Photo: Jay Mather.

Log Jams + Beaver Dams: Restoring Whychus Creek at Willow Springs Preserve

Mar 29, 2022 by Jana Hemphill
The Land Trust and our partners are embarking on a restoration of Whychus Creek at Willow Springs Preserve this year.

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After a pandemic delay, the restoration of Whychus Creek at Willow Springs Preserve will kick into high gear this summer! The Land Trust is collaborating with our restoration partners on a low-tech approach that uses natural processes to restore the creek over several years. If stream restoration conjures images of heavy machinery moving soil and sculpting a new creek channel, replace that image with one of small crews working together to build more than 130 structures by hand in a 3/4 mile stretch of Whychus Creek. What will these structures look like? Well, a lot like log jams and beaver dams.

Most of the structures used in the restoration will be Post Assisted Log Structures. These look like log jams in the stream, and are constructed with vertical wooden posts that are angled against placed logs in order to provide stability. Small juniper trees, ponderosa pine trees, and other branches will be used to create these structures.

These structures will extend partway across the creek and deflect the flow of water in different directions, helping Whychus Creek transform from a single channel into a braided series of channels that spread across the valley floor. This transformation will help create a variety of habitat types for fish and wildlife: deep pools, fast flowing sections, slower ponds of water, and plenty of wood in the creek. It will also allow the creek to spread across the valley floor, slow high waters, and connect the creek to underground water. This, in turn, helps cool the creek and keep it at a healthy temperature for fish and other wildlife. See what Post Assisted Log Structures look like.

Smaller beaver dam-like structures will also be built on side channels to create slow-water pools, offer different types of habitat for fish and wildlife, and help connect Whychus Creek to the surrounding meadow. These structures are designed so that water can flow through them, even though they will span an entire side channel of the creek. Some of these dam-like structures will first be built in the dry meadow. Once the log structures on the main channel have begun to do their work, water will flow towards these mini-dams and they will become part of the braided channel creek system. See what these mini-dams look like.

Neither type of restoration structure is intended to be permanent. Eventually, high flow water events will wash them away, and the woody debris will accumulate in other parts of Whychus Creek, creating additional habitat downstream.

With the restoration at Willow Springs Preserve taking several years to complete, we look forward to seeing how Whychus Creek evolves and changes over time. Stay tuned as this project continues!

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