Presenter/s: Aaron Zettler-Mann
Symposium Session: 2022 - 02 Big Challenges Need Adaptive Management
Topics covered: fish-salmon, floodplain, lessons learned, permits, riparian, and stream
ABSTRACT
During the California gold rush, hydraulic mining was prevalent throughout the Sierra Nevada. In the Yuba River watershed alone, three times more material was washed into the river than was excavated to construct the Panama Canal. This material was washed down river and settled in the lower Yuba River, burying the adjacent Central Valley farmland and aggrading the Yuba River channel up to 40 feet. Channel aggradation triggered increased flooding in surrounding farmland and downstream communities and in 1874 the Sawyer Decision banned hydraulic mining in the Yuba watershed and throughout California. The result of this was that the hydraulic mining debris was ‘re-worked’ using dredge mining creating the Yuba River Goldfields, an area of roughly 5,500 acres of gravel and cobble with piles more than 100 feet high. The California Debris Commission began to rework the gravels in 1899 and created ‘training walls’ to help convey flood flows and allow the material outside of the river channel to be more easily mined. Today, the Goldfields are a combination of privately held and BLM land which is largely unmanaged. Englebright Dam is the rim dam in the Yuba River watershed limiting spawning and rearing habitat for salmonids to roughly 25 miles. Over this 25 miles, the lower Yuba River (LYR) remains largely a single thread channel with disconnected, unvegetated floodplains, and course substrate.
The LYR is home to wild fall and spring-run Chinook salmon and steelhead/Rainbow Trout. Like the rest of the California Central Valley, LYR salmonid populations have experienced declines since the 1850’s due to habitat loss from the presence of impassible dams, mining activities, introduction of invasive piscivorous species, and other anthropogenic factors. The U.S. Fish and Wildlife Service, National Marine Fisheries Service, and California Department of Fish and Wildlife have all identified rearing and spawning habitat as a significant hurdle to salmonid population recovery. In the LYR, restoration involves removing millions of cubic yards (CY) of gravels and cobbles from the floodplain, and then building side channels and backwaters and planting woody riparian vegetation which can be utilized by juvenile salmonids. Two challenges exist here: 1) prohibitively expensive cost to remove material and 2) where do you dispose of millions of CY of gravel and cobble? By partnering with the existing aggregate mines in the Yuba Goldfields, we are able to address both challenges while encouraging economic investment in rural communities. The mining industry all but destroyed LYR salmonid populations, but today we are partnering with that same industry to work together towards restoring salmonid habitat to support population recovery.