Efforts to revive the endangered coho salmon in Lagunitas Creek are gaining momentum with a large-scale habitat restoration project launched by Marin Water.
The project, which begins its first phase of construction this fall, aims to restore the creek closer to its natural, pre-dam state, creating optimal conditions for spawning and rearing to preserve the salmon runs that have migrated through the redwood- and oak-lined watershed for thousands of years.
The restoration is expected to benefit not only coho but also other threatened species in the ecosystem, including endangered freshwater shrimp and threatened steelhead trout.
Over the next five to seven years, the district will strategically reintroduce gravel and logs to the creekbed to mimic the conditions that existed before dam construction disrupted the ecosystem, according to Jonathan Koehler, Marin Water’s fisheries manager.
Dams like the 227-foot-tall Peters Dam at Kent Lake and the 115-foot Seeger Dam on Nicasio Creek currently block these essential materials from reaching downstream spawning areas crucial for salmon and steelhead.
“If we could travel back in time to see Lagunitas Creek before human development, we’d find an old-growth redwood forest,” Mr. Koehler explained. “The creek would have been filled with fallen trees and debris. What might look like a tangled mess to us is actually ideal habitat for fish.”
Although Marin Water has been enhancing the creek bed with logs and boulders for over two decades, this initiative represents a more extensive and ambitious undertaking.
“We’ve been working on creek restoration for a while, but this project is on an entirely different scale—both in the sheer volume of materials and the broad geographic reach we’re covering,” Mr. Koehler said.
The estimated $10 million to $12 million project will involve installing 278 logs and, for the first time under the district’s management, nearly 12,300 tons of gravel across 13 sites within Samuel P. Taylor State Park. The initial phase will add gravel to the channel to restore spawning beds at three key locations. Funded primarily through grants, the district has already secured over $6 million in state and federal monies to complete the design and permitting for the first phase.
The placement of large logs will create deep pools and riffles and help retain gravel, which is crucial for salmon spawning and other aquatic life. To prevent the logs from being swept downstream, they will be anchored with heavy boulders.
Lagunitas Creek hosts the largest wild coho run between Humboldt and Monterey Counties, standing out as a rare stronghold of native salmon amid river systems increasingly dominated by hatchery-raised fish. The salmon swim the 33 miles from the Pacific Ocean into Tomales Bay and on into the San Geronimo Valley, where half of their spawning grounds lie within developed areas in the towns of Forest Knolls, Lagunitas, San Geronimo and Woodacre.
The fish, which can reach lengths of 35 inches and weigh up to 36 pounds, navigate through people’s backyards, lay eggs in gravel nests and die within two weeks of mating. Sixteen weeks after hatching, their progeny migrate to the ocean to become adults, eventually returning to the watershed to complete the cycle anew.
The restoration initiative comes at a crucial time. Recent surveys indicate a hopeful rise in coho salmon nests, known as redds—a term derived from a Scottish word meaning “to tidy up.” In streams monitored by Marin Water, 170 coho redds were observed during the 2023-24 spawning season, up from 158 during the previous generation’s spawning three years ago. In Olema Creek, a tributary of Lagunitas Creek, National Park Service surveyors recorded over 70 coho redds, a significant increase from just 14 recorded three years prior.
Salmon Protection and Watershed Network surveyors also documented 43 redds in the tributaries of San Geronimo Creek, up from only three in the previous survey. Across the entire watershed, at least 283 coho redds were recorded last year, marking an increase of more than 60 percent from three years ago.