Influence of Spatially Variable Precipitation and Burn Severity on Storm Event Runoff Response

Precipitation spatial variability has been observed to influence storm event-scale runoff response across watersheds in the US and Europe. Despite its importance, precipitation spatial variability has yet to be widely considered in connection with watershed disturbance, specifically wildfire. Recent advances in publicly available gridded precipitation data products and computational resources provide the opportunity to assess the effects of precipitation spatiotemporal variability on storm event-scale rainfall-runoff patterns. We demonstrate the effects of precipitation spatial variability and its connectivity with burned areas on rainfall-runoff patterns. This assessment is performed for nine burned mountainous watersheds in the western US with a wide range of precipitation regimes and contributing areas. The NOAA Analysis of Record for Calibration (AORC) hourly 1 km² gridded precipitation data product is used to characterize precipitation spatial variability for storm events across each watershed. Storm events are found to be variable with respect to storm center location relative to the watershed centroid and precipitation spatial patterns. We also evaluate post-fire storm connectivity, based on overlapping area between storm event precipitation footprint and burned area, and its effect on corresponding runoff event metrics (e.g. runoff peak, time to peak, etc.). The findings of this work can aid in post-fire flood prediction, risk management, and decision making in the face of climate change and increasing watershed disturbance regimes.