In California's Sacramento&inus;San Joaquin Delta, land surface elevations have subsided by as much as 25 feet below sea level, and large levees are now required to keep delta islands from flooding. Ducks Unlimited has worked with the California Department of Water Resources to deliver several subsidence-reversal projects in the Sacramento&inus;San Joaquin Delta, recently completing the Twitchell Island East End Project.

This project restored a semi-perennial wetland on former agricultural land by restarting the ecological processes that build up peat soils and increase land-surface elevation. Given the current understanding of accumulation rates, it will take 100 to 150 years for the project area to return to sea level. In the meantime, this project will provide 750 acres of new brood ponds for breeding ducks as well as habitat for a great abundance and diversity of other wildlife.

Swales and potholes were excavated to provide open-water habitat surrounded by dense stands of tules, and several small islands were built throughout the project area to provide secure nesting habitat for waterfowl and other wetland birds. Berms and water-control structures will be used to manage water surface elevations in the wetland.

"The key to making the whole project work was designing the infrastructure to carry water from each of the 13 wetland units and four separate water surface elevations," said Brett Williams, regional engineer for Ducks Unlimited.

Together, the Twitchell Island project and others like it will help create a sustainable ecosystem in the Sacramento&inus;San Joaquin Delta and increase local waterfowl populations.