The Water Forum has completed the construction of its 2024 Habitat Project at River Bend on the Lower American River. Monitoring is now underway to assess the project’s effectiveness in improving spawning and rearing conditions for fall-run Chinook salmon and steelhead trout.
“This site is the farthest downstream of our current habitat program sites and it plays a crucial role because it’s one of the first suitable areas our adult salmonids encounter as they migrate upstream to spawn,” said Erica Bishop, Water Forum Program Manager for Habitat and Science. “By enhancing conditions here, we’re diversifying and expanding spawning opportunities across the upper river.”
Salmonids need clean, loose, “right-size” gravel to lay eggs. The addition of clean gravel and cobble in the river improves localized water quality conditions at habitat sites. The mix of rock sizes within the new substrate supports oxygenation of the water flowing through the spawning riffle, which is vital for the health of incubating eggs. Once those eggs hatch, the juvenile fish need somewhere nearby to hide from predators and grow.
To support these needs, the project enhanced nearly 5 acres of habitat for adult fish by placing 6,800 cubic yards of gravel in the river to create a spawning riffle. The riffle was designed to replicate natural river features that would exist and be replenished periodically without upstream dams, which limit the natural flow of gravel and alter our river flows. Gravel, sourced from historic American River mining tailings at Mississippi Bar, was cleaned and sorted to the size preferred by salmonids before being placed in the river.
“These mining tailings consist of millions of tons of vital sediment taken from the river long ago. It has been sitting unused for decades,” Bishop said. We’re excited to use the river’s native material for our projects and are proud we’ve returned it to where nature intended, supporting the life cycle of fish that depend on these habitats.”
A 1,800-foot-long side channel, previously blocked by sediment, was widened, deepened, and reconnected to the river. This restored channel provides a safe refuge for juvenile fish and includes multiple sub-channels and seasonal floodplain benches. Crews also added 32 submerged woody structures, mimicking naturally occurring logs and branches that protect juvenile salmonids from predators.
Additionally, more than 2 acres of riparian habitat were enhanced with native willows, grasses, and perennials to improve the surrounding environment and support pollinators.
Work began in early July and concluded in late October, just in time for the fall-run Chinook salmon migration. Adult salmon generally arrive at River Bend from late October through December, while steelhead trout will spawn in the area from January through March.
Pacific lamprey, another important species, are also anticipated to benefit from these habitat improvements since their gravel size preference is similar to our salmonids.
Monitoring Underway
River Bend will be closely monitored throughout the spawning season. Teams will survey the area every three weeks, counting and measuring salmon nests, known as redds, both on foot and by kayak. Aerial surveys will complement these efforts.
A habitat project in 2013 near the same spot yielded immediate results. Before that project, no salmon were seen at River Bend. After that project, Chinook salmon and steelhead started using the site and kept using it; two years after enhancement, up to 159 Chinook nests and up to 21 steelhead nests were observed there, accounting for 25 percent of all steelhead nests seen that season.
Bishop is optimistic for similar results: “Our goal is to enhance habitat along the upper river in a way that allows salmon and steelhead to use it year after year,” said Bishop, explaining that natural processes will gradually degrade the site over the long term. “If this riffle is as successful as previous efforts, we expect it to support many redds.”
The 2024 Habitat Project was funded by a grant from the U.S. Bureau of Reclamation and supported by partners including the City of Sacramento, Sacramento County, Sacramento County Regional Parks, the U.S. Fish and Wildlife Service, and the Sacramento Area Flood Control Agency.
Learn more about the 2024 Habitat Project at https://waterforum.org/habitat2024/, and learn more about the Water Forum’s ongoing habitat improvement work at waterforum.org/habitat-enhancement.