Like many desert rivers, the San Rafael River in Price County, Utah has become degraded largely through human-induced alteration of the natural hydrology by over-allocation of water. The magnitude and duration of spring snowmelt floods has been diminished since the early 1900s while monsoon floods continue to deposit large quantities of sediment within the channel, floodplain, and along the channel margins. The altered hydrograph has left the lower San Rafael River in a transport limited condition where the amount of sediment supplied to the channel exceeds the river's ability to transport the sediment out of the system. This dynamic, coupled with dense populations of invasive tamarisks along the channel margins and floodplain, has led to channel narrowing and vertical incision, leaving much of the lower San Rafael disconnected from its historic floodplain. The incised condition, along with the lack of floodplain connectivity, has degraded the quality of instream and riparian habitat leading to a reduction in native fish populations, and a lack of cottonwood and willow recruitment on the floodplain.
A large collaborative restoration effort was developed with the primary restoration goals to: 1) improve native fish populations, specifically for three native fish species listed as sensitive species (e.g.,flannelmouth sucker (Catostomus latipinnis), the bluehead sucker (Catostomus discobolus), and the roundtail chub (Gila robusta)), 2) improve instream and riparian habitat and, 3) use adaptive management/experimental approach to restoration planning, implementation, and monitoring in order to learn as much as possible from this project to inform future restoration efforts on similar desert rivers. The project is a collaboration between the Bureau of Land Management, the Utah Division of Wildlife Resources, the United States Geological Survey, and Utah State University's Fish Ecology Lab, Fluvial Geomorphology Lab, the Utah Water Research Lab, and the Fluvial Habitat Center. The project consists of: 1) large-scale tamarisk removal from the banks and floodplain to allow for natural river migration and a transition to native riparian vegetation, 2) gravel augmentation to increase the complexity of instream habitat and learn about sediment transport dynamics within the lower San Rafael, 3) addition of boulders from the valley wall margins where the river naturally contacts the valley margin, and 3) use beaver and beaver dam analogs to improve instream and riparian habitat.
Beaver are naturally present in the lower San Rafael River, but the narrow incised condition and lack of suitable riparian vegetation prevents their dams from persisting for very long and likely limits the size of their population. The developers of the restoration plan for the San Rafael River recognized the critical role that beaver have historically played in structuring and maintaining a healthy riverine system and wanted to 'Partner with Beaver' to restore physical and ecological processes within the lower San Rafael River. This project is the first of its kind to use Beaver Dam Analogs (BDAs) in a primarily sand-bedded desert river. The Fluvial Habitat Center was contracted to develop a large scale pilot restoration design to test the effectiveness of using BDAs to improve instream and riparian conditions and beaver habitat within the lower San Rafael River. Dr. Joe Wheaton, Dr. Nick Bouwes, Wally MacFarlane, and Elijah Portugal are responsible for conducting this project for the Fluvial Habitat Center.
For more information about the project see below:
Originally posted Jun 16, 2015, 2:51 PM by Jeannine Huenemann
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Contributions from ETAL lab members.