Probability of post-fire debris flows and flooding following a wildfire and 10 year - 10 minute percipitation event, in Arizona's 4FRI region.

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.

Publication documenting our methods and results:
A Fraser, M Chester, and BS Underwood, Wildfire risk, post-fire debris flows, and transportation infrastructure vulnerability, 2022, Journal of Sustainable and Resilient Infrastructure, 7(3), pp. 188-200, doi: 10.1080/23789689.2020.1737785.

Wildfires and post-fire debris flows (PFDFs) threaten California infrastructure and are evolving with climate change. There is significant focus on the threat of utility-caused wildfires because electric power equipment has triggered wildfires leading to major damage. California's ambitious climate targets rely on electrification of transport and industry. As the state modernizes its electricity system to support increased demand, it must consider future climate hazards. To date, there is no rigorous characterization of the intersection of future fire threat, PFDFs, and electrical infrastructure. We estimate wildfire and PFDF threat to transmission lines, substations, and power generators in California and assess vulnerability of electric utilities by intersecting electrical infrastructure and current and future wildfire and PFDF threat, using two global climate models and two representative concentration pathways. We find clean, dispatchable power generators (e.g. hydroelectric and nuclear) and small, publicly-owned utilities are most vulnerable. Increasing threats will require additional resources and consideration of future threat distribution.

Publication documenting our methods and results:
E Hennessy and M Chester, 2025, Electric utility vulnerability to wildfires and post-fire debris flows in California, Environmental Research Infrastructure and Sustainability, doi: 10.1088/2634-4505/adb90a.