US Army Corps of Engineers
U.S. Army Corps of Engineers Headquarters Website

Los Angeles River, CA, Ecosystem Restoration Project, 16 July 2015

LA River Eco Restoration

ABSTRACT:  The proposed Los Angeles River Ecosystem Restoration project is located in Los Angeles County, California.

The Los Angeles River is the 51-mile-long backbone of an 870-square-mile watershed. It once anchored a system of riparian and freshwater marsh habitat that carried seasonal rains and subterranean flows across the coastal plain and linked significant habitat areas from the Pacific Ocean to the San Gabriel Mountains. Over time, a cycle of urban development, flooding and channelization diminished aquatic and riparian habitat, reduced plant and wildlife diversity, and disconnected the river from its historic floodplain and nearby significant ecological zones.  Today, 94% of the river’s banks and 75% of its bed are lined in concrete, a result of a 20th century Federal project to provide flood risk management to what is today the nation’s most populous county.

The 11-mile stretch of the river from Griffith Park to Downtown Los Angeles was identified as having the greatest restoration potential. It features a non-concrete bottom and is positioned to connect to habitat in major tributaries and regional areas.  The Corps and City studied the feasibility of providing ecosystem restoration measures in and along these 11 miles to reestablish scarce riparian strand, freshwater marsh, and aquatic habitat, while maintaining existing levels of flood risk management.  Habitat connections would be re-established to major tributaries, its historic floodplain, and the regional habitat zones of the Santa Monica, San Gabriel, and Verdugo mountains.

The Recommended Plan, which is a Locally Preferred Plan (LPP) approved by the ASA(CW), would restore approximately 719 acres by widening the river in four areas and reconnecting it to the historic floodplain at two of these areas; restoring riparian and marsh habitat; restoring two major tributary confluences; terracing and restructuring channel banks to support vegetation; creating side channels and off-channel marsh; daylighting thirteen small streams; and removing invasive vegetation.  Associated recreation features include trails, signs, and pedestrian bridges.  The LPP provides more intensive and extensive ecosystem restoration with greater benefits and higher costs than the National Ecosystem Restoration (NER) plan.

The effects of the Recommended Plan are largely beneficial.  Minimization measures and best management practices have been incorporated to avoid and reduce adverse impacts.  The plan requires conversion of lands currently designated for industrial uses to non-industrial uses in two areas. No compensatory mitigation is required.

Based on October 2015 (FY16) price levels, the estimated first cost of the Recommended Plan is about $1,356,608,000, of which $1,338,554,000 is allocated to ecosystem restoration and $18,054,000 is allocated to recreation.  The first cost of lands, easements, rights of way, relocations, and disposal sites (LERRD) is estimated at $771,025,000.  The total ecosystem restoration cost includes $12,250,000 for monitoring and adaptive management.  Average annual costs for the Recommended Plan total $61,485,000, including $60,507,000 for ecosystem restoration and $978,000 for recreation based upon a 3.375 percent discount rate and a 50-year period of analysis.  The ecosystem restoration features are projected to generate 6,782 average annual habitat units, with an average annual cost per habitat unit of $8,921.  Average annual benefits for the recreation plan are estimated at $3,510,000, with net average annual benefits of $2,532,000 and a benefit/cost ratio of 3.59.

The City will provide all LERRD for the project and has volunteered to forgo reimbursement for the value of LERRD that exceed its statutory share of total ecosystem restoration cost.  Under LPP cost sharing that incorporates the City’s offer, the Federal and non-Federal shares of restoration cost are estimated at $157,790,000 and $1,180,764,000.  Under a non-standard cost sharing option that would require specific statutory language for implementation, the Federal and non-Federal shares of restoration cost are estimated at $366,746,000 and $971,808,000.  Under either option, recreation cost would be shared equally, estimated at $9,027,000 each.  The City would be responsible for the operation, maintenance, repair, replacement, and rehabilitation (OMRR&R) of the project after construction, a cost estimated at $2,530,000 on an average annual basis.

Report Documentation:  Pertinent documentation on the project, the results of the Civil Works Review Board, and subsequent Washington-Level Review Actions are listed below (items not linked will be provided when available):

Additional Information: