Relationships between antecedent rainfall and debris flows in Jiangjia Ravine, China

Based on observations in Jiangjia Ravine, the occurrence of debris flow is examined on the basis of antecedent precipitation (AP). In this study, we distinguish between indirect antecedent precipitation (TAP), direct antecedent precipitation (DAP), and triggering precipitation (TP), which is helpful for establishing precipitation indices for forecasting debris flow. We carried out a case study oil 46 debris-flow events in Jiangiia Ravine with related precipitation data. Results show that the contribution of TAP and DAP to debris flow is 44% while the triggering precipitation (1 h intensity) is only 37%. Antecedent precipitation brings about changes in soil moisture and influences the intensity and quantity of rainfall necessary to trigger debris flows.