Decker Island Habitat Restoration Project

cbec performed site‐scale hydrodynamic modeling to evaluate restoration design alternatives at Decker Island in support of the DWR Decker Island Habitat Restoration Project.

Decker Island, immediately upstream of the Sacramento‐San Joaquin River confluence, currently functions as a wetland with limited tidal exchange.

The project aimed to restore tidal wetland habitat for Delta smelt at the site by degrading a levee and widening an existing breach to improve tidal exchange. cbec performed an initial alternative screening modeling effort to identify which of DWR’s five potential design configurations best met project objectives. cbec also modeled the site baseline condition. After coordination with DWR to finalize one design configuration to balance tidal exchange, breach maintenance and scouring velocities, and avoid potential predatory refugia creation, cbec modeled the final alternative. Model outputs such as maximum velocity maps and exceedence plots, water surface elevation time series, flow exchange and animations of tidal exchange were provided to support the permitting process.

The preferred design, including levee breaches, a levee degrade, and internal berm breaches, was constructed in the fall of 2018. The project restored 140 acres of tidal wetland habitat toward the 30,000 acres that the California EcoRestore Initiative aims to restore by 2020.

Waterbody / Watershed

Sacramento River