Augmentation of WRF-Hydro to simulate overland-flow- and streamflow-generated debris flow susceptibility in burn scars

Abstract. In steep wildfire-burned terrains, intense rainfall can produce large runoff that trigger highly destructive debris flows. However, the ability to accurately characterize and forecast flow susceptibility in burned terrains using physics-based tools remains limited. Here, we augment Weather Research Forecasting Hydrological modeling system (WRF-Hydro) simulate both overland channelized flows assess postfire over a regional domain. We perform hindcast simulations high-resolution weather-radar-derived precipitation reanalysis data drive non-burned baseline burn scar sensitivity experiments. Our focus on January 2021 when an atmospheric river triggered numerous within wildfire Big Sur – one of which destroyed California's famous Highway 1. Compared baseline, our simulation yields dramatic increases total peak discharge shorter lags between onset discharge, consistent with streamflow observations at nearby US Geological Survey (USGS) gage sites. For 404 catchments located simulated area, median catchment-area-normalized by ∼ 450 % compared baseline. Catchments anomalously high correspond well post-event field-based remotely sensed observations. suggest analysis demonstrates WRF-Hydro as compelling new tool whose utility could be further extended via coupling sediment erosion transport models and/or ensemble-based operational weather forecasts. Given high-fidelity performance augmented version WRF-Hydro, its potential usage probabilistic hazard forecasts, argue for continued development application hydrologic natural assessments.