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A currently quiescent stratovolcano, Mount Shasta, California, still poses a significant hazard to nearby communities thanks to impactful non-eruptive debris flows that can occur throughout the year. In this work, we have built a more complete record of debris flow occurrence using monitoring campaigns and research into historical newspaper records; analyze debris flow frequency and triggering in the context of regional weather and climate patterns; and forecast the future of debris flow hazards at Mount Shasta. This topic is timely because of its relevance to the ongoing efforts to create up-to-date, usable, and relevant hazards assessments at United States Volcanoes, as well as a need expressed by local land managers for debris flow data. Ultimately, this work will not only enhance our understanding of debris flow occurrence at Mount Shasta, but will also aid stakeholders in land planning, hazard mitigation, and preparedness.
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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.
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