RAINFALL THRESHOLD OF STORM-INDUCED LANDSLIDES IN TYPHOON AREAS：A CASE STUDY OF FUJIAN PROVINCE

Strong rainstorm can induce a burst of large number of small scale landslides. In typhoon areas, storm-induced landslides pose a high risk to the human lives and properties. It is therefore of great significance to study the occurrence of the landslides in typhoon areas. In this study, the critical duration of rainfall is estimated according to the reactivation period of extreme rainfall calculated using the Extreme Value Theory(EVT).Then, a threshold curve of the storm-induced landslides in typhoon areas is obtained based on a statistical approach. A typical typhoon region, the Fujian Province in the southeast China, is taken as a study area. Three typical regions with high occurrence of landslides are detected in the Fujian Province: the Nanping-Sanming region, the Quanzhou region and the Ningde region. It is found that, although the rainfall threshold of the Nanping-Sanming region is relatively higher, landslides happen more frequently and are mainly caused by continuous rainfall in three days. The Quanzhou region is susceptible to the influence of both short-term(3 days) and long-term(8 days) continuous heavy rainfall. The landslides in the Ningde Region are mainly caused by continuous rainfall in one day. This comparative study in different areas shows that the threshold of rainfall-induced landslide is affected by complex factors dominated with climate, geological environment and soil depth. The threshold of rainfall-induced landslide in typhoon areas is higher than that in non-typhoon areas, since the climate is the primary controlling factor of the threshold of rainfall-induced landslides.