Road Creek Passage Barrier Removal and Bridge Installation

The Road Creek Passage Barrier Removal and Bridge Installation project addressed a passage barrier and reduced sediment release in not only Road Creek, but also the East Fork of the Salmon River, a key spawning area. The new bridge allows fish passage at all life stages and provides a natural channel for fish movement upstream and downstream of the bridge. The lower reach of Road Creek is a spring fed channel that flows even in low water years and the cool spring water is of great importance in the late summer months. The streambed was shaped to meet fish passage criteria and the work site was revegetated to rehabilitate the stream’s riparian area. A small length of fence was installed to protect the new plantings.

Prior to the project the county road had washed out upwards of three times in the past 8 years. A secondary culvert was placed under the road to address some of the overflow but rainfall in 2020 caused a complete failure of the culvert and the road. Bridge installation eliminates the risk of a wash out on a seasonal basis. The Road Creek culvert replacement project, sponsored by the Custer Soil and Water Conservation District, is a collaborative effort with the Idaho Department of Fish and Game, Custer County Road and Bridge and Custer County Commissioners.

This project will remove a passage barrier on Road Creek to improve fish passage and/or flow. By removing the 4-ft diameter straight (not squash) culvert and installing a bridge to provide access over the county road at Road Creek, the project will essentially reconnect the lower reach of Road Creek to the main stem of the East Fork. The project also entails creating fish passage within the channel to improve upstream and downstream movement for all life stages. In the past five years, this culvert has been over-topped and washed sediment from the Road Creek into the East Fork of the Salmon River. As flows rise in spring runoff, the culvert plugs and washes out around the culvert, adding sediment to the stream. This has happened multiple times with a significant event in 2017. In August of 2021 a flash flood took out a large section of the road and cut a new channel of Road Creek through soft soil. This washed bedload and sediment into the East Fork in advance of spawning season. It is anticipated that this will continue unless the culvert is replaced with a structure large enough to carry high flows and provide passage for fish.

The goal of this project is to re-establish fish passage for Chinook salmon and Steelhead trout in Road Creek, a tributary to the East Fork, and to reduce sediment. The objective is to provide access to 1.18 miles of habitat as well as increase spawning habitat for adult salmonids and rearing habitat for juvenile salmonids in the lower reach of Road Creek near the confluence of East Fork. This will improve the limiting factors of fish passage, sedimentation and riparian condition.