Hallwood Fish Habitat Project
The Hallwood Side Channel and Floodplain Restoration Project is designed to enhance the lower Yuba River ecosystem by increasing available juvenile salmon habitat to improve the natural production of Chinook salmon and Central Valley steelhead. The project will also reduce flood risk through lower water surface elevations and velocities during flood events.
In the project area, the Yuba River is constrained by tall, linear cobble embankments called training walls, which were constructed in the early 1900s by hydraulic dredges following the Gold Rush. These training walls are within the highly modified Yuba Goldfields setting where hundreds of millions of cubic yards of hydraulic mining sediment was deposited in the lower Yuba River through the early 1900s. The area was subsequently dredged multiple times, creating significant impacts for the natural flow of the river and the floodplain. A large training wall in the middle of the river, known as the Middle Training Wall, runs more than two miles long the length of the project.
The Project Plan
The project design is based on the premise that restoration of natural river and floodplain processes, including the removal of large portions of the Middle Training Wall, will create a healthier, more natural, and therefore, more productive river. Improvements will enhance up to 157 acres of seasonally inundated riparian floodplain, approximately 1.7 miles of perennial side channels, and approximately 6.1 miles of seasonally inundated side channels, alcoves, and swales.
Enhancements will be made through land surface changes, riparian planting, and placement of large woody material embedded to simulate a more natural river at key locations. The total project cost is estimated to be $12 million, with Teichert’s in-kind contribution of rough grading and aggregate removal estimated at $70 million. Funding has been provided by grants from the California Natural Resources Agency, Wildlife Conservation Board, USFWS and Yuba Water Agency.
Phase 1 included the removal of approximately 1.2 million cubic yards of sediment from the elevated floodplain and a section of the Middle Training Wall, followed by enhancing 89 acres of side channel and floodplain habitat. Phase I was completed in 2020.
Phase 2 involved removal of approximately 800,000 cubic yards of sediment from the Middle Training Wall and surrounding floodplains in the upper reach and enhancing 34 acres of floodplain and seasonally inundated side channel habitat. Phase 2 was completed in 2021.
Phases 3 and 4 will remove large portions of the Middle Training Wall, yielding approximately 815,000 and 400,000 cubic yards of sediment, respectively, and enhancing an additional 13 and 21 acres of floodplain and seasonally inundated side channel habitat. The final phases of the project are expected to begin in 2023. The fourth and final phase of the Hallwood Side Channel and Floodplain Restoration Project is underway now and is expected to be complete in fall 2023.
- Why is the project being designed and constructed?
The Anadromous Fish Restoration Program aims to double the natural production of anadromous fish (fish that spend their adult life in oceans and return to the rivers to reproduce) like Chinook salmon and steelhead. The lower Yuba River can host up to 20 percent of all salmon spawning in the Sacramento River tributaries, but these emerging young fish face many challenges reaching the ocean. The primary focus of this project is to enhance productive juvenile salmonid rearing habitat, to allow juvenile fish to grow larger prior to their migration to the ocean, which will increase their chance of returning as adults. The U.S. Fish and Wildlife Service is funding the design and implementation of the Hallwood Project.
- How often will the floodplain at the project site inundate?
The floodplain surrounding the more than three miles of perennial side channels and four miles of seasonal side channels will inundate continuously for several weeks approximately every two years with shallow slow water favorable for juvenile salmonids. Groundwater-fed perennial side channels will stay connected all year, while seasonal side channels will inundate with typical spring flows to provide off-channel rearing habitat for juvenile salmonids.
- Who else besides fish benefits from the project?
The project will improve more than 170 acres of seasonally inundated riparian floodplain habitat for numerous riparian tree species, and the host of aquatic and terrestrial organisms that reside in these habitats. This project increases the connectivity of these habitats for a healthier, more productive river system; a resource benefit to the public for purposes such as aesthetics and recreation.
- How will we know that the project improves habitat?
Pre-project monitoring began in 2014. Following that, snorkel surveys were conducted and macroinvertibrates (aquatic bugs) and water temperature were monitored from 2014 - 2016. Riparian vegetation composition and recruitment, and dissolved oxygen and turbidity grab measures were performed in 2016. Pre-project monitoring studies designed to compare fish health in off-channel habitat to the main channel, using juvenile outmigration and predation experiments, were performed in spring 2016. As part of implementation, physical and biological variables such as these will be monitored into the future to assess the project's effectiveness and learn lessons for future projects like this in the Central Valley.
- Are there other places in California where this type of project has been successful?
This is the first project of its kind on the Yuba River, but similar actions have been take on other rivers in California. For example, on the Merced River, floodplain grading to create spawning habitat has led to high levels of spawning and floodplain utilization by juvenile salmonids. Additional projects on the Trinity, Stanislaus and American rivers have also improved main channel, off-channel and floodplain habitats for salmonids.