A number of earthquake debris flows were caused by the Wenchuan earthquake. This paper discusses the characteristics and happening conditions of the typical sequential debris flows in the earthquake area. Through field observation of the Xiaogou gully basin located in Hongkou,Dujiangyan, Sichuan Province and laboratory experimental data analysis, it reaches the conclusion that first, many landslides were triggered by the Wenchuan earthquake on May 12, 2008 and many potential landslides lost their balancé in the earthquake but were not triggered in the Xiaogou gully basin. Second, the landslides were mainly triggered by heavy rainfalls. The channel was blocked by landslides and formed some dams and lakes. Heavy rainfall and floods broke these dams, formed strong floods, eroded the bed of the channel, and therefore formed debris flows. Right now, there are still many potential landslides in the Xiaogou gully basin. They are easily triggered by heavy rainfalls block the channel with the effect of flood, and finally form debris flows. Because of their potentiality and concealment, these debris flows in the Xiaogou gully are much more dangerous.%汶川地震诱发了很多地震泥石流.通过对四川省都江堰市虹口乡小沟泥石流沟实地考察和室内实验数据分析,得出小沟泥石流暴发的主要原因是:(1)2008年5月12日汶川大地震导致大量山体滑坡,在四川省都江堰虹口乡小沟流域内大量滑坡体失去了原有稳定性但还没有滑动,(2)强降雨作用使滑坡体运动至沟道内,阻塞束窄沟道,后在洪水冲刷下溃决,摹发泥石流.目前小沟流域内还存在大量潜在滑坡,在强降雨作用下,很客易再次滑至沟道,并在洪水作用下启动形成泥石流,造成灾害.此类强震区泥石流的暴发具有一定的隐藏性,事前不易被发觉,危险性更大.
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