基于FLO-2D的泥石流危险性评价——以四川省汶川县绵虒镇簇头沟为例

Assessment on the hazard of debris flow based on FLO-2D:A case study of debris flow in Cutou Gully,Wenchuan,Sichuan

2013年7月10日四川省汶川县绵虒镇降持续性暴雨,促使簇头沟暴发降雨频率为2%的泥石流,导致岷江堵塞,严重威胁沟口居民及下游安全。以簇头沟的1∶10000等高线、2013年降雨数据与遥感影像等作为基础数据,结合野外考察资料,运用FLO-2D软件,模拟计算簇头沟在不同降雨频率下(5%、2%和1%)泥石流的运动堆积过程,研究簇头沟泥石流的危险性。在2%降雨频率(实际降雨频率)条件下,模拟得出最大泥石流流速为12.99m/s,最大泥石流泥深为15.7 m,堆积面积为9.55×10~4m^2,与实际堆积范围进行验证,精确率为77%,在合理误差范围内,成果可靠性高。通过泥深与流度来构建泥石流的强度模型,再与暴发的重现周期相结合而构建簇头沟泥石流危险性评价模型,获得堆积扇危险范围分布图,其中高危险面积占61%,中危险面积占19%,低危险面积占20%。为簇头沟泥石流的灾害防治提供科学的参考依据。

Debris flow at a rainfall frequency of 2% was triggered by rainstorm on July 10,2013 in Miansi town,Wenchuan County,Sichuan Province,blocking Minjiang River and endangering the settled population downstream area. Based on the 1∶ 10000 contour,rainfall data and remote sensing image of 2013 and the flied investigation in Cutou gully,FLO-2D software is used to simulate the movement and accumulation process of debris flow under different rainfall frequency（ 5%,2% and 1%） for studying the hazard of debris flow in Cutou gully. Under the condition of 2% rainfall frequency（ the actual rainfall frequency）,the simulated maximum debris flow velocity is 12. 99 m/s and the maximum debris flow mud depth is 15. 7 m,and the accumulation area is 9. 55 × 10^4 m^2. Verified by the actual accumulation zone,the accuracy rate was 77%. The simulation results are in a reasonable error range and show high reliability. The strength model of debris flow was created through the mud depth and flow velocity. In addition,the debris flow hazard assessment model is constructed by combining the strength of debris flow and the return period of the outbreak. In this way,the risk assessment of debris flow in Cutou gully is realized and the distribution map of hazard zone in fan area is obtained,where the high dangerous area accounts for 61%,the moderate dangerous area accounts for 19%,and the low risk area accounts for 20%. It provides a scientific reference for prevention and control of Cutou gully debris flow.