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Unconventional Wisdom and the
    Effects of Dams on Downstream
    Coarse Sediment Supply
    3 February 2009




    Byr...
OBJECTIVE



Consider the landscape context of a dam
before drawing conclusions about its
downstream effects.
CONCEPTS


THE FLUVIAL SYSTEM

  The watershed and river as a mechanism
  that routes water and sediment.
                ...
CONCEPTS

Dams affect downstream flux of sediment
and water.
Bed Coarsening
Channel Degradation
Loss of Spawning Gravel




                   South Fork Feather River
CONCEPTS



What About other outcomes?

Need to Consider…
Sediment Supply
Transport Frequency
EXCESS
                            Channel Aggradation
                            Island and Bar Formation
              ...
EXCESS
                            Channel Aggradation
                            Island and Bar Formation
              ...
EXCESS

                             UNCONVENTIONAL
                                 WISDOM
      Change in Relative
     ...
CONCEPTS


Geology and Geologic History
Topography
Climate and Hydrology
Land Use
Dam Position
Dam Operation
Case Studies



 Sultan River, WA
 McKenzie River, OR
 Deschutes River, OR


What are the primary sources of sediment t...
SULTAN RIVER
                       Washington


 WHAT      The Jackson
           hydroelectric project
           operat...
Sultan River, WA


Culmback
  Dam
                                                     Spada Lake




                   D...
LITHOTOPO UNITS         SEDIMENT INPUTS

 V-SHAPED VALLEY
• Dominated by debris
  flows
• High Sediment Yield
LITHOTOPO UNITS                        SEDIMENT INPUTS

  V-SHAPED VALLEY
• Dominated by debris
  flows
• High Sediment Yi...
LITHOTOPO UNITS                                     SEDIMENT INPUTS

  V-SHAPED VALLEY
• Dominated by debris
  flows
• Hig...
LITHOTOPO UNITS                                     SEDIMENT INPUTS

  V-SHAPED VALLEY
• Dominated by debris
  flows
• Hig...
Sultan River at present-day Spada Lake, 1949.
This reach was a depositional pool-riffle channel.
Sultan River at present-day Spada Lake, 1949.




Therefore, the river upstream of
Culmback Dam was a sediment sink, and
c...
EXCESS
      Change in Relative
       Sediment Supply



                           1965            Pre-dam




  DEFICIT...
Sultan River, WA

                          2003
1965               1983




                          Active channel
Acti...
EXCESS
      Change in Relative
       Sediment Supply



                           1965              2007




  DEFICIT
...
Sultan River, WA

                          2003
1965               1983




                          Active channel
Acti...
McKENZIE RIVER
                         Oregon


 WHAT      A Carmen-Smith
           hydroelectric project
           ope...
McKenzie River, OR

High Cascades Terrane
 • Young volcanics
 • Low drainage density
 • Hydrologically disconnected
 • Low...
McKenzie River, OR

Carmen Diversion
     Dam


  Smith Dam


  Trailbridge
     Dam
McKenzie River, OR

Upper McKenzie
    Basin


   Smith River
     Basin

   Deer Creek
     Basin



  Trailbridge
     D...
McKenzie River, OR


                            Trailbridge
                               Dam
               Deer Creek
DESCHUTES RIVER
                         Oregon


 WHAT      The Pelton-Round
           Butte hydroelectric
           pr...
Deschutes River, OR




    Annual Sediment
      Production




                      Figure From O’Conner et al. 2003
Deschutes River, OR

  Pelton Round
  Butte Project
    Annual Sediment
      Production




                      Figure ...
6000



 Mean Monthly Discharge (CFS)
                                                                                    ...
Recap



 Sultan: Sediment mass balance remains
  similar and Channel Adjustment.
 McKenzie: Downstream sediment mass
  ...
CONCLUSION



 Context Matters

 Because as we have seen, landscape
  attributes, land use, dam position, and
  operatio...
Acknowledgements



              THANK YOU

 Snohomish PUD
 Eugene Water and Electric Board
 Portland General Electric an...
Our modeling tells us that the modern and
historical mass balance are the same

 Modern Sediment       Historical Sediment...
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UnconVentional Wisdom and the Effects of Dams on Downstream Coarse Sediment Supply

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A presentation I gave at River Restoration Northwest\'s Annual Symposium in February 2009.

their website: http://rrnw.org/

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UnconVentional Wisdom and the Effects of Dams on Downstream Coarse Sediment Supply

  1. 1. Unconventional Wisdom and the Effects of Dams on Downstream Coarse Sediment Supply 3 February 2009 Byron Amerson, Jay Stallman, John Wooster, and Derek Booth Sultan River, WA
  2. 2. OBJECTIVE Consider the landscape context of a dam before drawing conclusions about its downstream effects.
  3. 3. CONCEPTS THE FLUVIAL SYSTEM The watershed and river as a mechanism that routes water and sediment. Schumm, 1977
  4. 4. CONCEPTS Dams affect downstream flux of sediment and water.
  5. 5. Bed Coarsening Channel Degradation Loss of Spawning Gravel South Fork Feather River
  6. 6. CONCEPTS What About other outcomes? Need to Consider… Sediment Supply Transport Frequency
  7. 7. EXCESS Channel Aggradation Island and Bar Formation Vegetation Encroachment Change in Relative Sediment Supply Subtle Effects Bed Coarsening Channel Degradation Habitat Loss DEFICIT Change in Relative Transport LOW HIGH Frequency Based on Grant, Schmidt, and Lewis 2003
  8. 8. EXCESS Channel Aggradation Island and Bar Formation Vegetation Encroachment Change in Relative Sediment Supply Subtle Effects CONVENTIONAL WISDOM DEFICIT Change in Relative Transport LOW HIGH Frequency Based on Grant, Schmidt, and Lewis 2003
  9. 9. EXCESS UNCONVENTIONAL WISDOM Change in Relative Sediment Supply CONVENTIONAL WISDOM DEFICIT Change in Relative Transport LOW HIGH Frequency Based on Grant, Schmidt, and Lewis 2003
  10. 10. CONCEPTS Geology and Geologic History Topography Climate and Hydrology Land Use Dam Position Dam Operation
  11. 11. Case Studies  Sultan River, WA  McKenzie River, OR  Deschutes River, OR What are the primary sources of sediment to the river downstream of the dam?
  12. 12. SULTAN RIVER Washington WHAT The Jackson hydroelectric project operated by Snohomish PUD Annual sediment KEY mass balance FINDINGS remains similar before and afte damming. Culmback Dam
  13. 13. Sultan River, WA Culmback Dam Spada Lake Data for this LiDAR DEM was provided by the Snohomish PUD
  14. 14. LITHOTOPO UNITS SEDIMENT INPUTS V-SHAPED VALLEY • Dominated by debris flows • High Sediment Yield
  15. 15. LITHOTOPO UNITS SEDIMENT INPUTS V-SHAPED VALLEY • Dominated by debris flows • High Sediment Yield TERRACED VALLEY • Dominated earth flows • Moderate Sediment Yield ROCK FALLS EARTHFLOWS GULLIES
  16. 16. LITHOTOPO UNITS SEDIMENT INPUTS V-SHAPED VALLEY • Dominated by debris flows • High Sediment Yield TERRACED VALLEY • Dominated earth flows • Moderate Sediment Yield ROCK FALLS EARTHFLOWS GULLIES ALLUVIAL VALLEY •Sediment input from TRIBUTARIES upstream •Low Sediment Yield BANK FAILURE
  17. 17. LITHOTOPO UNITS SEDIMENT INPUTS V-SHAPED VALLEY • Dominated by debris flows • High Sediment Yield TERRACED VALLEY • Dominated earth flows • Moderate Sediment Yield ROCK FALLS EARTHFLOWS GULLIES ALLUVIAL VALLEY •Sediment input from TRIBUTARIES upstream •Low Sediment Yield BANK FAILURE
  18. 18. Sultan River at present-day Spada Lake, 1949. This reach was a depositional pool-riffle channel.
  19. 19. Sultan River at present-day Spada Lake, 1949. Therefore, the river upstream of Culmback Dam was a sediment sink, and contributed relatively little to the downstream sediment budget.
  20. 20. EXCESS Change in Relative Sediment Supply 1965 Pre-dam DEFICIT Change in Relative Transport LOW HIGH Frequency Based on Grant, Schmidt, and Lewis 2003
  21. 21. Sultan River, WA 2003 1965 1983 Active channel Active channel 175 feet wide 350 feet wide
  22. 22. EXCESS Change in Relative Sediment Supply 1965 2007 DEFICIT Change in Relative Transport LOW HIGH Frequency Based on Grant, Schmidt, and Lewis 2003
  23. 23. Sultan River, WA 2003 1965 1983 Active channel Active channel 175 feet wide 350 feet wide
  24. 24. McKENZIE RIVER Oregon WHAT A Carmen-Smith hydroelectric project operated by Eugene Water and Electric Board Sediment mass KEY balance Downstream FINDINGS of Trailbridge Dam is similar to reference conditions. Trailbridge Dam
  25. 25. McKenzie River, OR High Cascades Terrane • Young volcanics • Low drainage density • Hydrologically disconnected • Low Sediment Yield Western Cascades Terrane • Older volcanics • High drainage density • Hydrologically connected • High Sediment Yield
  26. 26. McKenzie River, OR Carmen Diversion Dam Smith Dam Trailbridge Dam
  27. 27. McKenzie River, OR Upper McKenzie Basin Smith River Basin Deer Creek Basin Trailbridge Dam
  28. 28. McKenzie River, OR Trailbridge Dam Deer Creek
  29. 29. DESCHUTES RIVER Oregon WHAT The Pelton-Round Butte hydroelectric project operated jointly by Portland General Electric and the Confederated Warm Springs Tribes Subtle response - bed KEY texture and spawning FINDINGS gravel area are similar to pre-dam conditions. Pelton Reregulating Dam
  30. 30. Deschutes River, OR Annual Sediment Production Figure From O’Conner et al. 2003
  31. 31. Deschutes River, OR Pelton Round Butte Project Annual Sediment Production Figure From O’Conner et al. 2003
  32. 32. 6000 Mean Monthly Discharge (CFS) 1924-1956 1964-2007 5000 4000 3000 2000 1924 -1956 1964 - 2007 1000 0 May Mar Apr Aug Jul Jan Feb Jun Sep Oct Dec Nov Low Sediment Yield and a Subdued Hydrograph
  33. 33. Recap  Sultan: Sediment mass balance remains similar and Channel Adjustment.  McKenzie: Downstream sediment mass balance is similar to reference conditions.  Deschutes: Subtle response, though reduced sediment supply.
  34. 34. CONCLUSION  Context Matters  Because as we have seen, landscape attributes, land use, dam position, and operation all influence downstream physical process outcomes.
  35. 35. Acknowledgements THANK YOU Snohomish PUD Eugene Water and Electric Board Portland General Electric and the Confederated Warm Springs Tribes
  36. 36. Our modeling tells us that the modern and historical mass balance are the same Modern Sediment Historical Sediment Average Annual Transport Capacity Transport Capacity Sediment Input (KT/yr) (KT/yr) (KT/yr) 0.7 - 12 0.2 - 9 ~11 Estimated Modern Mass Estimated Historical Balance (KT/yr) Mass Balance (KT/yr) -1 to 10 2 to 10

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