Controls on Sediment Connectivity in Fluvial Networks Impacted by Wildfire Across Utah
Abstract
Wildfire-induced flooding and sedimentation are among the greatest threats to watersheds, fish populations and reservoirs in the western US. Burned landscapes are highly susceptible to runoff and erosion and have the potential to produce large, episodic pulses of sediment that put downstream resources at risk; however, the degree of impact will largely depend on the sediment connectivity of the watershed. Sediment bottlenecks are locations within the riverscape where local conditions produce a persistent decrease in connectivity of sediment with downstream reaches, resulting in a measurable deposition of fluvial sediment and the potential modification of local morphology. The primary objective of this research is to evaluate controls on the volume, location, and prevalence of sediment bottlenecks in fluvial networks after wildfire. We identified and surveyed 89 sediment bottlenecks linked to 15 wildfires across Utah. The mechanisms responsible for these sediment bottlenecks were attributed to either valley bottom morphology or structural factors, including large in-stream wood, beaver dams, debris flow deposits, and human infrastructure. We developed a suite of geomorphic and landscape-based reach metrics, which we then analyzed as predictor variables on the volume and location of these sediment bottlenecks. Additionally, we digitized large wood and debris flows at each site from aerial imagery, as both often increase considerably after wildfire and can significantly influence the prevalence of sediment bottlenecks. Our preliminary results suggest that while valley bottom morphology is a primary control on sediment bottlenecks in burned catchments, the impacts from wildfire on watersheds have a significant influence on the recruitment and transport of sediment and wood. These findings will help refine sediment routing models, assist in identifying the magnitude and location of potential sedimentation risks, and better inform the management of infrastructure and aquatic habitat after wildfire.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMEP45A..03A