The triggered mechanism of typhoon-induced debris flows and landslides over mainland China

Typhoon-induced rainstorms can trigger debris flow and landslide, causing severe losses and casualties in China. Analysis of antecedent precipitation (P-A), threshold precipitation (P-C), mean precipitation intensity (Pm), precipitation duration (T-D) and the lag time (T-L) for typhoon- and non-typhoon-induced shows that: 1) Pc is greater and PA is lower for typhoon-induced rainstorms. For typhoon-induced rainstorms, when PA is within 50-100mm and P-C is greater than 200mm/d, landslides and debris flows are mostly likely to happen. As for non typhoon-induced rainstorms, PA is within 100-150mm and Pc is within 150-200mm/d. 2). After one day of typhoon precipitation, debris flow and landslides are more likely to happen. However, for non-typhoon-induced rainstorms it is usually 2-3 days. 3) For typhoon-induced rainstorms, 75% of debris flow and landslides happen during the day when maximum precipitation intensity occurs; for non-typhoon-induced rainstorms, 45% of hazards happen 2-12 days after the maximum precipitation day. 4) Typhoon-triggered debris flow and landslides have a lower environmental danger value compared to those that are non typhoon triggered.