Mounting damage and losses in the United States from postwildfire flash floods and debris flows

Considerable progress has been made in forecasting the likelihood, magnitude, and mobility of postwildfire flash floods and debris flows; however, we lack systematic observations of the physical and financial effects of these hazards, which can be used to close gaps between scientific understanding of the hazard and risk reduction. Here, we introduce a 147-year inventory of damage and losses associated with postfire flows in the United States. These observations enable an assessment of the geographic convergence and frequency of damaging postfire flow events, as well as their multi-asset damage profiles and loss distributions. Ultimately, this dataset provides an empirical baseline that can be used for long-term hazard planning amid pressures compounded by wildland-urban interface expansion, increased wildfire activity, and rainfall intensification.

Mounting damage and losses in the United States from postwildfire flash floods and debris flows, Thomas and Kostelnik (2026), USGS Landslide Hazard Seminar, 21 October 2026.