Little Egbert Tract Feasibility Study and Multi-Benefit Project

cbec assisted in the initial development of a feasibility study for Little Egbert Tract, a project that aims to achieve flood risk reduction and habitat restoration benefits in the region, while creating a more sustainable landscape for agriculture. This restored aquatic land will provide habitat to a multitude of species including Swainson’s Hawk, Giant Garter Snake, Green Sturgeon, Delta Smelt, Chinook Salmon, and California Black Rail.

Under contract with SAFCA, the feasibility study team defined draft project objectives and setting in terms of its physical, flood, and agricultural functions, identified opportunities and constraints, and developed early project concepts. During the conceptual design and evaluation process, multiple design charrettes were held with the steering committee and other invited agencies and local stakeholders to review, refine, and rank the benefits of each alternative leading to the selection of a preferred suite of alternatives. Notable project stakeholders are Westervelt Ecological Services, Larsen Wurzel & Associates, Reclamation Districts 2084 and 536, Solano County, California Natural Resources Agency, California Departments of Water Resources and Fish and Wildlife. The feasibility study is complete, with planning ongoing.

In support of this study, cbec conducted single-beam bathymetric surveys to verify changes in bed topography after flooding, interviewed the land manager and tour of the farming operations, developed potential restoration alternatives, prepared grading volumes to support a rough construction cost estimate, and performed extensive tidal, flood and flood combined with sea level rise screening level modeling to inform benefits and impacts to habitat, agriculture, and water quality. These hydraulic models were then run to simulate the existing conditions of the project over a range of discharges. Different project designs were then screened for juvenile Chinook Salmon fry rearing and Delta Smelt spawning and rearing habitat, as well as assessed for flood inundation patterns. The project designs were compared to the existing conditions to serve as an assessment of each design’s effectiveness. Using the hydraulic models results, a custom particle tracking model was implemented to show how long particles spend within a given area, which assess food web productivity and exchange using exposure time. Particles were also analyzed to understand their transport patterns and final locations after a 2 week long simulation.

cbec is currently developing a Delft 3D hydraulic model to further evaluate a refined set of alternatives for flood conveyance, regional water quality, salinity, and sedimentation impacts. The modeling effort includes a coupled Delft Flow – Wave 3D hydraulic model to evaluate wind wave impacts, sedimentation, flocculation, turbidity, wave run-up, and overtopping for different restoration designs. These designs include natural and nature-based wind wave break islands, wetland marsh habitats, and natural slough networks.