Post-wildfire sediment source and transport modeling, empirical observations, and applied mitigation: an Arizona USA case study.

Post-wildfire floods are receiving greater attention as wildland-urban interfaces become more common and as catastrophic wildfires have increased in frequency. Sediment sourcing, transport, and deposition in the post-fire environment receive attention due to the severity of risk caused by debris flows and concentrated sediment flood flows. This study provides a series of sediment model predictions based on MUSLE and the WARSSS suite of models that included: ERMIT, BANCS, and FLOWSED/POWERSED for the 2019 Museum Fire (809 Ha of steep slope Pinus ponderosa forest in the Spruce Wash watershed). A comparison is provided for the internet-based WEPPcloud post-fire sediment model. Empirical evidence from four floods in 2021 indicated 9,900 Mg of sediment yield to city of Flagstaff neighborhoods, the WEPP model estimated 3870 Mg/year, MUSLE predicted 4860 Mg/year (based on the four events), and the WARSSS suite of models predicted 4630 Mg/year. Both WEPP and WARSSS estimated more sediment yield from channels than hillslope (51%/49% and 60%/40% respectively) though the spatial patterns differ between the models. Sediment mitigation structures, or "work areas", are discussed as real-world applications of sediment forecasting for reducing downstream impacts. Continued revisions of sediment forecasts, based on case studies such as this one, can provide managers and policy makers with tools for risk mitigation and emergency management. [ABSTRACT FROM AUTHOR]