The Sinclair Creek watershed is a primary tributary to the Tobacco River in the Upper Kootenai River watershed. Sinclair Creek joins the Tobacco River approximately 0.5 miles south and east of Eureka, Montana. The watershed is approximately 11.5 square miles and is comprised of private and public lands (U.S. Forest Service) and supports a variety of land use activities including farming, ranching and residential development.
Sinclair Creek is a critical stream for supporting all life stages of native salmonids including Westslope cutthroat trout (Oncorhynchus clarki lewisi), a species of concern, and historically the threatened Bull trout (Salvelinus confluentus). Threats to resident and migratory life forms of native species includes habitat degradation, introduced fish species, rural residential development, forestry, stream crossings, and agricultural land uses.
In June of 2006, Sinclair Creek experienced a significant flood event in response to consecutive days of above average precipitation. The storm generated widespread flooding throughout the Sinclair Creek watershed causing accelerated channel migration, bank erosion, downcutting, loss of floodplain connectivity, and impacts to 1,000 feet of aquatic habitat. Since the flooding event, the Welch Ranch has worked with the U.S. Fish and Wildlife Service/ Montana Partners for Fish and Wildlife Program, the Lincoln Conservation District, Lincoln County Road Department, Glen Lake Irrigation District, Town of Eureka, Lincoln County Commissioners, Eureka Rural Development, and adjacent landowners to develop strategies in restoring the fishery, water quality, aquatic habitat, and channel stability in the project area.
In 2009, an abandoned water supply structure was removed from the project area. The goal was to remove the abandoned intake structure and infiltration gallery to improve the hydraulics and sediment transport characteristics in the Sinclair Creek drainage. As part of a two-phased project the water supply structure and infiltration gallery were removed while an existing cross-channel concrete sill was left in place to prevent further channel headcutting. The sill was scheduled to be removed during the second phase of the project. In 2013, the second phase of stream restoration work was implemented to include appropriate restoration and stabilization measures for 800 feet and 1,000 feet of riparian revegetation of Sinclair Creek. The project was developed to improve river and floodplain processes while providing for adequate flood protection of the Sinclair Creek Road and the Glen Lake Irrigation District siphon. The siphon spans Sinclair Creek in the lower end of the project area and had been threatened by flood flows and erosion. The siphon provides irrigation water delivered from Grave Creek to Eureka residents for agricultural purposes. Further objectives for the restoration work included:
- Incorporating restoration techniques that will improve water quality by reducing inputs of sediment to the channel while enhancing aquatic habitat conditions;
- Stabilizing the channel boundaries to minimize lateral channel migration;
- Increasing the width of the floodplain in several locations to buffer flood flows from the adjacent Sinclair Creek Road embankment;
- Implementing a streambank and floodplain revegetation plan to increase floodplain roughness, reduce erosion potential, and lower overbank flood velocities to the greatest extent;
- Removing fill and existing rip-rap to minimize encroachment on the active channel and floodway;
- Regrading portions of the existing fillslope to promote stability and vegetation establishment adjacent to the roadway.
This project serves as a Demonstration project for the Eureka community to illustrate: stream restoration techniques as well as natural stream channel and floodplain design with improved function to increase the availability of complex aquatic habitat for target fish species including bull and westslope cutthroat trout; mitigate existing chronic sources of sediment to the channel to improve water quality; and provide public benefits through collaborative community-based resource planning. The completed projects compliment the on-going stream and wetland habitat improvement projects completed by various governmental agencies, non-profit organizations, and landowners in Grave, Therriault, and Fortine Creek drainages as well as in the mainstem of the Tobacco River.