Fallen trees in Sonoma County creeks add to salmon habitat
Walking along the shaded banks of Dutch Bill Creek outside Occidental, geomorphologist John Green and environmental scientist Derek Acomb are satisfied with the winter that just passed. A deluge of water swelled thirsty watersheds, and strong winds knocked down an untold number of trees throughout the Sonoma County.
“It’s been a good year for trees coming down,” said Acomb, with the California Department of Fish and Wildlife. “It’s all about context; it’s all about where you are.”
While falling trees are a threat to both life and property, they create healthy habitats for coho salmon and steelhead trout. As much as dams, logging, agricultural runoff and overfishing throughout the decades have contributed to the collapse of salmon and trout populations, clearing creeks and rivers of downed trees and upended roots has been a major driver, too, Acomb said.
With more than 90 percent of the county’s watershed in private hands, the onus is on landowners to protect riparian habitat on their property. Before an individual can alter downed trees, logs and other forest material in waterways on their property, they must first receive a free permit from Fish and Wildlife — unless there is an immediate threat to life and property. The Gold Ridge Resource Conservation District can also assist in the process, said Green, the lead scientist and program manager there..
There are times when property owners call Fish and Wildlife, afraid debris in a nearby stream might flood their property or their homes. While there are serious emergencies, he said, most trees don’t pose an immediate threat.
“When they call, they’re in a survival state-of-mind,” Acomb said. “Then the following day the water has subsided and they see they’re going to be OK.”
Until the late 1990s, flood protection was the primary focus when managing creeks, streams and rivers, not habitat protection, said Green, overlooking a creek flowing through Westminster Woods where he has devoted a decade of work. The faster the water flows, the more quickly it can drain water when the rivers hit flood levels.
But without the protection from pools created by debris shaping the creek beds and slowing down the flow of water, juvenile salmon and trout are vulnerable to predators like river otters, raccoons and blue herons, Green said. Pools created by fallen timber also provide a place for coho to wait out a long, dry Californian summer before they finally venture out to the ocean in the winter months, he continued.
“With a little less flood capacity you can have a huge increase in habitat,” Acomb said, standing on the mossy bank next to Green. While the two work for different agencies, they have partnered to restore habitat in west Sonoma County.
With not enough lumber falling into creek systems, the Gold Ridge RCD implemented the Dutch Bill Creek Coho Habitat Enhancement Project. In the past two years, 27 structures using root wads, logs and boulders have been placed on the banks of the creek to slow down the flow and create pools where young coho can hide from predators.
Acomb pointed out a pink ribbon tied to a small branch at the edge of the creek, and said — with a brimming smile — it was put there by University of California salmon-monitoring program to mark the place where coho and steelehead were found spawning.