基于Massflow模型的甘肃省岷县二马沟泥石流危险性评价

Massflow Model-based hazard assessment on Erma Gully Debris Flow in Minxian County of Gansu Province

二马沟位于甘肃省岷县茶埠镇上半沟村,曾多次暴发泥石流,对当地居民的生命安全和生产生活造成了极大的损失。为了研究二马沟泥石流的危险性,以2012年5月10日发生的泥石流灾害为基础,选取了二马沟及其左岸的河沟沿、扁坡沟、鹞子沟泥石流沟为研究对象,经过详细的资料收集和野外调查,获得了该流域内地形、物源、水源等资料,通过试验和计算分析得到了模拟所需的参数值,结合网络化的数字高程模型,在ArcGis中将研究区DEM栅格数据转换成Massflow软件可以读取的ASCII格式,建立计算模型。利用Massflow软件模拟了1%、2%、5%降雨频率下泥石流冲出物的流动速度、堆积深度、堆积范围,根据泥石流的强度与危险性分区标准,将研究区划分为高危险、中危险、低危险三个区域。结果表明:在实际降雨频率下模拟得出主沟泥石流最大流速为11.05 m/s,最大泥深为13.05 m,堆积范围为3.47×10^4 m^2,堆积方量Qz为18.55×10^4 m^3,模拟精度到达80%以上;高危险范围占据了整个危险范围的60%以上,中危险和低危险分布面积较小,说明二马沟是一条危险性较大的泥石流沟,研究成果为当地的防灾减灾工作提供一定的科学指导意义。

Erma Gully is located in Bangou Village of Chabu Town in Minxian County of Gansu Province, from where debris flows occurred for several times, thus great losses are caused to the lives and production of the local residents. In order to study the hazard of the debris flow in Erma Valley, Erma Valley and the debris flow valleys of Hegouyan, Pianpo and Yaozigou on its left bank are taken as the study cases based on the debris flow disaster occurred on May 10, 2012, and then the data of topography, material sources, water sources, etc. within the watershed are obtained through detailed data collection and field investigation, while the parameters necessary for simulation are obtained through the relevant experiments and calculation analyses as well. In combination with the networking digital elevation model, the DEM raster data in the study area is converted into ASCII formatwhich can be read by the software-Massflow in ArcGis for establishing the relevant calculation model. By means of the software-Massflow, the flow rates, deposit depths and deposit ranges of debris flow effluent under the rainfall frequencies of 1%, 2% and 5% are simulated, and then the study area is divided into three zones, i.e. high hazard, medium hazard and low hazard, in accordance with the intensity and hazard zoning criteria for debris flow. The result shows that the maximum flow rate of the debris flow is 11.05 m/s with the maximum depth of 13.05 m, the deposit range of 3.47×10^4 m^2 and the deposit volume Qz of 18.55×10^4 m^3 in the main gully obtained through the simulation made under the actual rainfall frequency, for which the simulation accuracy reaches over 80%, while the high hazard zone accounts for more than 60% of the total hazard area with smaller distributed areas of medium hazard and low hazard. The study indicates that Erma Gully is a debris flow gully with larger hazard, thus the study result can provide a certain scientific guidance for the local disaster prevention and mitigation.