汶川震区映秀镇“8·14”特大泥石流灾害调查

Field Investigation and Research on Giant Debris Flow on August 14,2010 in Yingxiu Town,Epicenter of Wenchuan Earthquake

2010年8月14日强降雨过程导致汶川震区映秀镇红椿沟泥石流暴发,泥石流堰塞堆积体堵断岷江主河道,导致河水改道冲入映秀新镇,引发洪水泛滥;造成映秀镇13人死亡、59人失踪,受灾群众8000余人被迫避险转移.由于这场泥石流灾害发生在汶川地震震中区,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.根据现场调查和航空图像解译,分析了红椿沟泥石流流域特征,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.红椿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.

A rainstorm triggered debris flow hazard occurred in Hongchun valley,Yingxiu town,epicenter of the Wenchuan earthquake on August 14,2010. This event transported huge material sediment to the watercourse of the Minjiang River and produced a natural dam,resulting in flash flood in the new Yingxiu town. The flood claimed 13 lives,with a further 59 listed as missing. About 8 000 local residents were rapidly evacuated from their homes. The debris flow resulted from the coaction of the rainfall and earthquake. Therefore,it is significant for better understanding of development characters of debris flows to conduct the research on the initiation and movement process in high seismic intensity area. This paper studies characteristics of the initiation conditions and depositional fans of the debris flow based on field reconnaissance and interpretations of aerial photographs,focusing on loose sediment supply in source areas of debris flows. On the basis of the above analysis,the initiation and deposition process of debris flows are discussed. The catastrophic event indicates that the areas impacted by the Wenchuan earthquake become more prone to debris flow occurrences in the future. So it is important to assess debris flow risk and take measures to enhance hazard monitoring and offer early warnings for debris flows in the earthquake areas. The control work is also necessary for debris flow hazard mitigation.