梯级水库溃坝洪水对下游城市的淹没过程分析

Inundation Process of Downstream Cities by Dam Break Flood from Cascade Reservoirs

溃坝洪水的演进过程及其对下游城市的淹没影响是大坝安全的重要研究内容之一。以我国南方某山区河流为例,采用数值计算方法,针对该流域上并(串)联的4座水库在多种溃坝模式下,对下游城市的淹没过程进行了计算和讨论分析。研究结果表明:溃坝洪水在下游城市的淹没速度和最大淹没面积主要与最大溃坝流量相关,即与溃坝水头和溃口大小相关;最大淹没面积的达到时间主要与城市与水库间的行洪距离有关。梯级水库发生连溃时,溃坝洪水对下游城市的淹没速度和淹没面积都较单个水库溃坝更加严重,不过连溃洪水在下游城市呈现淹没快、退水也快的特征。城市洪水的淹没历时主要与溃坝水库的容积相关,与最大溃坝流量的关系不大。

The propagation of dam break flood and its influence on cities in the downstream are important issues in dam safety research. In this paper, the inundation process of downstream cities were simulated and analyzed through numerical approach. A mountain river in south China with four cascaded reservoirs was selected as case study. The simulation was conducted with multiple dam break modes. Results suggest that the inundation speed and maximum inundated area are closely related to the maximum dam break discharge, i.e., related to the water head and size of the breach. The time required for maximum inundated area is related to the distance between city and reservoir. The speed as well as inundated area and inundated volume in the case of single break are less severe than those caused by successive cascaded break flood, which, however, floods and recedes dramatically. The duration of the inunda- tion process for a city is related to the volume of the reservoir rather than to maximum break discharge.