How long do runoff-generated debris-flow hazards persist after wildfire?

Andrew Paul Graber; Matthew A. Thomas; Jason W. Kean

doi:10.1029/2023gl105101

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How long do runoff-generated debris-flow hazards persist after wildfire?

Andrew Paul Graber·Matthew A. Thomas·Jason W. Kean

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Abstract

Runoff-generated debris flows are a potentially destructive and deadly response to wildfire until sufficient vegetation and soil-hydraulic recovery have reduced susceptibility to the hazard. Elevated debris-flow susceptibility may persist for several years, but the controls on the timespan of the susceptible period are poorly understood. To evaluate the connection between vegetation recovery and debris-flow occurrence, we calculated recovery for 25 fires in the western United States using satellite-derived leaf area index (LAI) and compared recovery estimates to the timing of 536 debris flows from the same fires. We found that the majority (>98%) of flows occurred when LAI was less than 2/3 of typical prefire values. Our results show that total vegetation recovery is not necessary to inhibit runoff-generated flows in a wide variety of regions in the western United States. Satellite-derived vegetation data show promise for estimating the timespan of debris-flow susceptibility.

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Geophysical Research Letters Article

Source-reported bounding extent: 30.13526525190572° to 50.89584069263282° latitude; -127.73580454866216° to -101.983851423662° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Andrew Paul Graber, Matthew A. Thomas, Jason W. Kean. 2023-10-03. How long do runoff-generated debris-flow hazards persist after wildfire?. https://doi.org/10.1029/2023gl105101

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