Hayden Creek Hermits Habitat Improvement

Hayden Creek is the largest tributary to the Lemhi River and contributes a significant portion (average of 30-40%) of the Lemhi Rivers total annual streamflow. It remains a productive spawning stream for wild steelhead and Chinook Salmon with as much as half of all Lemhi basin redds occurring between the mouth and the East Fork of Hayden Creek. Although spawning does not appear to be limiting, juvenile migration data suggests poor rearing habitat for early life stages in Hayden Creek. Lower Hayden Creek primarily flows through agricultural land where the channel has been modified and removal of woody debris has altered natural stream processes. The Hayden Creek Hermits Habitat Improvement Project improved and increased vital rearing habitat for early life stages of Chinook Salmon and steelhead trout on Hayden Creek. Work included the construction of a variety of wood structures including anchored and unanchored individual logs, engineered log jams, stumps with rootwads, unanchored boulders, and willow weaves. These structures increased habitat diversity on Hayden Creek and provided crucial habitat for juvenile salmonids. Unanchored logs and boulders will move naturally during future highwater events and continue to add diversity and complexity to Hayden Creek. Native seed and potted plants, including cottonwood, willows, dogwood, and water birch were planted throughout the project reach to help expand and improve riparian vegetation. The project provided an immediate improvement to fish habitat on Hayden Creek, and the large wood material added to the system will allow the reach to be dynamic and continue to develop fish habitat over time.



This project received two amendments; 1) to extend the contract and increase the award amount due to an increase in construction costs of phase 1, and the addition of a 2nd phase of the project to increase instream treatments and include riparian plantings, and then 2) to further extend the contract and reduce the amount of the award after costs for the 2nd phase came in under budget.



The project underspent its awarded funds by $25,537. These funds had been expected to be used to complete adaptive management following a spring highwater event, but it was determined that the project was functioning as intended and no adaptive management was needed.

Restoration treatments will focus mainly on increasing the amount of instream rearing habitat for juvenile fish species by encouraging overbank flow, accumulation of woody debris for cover, erosion/deposition, and formation of new, low-velocity channel units. Along with this juvenile habitat, restoration treatments will create low velocity pools with overhead cover for adult fish to hold, and recruitment of spawning gravels.



Project objectives identified to reach this goal:



1) Increase the spatial variability of channel depths and velocities preferred by juvenile fish by mimicking natural processes via log structures, loose woody debris, and gravel bar construction (contingent upon accumulation rates).

2) Increase the amount and variety of shelter/cover by adding cover to banks where needed, incorporate small woody material in log structures, and place structures to reduce distance between various cover types (whether existing or constructed).

3) Promote deposition of finer gravel substrate suitable for redd construction by increasing the variety of hydraulic zones (areas of similar depth, flow field, and bed shear stress).