Habitat restoration

California tears down levee in 'largest tidal habitat restoration in state history'

By Amy Graff

A piece of heavy construction equipment called a backhoe loader dug into a levee in the Sacramento-San Joaquin Delta Wednesday, breaking down a portion of the earthen embankment and allowing tidal waters to flow across 3,400 acres of land for the first time in 100 years, officials said.

The tearing down of the levee is among the final steps in a public-private project to restore tidal land — which was turned over to farmers and duck hunters — to its natural state. The plot of land, located in Solano County and just upriver from Rio Vista, is being called Lookout Slough, and it will provide new habitat for fish and wildlife and increase flood protection for the greater Sacramento area by boosting water storage capacity in the Yolo Bypass, Charlotte Biggs, an assistant division manager with the California Department of Water Resources and the lead on this project, told SFGATE.

Lookout Slough marks “the largest tidal restoration project in California history,” Wade Crowfoot, California’s natural resources secretary, said in a video posted on social media.

The Yolo Bypass, stretching 40 miles between Sacramento and Rio Vista, is a massive flood plain that absorbs water during heavy rains, preventing it from overwhelming levees and flooding communities in the greater Sacramento area. Anyone who has traveled Interstate 80 between Davis and Sacramento has been on the 3.2 mile-long elevated Yolo Causeway, which crosses over this area.

A 1,920-foot-long weir equipped with 48 gates prevents water from flooding populated areas in wet winters, diverting it into the farmland, duck-hunting clubs and protected wildlife habitat of the bypass. Lookout Slough will permit more than 40,000 acre-feet of additional flood storage within the Yolo Bypass. “In high water events it will take on more water that helps protect our urban areas,” said Biggs.

Sabrina Washington, a spokesperson for the California Department of Water Resources, explained that before urban development in the Sacramento Valley, rivers naturally overflowed during the rainy season and the area flooded. “Then we built a bunch of levees for agriculture and for people to live and we’ve been redirecting the water,” Washington said. “Now, what DWR has been doing is removing some of those levees in order to restore habitat, where habitat had originally been.”

A key part of the project is also providing habitat for native creatures, including salmon and the endangered Delta smelt, officials said. The Delta smelt is a small, slender-bodied fish that sits at the bottom of the food chain. This species may seem insignificant, but, “bigger fish depend on them,” Biggs said. If this fish were to disappear, there would be repercussions. “It’s the first indicator of your food web crashing when your base is crashing,” she said. 

A wildlife haven, the Yolo Bypass is stop for many birds on the Pacific Flyway. Biggs said portions of the levee were not destroyed, allowing small islands of land to remain for waterfowl. 

Construction on the project began in June 2022, and included a new 3-mile-long, 25-foot-tall levee that is set back farther from the water. The previous levee at the site allowed some seepage, such that farmland there eventually became unusable for agriculture. Biggs said the new levee was built to “prevent seepage.” On Wednesday, workers removed 600 feet of dirt from the old levee; it marked the first of nine breeches that are slated to be completed in October. 

“The Delta is a biodiversity hotspot where we’re making progress on a large scale to restore natural habitat for fish and wildlife,” Crowfoot said in a statement. “This project is a big step forward toward our ambitious restoration goals, and we’ll continue to build momentum and make more progress in the months and years to come.”

When the project is fully complete, which is expected to be in the coming months, the restored slough is slated to also be open for recreation like fishing and viewing wildlife, but it’s not the last of the construction planned for this area in 2024. This fall, Caltrans is expected to begin a highway widening project on Interstate 80 that would create 17 miles of express lanes beginning at the border of Solano County, including the Yolo Causeway.