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

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.