Lemhi River Mile 32 Habitat Enhancement Project - Island Phase

The Lemhi River Mile 32 Habitat Enhancement Project - Island Phase will improve 0.72 miles of habitat along the Lemhi River, just downstream of its confluence with Hayden Creek. Hayden Creek, the most productive tributary of the Lemhi, supports up to 40% of the basins spawning Chinook Salmon each year, along with populations of Steelhead and Bull Trout. This section of the Lemhi is primarily a single-channel system, with one side channel diverging around a large island. The existing channel is characterized by steep gradients with fast flowing water and limited rearing or overwintering habitat. The project will enhance

habitat complexity by raising riffles within the mainstem Lemhi, grading inlets to re-engage relic side channels, creating new channels and floodplains, and installing in-stream wood structures. These efforts will expand the riparian corridor and establish a network of off-channel and side-channel habitats, giving juvenile salmonids more areas for rearing and overwintering in the Lemhi. A fence will be constructed to protect the completed project, and seeding and weed treatment will occur.



The design builds on existing vegetation and relic channels to enhance floodplain connectivity and boost habitat diversity and ties into the work that was completed during the Lemhi River Mile 32 Habitat Enhancement Project- Confluence Phase of the project in 2024 (PCSRF project 014 21 SA).



Other Engineered Structures in the metrics refer to engineered riffles.

Expanding and enhancing side channel habitat will boost habitat capacity for juvenile Chinook Salmon and steelhead. By reactivating old side channels and creating new ones, the project will broaden the riparian corridor and create additional fish habitat, while

incorporating wood structures will add habitat complexity. Constructing riffles in the Lemhi River channel will activate more of the floodplain, expanding fish habitat and supporting healthier riparian vegetation. The projects location downstream of spawning grounds on the

Lemhi River and Hayden Creek provides an opportunity to provide habitat for rearing parr and overwintering pre-smolts, keeping them in the Lemhi River longer.