Rainfall thresholds of typhoon rainstorm induce landslides: A case study over Taishun County

In the southeast coast of China, typhoon rainstorms resulted in lots of landslides. Investigating rainfall thresholds and patterns of typhoons is of great importance for the early warning of landslides. In this study, the landslide information obtained from multiple sources and typhoon rainstorm data were used to analyze landslide and rainfall characteristics in Taishun 2007 to 2022; the rainfall threshold of typhoon rainstorm-induce landslides was defined for Taishun area based on the rainfall intensity–duration (I-D) model. It finds that a large number of typhoon rainstorm landslides occur at the windward slope close to the landing direction of the typhoon, where the main vegetation types of the landslide are arbors and herbs with tall trunks and shallow roots. The duration of rainfall events inducing landslides is usually 2～3 days, with concentrated rainfall and total rainfall more than 200 mm. The threshold of typhoon rainstorm-induced landslides is significantly higher than that of rainfall-induced landslides in other regions. With the backward position of rainfall peak in rainfall process, the thresholds become lower and steeper, indicating that more rainfall is needed to trigger landslides when the rainfall peak appears earlier than when it is late. Typhoon rainstorm-induced landslides are more sensitive to the heavy rainfall event after a long rainfall. The threshold model established in this study is consistent with the observation, indicating that it is effective for landslide monitoring during the typhoon season.