Hallwood fish habitat project already showing signs of success

by Alex Boesch, Yuba Water Agency

As work to enhance the lower Yuba River ecosystem and reduce flood risk for downstream communities continues, initial reports show that fish are already using the habitat restored as part of the 157-acre Hallwood Side Channel and Floodplain Restoration Project. This collaborative effort has been funded by Yuba Water Agency, the California Natural Resources Agency and the U.S. Fish and Wildlife Service, and is supported by a diverse coalition of partners, including the South Yuba River Citizens League, cbec eco engineering, Cramer Fish Sciences, Teichert and Western Aggregates.

The 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. Restoring the habitat to more natural river conditions will give young salmon and steelhead areas to hide from predators, so that they’re able to eat and grow in preparation for their journey to the ocean. As part of the restoration, the removal of 3.2 million cubic yards of Gold Rush-era sediment will also reduce flood risk by lowering water surface elevations and slowing water speed during flood events.

“It is amazing to see that adult salmon and steelhead are beginning to use the restored habitat, as well as thousands of juvenile fish heading to the Sacramento-San Joaquin Delta enroute to the Pacific Ocean,” said Jeff Mathews, the agency’s habitat enhancement project manager. “This is especially valuable due to the current drought, which has impacted habitat and fish populations in neighboring rivers and watersheds.The timing of this work is really critical."

A juvenile rainbow trout/steelhead using one of the recently constructed side channels. Photo courtesy of Tyler Goodearly, SYRCL.

The second phase of the four-phase project, which includes aggregate mining and grading on 34 acres in the lower Yuba River watershed and the removal of 800,000 cubic yards of material from the floodplain, is almost complete.

Photo: Mathews checks out one of the new side channels to see if he can spot any fish.

The work also includes planting of up to 54 acres of riparian vegetation to support floodplain ecosystem restoration. In the first and second phase areas, approximately 11,000 pole cuttings and container seedlings have already been planted, with an additional 5,000 expected to be planted by early November. The planting includes cottonwoods, various willow species and elderberries, and is located along previously constructed side channels, as well as on open gravel bar surfaces. Sites were chosen based on groundwater elevations.

Bundles of pole cuttings before being planted in the ground (top left). A Triangle Properties employee drills into the ground to locate the depth of groundwater (top right). A Triangle Properties employee uses a pneumatic post driver to push pole cuttings into the ground until they reach groundwater (bottom left). A group of pole cuttings after being planted (bottom right).

"This planting work is an opportunity to kick-start the riparian vegetation evolution at the site, now that we have reset floodplain elevations to be more connected to groundwater,” said April Sawyer, senior ecohydrologist with cbec eco engineering. “It is intended to provide shade, cover and food resources for the rearing juvenile salmon and steelhead, as well as refuge from predators and from higher velocities during floods. We'll be watching how the site evolves and taking a look at how the planted vegetation compares to natural vegetation recruitment as well."

Photo: A young willow tree that was planted from a pole cutting grows in an open gravel bar.

Another key feature of the second phase was the installation of a 140-foot-long temporary bridge over the north channel of the Yuba River, approximately 6,000 feet downstream from Daguerre Point Dam. The bridge provides access to the current excavation area and facilitates the removal of aggregate materials from the Yuba River.

These materials are moved using an electric-powered conveyor system that is more than a mile long, running from the excavation area to the Teichert plant for processing. The system allows the material to be moved continuously without using diesel-powered trucks, which saves time, money and helps keep emissions low during construction.

The 140-foot-long temporary bridge stretches across the north channel of the Yuba River (left). A section of the temporary electric-powered conveyor belt that moves aggregate materials from the excavation area to Teichert's facility located next to the lower Yuba River (right).

Last year, 89 acres of floodplain habitat were restored as part of the first phase. The third phase of the project is expected to begin in April 2022, which will restore an additional 13 acres of floodplain habitat and remove an additional 815,000 cubic yards of material from the middle of the Yuba River. The fourth phase is planned to begin in 2023 and will restore 21 acres of floodplain habitat through the removal of 400,000 cubic yards of material. The entire project is expected to be complete in November 2023.

A timelapse taken during the first phase of sediment removal from October 2019 to November 2020 that removed approximately 1.5 million cubic yards of coarse surface material. Video courtesy of cbec eco engineering, inc.

Partners on the project include Yuba Water, U.S. Fish and Wildlife Service, California Natural Resources Agency, South Yuba River Citizens League, cbec eco engineering, Cramer Fish Sciences, Teichert and Western Aggregates.