Permanent Flood Protection, Novel Ecosystem Restoration
Design and implementation of habitat restoration within the floodway and levee setback area for the 2-mile Bear River Levee Setback Project was a collaborative feat that will forever improve flood safety.
Few places in California have the flooding history that Yuba City and Marysville share. River Partners engaged with a collaborative entity, the Three River Levee Improvement Authority (TRLIA) to design and implement green flood protection infrastructure and habitat restoration within the floodway and levee setback area.
At the time of the project design, there was considerable concern that the newly created floodplain would become a fish-entrapment hazard as floodwaters drew down off the site. To remedy this, a swale was graded into the downstream end of the project to direct floodwaters back to the river channel. After monitoring the swale in 2017, TRLIA reports that the swale is still in place and functioning as expected.
Vegetation communities were designed to meet target roughness values provided by flood engineers ranging from open grasslands to shrubby savanna to dense riparian forest. Native elderberry shrubs in the levee construction footprint were transplanted and incorporated into the restoration site. A portion of the site was reserved for Swainson’s hawk compensatory mitigation, and the hawks are often seen here nesting in the restoration site, and foraging over the grasslands and shrublands of the mitigation site and its surroundings.