Wildfire-induced enhancement in downstream flood discharge in watersheds of California

Global climate change is increasingly associated with the prevalence of extreme precipitation and large wildfires. The influence of large wildfires on downstream flood discharge is concerning, particularly from a flood risk management perspective, where understanding the impact at a watershed scale is still fairly limited. This study investigates the impacts of wildfires on down-stream flood discharge in 30 Californian watersheds using a Soil and Water Assessment Tool.

Substantial post-fire discharge increases, with an average 17.1% increment in 83.3% of watersheds, were found during the first post-fire year. Statistically significant positive correlations were found between the enhancement in discharge volume and the percentage of burned watershed area. The study also showed that incorporating historical wildfire activity significantly raised the probable maximum flood. These wildfire-induced increases are on par with California's climate change projection, underscoring the need to factor in wildfire effects in flood risk assessments and water management strategies at this type of location.