Yolo Ranch Tidal Wetland Restoration Project
cbec was contracted by SFCWA to develop the largest restoration project in the Lower Yolo Bypass in Yolo County, California.
The project is being completed in partial fulfillment of the contractors’ requirement to provide mitigation restoration for the endangered Delta Smelt. cbec undertook water quality monitoring/ bathymetric survey, performed 2D hydrodynamic modeling, and developed 100% design plans and specifications for the project, as described below. The tidal wetland restoration design will be constructed in 2014.
Field Data Collection: Water level, temperature and conductivity were monitored at sixteen locations to assess aquatic habitat resources, understand inundation and tidal regimes, and support the restoration design. Groundwater levels were monitored at three locations to support the restoration design and inform project construction. Numerous soil pits and six geotechnical borings were collected to understand the morphology of the site, identify location specific features (i.e., duripans, massive clays), and generally support the restoration design and inform project construction. Multiple topographic and bathymetric surveys were also conducted over the life of the project to refine the LiDAR data, correct the LiDAR data for vegetation and ponded water, describe channel conditions, and generally support the restoration design and inform project construction. The surveys were often challenging due to the size of the site, and site complexity, and were mostly performed using RTK GPS technologies.
Tidal Hydrodynamic Modeling/Channel Sizing: cbec developed a MIKE 21FM (2D flexible mesh) model for the restoration site and Cache Slough Complex to support the restoration design. The restoration design and proposed tidal channel alignments were incorporated into the model to understand site inundation regimes, food web export, and select for channel geometries that provided in-channel velocities sufficient to promote self-maintenance and tidal prism conveyance. The model was also used to understand project impacts on water supply for irrigation and drainage and provide design solutions that supported existing demands.
Restoration Design Plan and Specifications: Restoration design grading plans and specifications (100%) were developed in 2013. Restoration features included new tidal channels, berm breaches, new tide gates, new diversion structures, a relocated lift pump structure, new drainage ditches, and integration with irrigated agriculture.