Restoring Two Creeks for Coho
by Aleta George on January 01, 2010
Adding woody debris to Redwood Creek, near the mouth at Muir Beach.
Photo courtesy GGNRA.
After seven years of planning and several months of moving dirt, the National Park Service has completed the first phase of the restoration of Redwood Creek at Muir Beach. The 8.9-square-mile Redwood Creek watershed begins high on Mount Tamalpais, passes through the redwood cathedral at Muir Woods National Monument, and empties into the Pacific Ocean at Muir Beach in the Golden Gate National Recreation Area. The goal of the project, which project manager Carolyn Shoulders estimates will take four years to complete, is to make the creek a functional, self-sustaining ecosystem once again. Although the creek has suffered waves of human impact, particularly at Muir Beach, it’s considered a good candidate for restoration because much of the watershed is protected.
One species that should benefit is the southernmost run of the state- and federally endangered coho salmon. In 2004-05, winter surveys in Redwood Creek tallied 171 adult coho. In 2008-09, when coho populations crashed across the region, only two spawners were observed here. Although the actual spawning occurs farther upstream, juvenile fish moving down the creek toward the ocean need low-velocity hangouts so they’re not flushed out of the system during high flows. Alterations over the last century have narrowed the channel, disconnected the pools, and decreased the number of refuge areas. “What we’re doing is creating suitable conditions for the survival of the offspring,” says Shoulders.
Most of the work completed in 2009 was at Muir Beach, a beautiful and popular recreational destination that draws about 250,000 people a year. The large parking area built years ago to handle these crowds bisects the floodplain and impedes the flow of the creek. The park service has shortened the parking lot to expand the floodplain, and lowered the floodplain’s elevation around the parking lot by removing fill, nonnative trees, and invasive plants. A short distance upstream a pond was excavated in a pasture at Green Gulch Farm to provide habitat for a dwindling California red-legged frog population, the only one in the watershed. “We are close to losing the frogs at this site, so we were in a hurry to create the pond,” says Shoulders.
Next year the team will return the creek channel to its more natural location as it flows through the Green Gulch pasture, reconnecting the creek to its floodplain. Eventually, the parking lot will be relocated away from the creek. “When we’re finished visitors will experience a well-connected landscape where the creek, the wetland, and the beach are all connected,” says Shoulders.
Just to the north, Lagunitas Creek and its tributaries sustain from 10 to 20 percent of California’s total wild coho salmon population. “The Lagunitas run is key to the recovery of other watersheds in the region,” says Paola Bouley of Salmon Protection and Watershed Network (SPAWN). Most salmon return to their birthplace, but about 2 percent stray to neighboring watersheds, she explains. The offspring of these “rebel teenagers” are key to recovery because, if stream conditions are right, most will return to the stream to which their parents strayed, thus reseeding that watershed.
Though the San Geronimo Valley constitutes less than 10 percent of the Lagunitas watershed, it hosts 50 percent of spawning habitat for Lagunitas coho. Much of the watershed is protected, but the San Geronimo Valley has a diverse mix of homes, a golf course, and roads, including Sir Francis Drake Boulevard, all right along the creek.
SPAWN expects about 250 fish to return to the Lagunitas Creek watershed this year, a 98 percent decline compared to historical runs. Wide fluctuations in salmon numbers and probable cumulative impacts from development projects have prompted the creation of a San Geronimo Valley Salmon Enhancement Plan. The Marin County Board of Supervisors will vote in February 2010 on its adoption. Find more about the plan at spawnusa.org.