Lower Yuba River Hallwood Channel and Floodplain Restoration Project

This project is designed to restore and enhance ecosystem processes within an important reach of the Yuba River.

The primary project focus is on enhancing productive juvenile salmonid rearing habitat to increase the natural production of fall‐run and spring-run Chinook salmon (Oncorhynchus tshawytscha) and Central Valley steelhead (O. mykiss), by removing unnatural constraints from the river corridor and allowing the project reach to evolve more naturally. cbec leads the project team that is working to directly address (project granter) U.S. Fish & Wildlife Service’s Anadromous Fish Restoration Program’s doubling goal for anadromous salmonids.

The project will enhance and create up to 157 acres of seasonally inundated riparian floodplain habitats, more than 1.7 miles of perennial side channels and alcoves, and more than 6.1 miles of seasonal side channels, alcoves, and swales. The design approach focuses on removing unnatural constraints (such as a mid-river training wall and coarse surface materials) in order to allow natural river and floodplain processes to function. cbec leads the consultant team with primary support from Cramer Fish Sciences, and the South Yuba River Citizens League. Phase 1 construction began in October 2019 and was completed November 2020. This is a large multi-year project and implementation is expected to take between 4 and 6 years to implement.

This drone imagery looks upstream, revealing the perennial channel and alcoves that replaced deep ponds downstream, and dry gravel bars upstream on the floodplain. The Middle Training Wall separates the main channel on the right from the floodplain on the left. Phase 1 involved removing 1,200,000 CY of sediment from the Middle Training Wall to facilitate connectivity between the main channel and floodplain, and created/enhanced 89 acres of habitat for rearing juvenile salmonids.

cbec developed initial project concepts in 2012, and has since led, project design to 100% level, implementation planning, and the Central Valley Flood Protection Board (CVFPB) Encroachment, USACE Section 408, and State Mining and Geology Board permitting efforts. cbec has performed several topographic and bathymetric surveying efforts in support of the hydrodynamic modeling and design process. Survey work has included foot-based RTK GPS surveys of the floodplain areas, drone-based structure-from-motion topographic surveys, and bathymetric surveys with both a remote-controlled boat and a jon boat outfitted with a single-beam echosounder. Survey data have been incorporated into a topographic surface that has allowed differencing analysis with prior LiDAR data to understand geomorphic change of the site. Field campaigns also verified extents of vegetative cover to inform roughness values used in the hydrodynamic model.

As part of leading the design development, cbec developed and calibrated one-dimensional (HEC-RAS) and two-dimensional hydraulic models (SRH-2D by USBR) for both high flows and low ecologically functional flows. The high flow models were used to support the CVFPB Encroachment Permit process. Low flow models were used to inform design and to quantify project benefits as suitable habitat areas using habitat suitability indices for target species. Geographic information systems (GIS) were utilized to map and analyze project data as needed. Cramer Fish Sciences led pre-project biological monitoring, environmental permitting (NEPA/CEQA, CDFW, Section 401 and 404, cultural resources, State Lands Commission), provided biological rationale for the project design, and perform pre- and during-construction biological monitoring. SYRCL vegetation ecologists led vegetation impact analysis, planting plan design and vegetation monitoring efforts.

As of winter 2020, Phase 1 of this multi-phase project was be completed, with Phases 2 through 4 to proceed in the coming years, depending on funding availability.

Learn more about this project at hallwoodproject.org.

Typical cross sections for existing and proposed conditions showing created habitats such as seasonal side channels and vegetated floodplain areas.
Timelapse of Phase 1 sediment removal from October 2019 to November 2020.
This video provides a bit of history of the project. Watch and learn how the hydraulic mining during the California Gold Rush played a part in the need for this project, and how the project team is turning that environmental legacy into a multi-benefit collaboration.