USGS M1 모델 기반 산불 이후 고속도로 인접 유역의 토석류 발생가능성 평가

초록

Post-wildfire debris flows can occur rapidly during short-duration rainfall events because wildfires alter vegetative cover, soil properties, and surface runoff processes. However, conventional debris-flow risk-assessments for Korean expressways have primarily focused on topographic and structural vulnerability factors without explicitly considering wildfire-induced changes in the debris-flow likelihood assessment. Therefore, this study examines the preliminary applicability of the U.S. Geological Survey M1 post-wildfire debris-flow likelihood model to a wildfire-affected watershed adjacent to an expressway in South Korea. The model was implemented using a satellite-derived difference normalized burn ratio, a digital elevation model, rainfall data from a nearby automatic weather station, and information on soil erosion. The calculated likelihood based on the M1 model exceeded 80% for the investigated watershed under the selected post-wildfire rainfall conditions. Additionally, based on the existing expressway debris-flow assessment, the site was classified as grade C. The estimated debris-flow volume was <1,000 m3, which corresponds to a moderate volume class in the USGS framework. These results indicate that the M1 model provides useful supplementary information for screening post-wildfire debris-flow-prone watersheds. However, further validation and regional calibration are required for Korean geomorphological, hydrological, and soil conditions.

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