes. The primary goals for the site visit included: 1. Make detailed observations and video recordings along the main channel of Battle Creek and the South Fork of Battle Creek regarding the production, transport, and storage of sediment 2. Make observations of the drainage divides in the headwaters of the West Fork of Upper Battle Creek and the South Fork of Battle Creek to complete refinements to basin delineations 3. Make on-the-ground observations of the transition from the outwash plain of the Battle Glacier into the upper canyon of Battle Creek 4. Make on-the-ground observations of the existing East Fork of Upper Battle Creek diversion structure and the channel downstream of the diversion structure 5. View the Middle Fork Bradley River basin and make a determination of the area of the basin covered by glaciers The weather during the site visit was mostly clear in the morning and partly cloudy in the afternoon. Winds were light and temperatures were in the 50s and 60s. The R&M team arrived in Homer at about 10:30 a.m. and then proceeded to the Maritime Helicopters hangar. We took off from Homer at about 11:00 a.m. and flew to the mouth of Battle Creek at tidewater. We flew up the channel of Battle Creek to the confluence with the South Fork of Battle Creek, and then followed the South Fork of Battle Creek to the drainage divides of the two upper branches of the stream. We then flew back down the channel of the South Fork to the confluence with the main channel, and then up the main channel to the terminus of the 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 2 Date: August 03, 2012 Battle Glacier. (Video footage was captured of the flights over the main Battle Creek and South Fork of Battle Creek channels.) The helicopter was landed near the downstream end of the outwash plain of the glacier, and on- the-ground observations were made near the location where the stream enters the upper canyon. The helicopter was then flown along the general alignment of the proposed diversion and canal system to the location of the existing diversion structure on the East Fork of Upper Battle Creek. The helicopter was landed adjacent to the U.S. Geological Survey (USGS) gage on the East Fork of Upper Battle Creek (15238978 - Battle Creek Diversion Above Bradley Lake Near Homer, Alaska). On-the-ground observations were made of the existing diversion structure, the small lake adjacent to the diversion structure, and the channel of the East Fork of Upper Battle Creek between that upper lake and the next lake downstream. After completing the observations near the existing diversion, the helicopter was flown into the Middle Fork Bradley River basin. The stream channel was flown from where the diverted flows of the stream enter Bradley Lake up to the location of the diversion structure, beyond the existing USGS Middle Fork Bradley River stream gage (15239050 — Middle Fork Bradley River Near Homer, Alaska) and the adjacent Natural Resources Conservation Service (NRCS) snowpack telemetry (SNOTEL) site, and then up to the drainage divides of each of the three upper branches of the basin. Observations were made of the apparent glacier coverage in the upper reaches of the basin. After completing the observations in the Middle Fork Bradley River basin, the helicopter returned to the base of the upper canyon of Battle Creek near the site of the proposed diversion, and then the channel was followed to tidewater. Specific observations made during the course of the site visit are summarized below. Battle Glacier Outwash Plain and Upper Canyon of Battle Creek The helicopter was landed on a stable vegetated terrace along the right bank of Battle Creek (with respect to a viewer facing downstream). The stream is braided in this area, and makes two sharp 90-degree bends (first to the left and then to the right) before flowing into the upper canyon of Battle Creek. The stream is actively eroding its right bank at the upper bend as it migrates into the terrace (see Photo 1). Numerous clumps of vegetation eroded from the bank were scattered across the braidplain of the stream (the active braided channel and gravel bar system; see Photo 2). The eroding banks are composed of relatively fine-grained, silt- to gravel- sized, glaciofluvial material (see Photo 3), which is being deposited on sand and gravel bars in 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 3 Date: August 03, 2012 the adjacent braidplain (see Photo 4) a short distance upstream of the canyon. The deposited material is generally finer grained than the material in gravel bars on the opposite side of the stream. This material will be added to the normal sediment load of the stream during high flow periods. A high vegetated bank is present on the left side of the stream above the head of the canyon. There is a lower gravel bar surface in this area that is becoming vegetated (see Photo 1). This is consistent with aerial observations of the Battle Glacier outwash plain between the terminus of the glacier and the upper canyon of Battle Creek that show that the margins of the outwash plain and some higher gravel bar surfaces are gradually stabilizing, as evidenced by sparse vegetation growing on higher surfaces. Vigorous bank migration like that noted at the downstream end of the outwash plain is relatively uncommon. The channel of Battle Creek is composed of bedrock where the stream flows into the head of the upper canyon (see Photo 5). This bedrock lip effectively prevents head cutting of the stream into the outwash plain. Once bed load is washed over the bedrock lip and into the canyon, the steepness of the canyon, and the turbulent high velocity character of flows (see Photo 6) will wash sediment downstream to the location of the proposed diversion structure, with little to no opportunity for storage within the canyon. Existing East Fork of Upper Battle Creek Diversion and Downstream Channel After landing the helicopter near the site of the USGS gage on the East Fork of Upper Battle Creek, Irene and | walked upstream to the existing diversion structure. The structure appears to be a gravel embankment with a top width of 10 to 15 feet, and coarse riprap on both its upstream and downstream faces. The structure is covered with dense alders and does not appear to have been recently maintained (see Photo 7). The full length of the structure was investigated. R&M field crews had noted significant flows downstream of the diversion structure in 2011. During the July 17 site visit, a flow of approximately 3 cubic feet per second was noted on the downstream side of the structure in what had formerly been the stream bed of the East Fork of Upper Battle Creek. This flow was traced upstream to where the diversion structure blocks the former stream bed (see Photo 8). Water from a small lake is ponded on the opposite side of the diversion structure at this location (see Photo 7). The combination of standing water ponded against the permeable gravel-cored structure and the increased permeability resulting from root growth of the thick alders growing 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 4 Date: August 03, 2012 on top are allowing a significant amount of water to leak through. If the flow rate of leakage seen during the site visit is typical, then approximately 6 acre-feet (260,000 cubic feet) of water per day is being directed away from Bradley Lake during the summer flow season. This structure will need to be either completely rebuilt with an impermeable core or replaced by a concrete structure in order to assure that the leakage does not continue after construction of the Battle Creek Diversion project. After the inspection of the diversion structure, we walked along the channel connecting the upper lake at the diversion structure to the next lake downstream, which is a distance of approximately 1,400 feet. There is a concern that the significant increase in flows resulting from the construction of the diversion project will produce a large amount of erosion along the flow path of the East Fork of Upper Battle Creek between the existing diversion and Bradley Lake as the stream adjusts to the higher flow rates. The upper half of the channel between the existing diversion structure and the next lake downstream, in the area of the USGS gage, has a relatively gradual profile, a regular cross-section with a width of approximately 10 feet, a gravel and cobble bed, and low, stable, grassy banks (see Photo 9). Approximately halfway between the two lakes, the channel becomes significantly steeper, banks become higher and less stable, and the bed of the stream is carved into bedrock (see Photo 10). Instabilities were noted both along the stream banks and on the hillsides above the influence of the stream (see Photo 11). Additional stream bank erosion can be expected after construction of the diversion project, but the bedrock stream bed along this lower section of the channel will be highly resistant to erosion. If efforts are not made to enlarge the channel prior to completion of the diversion, the channel will adjust to the new flow regime by eroding its banks (and also its bed above the bedrock transition), and the eroded material will be carried downstream to the next lake (see Photo 12). The lake immediately downstream is the middle of three lakes along the flow path of the East Fork of Upper Battle Creek between the existing diversion and Bradley Lake. Eroded material — either vegetation or sediment - will be unlikely to travel downstream of the next lake. Between the middle and third lakes along the East Fork of Upper Battle Creek flow path, the stream splits into two bedrock cascades (see Photo 13). The channel erosion potential is low along these two cascades. However, vegetation will likely be eroded along the margins of the cascades and carried down to the lowest of the three lakes in the system if it is not cleared prior 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 5 Date: August 03, 2012 to completion of the diversion. Downstream of the third lake, the stream flows to Bradley Lake within a steep bedrock and boulder bed channel with low erosion potential (see Photo 14). Middle Fork Bradley River It was not possible to view the upper Middle Fork Bradley River drainage during the June 29, 2012 site visit. Flow from the drainage was noted on that trip to be relatively clear, which was surprising given the presumed presence of several glaciers in the headwaters of the basin. The good weather conditions on the July 17 site visit allowed an unrestricted view of the upper basin. The flow of the river was again noted to be relatively clear, which was unexpected. At that late date in the summer, it had been assumed that strong glacial melt would be occurring, and that the meltwater would be carrying a high suspended sediment load. The upper portion of the Middle Fork Bradley River valley has three main branches, and observations were made in each. Clear to relatively clear water was noted to be draining from all three branches. The only exposed glacier ice was observed on the north-facing southern flank of the southernmost branch (see Photo 15). Remnant medial moraines are present in the middle branch (see Photo 16), and some limited bergschrunds are visible along the headwall of the basin. There was still extensive snow cover in the uppermost portion of the basin, but the generally concave shape of the snow surface, and the significantly lower elevation of the snow surface relative to the medial moraines, did not strongly suggest the presence of underlying glacier ice. The terrain in the northernmost branch was interpreted as a rock glacier under the remaining snow cover. After returning from the field, a conservative estimate of 1.3 square miles was made of the remaining glacier cover in the upper Middle Fork Bradley river basin. Channel Sediment Observations Aerial observations were made of the main channel of Battle Creek between the terminus of the Battle Glacier and tidewater, and of the channel of the South Fork of Battle Creek between the headwaters of the tributary basin and the confluence with the main channel of Battle Creek. Stream miles for the main channel of Battle Creek begin at the mouth of the stream along Kachemak Bay, as shown on USGS topographic mapping, and extend 8.3 miles to the existing terminus of the Battle Glacier. Stream miles on the South Fork of Battle Creek begin at the confluence with the main channel of Battle Creek and extend 6.4 miles to a cirque bowl in the 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 6 Date: August 03, 2012 upper southeast portion of the tributary’s headwaters. Stream miles are shown on the attached Figure 1. Main Battle Creek Channel Sediment Observations Battle Creek begins at the terminus of the Battle Glacier at stream mile (SM) 8.3. This branch of the stream is referred to as the West Fork of Upper Battle Creek. Between the glacier terminus and SM 6.6 the stream flows in a braided channel across the outwash plain of the glacier. Sediment in the outwash plain ranges in size from silt to boulders, but is typically silt to gravel sized on exposed surfaces. The stream probably carries a high suspended sediment load through this reach at all flow stages, except during the late fall through early spring period. During high flows, it is likely that the stream also carries a significant bed load in this reach. Bed load material is expected to come from subglacial sources and from mobilization of the bed of the stream within the outwash plain. Sediment will also be introduced to the stream from eroding banks during high flows (see outwash plain discussion above). The glacier and the stream reach between SM 8.3 and 6.6 probably produce a large proportion of the total bed load of the stream and probably almost all the suspended load. Between SM 6.6 and 5.5, the stream flows within a deep, steep-walled canyon. The diversion structure for the Battle Creek Diversion project will be located in this canyon near SM 6.0. Landslides in the canyon (see Photo 17) will periodically introduce sediment to the system. Occasional rock fall associated with normal weathering processes on canyon walls will also shed debris into the stream. The rate at which this debris is produced will depend on the geology, elevation, and aspect of the canyon. Landslide fans are probably the only form of unconsolidated sediment stored within canyon sections, except for boulders. The swift, turbulent character of flow in steep canyon reaches of the stream likely flushes material that is cobble- sized or smaller through the system. The slope of Battle Creek is relatively steep between SM 5.5 and 5.0, with a boulder and bedrock bed, and little to no storage of sediment in bars, with the exception of a few areas where there appear to be short sections of medial bars composed of boulders (see Photo 18). The steam flows over a waterfall near SM 5.3. Numerous landslide debris fans are present along the base of the right (south) canyon wall near SM 5.0, and are introducing sediment to the system. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 7 Date: August 03, 2012 Between SM 5.0 and 4.3, the stream flows across a broad structural bench and the gradient drops dramatically. The channel pattern becomes gently meandering, and the stream develops gravel bars (see Photo 19) and a floodplain before flowing into a steep canyon between SM 4.2 to 4.0. Waterfalls are present at either end of this short canyon section. Between SM 4.0 and 3.3, the stream flows swiftly through a steep section with a boulder and bedrock bed, and no visible storage of sediment in or along the channel. The stream again flows in a steep canyon between SM 3.1 and 3.3, and a waterfall is present at SM 3.2. At SM 3.1, the stream once again flows across a broad structural bench, causing the gradient of the stream to drop significantly over the course of 0.6 stream miles. The channel pattern becomes gently to tightly meandering, and a system of large, well-formed point bars and medial bars is formed (see Photo 20). Sediment stored in bars in this reach of the stream appears to be sand and gravel sized. The gradient begins to steadily steepen downstream between SM 2.5 and 2.2. Downstream from SM 2.2 to the confluence with the South Fork of Battle Creek at SM 1.75, the gradient is steep and the bed is dominated by boulders and bedrock (see Photo 21). Little to no storage of sediment occurs in this section. From the confluence with the South Fork of Battle Creek downstream to approximately SM 1.2, the gradient of the channel gradually drops. The channel pattern is still relatively straight, and although the stream bed substrate is still dominated by boulders (see Photo 22), a wider range of sediment sizes becomes apparent. Downstream of SM 1.2, the channel begins to meander within a broad floodplain. Large well-formed point bars and medial bars composed of sand and gravel are present. A split-channel form is occasionally present (see Photo 23). Downstream of SM 0.5, the stream enters the intertidal zone, and the channel pattern changes to a braided, distributary system, and sediments are very fine-grained. South Fork Battle Creek Channel Sediment Observations The main channel of the South Fork of Battle Creek begins high in a cirque basin and flows approximately 6.4 miles to its confluence with the main channel of Battle Creek. USGS topographic mapping produced from 1950s-era aerial photography shows a small glacier in this basin, but observations made on the site visit showed no signs of a glacier in this cirque or in a more minor cirque in the other upper branch of the stream to the west. All of the flow on the South Fork was noted to be clear on the day of the site visit. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 8 Date: August 03, 2012 At SM 4.5, the stream enters a steep gorge and drops almost 1,000 vertical feet before entering a broad, flat, structural bench (see Photo 24) near SM 4.1. The western branch of the upper stream joins the main branch near SM 3.8, and the stream gently meanders through this broad valley to SM 2.5. The stream has an anastomosing pattern in this reach, with a number of smaller branches breaking off from, and then rejoining, the main branch of the stream. This pattern may be the result of past beaver activity in the valley, although no signs of recent activity such as ponds or lodges were noted. Stable, thickly vegetated stream banks are common in this reach, and sand and gravels bars are rare. Between SM 2.5 and 2.4, the stream drops through a narrow canyon with a waterfall (see Photo 25). Below the canyon, the stream flows in a meandering pattern across a second structural bench for approximately 0.5 miles. Sand and gravels bars and a floodplain are evident along this reach (see Photo 26). The stream drops off of this bench into a steep canyon, and remains in this canyon all the way to the confluence with Battle Creek. The lower 2 miles of the stream is characterized by a steep boulder and bedrock bed (see Photo 27). Sediment from landslides and rock fall will be introduced to the stream in this lower reach, and will be quickly flushed through the system except for boulder-sized material. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 9 Date: August 03, 2012 Photo 1 — Transition of Battle Creek from the Battle Glacier outwash plain into upper canyon. Note the eroding right bank (with respect to a viewer facing downstream). Photo 2 — Clumps of eroded vegetation scattered on the braidplain of Battle Creek upstream of the upper canyon. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 10 Date: August 03, 2012 Photo 4 — Fine-grained material from the eroding right bank of Battle Creek deposited on the surface of the braidplain a short distance upstream of the upper canyon. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 11 Date: August 03, 2012 3 he *. me Photo 5 — Bedrock channel at the head of the upper Battle Creek canyon. Photo 6 — Turbulent, high velocity flow in the upper Battle Creek canyon. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 12 Date: August 03, 2012 Photo 7 — The East Fork of Upper Battle Creek and existing diversion structure. Note the dense alder growth on the unmaintained structure and ponded water in right center of photo. Photo 8 — Point where the existing diversion structure blocks off the former East Fork of Upper Battle Creek channel and where flows were leaking through the structure. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 13 Date: August 03, 2012 Photo 9 — East Fork of Upper Battle Creek channel near the USGS gage. Photo 10 — East Fork of Upper Battle Creek channel at transition to bedrock bed. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 14 Date: August 03, 2012 Photo 11 — Unstable stream banks along the East Fork of Upper Battle Creek. Middle lake in system is visible in photo center, with Bradley Lake just visible beyond. Photo 12 — Middle lake along the East Fork of Upper Battle Creek flow path. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 15 Date: August 03, 2012 Photo 13 — Bedrock cascades between the middle and lower lakes in the East Fork of Upper Battle Creek system. Photo 14 — Lower segment of channel along the East Fork of Upper Battle Creek flow path where it enters Bradley Lake. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 16 Date: August 03, 2012 Photo 15 — Small exposures of glacier ice on a north-facing aspect in the southernmost branch of the upper Middle Fork Bradley River basin. Photo 16 — Remnant medial moraines in the middle branch of the upper Middle Fork Bradley River basin. The large snowfields in the upper basin may be underlain by glacier ice. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 17 Date: August 03, 2012 Photo 17 — Landslide deposits in the upper canyon of Battle Creek near SM 6.4, upstream of the proposed diversion structure site. Photo 18 - Boulders in Battle Creek near SM 5.4. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 18 Date: August 03, 2012 Photo 19 — Sand and gravel bars downstream of a number of landslide deposits near SM 5.0. Photo 20 — Sand and gravel bars near SM 2.8 downstream of a long section of canyon. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 19 Date: August 03, 2012 Photo 21 — Canyon near SM 1.9 upstream of the confluence with the South Fork of Battle Creek at SM 1.75. Photo 22 — Battle Creek channel near SM 1.5, downstream of the confluence with the South Fork of Battle Creek. Note boulders and high velocity flow. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 20 Date: August 03, 2012 Photo 23 — Battle Creek near SM 1.0. Note the split channel pattern and well-formed sand and gravel bars. Photo 24 — South Fork of Battle Creek within its broad, flat valley near SM 3.8. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 21 Date: August 03, 2012 Photo 26 — South Fork of Battle Creek flowing over a flat bench near SM 2.1. Note bar formation and presence of floodplain. 1158.27 — Battle Creek Diversion July 17, 2012 Site Visit Summary Page 22 Date: August 03, 2012 Photo 27 — South Fork near SM 0.3. Note steep slopes, boulder bed, and high velocity flow. Spa 59°45.000' N "a wend : Seq EAST FORK UPPER BATTLE FR CREEK ae 4 SOUTH FORK BATTLE ) > CREEK 59°44.000' N J ‘ = ‘et WEST BRANCH OF MIDDLE FORK UPPER BATTLE CREEK \ ee 7 os mon i P WEST FORK UPPER BATTLE CREEK 59°43.000' N Z:\project\1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\NEW Battle Creek Watershed-IT.dwg 59°42.000' N BATTLE CREEK DIVERSION JULY 17, 2012 SITE VISIT MAP PROJECT AREA AUGUST 2012 FIGURE 1 DEVELOPED By: ~ 9 Rem CONSULTANTS, INC. Plotted 8/3/2012 9:02 AM by Irene Turletes APPENDIX B FLOOD FREQUENCY ANALYSIS DOCUMENTATION Lower Canal Transition R&M CONSULTANTS, INC. 9101 Vanguard Drive ANCHORAGE, ALASKA 99507 (907) 522-1707 Flood Frequency Analysis SHEET NUMBER 1 | OF | 2 CALCULATED BY Using methods presented in USGS WRIR 03-4188 "Estimating the Magnitude and Frequency of Peak Streamflows for Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada" Qry, T-year peak streamflow, in cubic feet per second; A, drainage area, in square miles; ST, area of lakes and ponds (storage), in percent; P, mean annual precipitation, in inches; J, mean minimum January temperature, in degrees Fahrenheit Region 1, Region 3 (93 gaging stations) Applicable range of variables: A: 0.720-571; ST: 0-26; P: 70-300; J: 0-32 Q# = (1):A®-(ST+1)- P.(J+32) Conatont Exponent} Exponent | Exponent | Exponent Normalized (1) forA for ST Discharge 2 (3) 4 (5) cfs/sq mi 0.004119 | 0.8361 0.9110 | 1.635 720 79 0.009024 | 0.8322 -0.3670 Q10 0.01450 0.8306 -0.3691 Q25 0.02522 0.8292 -0.3697 0.7165 1.588 1,530 0.03711 0.8286 -0.3693 0.6847 1.559 1,740 Q100 | 0.05364 0.8281 -0.3683 0.6556 1.527 1,950 1.640 1,030 Q200 | 0.07658 0.8276 -0.3669 0.6284 1.495 2,180 Q500 0.1209 0.8272 -0.3646 0.5948 4/12/2013 R&M CONSULTANTS, INC. 9101 Vanguard Drive ANCHORAGE, ALASKA 99507 Basin (907) 522-1707 Battle Creek Diversion | Flood Frequency Analysis SHEET NUMBER Z | OF | 2 CALCULATED BY IST DATE 3/26/2013 CHECKED BY 3/26/2013 Diversion Structure Basin Area [sq mi] 7.4 Uppe: r Transition 7.76 Lower Transition Lower Canal Transition _[cfs/sq mi] Diversion Structure [cfs] Upper Transition [cfs] Lower Transition [cfs] 79 580 113 840 610 136 166 720 1,030 1,250 1,530 190 213 238 271 1,950 -———|—_____, 1,740 1,950 2,180 2,220 2,480 4/12/2013 APPENDIX C HEC-HMS EXTREME FLOOD ANALYSES DOCUMENTATION are UM i Sees TY Ce BASIN INFORMATION by Ae Foy MEAN MINIMUM WATERSHED | AVERAGE |AREA OF LAKES] DETERMINED JANUARY AREA ELEVATION IN BASIN PRECIPITATION TEMPERATURE , 59°48,000' N z o 9° S $ ° a n 59°47.000' N 59°47 ,000' N SNOTEL 1064 - MIDDLE FORK BRADLEY oy Ws AVG ANNUAL PRECIP = 54’ NEW Battle Creek Watershed—IT.dwg 59°45.000'N 59°46.000' N 59°45,000' N 59°44,000 59°44,000'N aes ; MEAN BASIN ELEVATION iC 59°43,000' N 59°43,000'N SNOTEL 1063 = KACHEMAK CREEK AVG ANNUAL PRECIP = 63° 2:\project\ 1158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology And Hydraulics\ACAD\ 1158.27 59°42,000' N BATTLE CREEK Sa Oe NOTEL 1037 - NUKA GLACIER BASIN 7 Uy ‘ VG ANNUAL PRECIP = 94° BATTLE CREEK DIVERSION HYDROLOGY REPORT 2 o of 2 + ° a USGS MEAN ANNUAL PRECIPITATION . ANE REGRESSION ANALYSIS CONTOURS IN INCHES ™ APRIL 2013 - FIGURE Bi DEVELOPED BY: RSM CONSULTANTS, INC. NE a Plotted 4/15/2013 3:18 PM by Irene Turletes P32 MIL R&EM CONSULTANTS, INC. (907) 522-1707, FAX (807) 522-3403, www.rmconsult.com 9101 Vanguard Drive, Anchorage, Alaska S9507 Memorandum To: file From: David Pyeatt, P.E., Nick Straka, P.E. Subject: Probable Maximum Flood and Spillway Design Flood Calculation Date: 8-02-2012 Project #: Battle Creek Diversion, R&M Project No 1158.27 The Probable Maximum Flood (PMF), based on the 1,000 year, 12-hour duration rainfall event, is expected to yield an instantaneous peak flow of 4,000 cfs at the diversion site.'- The Spillway Design Flood (SDF), based on the 100 year, 12-hour duration rainfall event, is expected to yield an instantaneous peak flow of 1,800 cfs at the diversion site. An input variable that is crucial to the calculation of the PMF and the SDF is lag time. The lag time, TL ac. was computed using the SCS Lag Time Equation: palit 1900/7 L, the hydraulic length of the watershed, is the distance from the most hydraulically distant point in the West Fork of Upper Battle Creek to the diversion structure. This length is theoretically determined by the path the water traverses. While the exact length the water traverses while passing inside the glacier cannot be known, we do know that the water is delayed significantly. Once exiting the glacier, the water continues via a braided stream bed until it coalesces to a single channel a few hundred feet above the diversion structure. The straight-line length of the basin is approximately 25,000 feet (or 5 miles) with slopes, Y, equal to 11% to 13%. With the detours in the glacier and the braided stream channel, the length the water takes could be as much as double (50,000 feet or 10 miles) with slopes as flat as 2.5%. Calculated velocities range between 1.3 feet/sec to 5.0 feet/sec, depending on slope and location of the flow. Tiac= S, is the maximum retention and is related to the inverse of the Curve Number (CN). For a CN of 77, S = 2.98 (unitless). y= 1000 1, CN The SCS curve number is weighted for the entire watershed as defined by the loss method in the HEC- HMS manual. Tac = 5.2 hrs or 315 minutes Z:\project\1 158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology and Hydraulics\Extreme Flow Calculation\2012-08- 02 Extreme Flow Conditions.docx INPUT: Area Initial Storage® Max Storage* Curve Number 77 Group C_ soils bedrock, tundra, ice Ground Cover gravel and snow Hydrologic Condition Poor Transform 315 minutes Storm Events Duration 12 hours Storm Type IA 1000 year 12.6 inches 100 year 7.62 inches OUTPUT: Storm Events Duration 12 hours 1000 year 4,000 cfs 1,800 cfs e Neither the SDF nor the PMF take into account the effects of glacial melting during the tested rainfall events. e It is assumed that the rainfall events will occur between August through October and any effects from snowmelt during the event are negligible. 'A synthetic type IA rainfall distribution curve was used. The flow rates calculated used HEC-HMS Version: 3.5 Build: 1417 Date: 10AUG2010. °NOAA ATLAS 14 point precipitation frequency estimates: AK * The initial condition of the surface specifies the percentage of storage that is full at the beginning of the calculations “Max storage represents the maximum amount of water that can be held before “through-fall” to the surface begins * The standard “lag time” is defined as the length of time between the centroid of precipitation mass and the peak flow of the resulting hydrograph. Z:\project\1 158.27 AEA Bradley Lake Hydro Preliminary Design\Civil\DESIGN\Hydrology and Hydraulics\Extreme Flow Calculation\2012-08- 02 Extreme Flow Conditions.docx CHUCICUISU Project: Battle Creek Bradley Lake D Simulation Run: 1000 year Subbasin: Start of Run: End of Run: Volume Units: Computed Results Peak Discharge : 4018.1 (CFS) Total Precipitation: | 4971.6 (AC-FT) Total Loss : 1625.2 (AC-FT) Total Excess : 3346.4 (AC-FT) 01Jan2000, 00:00 03Jan2000, 00:00 Compute Time: 01Aug2012, 16:12:25 Basin Model: Meteorologic Model: Control Specifications: AC-FT Date/Time of Peak Discharge : Total Direct Runoff : Total Baseflow : Discharge : BATTLE CREEK BASIN Battle creek 1000 year Control 1 01Jan2000, 11:30 3346.4 (AC-FT) 0.0 (AC-FT) 3346.4 (AC-FT) crucreuroU gweyeerd Flow (cfs) Subbasin "BATTLE CREEK BASIN" Results for Run "1000 year" os 4.5007 —— 4,000~) 3,5007 3,000 2,500 1,5005 1,000~4 ot T 00:00 12:00 | 01Jan2000 ae Run:1000 year Element:BATTLE CREEK BASIN Result:Precipitation Run:1000 YEAR Element:BATTLE CREEK BASIN Result;Outflow T ne 00:00 12:00 00: ‘00 02Jan2000 =—" Run:1000 YEAR Element:BATTLE CREEK BASIN Result:Precipitation Loss ——— Run:1000 YEAR Element:BATTLE CREEK BASIN Result:Baseflow CruciCUrDU gwgeerd Project: Battle Creek Bradley Lake D Simulation Run: 100 year Subbasin: 01Jan2000, 00:00 03Jan2000, 00:00 Compute Time: 01Aug2012, 16:13:54 Start of Run: End of Run: Volume Units: Computed Results Peak Discharge : 1742.2 (CFS) Total Precipitation : 3005.6 (AC-FT) Total Loss : 1624.1 (AC-FT) Total Excess : 1381.5 (AC-FT) Basin Model: Meteorologic Model: Control Specifications: AC-FT Date/Time of Peak Discharge : Total Direct Runoff : Total Baseflow : Discharge : BATTLE CREEK BASIN Battle creek 100 Year Control 1 01Jan2000, 13:00 1381.5 (AC-FT) 0.0 (AC-FT) 1381.5 (AC-FT) ChUCICUISU yvyeoucg Subbasin "BATTLE CREEK BASIN" Results for Run "100 year" 0.30 1,800 7- 1,600 1,2007 1,000 4007 2007 o+ + 00:00 12:00 | 01Jan2000 —== Run:100 year Element:BATTLE CREEK BASIN Result:Precipitation Run:100 YEAR Element:BATTLE CREEK BASIN Result:Outflow + — Ss 00:00 12:00 | 02Jan2000 ==" Run:100 YEAR Element:BATTLE CREEK BASIN Result:Precipitation Loss ——— Run:100 YEAR Element:BATTLE CREEK BASIN Result:Baseflow 00: