汶川震区暴雨泥石流激发雨型特征

汶川地震后暴雨诱发的泥石流不断增加，通过收集整理降雨资料，分析汶川震区不同地域泥石流暴发的激发雨强及前期有效累计降雨量变化过程，揭示震区暴雨泥石流的激发雨型特征，为暴雨泥石流的预报提供科学依据。研究结果表明，汶川震区的暴雨泥石流激发雨型可分为短期突然降雨型、中期持续降雨型和长期间断降雨型3种类型，主要表现为引发泥石流的激发雨强及前期有效累计降雨量的不同。暴雨泥石流的形成机制体现为降雨导致流域内松散土体渗透、饱和及侵蚀移动的过程。激发雨型与激发雨强及前期有效累计降雨量存在相关关系，短期突然降雨型的激发雨强最大，前期有效累计降雨量最少；中期持续降雨型的激发雨强居中，前期有效累计降雨量最多；长期间断降雨型的激发雨强最小，前期有效累计降雨量居中。对四川茂县叠溪镇新磨村突发山体高位垮塌碎屑流进行验证，初步判定是由长期间断降雨型引发岩体抗剪强度降低而引起的。对不同激发雨型特征的研究能够为汶川震区泥石流监测预警提供科学依据。

Critical Rainfall Patterns for Rainfall induced Debris Flows in the Wenchuan Earthquake Area

To obtain the rainfall characteristics and enhance the early warning system for rainfall induced debris flows, the post debris flow rainfall data in the Wenchuan earthquake area are collected, and the rainfall intensity and early stage effective accumulative rainfall are analyzed. The results show that the rainfall induced debris flows in the study area can be classified into three types, ie, short term rainfall, persistent rainfall and intermittent rainfall. The main differences among the three rainfall types occur in the rainfall intensity, duration and effective accumulation, which can result in different soil percolation, saturation, and erosion mechanisms in provenance for debris flow initiation. Critical rainfall intensities and effective accumulative rainfall could be related to critical rainfall types. The short term rainfall type may be associated with the highest rainfall intensity and the least effective accumulation;persistent rainfall type is associated with medium rainfall intensity and the most effective accumulation, whilst the intermittent rainfall type can be related to the lowest rainfall intensity and the medium effective accumulation. After a verification for the sudden collapse induced by the high mountain formation debris flows in Xinmo Village of the study area, the result showed that the prime reason was the decrease of rock shear strength caused by long term intermittent rainfall.This work provides scientific basis for the early warning system for debris flows in the Wenchuan earthquake area.