汶川震区暴雨泥石流激发雨量特征

利用搜集的汶川震区典型泥石流暴发前后的降雨过程资料,分析了泥石流的激发雨量过程,获得了汶川震区的泥石流激发雨量特征,以期为泥石流的预测预报提供依据。结果表明,汶川地震区的泥石流激发雨型可分为快速激发型、中速激发型和慢速激发型3类,其差异主要体现在降雨的持续时间和强度方面。不同激发雨型下的泥石流形成过程的差别主要体现在松散土体饱和过程。雨型的差异(降雨的持续时间和强度)使得土体饱和产生超渗产流的时间出现差异,进而使得泥石流暴发的时间存在差异。激发雨强跟激发雨型存在一定的关系,激发雨强最大者为中速激发雨型,其次是慢速激发雨型,最小者为快速激发雨型。与地震之前相比,地震后的泥石流暴发时的累积雨量和临界雨量都有所降低。

Critical rainfall characteristics for rainfall-induced debris flows in Wenchuan earthquake affected areas

The rainfall data before and after the occurrence of the debris flow event in Wenchuan earthquake affected area are collected and analyzed in order to better understand the critical rainfall characteristics for rainfall-induced debris flows.The study can provide the scientific base for the establishment of an advance warning system for debris flows.The results show that the critical rainfall pattern for the debris flow event during the earthquake can be classified into three types including the rapid triggering response pattern,the intermediate triggering response pattern,and the slow triggering response pattern.The main differences among the three patterns are in the duration and intensity of rainfall,which can result in different saturation mechanisms in loose zones for debris flow initiation.The timing of the occurrence of infiltration excess runoff is different for different rainfall patterns,and so do the triggered debris flows.Critical rainfall intensities could be related to critical rainfall patterns.For example,the intermediate triggering response pattern can be associated with the highest rainfall intensity,and followed by the slow triggering response pattern.The lowest rainfall intensity can be related to the rapid triggering response pattern.The threshold values of both accumulated precipitation and critical rainfall have been decreased after the earthquake.