This study uses the weight of evidence method (WEM) to determine the relationship between the physiographical
factors and the occurrence of debris flow, in order to determine the potential for the occurrence of debris
flow. The chances and their ratios are used in a WEM to determine the weighting factors for 12 physiographical factors that relate to the occurrence of debris flow. The linear sum of 12 weighting factors forms an integrated physiographical susceptibility index (SI). The higher the value of the SI for a watershed, the greater is the potential for debris flow. Debris flow events that occurred in the Gaoping River Basin (GRB) from 2005 to 2012 are studied using WEM in this study. The SI-values for debris-flow-stream watersheds are calculated and ranked to produce successive rate curves. The area under the successive rate curves (AUC) in GRB is then calculated for 8 severe rainfall events during this period. The result shows that the values for the AUC are between 0.7 and 0.9, so WEM and the proposed-SI accurately predict the potential for the occurrence of debris flow.
Key Words: Debris flow, Weight of evidence, physiographical factors.