Southport Levee Improvement Project

West Sacramento Southport Levee Improvement Project (SLIP)

Southport Levee Improvement Project

Flood Protection for Residents and Businesses of West Sacramento

Surrounded by water during the winter months, the City of West Sacramento depends on levees for its residents' safety. A failure at any location in the levee system during a 50-year or greater flood event results in an inundation of more than 90% of the entire City, with floodwater up to 6.1 metres deep. Evacuation routes, including freeway on/off-ramps, would be compromised in as little as two hours, impacting the ability to get to higher ground. The West Sacramento Area Flood Control Agency moved to address this risk proactively through the Southport Levee Improvement Project, a program consisting of several flood risk management projects.  

The $180 million project, financed and constructed by the WSAFCA, is its largest capital improvement to date. Levee improvements along this 9-km section include renovating the existing levee structure and constructing a new setback levee.

We provided engineering services and facilitated the Envision process for SLIP, WSAFCA’s first Envision-verified project and the first flood control project to receive Platinum recognition. WSAFCA’s goal is to achieve a minimum 200-year level of levee performance for the entire West Sacramento levee system. The project brings the levee into compliance with federal and state levee design criteria, as well as providing opportunities for ecosystem restoration and public recreation.

SLIP is a three-phase, multi-benefit, flood risk reduction and ecosystem enhancement project. Measures included 2.9 kilometres of fix-in-place levee improvements and a new 6.1-km-long setback levee with cutoff walls, seepage berms, demolition, rock slope protection, utility relocation and the use of borrow sites. Project transportation improvements included realigned roadways, new access roads and driveways, turnouts, cul-de-sacs and maintenance corridors. 

The project is relatively unique for an urban area in that it returns several hundred acres of land to riparian and oak savanna habitat. This project was constructed as part of the federal West Sacramento Project, a partnership with the U.S. Army Corps of Engineers, WSAFCA and the Central Valley Flood Protection Board acting through the Department of Water Resources Division of Flood Management. 

Restoration design increases river-floodplain connectivity and restores ecologically functional floodplain habitat consistent with the flood risk reduction goals of the project. The project is restoring 212 acres of habitat, with a net increase of 114 acres of habitat that did not exist before the project. This includes new wetland habitat developed on the water side of the new levee to expand much-needed protected habitat for local biodiversity. 

West Sacramento Southport Levee Improvement Project (SLIP)
West Sacramento Area Flood Control Agency

West Sacramento, CA
United States

9 kms of new and improved levees
Envision Platinum Award for Sustainable Infrastructure