Influence of Wildfire Soil-Burn Severity on Post-Fire Debris Flow Occurrence

Abstract

As climate continues to change under the weight of anthropogenic forcing, wildfires respond in kind. In fire-abundant southern California, wildfire incidents are increasing in frequency and magnitude causing widespread short- and long-term complications to human society while also altering natural ecosystems. Though current research anticipates changes to largescale fire regimes (the “new normal”), such as increases in future fire incidents and burn severities, predictive studies that analyze changes in ecosystem responses to changing fire regimes are still lacking. As a result, questions surrounding future trends in post-fire erosion patterns arise. Specifically, will an increase in wildfire soil-burn severity result in more post-fire debris flows? Answering this question is critical for increased human resiliency in light of climate change given the relative historical abundance of post-fire debris flows in the region, intensifying climate patterns, and continued acceleration of human development and densification of the Wildland Urban Interface (WUI). This research addressed this concern by utilizing a descriptive approach to analyze southern Californian post-fire debris flows from 2001 to 2018. It was found that if fire patterns continue to intensify, the number of post-fire debris flows in the region will also increase. This finding highlights the interconnectivity between natural erosive processes, wildfires, humans, and climate change.