城市地区流域洪水过程模拟:以清河为例

Urban area watershed flood simulation with hydraulic model:A case study of Qinghe river in Beijing

城市地区流域洪水模拟是当前洪水过程计算分析的热点和难点,本研究基于Mike洪涝模拟平台的河道一维水动力学模型（MIKE11）,综合考虑城市地区不透水下垫面产流、多闸坝调度、城市排水、支流汇入等因素,系统构建了北京市主要排洪河道清河流域洪涝模拟模型,以设计流量、水位资料和实测场次洪水过程资料分别对河道、水工建筑物参数及运行规则进行了验证,模型模拟结果显示模型能够较好模拟城市流域复杂环境条件下的河道结点水位,情景模拟分析不同降雨重现期流域现状河道行洪能力和河湖雨水综合利用能力,显示清河流域具有明显的低水位、大流量的特点,可以满足20年一遇降雨行洪要求。在特大暴雨条件下清河干流中段清河闸至羊坊闸是河道洪涝的重点防护区域。从1年到20年一遇重现期设计降雨条件下,模拟蓄水占总库容的33.5%-54%。研究为城市流域防洪调度和雨水资源利用提供技术支持。

Watershed flood simulation for urban areas is important for river safety and flood control, but it is a difficult issue due to its complicated factors. Based on a one-dimensional MIKE11 model, we integrated on the model Platform the processes of runoff generation in impervious areas, multi water projects control, regional drainage, and tributaries confluence, and constructed a coupled modeling system of Qinghe watershed flood in the urban area of Beijing. The river and floodgates hydraulic parameters are validated with design flood volume and its corresponding water level data of 20 year and 50 year return periods. And the floodgates operating rules are validated with the water level data from the storm and flood events in July 21 in 2012. The simulations shown a good agreement with the water level, total flood volume, and peak value monitored at eight floodgates. Application of this model to different scenarios of design storms shows that low water level corresponds to relative high flood volume and the river can undertake flood volume of 20 year rainfall return period. The riverbank in the middle reach between the floodgates of Qinghe and Yangfang is the most serious area for flood control. For the rainfall return periods from 1 year to 20 year, the ratio of fmal volume of storm water into the river over the river storage capacity is in the range from 33.5% to 54%. This study would supply a guide to flood control and storm water utilization assessment in the watershed of urban area