ASSESSING PRE- AND POST- WILDFIRE STREAM RUNOFF FROM THE BOBCAT FIRE IN LOS ANGELES BASIN

With wildfires becoming increasingly common in Los Angeles and the surrounding areas, understanding their impact on surface runoff from storms is more critical since it can lead to flooding and landslides. The 2020 Bobcat Fire burned 115,997 acres of the San Gabriel Mountains Angeles National Forest from September to November, and is one of the largest fires in Los Angeles County’s history. In this study, we utilized the Army Corps of Engineers’ Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) software, to simulate discharge under pre- and post-fire conditions for the Bobcat Fire. This approach allowed us to examine the fire’s impact on runoff response within the burned watershed. We selected rainfall events occurring before and after the Bobcat Fire to model the pre-fire conditions and post-fire responses. The model is validated with the streamflow records obtained from the United States Geological Survey stream gages, located either within or downstream of the burned area. This study shows how wildfires affect hydrologic and land surface properties provides a tool for managing the post-fire environment and for long-term environmental and resource planning.