高寒小流域措普沟山洪风险分析

已有山洪泥石流灾害的风险评估主要针对暴雨或者冰川融水激发条件下的风险评估,而当高寒山区流域源头存在冰湖发育时,如何考虑冰湖对下游铁路、公路等线性工程影响的研究并不多见。以巴塘县措普沟及其支沟上游绒伊措冰湖为例,在分析冰湖孕灾环境背景的基础上,通过遥感解译和详细的野外调查,获得了绒伊措冰湖几何参数与沟道断面特征参数;结合坝体结构与物质组成特征,分析了坝体结构的稳定性;依据措普流域水文计算成果,评估了山洪对拟建铁路的影响。研究表明:绒伊措冰湖坝体由坚硬的花岗岩组成,坝体完整性好,在不考虑高烈度地震等极端条件下,绒伊措冰湖坝体稳定性较好,发生溃决的可能性较小,绒伊措冰湖对下游拟建铁路的影响小;在考虑P=1%设计频率暴雨与冰川融水情景下,措普流域山洪洪峰流量为448 m³/s,桥位所处断面的平均流速2.75 m/s,水深4.62 m,与铁路梁底的高差为53.89 m,对铁路线路安全不构成威胁。

Risk Analysis of Flash Flood in Cuopu Gully in High and Cold Mountain Area

Existing risk assessment of flood/debris flow disasters is based mainly on the analysis of heavy rainfall or glacier-melt water.In some areas,especially in high and cold mountainous areas with glacial lake developing,researches on the impact of glacial lakes on proposed railways, highways and other linear projects downstream are rarely reported. In this paper, the key geometric parameters of Rongyi glacier lake in the upstream catchment of Cuopu Gully and the characteristic parameters of channel section are obtained based on the analysis of the environmental conditions of the glacial lake via remote sensing interpretation and detailed field surveys. The structure and material composition of lake dam are analyzed, and the stability of the dam structure is analyzed. Moreover, according to hydrological calculation of Cuopu Gully catchment, the impact of flash flood on proposed railway project is evaluated. Results reveal that the dam of Rongyi glacier lake is composed of hard granite with good integrity, indicating small possibility of dam failure in the absence of extreme conditions such as highly intensive earthquake. In the scenario of P=1% design frequency rainfall in association with glacier-melt water, the peak flow of mountain flood in Cuopu gully catchment is 448 m³/s, the average flow velocity at the railway bridge section is about 2.75 m/s,and the water depth is about 4.62 m. According to the railway design, the elevation difference between the bottom of railway beam and the flow surface is 53.89 m,which is considered to be safe for the proposed railway.