基于Flow-R和FLO-2D的沟谷型泥石流危险性评价

Gully debris flow hazard assessment based on Flow-R and FLO-2D coupling models

泥石流是中国西南山区频发的地质灾害之一,具有突发性、流速快以及破坏力强等特点,往往造成巨大的人员伤亡和经济损失。地质灾害危险性评估是防灾减灾管理和防治环节中的有效措施之一,用于合理量化泥石流运动堆积线路沿程泥石流灾害危险性的空间分布特征。以四川省都江堰市龙池镇麻柳沟为研究对象,选取坡度、平面曲率和上坡汇水面积作为沟谷型泥石流启动区识别因子,基于Flow-R模型识别出的泥石流启动点,耦合FLO-2D模型模拟麻柳沟泥石流运动堆积过程,将泥石流堆积深度、运动速度和暴发频率相结合分析泥石流的危险性,并采用混淆矩阵对模拟结果进行了精度评估。结果表明:基于Flow-R和FLO-2D耦合模型的麻柳沟泥石流的运动堆积模拟结果与实际情况吻合度较高。模拟泥石流堆积区面积2.19万m^(2),堆积体积4.92万m^(3),泥石流危险性由沟道中心向两侧逐渐降低,高危险区占比42.3%,中危险区占比23.1%,低危险区占比34.6%。麻柳沟形成区、流通区沟道中散落堆积物体积大约为30万m^(3),麻柳沟泥石流仍处于高度活跃阶段,危险性较高,今后在降雨和水动力充分的条件下大量松散物质可能将被重新激活,一旦发生泥石流将有可能造成重大地质灾害。

Debris flow is one of the frequent geological disasters in southwest mountainous areas of China.It is characterized by sudden occurrence,fast velocity and strong destructive force,which often causes huge casualties and economic losses.Risk assessment of geological hazards is one of the effective measures in disaster prevention and mitigation management and prevention,which can reasonably quantify the spatial distribution characteristics of debris flow hazard along the debris flow movement and accumulation route.Taking Maliu gully in Longchi Town,Dujiangyan City,Sichuan Province as the research object,slope,plane curvature and upslope catchment area were selected as the identification factors for the initiation area of gully debris flow.Based on the starting point of debris flow identified by Flow-R model,the FLO-2D model was coupled to simulate the movement and accumulation process of debris flow in Maliu gully.The debris flow hazard can be determined by combination of accumulation depth,velocity and outbreak frequency of debris flow.In addition,the accuracy of the simulation results was assessed by confusion matrix.The results showed that the simulation results of Maliu gully debris flow by Flow-R and FLO-2D coupling models was in good agreement with the actual conditions.The simulated debris flow accumulation area is 2.19×10^(4)m^(2),and the accumulation volume is 4.92×10^(4)m^(3).The debris flow risk gradually decreases from the center of the channel to both sides.High risk area accounts for 42.3%,medium risk area accounts for 23.1%,and low risk area accounts for 34.6%.In formation area and circulation area of Maliu gully,the volume of scattered accumulation materials in the channel is about 300000 m^(3).The Maliu gully debris flow is still in a highly active stage with high risk.In the future,under the condition of sufficient rainfall and hydrodynamic force,a large quantity of loose materials may be reactivated,which may cause major geological disasters once it occurs.