Study on rainfall threshold of geological disasters based on effective rainfall model in Wenzhou City

Wenzhou is located in the coastal area of southeast China, where frequent occurrences of extreme rainfall have resulted in a high incidence of geological disasters over the years. This study collects the historical geological disasters and rainfall data of Wenzhou (a total of 2692 geological disaster samples, of which 2,615 are accurately dated to the month, spanning from 1905 to 2023) to analyze the development, spatio-temporal distribution patterns of geological disasters, and their relationship with rainfall. Based on the effective rainfall model, we statistically analyzed the rainfall thresholds of different types of geological disasters in Wenzhou. The results show that the geological disasters in Wenzhou are mainly classified into two categories: (1) the cluster disasters triggered by typhoon-rainstorm and (2) the single-point sudden disasters. Among them, the cluster disasters triggered by typhoon-rainstorm is closely related to typhoon rainstorm activities, and strongly correlated with rainfall extreme, while the single-point sudden geological disasters has less correlation with heavy rainfall. The statistical analysis derives the intensity–duration (I-D) curves of rainfall thresholds at various probabilities for cluster landslide and debris flow disasters triggered by typhoon-rainstorm in Wenzhou. Additionally, it recommends rainfall-threshold values for different types of geological disasters in Wenzhou. This study provides theoretical support and scientific evidence for early warning of geological disasters in Wenzhou, which has significant practical importance and application value.