Wildfire risk, post-fire debris flows, and transportation infrastructure vulnerability

Wildfires have grown in number, size and intensity in the American West and forecasts predict worsening trends. Evidence mounts that post-fire debris flows pose a major hazard to infrastructure, particularly roadways. Vulnerabilities of assets to post-fire flows requires consideration of geologic, vegetative, and hydrologic conditions. A model that considers environmental conditions, post-fire effects, and transportation asset use is developed, and applied to a fire prone region in Arizona. 17% of watersheds have a greater than 20% chance of post-fire debris movements and flooding under a minor precipitation event. Additionally, there is a greater than 50% probability of post-fire debris flows where recent fires have occurred, validating the underlying model. The model shows the vulnerability of infrastructure to environmental and technological variables, drawing attention to the need to manage the risk as a broader system.