Update on the Dutch Bill Creek Winter Habitat Project after 2023 January Storms
Each winter and spring, coho salmon and steelhead trout hatch from eggs laid in streambed gravels by spawning adult fish. Juvenile coho and steelhead spend the first year of their lives in the creek before migrating to the ocean the following spring. These fish are only a few inches long and are susceptible to being washed downstream and injured or killed by high streamflow that occurs during winter storms. Areas of relatively calm water are thus critical to the survival of juvenile fish, providing them with places to shelter during high flows. Under natural conditions, sheltered, low-velocity zones are created by trees that fall into the stream and deflect the water’s flow, creating sheltered areas around the wood and on the margins of the stream channel. Smaller wood pieces moving downstream in high flows accumulate on the larger pieces, forming large wood jams. In addition to providing shelter, wood provides a multitude of other benefits for salmon and steelhead during different stages of their life.
Because of specific characteristics of its watershed, Dutch Bill Creek is more likely to see high velocity flows during winter storms. Dutch Bill is also notable for the relative scarcity of wood in the creek, despite the fact that it flows through redwood-fir forest for most of its length. The lack of wood in Dutch Bill Creek is due to many factors, including the condition of the forest it flows through and past stream management practices. To remedy this scarcity of wood (and the resulting lack of sheltered habitat for juvenile fish), the RCD and our partners have constructed a number of projects to place wood in the stream in the form of engineered and anchored wood jams. These structures mimic natural wood accumulations but are intended to be stable and remain in place. In 2019–2020, the Gold Ridge RCD worked with Dragonfly Stream Enhancement to construct the Dutch Bill Creek Winter Habitat Project. The project was intended to enhance salmon habitat in a reach of the creek on the Westminster Woods property, with the specific goal of providing a low-velocity areas for juvenile coho and steelhead. It involved the construction of large and complex wood jams at eight locations along 750 feet of the creek. These structures are much larger and contain more wood than any we had constructed previously.
The Dutch Bill project was constructed during a time of severe drought, and because of the lack of rain there had not been a period of sustained high flow since construction. This changed in early January 2023, when a number of sizable storms occurred back-to-back over two weeks. Gold Ridge RCD staff revisited the project site during the resulting high flows, and we are pleased to report that the large wood jams are functioning as designed, creating new habitat elements by deflecting flow, among them areas of calm, sheltered water around the wood jams and along the channel margins. This reach of creek, which previously had experienced high water velocities even in moderate flows, is now a much safer and more hospitable place for juvenile fish. Staff will continue to monitor the project site periodically during high flows, and we hope to replicate this approach at other locations.
The Resource Conservation Network gathers and shares the stories and ideas from its partners and colleagues. The opinions expressed do not necessarily reflect those of the RCDs managing this publication.
