Abstract
Understanding the spatial heterogeneity of the debris-flow rainfall threshold is meaningful for regional warning systems. However, regional topographical and geological impacts have not been well quantified. Using the Hengduan Mountains with distinct climatic, topographical, and geological settings as a typical study area, this study focused on the geological and topographical variations of effective rainfall for debris-flow occurrence from a large-scale perspective. Results showed that the probability of debris-flow occurrence was smallest in the cold-arid zone and largest in the humid zone. The mean dimensionless effective rainfall (the ratio of effective rainfall to mean annual precipitation) was about 5.2% for an initial warning and 7.7% for serious warnings. The contributions to the differences are regional climate, geomorphology, and geology, in sequence of importance. The zone with more complex terrain, thicker soil, and higher sand content would be more beneficial to debris-flow formation. Multiple regression analysis suggested that the geologically-related aspects may have a slightly greater effect than topographical factors on effective rainfall. In general, this work could be in favor of other similar regional, national, and even global work for debris-flow early warning.
Published Version
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