Little Hoko River Restoration Design

The Little Hoko River is the largest tributary to the Hoko River, which is the largest watershed in WRIA 19. The river supports populations of chinook, coho, and chum salmon as well as cutthroat, steelhead and lamprey. The lower portions of the Little Hoko River were conserved in the early 1990s when the Cowan homestead was purchased by Washington State Parks. Simultaneously, a large scale restoration project was implemented by the Lower Elwha Klallam Tribe between 1994-1998. In this project cattle were initially fenced out of the riparian zone (and later removed), extensive riparian plantings completed, several off-channel habitats created, and additions of wood made to the channel. The type of wood additions used in the 1990s consisted of mostly single log structures and small logjams built with cut logs. While the original restoration effort has improved channel and riparian habitats, the majority of wood placements have been buried under accumulated gravel. This has greatly improved spawning habitat, however additional restoration work using complexes of large wood are necessary to improve spawning and rearing habitat. In support of those goals, we conducted a geomorphic, hydrologic and hydraulic analysis of the watershed that resulted in a basis of design report. This provided the necessary information to support an engineering design of restoration treatments in the watershed. Those designs were reviewed and advanced by project partners including State Parks, Makah Tribe and North Olympic Salmon Coalition. The preferred alternative was selected that includes 62 logjams in a 2.5 reach of the Little Hoko River. Those designs were completed and used to advance the project toward permitting and construction.

The goal of this project is to develop an engineering design and cost estimate for restoration design for the Little Hoko River. The preferred alternative was selected that includes 62 logjams in a 2.5 reach where wood accumulations will slow peak stream flows and result in channel aggradation and the formation of stable, well sorted gravel deposits that are the site of spawning for Chinook, chum, coho, and steelhead. Large and deep pools created by the structures will provide complex cover for rearing areas for juvenile salmon and hiding cover for adult salmon prior to spawning.