Historic Channel Change and Post-Project Analysis of a Habitat Restoration Project on the Upper Strawberry River, Utah

Restoration of the upper Strawberry River included bank stabilization techniques because it was assumed that excessive bank erosion was degrading spawning habitat for Bonneville cutthroat trout (Oncorhynchus clarki Utah)(BCT). Using a long-term aerial photograph record, we determined the historic range of variability in bank erosion rates and channel geometry, and used this information to assess present-day conditions and the rationale for restoration. Relative to historic variability, bank erosion rates were low and channel morphology was stable in the decade prior to restoration. Although a historic loss of riparian vegetation coincided with a shift to a wider and more sinuous channel, lateral migration rates declined to lowest levels in the period-of-record and the channel narrowed as riparian cover increased in the decades prior to restoration. Additionally, the percentage of fine sediment in the streambed prior to restoration was insufficient to impact BCT spawning success. Furthermore, using a 1-D hydraulic model we examined pre- and post-restoration channel morphology and hydraulic variables related to habitat conditions for BCT. The results of the historical analysis suggest that bank erosion and fine sediment did not affect the quality of spawning habitat or the abundance of BCT on the upper Strawberry River. Furthermore, the 1-D hydraulic model shows that the physical in-channel manipulations made little improvements in achieving marketed changes in habitat and as such may have little effect on BCT spawning and resident population success. Our results highlight how a historic analysis can be used to identify the sources of habitat degradation and inform the selection of restoration goals and strategies as well as how surveyed cross-sections coupled with a 1-D hydraulic model can examine initial success of in-stream manipulation for habitat enrichment of a restoration project