The culvert had provided vehicle access across the creek on a U.S. Forest Service road, but it was a barrier to resident fish species and was at risk of failing and sending sediment to salmon habitat downstream.
“The culvert didn’t contain streambed material and had a 3- to 4-foot outfall drop, so it likely prevented upstream passage for resident fish species,” said Devin Smith, restoration ecologist for the SRSC. The SRSC is the natural resources arm of the Sauk-Suiattle and Swinomish tribes.
Tenas Creek is a productive tributary that is used by a number of fish species, including chinook, pink and coho salmon, native char and steelhead. Spring chinook populations have especially low numbers and are a high priority for recovery efforts. The glacial-fed Suiattle River has very high sediment loads naturally, so spring chinook depend on cool, clear tributary streams like Tenas Creek for spawning and rearing.
The culvert removal was part of a three-year project in partnership with the Forest Service to upgrade and decommission approximately 18 miles of forest roads in the Suiattle River basin. The primary goal of the project is to improve habitat for spring chinook and other species by reducing landslides and other sediment impacts from poorly maintained forest roads. Removing the large culvert on Tenas Creek had the additional benefits of restoring the floodplain to natural stream function and providing fish passage through the road crossing.
Roads are upgraded by improving drainage conditions. That can include replacing existing stream crossings with larger culverts, improving ditches, removing fill from unstable slopes, and reducing fill over stream crossings. The roads remain drivable and require future maintenance.
Decommissioning roads involves removing all culverts, constructing water berms to increase drainage across the road, removing hazardous fill material from stream crossings and unstable slopes, and blocking the road to vehicle access. Properly decommissioned roads require no further maintenance.
The Tenas Creek road project fulfills a priority in the tribal and state co-managers’ Skagit Chinook Recovery Plan – to control sediment in the Suiattle River basin.
Sediment degrades salmon habitat by smothering spawning gravel, which reduces survival of salmon fry. It also can reduce the quantity and quality of rearing habitat.
“The Suiattle River already has a naturally high sediment load,” said Richard Wolten, Sauk-Suiattle natural resources director. “This project will prevent chinook habitat from being further degraded by sediment loads from poorly maintained forest roads.”
For more information, contact: Devin Smith, SRSC restoration ecologist, 360-391-1984 or [email protected]; Kari Neumeyer, NWIFC information officer, 360-424-8226 or [email protected].