North Fork Stilly ELJ’s

Last summer, Washington Trout participated with the University of Washington, Snohomish County, and federal, state, and tribal agencies, in Phase I of the North Fork Stillaguamish Engineered Logjam (ELJ) Project, building five ELJs at approximately river mile 21 of the North Fork of the Stillaguamish River. The project was funded by Jobs for the Environment, the WDFW, and the Interagency Committee for Outdoor Recreation. Tim Abbe and Tracy Drury, of the University of Washington, designed the ELJs and served as technical construction coordinators.

"Studies have indicated that the recovery of North Fork chinook will depend in part on an increase in large holding pools."

Studies have indicated that the recovery of North Fork chinook (now protected under the ESA) will depend in part on an increase in large holding pools. The North Fork contains reaches with ample spawning habitat, but limited chinook use, do to the absence of large holding pools in close proximity to the spawning areas. Other studies, including work by Tim Abbe, identified the role of logjams in forming the deep scour pools that chinook use for holding areas. The ELJs are designed to provide holding habitat in proximity to the existing but underutilized spawning gravel. Preliminary assessments indicate the ELJs have performed as expected, creating significant summer chinook holding habitat.

"ELJs (Engineered Logjams) provide vital holding habitat for chinook salmon"

This past summer WT participated in a second phase of the project. Three additional ELJs were built near the “Hazel Hole,” at approximately river mile 22.5. The area where the ELJs were installed is currently a plane-bed channel with ample spawning area, but limited chinook use. The new ELJs will provide the vital holding habitat chinook need to access to this available spawning gravel, increasing summer chinook holding habitat at least three fold in this reach. The ELJs will also increase off-channel habitat by increasing the frequency and magnitude of side-channel flows.

Each ELJ contains approximately 300 tons of material, large root-wadded logs, some as long as 70 feet and over four feet in diameter. Washington Trout provided baseline monitoring, coordinated the acquisition of the large logs, and administered the heavy equipment for this ambitious project that promises to significantly increase chinook production in the North Fork Stilly.

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