USGS’s New Postfire Debris-Flow Runout Hazard Maps
Starting in the summer of 2026, the USGS Geologic Hazards Science Center has the capability to generate post-fire debris flow runout hazard maps upon request for certain fires. Postfire debris flows pose a unique hazard to human life, property, and infrastructure when they travel from steep areas to urbanized alluvial fans or other developed areas. For nearly 15 years the USGS has been generating rapid (<1 week) postfire debris-flow hazard assessments to document the increase in the likelihood and size of debris flows but these hazard assessments do not indicate how far a debris-flow might travel. A new method to generate runout hazard maps is now able to indicate how far debris flows may travel. These maps may support the identification of potentially hazardous areas immediately following a fire and to provide approximate runout forecasts when interpreted alongside a weather forecast. Katy Barnhart described the USGS’s new method for generating postfire debris-flow runout hazard maps and shared case studies that show events that were triggered by a range of rainfall intensities and how the observed debris flow runouts compared to model predictions.
Detailed background information and research reference: Barnhart, K. R., Kean, J. W., Lindsay, D. N., & Bilderback, E. L. (2026). Multi-site evaluation of a postfire debris-flow runout forecast method. Earth's Future, 14, e2025EF007004. https://doi.org/10.1029/2025EF007004
Presenters:
- Katy Barnhart, Research Civil Engineer, U.S. Geological Survey Geologic Hazards Science Center, Golden, CO
Link to Materials and Other Resources:
Date: April 28, 2026