Rainfall Patterns of Post-seismic Debris Flows in the Wenchuan Earthquake Area

Abstract

Several giant debris flows occurred in southwestern China after the Wenchuan Earthquake, causing serious casualties and economic losses. Debris flows were frequently triggered after the earthquake. A relatively accurate prediction of these post-seismic debris flows can help to reduce the consequent damages. Existing debris flow prediction is almost based on the study of the relationship between occurrence of post-earthquake debris flows and cumulative rainfall. The authors collected rainfall data associated with the occurrence of representative debris flows in the Wenchuan Earthquake area and analyzed the rainfall data and obtained rainfall patterns of rainfall-induced debris flows in the Wenchuan Earthquake area. The critical rainfall patterns related to debris flows in the Wenchuan Earthquake area can be divided into three categories: (1) a rapid triggering response pattern, (2) an intermediate triggering response pattern and (3) a slow triggering response pattern. The difference among the three triggering patterns is the antecedent rainfall duration and intensity. These critical rainfall patterns influence soil mass failure and debris flow initiation significantly.