Hazard Assessment of Typical Debris Flow Induced by Rainfall Intensity

A large number of landslides and rock falls were produced in the meizoseismal area by the "5·12" Wenchuan earthquake. If an extreme rainfall occurred, lots of materials could be transformed into debris flow, with larger size and higher damage degree than expected. On 13^th October 2010, debris flow occurred in Bayi gully in Dujiangyan County under rainstorm condition, destroying dam, burying road, houses and farms, and seriously affecting the daily life of local people. In order to reduce these damage, Bayi gully was selected as the research object. Combined debris flow intensity under the different rainfall frequency and period of the outbreak, this paper aims to obtain Bayi gully hazard assessment by the FLO-2D numerical simulation. First, the Bayi gully numerical simulation accuracy can reach 77% according to field test. Then, according to the different frequency of rainfall (5 years, 20 years, 50 years, 100 years, 200 years) and the debris flow velocity and deposit depth, the hazard assessment model is established. Finally, the hazard map of Bayi gully is obtained. The results show that the high hazard area accounted for 62% in the Bayi gully, the medium hazard area accounted for 28%, and the low hazard area accounted for 10%. The hazard assessment of Bayi gully can provide a reliable basis for the post-disaster reconstruction and the key area prevention.