30 Jun Salmon Habitat Restoration in the Face of Drought
Salmon Habitat Restoration in the Face of Drought
Written by Ayano Hayes, SPAWN Watershed Biologist
The Salmon Protection And Watershed Network (SPAWN) is approaching one year from removing Roy’s Dam on San Geronimo Creek, which was NOAA’s highest priority fish barrier for recovering endangered central California coast coho salmon (Oncorhynchus kisutch). The removal of Roy’s Dam, and the formation of what we’re calling “Roy’s Riffles,” now creates unimpeded fish passage above (and soon below when Marin County modifies the sill under San Geronimo Valley Drive) the former dam. However, we are currently in a historic drought. Little streamflow matched with increased temperatures have exacerbated drought conditions across California and we’re seeing significant effects of the drought in our streams and rivers. Throughout San Geronimo Creek, creek flow is becoming disconnected, habitat is limited, water quality has declined, and algae blooms persist. This is even happening at the Roy’s Riffles site.
During the first winter after dam removal, the site experienced a few small storms that brought a large volume of sediment down into the constructed channel. This sediment is made up of spawning gravels and small stones that make great salmon habitat. However, with little rainfall and not enough water to flush the sediment further downstream, the low flow path of Roy’s Riffles – which allows continuous surface flow during summer – has piped under the loose gravel in some places. It’s normal for sediments to shift, settle, and move over time. Rivers are dynamic systems and with enough sediment transport, streambeds become resilient to changes in sediment patterns, always providing habitat and surface flow.
As part of SPAWN’s on-going management and maintenance practice, we continue to make small adjustments under the severe drought conditions, including placing brush bundles over the stream to help shade and provide cover for fish. This adaptive work is an easy and simple way to assure that surface flows continue through this historic drought.
In spite of these small issues that have easily been remedied, SPAWN, the California Department of Fish and Wildlife, and the engineers with the Environmental Science Association are excited about the signs of recovery that are are apparent at the site: streamside willows are thick and growing tall, upslope trees are putting on fast growth, and birds, mammals, reptiles, and other wildlife have been seen foraging at and near the site, including a bald eagle! We can’t forget to mention that during the critical months of fish migration, adult coho salmon and steelhead were observed navigating through the restored area heading upstream to spawn, and a healthy population of coho smolts were recorded moving downstream through the low flow channel to make their way to the ocean.
The native plants planted in the winter have been doing exceptionally well, with a high survival rate. A lot of energy has been put into revegetation and irrigation of the site to allow plants to become well established within their first year. More than 65 different species of native plants – grown with the help of hundreds of SPAWN volunteers – consist of trees, shrubs, perennials, annuals, and grasses and have been planted onsite already. Additional plantings will occur in subsequent years. Some of the native trees planted include arroyo willow (Salix lasiolepis), Sitka willow (Salix sitchensis), big leaf maple (Acer macrophyllum), California buckeye (Aesculus californica), blue elderberry (Sambucus nigra), and coast redwood (Sequoia sempervirens). The trees, shrubs, perennials, and grasses will quickly revegetate the site and will form a fully native riparian habitat. Weed management is currently underway to control the spread and dispersal of invasive plants and grasses. SPAWN staff, interns, and volunteers are frequently at the site removing weeds, mulching, and maintaining the plantings and we welcome all who want to help!
To commemorate the special nature of this site, redwoods have been planted on the north-facing slope of the restoration area. The redwoods are dedicated to our volunteer base, who have devoted their time and support to SPAWN throughout the years. Several volunteers have been working with SPAWN for more than 15 years. This grove of redwoods, called the Volunteer Grove, is for all of our volunteers, who form the core of the organization. The Volunteer Grove will grow and stand long after us, reminding us that this kind of work can never be done alone, and that small actions taken by individuals can make a significant impact in the world. The first redwood that was planted by SPAWN overlooks Roy’s Riffles.
The impacts of removing a nearly 100-year-old dam do not occur overnight. Restoration efforts take time to fully mature, but immediate progress is obvious and wildlife have quickly adapted to using the new habitat.
The protection of the endangered coho salmon population that resides within the Lagunitas Watershed is what drives the work we do. We strive to not only create more available habitat, better fish passage, and refuge within these streams, but to also restore the land for the benefit of all wildlife and people. We appreciate the support that the community has given to this important restoration project and we’re so grateful to be part of a community that cares so much about the health of the riparian ecosystem which is the heart of the San Geronimo Valley.