Updating methods for postfire debris-flow hazard assessment

For more than a decade, the U.S. Geological Survey (USGS) has provided stakeholders and land managers with postfire debris-flow hazard information to assist them in considering important questions about postfire debris flows, such as “Where will they happen?”, “When will they happen?”, or “How big will they be?” Alongside assessing postfire debris-flow hazards for hundreds of burned areas to date, USGS and partners have identified additional aspects of these hazards that are not well addressed by existing predictive frameworks, such as developing rainfall thresholds for partially recovered conditions, or considering how susceptibility to postfire debris flows might be modified by regional differences in topography or rainfall climatology. This talk will discuss recent work to address these challenges by 1) developing a new method to track the evolution of debris-flow likelihood and rainfall thresholds with time and recovery after fire, and 2) calibrating new regional models to improve prediction of debris-flow likelihood and rainfall thresholds across the western United States.