Reasonable demonstration of impact from dam- break flood is of great significance to dam risk assessment and emergency management. When it comes to cascade dams failure, a 1D and 2D hydraulic coupling model is established to analyze the propagation of dam failure flood and the inundation of floodplain downstream the dam. Taking cascade hydropower stations on W river as an example, the impact of dam failure under two reservoir operation conditions in flood season and non-flood season, is considered in the model. The propagation of dam break flood is analyzed from aspects such as the peak discharge, maximum water level and timing of flood on typical section. On this basis, taking the maximum inundated depth of the flood plain as a representative index, dam failure flood risk level is divided and the flood risk map is drawn. The areas with high risk in case 1 and case 2 are 431.31 km² and 575.76 km² respectively, indicating the great impact of dam break flood on downstream areas. The simulation results have important reference value for developing emergency plans as well as disaster prevention and mitigation.

合理论证溃坝洪水灾害影响对大坝风险评价和应急管理具有重要意义。针对梯级水电站大坝连溃风险，建立一、二维耦合模型，对溃坝洪水演进规律及大坝下游平原洪泛区淹没影响开展分析。以W江梯级水电站为例，考虑汛期与非汛期水库不同运行情况下两种工况的溃坝影响，从典型断面洪峰流量、最高水位以及峰现时间等角度分析溃坝洪水演进规律。在此基础上，以洪泛区最大淹没水深为代表性指标，对溃坝洪水风险等级进行了划分，并绘制洪水风险图，工况1、工况2高风险区面积分别达到431.31 km²和575.76 km²，表明溃坝洪水对下游地区影响严重。相关成果可为应急预案制定和防灾减灾提供重要参考。