Basin and Lower Santa Ana River

choppedspleenMechanics

Feb 21, 2014 (3 years and 5 months ago)

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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

Dam

Prado Basin

Area = 11,500 acres

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


Sediment
-
deficient high flows change sediment
characteristics below Prado Dam


Cause armoring and coarsening


Percolation reduced


Percolation Impacts

Changes in Sediment
Characteristics

SAR at

Imperial

SAR at

Five Coves

SAR at

Weir Canyon

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