Mainstem Scott River BDAs
Project Goals and Objectives
Increase structural diversity in the simplified channel of the Scott River and create habitat for Coho Salmon. BDAs placed upstream and downstream of tributary confluences to backwater the confluence and improve access to the tributaries for spawning salmon.
Structure Construction Elements
Post with willow wicker weave, berm constructed with native alluvium, straw, native plants and rock. 4 BDAs, two at each of two sites. Placement and number of structures was limited by regulatory constraints as these were the first generation of BDAs constructed in California and they were deemed "experimental". The first winter after construction had a large flood event and 2/4 BDAs were entirely washed out. One of the BDAs was placed at an angle to the river thalweg to create habitat and deflect flow from a bank eroding into productive agland. This structure is still in place today. One BDA has approximately 0.25 of the length remaining and has created a pool downstream. Both of these BDAs were upatrem of the tributary confluence, whereas the BDAs that entirely washed out were downstream. Lesson learned, BDAs in a mainstem river with sandy substrate placed perpendicular to the flow and downstream of a major tributary confluence have a low likelihood of longterm duration.
Project Photos
Cover Photo
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BDA under construction
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BDA capturing salmon carcasses.
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BDA breaching during flood event