Cooperative Fish and Wildlife Research Units Program: Utah
Education, Research and Technical Assistance for Managing Our Natural Resources

Widespread hydrologic alterations have simplified in-stream habitats in rivers globally, driving population declines and local extirpations of many native fishes. Here, we examine how extreme geomorphic change in a historically degraded desert river has impacted habitat diversity and persistence. Due to the introduction of a sediment plug from a tributary wash in 2010, a large reach of the degraded and simplified San Rafael River, Utah, began to actively change from a single-thread channel to a complex, multi-threaded riverscape. We combined field measurements and drone-collected imagery to document habitat changes due to this new habitat feature and monitored habitat use by native and endemic fishes. Our results demonstrate the habitat feature is more diverse than any other stream reach along the lower SRR, with reaches located at the edge of the expanding wash feature containing 17% more complex habitat (e.g., pools, riffles, backwaters) on average than reference reaches, and containing 641% more diverse habitat overall than 5 years prior to the start of our study. The wash feature is also retaining water for periods beyond what is expected during seasonal drying, with the total extent of inundation within the riverscape increasing by over 2,800%. Since the formation of the 2010 sediment plug, riparian habitat has increased by 230% since 2009, and channel networks have expanded from a single thread channel to more than 50 distinct channels throughout the sediment plug’s zone of influence. These results will inform management and conservation of habitat for imperiled desert fishes and encourage the use of process-based restoration tools such as “low-tech” habitat restoration in order to mitigate the impacts of simplification and increase habitat persistence in the face of increasing aridity in the desert Southwest.