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. This multi-benefit project aims to enhance 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.

The project directly addresses (project granter) U.S. Fish & Wildlife Service’s Anadromous Fish Restoration Program’s doubling goal for anadromous salmonids. cbec leads the consultant team with primary support from Cramer Fish Sciences and the South Yuba River Citizens League.

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. This multi-benefit project focuses on enhancing juvenile salmonid rearing habitat by removing unnatural constraints from the river corridor, allowing the project reach to evolve more naturally. Historically, the Lower Yuba River provided a thriving environment for salmonids. This was adversely affected by the introduction of hydraulic mining during the California Gold Rush. The sediment tailings were transported down river, raising the riverbed where they settled. Subsequent management activities created large training walls that disrupted the floodplain’s flow, affecting instream and riparian conditions in the river. A vital component of Hallwood’s multi-benefit design approach focuses on removing unnatural constraints, such as a training wall that separates the main channel from the floodplain, and lowering high elevation gravel terraces. By teaming with a landowner with an adjacent aggregate processing facility, the sediment is removed directly from the river by conveyor system where excavated materials are processed for infrastructure needs. Given the volumes of material to be removed from the river corridor, this unique teaming arrangement makes the project feasible and leads to low cost implementation. Truly a win-win for all project partners.

To date, Phase 1 construction has removed more than 1.2 million cubic yards of  sediment, reclaiming channel and floodplain habitats for Chinook salmon and steelhead trout. Additionally, 89 of the project’s total 157 acres of grading, including seasonal and perennial side channel habitats, have been implemented to restore valuable rearing habitat for these native salmonids. Phase 2 construction began in April 2021 on this large multi-stakeholder, multi-year project. Further implementation is expected to take an additional 2 to 4 years based on future funding availability and aggregate demand.

Phase 1 pre- and post-fine grading completed in 2020 at the perennial channel in the upper half of the site. Note the perennial channel now running in the previously dry floodplain, and the absence of the Middle Training Wall at the bottom, now an open floodplain with a seasonal channel that can connect to the main channel.

cbec has led implementation planning, the Central Valley Flood Protection Board (CVFPB) Encroachment, USACE Section 408, and State Mining and Geology Board permitting efforts, and since 2012, developed initial project concepts through 100% design level. cbec 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. The design also addresses reduction of predator habitat through the filling of deep pools. 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.

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, that removed approximately 1.5 million cubic yards of coarse surface material.
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.