Channel restoration in an urban salmonid stream

摘要

In 1997 the Sacramento Watersheds Action Group (SWAG) conducted an assessment of the Sulphur Creek Watershed, a tributary to the Sacramento River. The analysis included documentation of land uses, an inventory of erosion and sediment sources, an analysis of riparian conditions and stream habitat, and a preliminary hydrologic analysis. The watershed analysis revealed that extensive dredger mining, road building, and railroad construction within the Sulphur Creek watershed--combined with dam releaseswhich caused backwater conditions at the mouth of Sulphur Creek--have resulted in channel degradation and severe deterioration of fisheries and wildlife habitat. The erosion inventory for this analysis was an important step in making recommendations forwatershed restoration projects. The erosion inventory indicated that streambank erosion within the lower reaches of Sulphur Creek (also the location of the Redding Arboretum) is the primary source of sediment negatively impacting adjacent spawning areas. Near the confluence with the Sacramento River, a 200 m (600 ft) segment of Sulphur Creek became a depositional area for sediment. A median sandbar resulted from the combined effects of these sediment inputs and the backwater from the River. This causedthe channel to "jump" over into an open meadow, forming a high vertical bank that was eroding at an alarming rate. Using the watershed analysis as a basis, SWAG, with the assistance of Shasta College students, embarked on a project to return the streamto its "historic" channel. The project was to be implemented as a community-based, worksite learning opportunity for the Shasta College Watershed Restoration and Heavy Equipment Operations classes. This paper discusses the design, implementation, and results of a channel realignment project within the Sulphur Creek Watershed. This project involved the removal of a median sandbar, reshaping an eroding vertical bank, and realignment of approximately 200 m (600 ft) of Sulphur Creek. The channel was reconstructed in a meandering alignment while the banks were stabilized with Biotechnical Erosion Control techniques. Fish habitat features were installed, such as boulder clusters, root wads, riparian vegetation, and spawning gravel (which was uncovered duringexcavation of the sandbar). The dynamics of the new channel changed dramatically during the wet winter following the realignment. These changes have led to unique results as the channel reaches equilibrium. The total cost for this project was originallyestimated at 53,540 dollar. However, through extensive volunteer efforts supported by the local college and in-kind contributions, the project was completed with only a 3,000 dollar mini-grant.