Project Name

Twin Creek Watershed Assessment

Watershed and Stream Assessments
Client / Agency
Avista Corp. and Idaho Fish & Game
Clark Fork, Idaho
2008 to 2009
Project Description
Twin Creek is a tributary to the Clark River between the Idaho border and Lake Pend Oreille, near the town of Clark Fork, Idaho. The Twin Creek watershed is comprised of mainstem Twin Creek, Delyle Creek, and three unnamed tributaries. Dry Creek joins Twin Creek shortly before Twin Creek's confluence with the Clark Fork River. Encompassing nearly 12 square mile, the Twin Creek watershed provides habitat for bull trout and westslope cutthroat trout as wll as other fish species and wildlife. Bull trout are limited to the lower watershed downstream from Twin Creek Falls. Westslope cutthroat trout inhabit from the falls upstream to the headwaters. Bull trout may inhabited the headwaters historically, but are no longer believed to occupy the upper watershed. Avista Corp. and Idaho Fish & Game requested assistance in completing a watershed assessment and restoration project prioritization plan for the Twin Creek watershed excluding Dry Creek. The effort served two purposes: as a watershed assessment, it presented informationon historical and existing conditions based on field data collection, remote sensing, and existing data review. Secondly, the document served as a stream corridor restoration plan that prioritized aquatic habitat improvement projects in the Twin Creek watershed. Restoration efforts were intended to enhance aquatic and riparian habitat, improve fish passage, and/or decrease sediment delivery to the channel network.
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Twin Creek reach inventory and land ownership map.
Sediment sources located in the Twin Creek watershed.
Bank erosion hazard results for Twin Creek watershed.
Second growth cedar forests shade the Twin Creek headwaters.
Large wood influences channel morphology in the headwater reaches of Twin Creek.
Alluvial reaches in the middle watershed support an alder riparian zone and conifer upland canopy.
Twin Creek Falls limits fish passage in the watershed.
Channel instability in lower Twin Creek is related to periodic rain-on-snow events, degraded riparian conditions, and past land use.
Sediment deposition in lower Twin Creek influences habitat and channel stability.