Lower Yuba River Long Bar Restoration Project
cbec is working as part of a team on this floodplain restoration project aiming to create rearing habitat for salmonids on a roughly 50-acre riverside gravel mine property at Long Bar on the Yuba River.
It is funded by the U.S. Fish and Wildlife Service (USFWS) Anadromous Fish Restoration Program (AFRP), and ensures its doubling goal for fall-run and spring-run Chinook salmon (Oncorhynchus tshawytscha) and Central Valley steelhead (O. mykiss) by increasing seasonal and perennial salmonid rearing habitat. Project activities include floodplain lowering, side channel enhancement, riparian planting, and large woody debris placement. cbec provided site surveys, data acquisition and analysis, and design concept development. Current project site conditions were created by a history of massive aggradation of hydraulic mining sediment during the late 1800s and early 1900s, followed by rapid channel incision. This was followed by dredging and mining activity within the river corridor. Projected activities include floodplain lowering, side channel enhancement, riparian planting, and large woody debris placement. To date, cbec has provided site surveys, data acquisition and analysis, design concept development, final construction drawings, generated a Basis of Design report to support permitting, and provided construction observation in 2022.
An updated conditions surface model was essential for understanding current topographic and river hydraulic conditions. This was accomplished through the use of unmanned aerial vehicle (UAV – drone) technology, where orthorectified images were collected and analyzed with a Structure from Motion technique to create a topographic surface. Updated channel bathymetry was collected in a boat-based single-beam sonar survey. Ground truthing for the UAV surface and additional topography and bathymetry data were collected using Real Time Kinematic Global Positioning System (RTK GPS) survey equipment. cbec staff processed this data using AutoCAD Civil3D and ArcGIS to provide the basis for developing grading designs, assessing distance to groundwater, and identifying viable planting locations and potential for vegetation recruitment on the developed site.
The process for creating and refining the design was iterative and involved developing a design surface, testing the design with a hydrodynamic model, evaluating results to determine the amount of usable area produced, then continuing to refine and evaluate the design to optimize the usable area. Usable area was determined according to habitat suitability indices for juvenile salmonids that indicate their preference for velocity and depth of flow. Project designs include plans to remove a portion of the legacy hydraulic mining substrate on Long Bar to create improved floodplain connectivity, and habitat heterogeneity to promote riparian vegetation recruitment and salmonid rearing habitat.