final Sedimentation Report - City and Borough of Sitka

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3500 3000 2500 2000 1500 Distance along creek (ft) 1000 1957 Topo/2007 LiDAR 2008 Survey 2008 Survey Extended 500 450 430 410 390 370 350 330 310 290 270 250 0 Existing Spill Existing Max Drawdown Estimated Expansion Delta Expansion Spill Expansion Max Drawdown Figure 21. Estimated Existing and Expansion Becky Creek Delta. Brad Creek Brad Creek has a drainage area of approximately 3.7 square miles. Photos of the existing Brad Creek delta (Figure 22) show several delta surfaces formed at the mouth of the canyon where Brad Creek enters the wider valley floor. It appears that moderate Brad Creek flows may not be sufficient to transport the cobble and gravel material in the delta; the existing delta is not graded to low lake levels like the Blue Lake or Becky creek deltas. Blue Lake Reservoir Sedimentation Report 26 Blue Lake Project Expansion Watershed GeoDynamics FERC No. 2230 December 2009 Elevation (ft)
Figure 22. Photo of Existing Brad Creek Delta. A longitudinal profile of Brad Creek was plotted from the 1957/2007 data (Figure 23). There are no data on the existing delta profile, but an estimated delta profile was plotted based on the photograph in Figure 22. The Expansion delta will be formed in a higher gradient, confined section of Brad Creek and will likely have similar characteristics to the mobile delta deposits in the canyon section of the current Becky Creek delta (described in the previous section). A lower gradient section of Brad Creek (at approximately elevation 400) may retain some of the gravel and cobble materials through the fluctuating lake levels. The stream length of spawning habitat available at the interface of Brad Creek will be approximately equal to the existing project. Blue Lake Reservoir Sedimentation Report 27 Blue Lake Project Expansion Watershed GeoDynamics FERC No. 2230 December 2009
Page 1: FINAL RESERVOIR SEDIMENTATION STUDY
Page 4 and 5: Figure 11. Cross Sectional Profiles
Page 6 and 7: Brad Creek Figure 1. Proposed Expan
Page 8 and 9: 2. Evaluate probable future fish ha
Page 10 and 11: The mapping units were transferred
Page 12 and 13: in June flows were greater than 541
Page 14 and 15: Peak flows in Blue Lake Creek were
Page 16 and 17: In lakes and reservoirs with fluctu
Page 18 and 19: 2. The operations model provides a
Page 20 and 21: Elevation (ft) Elevation (ft) 370 3
Page 22 and 23: Under expansion operation condition
Page 24 and 25: Relative Elevation (ft) Relative El
Page 26 and 27: 100% 90% 80% 70% 60% 50% 40% 30% 20
Page 28 and 29: Table 5. Estimated Spawning Use, Me
Page 32 and 33: 3500 3000 2500 2000 1500 Distance a
Page 34 and 35: volume of sediment deposition and e
Page 36 and 37: Comment Number Comment Summary Resp
Page 38 and 39: Blue Lake Creek Delta Sediment Samp
Page 40 and 41: pan 3,876 14.36 mm 0.0471 ft Blue L
Page 42 and 43: December 2009 Blue Lake Creek Reser
Page 44: Blue Lake Creek Delta Sediment Samp

final Sedimentation Report - City and Borough of Sitka

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