中文摘要：

2008—09—24强降雨过程导致汶川震区北川县城魏家沟泥石流暴发，对老北川县城造成了严重的破坏。由于这场泥石流灾害发生在汶川地震高烈度区，是地震与降雨共同作用下的结果，研究其形成与成灾过程，对于进一步认识强震区泥石流发育特征具有重要的意义。根据现场调查和高分辨率航空图像解译，分析了魏家沟泥石流流域特征，特别是地震条件下的泥石流物源特征，在此基础上讨论了泥石流起动过程和堆积过程。魏家沟泥石流典型实例表明了汶川震区泥石流已进入一个新的活跃期。因此，应该开展对汶川地震区的泥石流风险评估和监测、早期预警等研究，采取有效的工程措施控制泥石流的发生和危害。

英文摘要：

A rainstorm induced debris flow hazard occurred in Beichuan City of Sichuan Province of the Wenchuan earthquake affected area on 24 september,2008. Debris flow occurrence is the result from the combination rainfall and earthquake. Therefore, it is significant that make further clear of development characters of debris flows through research on the formative and movement process in high seismic intensity area. This paper analyzed the watershed and cause condition of the debris flow based on field reconnaissance and Interpretations of aerial photographs. The emphasis was focused on loose material concentration in source areas of debris flows. On basis of above analysis, The initiation and deposition process of debris flows were discussed in this paper. The typical case of the Xishanpo debris flow indicated that the region affected by the Wenchuan Earthquake become more vulnerable to debris flows in future period. Therefore it is important to assess debris flow risk and take hazard monitoring and early warning for debris flow occurrence in the earthquake areas. The control work is also necessary for debris flow hazard mitigation.