Transforming pastureland into a productive tidal marsh

Creating new sources of food to aid the recovery of endangered native fish is an important step in addressing habitat restoration in the face of climate change.  
acres of tidal marsh restored
The Yolo Bypass is a critical part of the Sacramento River Flood Control System, taking flood water out of the Sacramento River during high water events and releasing it 40 miles to the south in the Cache Slough Complex portion of the Sacramento San Joaquin River Delta. The Yolo Bypass and Cache Slough Complex are important rearing and migration areas for native fish—including the delta smelt—but most of the area consists of farmland or irrigated pasture, a result of habitat conversion that occurred in the late 19th and early 20th centuries.


Tidal marsh habitat restoration in this region can provide many direct and indirect benefits to native fish, but finding the right landscape to restore is critical for near term success and future resilience in the face of sea level rise. The goal of the Lower Yolo Restoration Project was to find that balance between immediate habitat functionality and habitat longevity by converting existing irrigated livestock pasture to natural tidal marsh habitat. 

The scale of the Lower Yolo Restoration Project was a key challenge. The combination of significant haul distances for excavated soil (at times, over three miles round trip), construction window constraints due to proximity to special status species habitat, and variable site conditions presented a number of complications from regulatory compliance and constructability standpoints. That the project had to be constructed within months added another layer of complexity.


In conjunction with the construction contractor and other project partners, our team developed a comprehensive approach to project implementation that established clear roles and responsibilities that resulted in the project being constructed on-time and within budget. 

Our biologists also provided construction monitoring during three months of project implementation during the summer of 2020. This work included a large fish rescue and relocation effort over several days prior to some in-water work. The team also encountered several special status species (including the giant garter snake, western pond turtle, and Swainson’s hawk) and had to get the contractor to modify the construction schedule and methods in order to avoid direct or indirect impacts to the species.


The Lower Yolo Restoration Project was completed in October 2020 and now represents one of the largest habitat restoration projects to ever be completed in the Western United States. Over 1,700 acres of tidal marsh habitat is now functioning as designed with full tidal exchange with surrounding natural tidal channels. Consisting of a mosaic of intertidal floodplain and subtidal channels, it helps to facilitate the food web (e.g., invertebrates and plant detritus) to the larger Cache Slough Complex. 

Performance monitoring of the restored habitats has begun and will continue into the future. The data from the monitoring effort will help inform future habitat restoration projects in the Sacramento San Joaquin Delta and beyond.
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