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Sediment Management in Prado Basin and Lower Santa Ana River. Greg Woodside, P.G., C.Hg Executive Director of Planning & Natural Resources September 20, 2011. Prado Dam. Main purpose is flood control Water conservation is additional beneficial use. Prado Basin Area = 11,500 acres. Prado

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Sediment Management in Prado Basin and Lower Santa Ana River

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Sediment Management in Prado Basin and Lower Santa Ana River

Greg Woodside, P.G., C.Hg

Executive Director of Planning & Natural Resources

September 20, 2011


Prado Dam

  • Main purpose is flood control

  • Water conservation is additional beneficial use

Prado Basin

Area = 11,500 acres

Prado

Dam


Water/Sediment Mechanics

  • Sediment laden water enters Prado Basin

  • Velocity of water slows and sediment settles out in Prado Basin

  • Water released through Prado Dam is sediment deficient

    • >95% sediment trap efficiency estimated by Warrick & Rubin (2007) for Prado Dam


Impacts of Prado Basin Sedimentation

  • Prado Basin

    • Water conservation reduced

      • 25,000 af lost below elev. 505 since 1941

    • Sedimentation threatens infrastructure

    • Impacts to endangered species habitat

  • Lower Santa Ana River

    • Scouring threatens infrastructure

      • SAR channel has incised between 5 and 15 feet from Prado Dam to Weir Canyon with localized incision exceeding 15 feet

    • Channel incising harms riparian habitat

    • Beach replenishment reduced

    • Marine ecosystems starved of sediment

    • Riverbed armoring & coarsening reduces percolation rate


Percolation Impacts

  • Sediment-deficient high flows change sediment characteristics below Prado Dam

    • Cause armoring and coarsening

  • Percolation reduced


Changes in Sediment Characteristics

SAR at

Weir Canyon

SAR at

Imperial

SAR at

Five Coves


Proposed Solution

  • Perform demonstration project to remove sediment from Prado Basin and place it below Prado Dam

  • Demonstrate feasibility of re-establishing natural sediment transport regime

  • Allow high flows released from Prado Dam to redistribute sediment down river

  • Use results from demo project to assess feasibility of long-term sediment management solution


Prado Basin


Sediment Management Demonstration Project Layout

  • Dredging

    • Hydraulic dredge

  • Pump sediments to temporary storage area

  • Slurry pump sediments to re-entrain in SAR below Prado Dam


Project Outreach

  • U.S. Army Corps of Engineers

  • U.S. Fish and Wildlife Service

  • CA Department of Fish and Game

  • CA State Parks

  • Regional Water Quality Control Board

  • Flood control districts

  • OC Coastkeeper / Inland Empire Waterkeeper

  • Santa Ana Watershed Project Authority

  • Local cities


Near-Term & Long-Term

  • Near-Term

    • Prado Basin Demonstration Project

      • Test in field

      • Collect data to measure benefits, assess potential impacts

  • Long-Term

    • Corps’ Prado Basin Feasibility Study

    • Implementation of project(s) from FS


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