考虑圩区分布的平原河网区暴雨洪涝分析模型建立

针对圩区众多的平原河网区域,基于已有的一、二维非恒定流水动力学理论建立的城市洪涝仿真模型,引入"小蓄水面"的概念,将圩区内外在水动力学模型中未被概化但对降雨的调蓄作用不可忽略的小河、塘坝、小湖泊等根据其实际空间分布统一概化为所在网格的小蓄水面,并考虑圩区堤防标准、抽排能力和调度运行规则对河网区域洪涝时空分布的影响,对模型中网格淹没水深、圩区排涝和闸泵调度的计算方法进行了改进。选择嘉兴市为案例区域建立了暴雨洪涝分析模型,利用模型对嘉兴市近年来典型场次暴雨进行模拟计算,与河道实测水位及洪涝分布调查结果对比表明,模型对区域的概化合理,能反映嘉兴市在受本地降雨和上游洪水影响、下游潮位顶托及复杂的工程调度规则综合作用下水流的运动特点和洪涝的分布特征,模拟结果可靠,模型可以为区域洪水风险图编制和防汛风险管理提供支持。

Establishment of numerical model for simulation of storm flooding in flat river network area considering polders distribution: A case study of Jiaxing City,China

Based on the existing numerical model for urban area which is built by means of one and two-dimensional unsteady flow theory, a concept called small water storage surface is put forward for flat river network area with numerous polders to reflect the storage function of small rivers,ponds and lakes to rainfall process inside and outside polders,which is hard to generate in two-dimensional hydraulics models but can''t be ignored,and the area ratio of small water storage surface for each mesh is abstracted according to the real river distribution. Meanwhile,considering the factors of polders which have impacts on spatial and temporal distribution of flooding and water-logging in flat river network area including flood control standard of levees, drainage capacity, as well as complicated operation rules, the calculation methods of grid inundation water depth,drainage process of polders and controlling of gates and pumps are improved. The storm flooding simulation model for Jiaxing city is established and several typical historical rainstorm processes in recent years are calculated to calibrate and modify the model. The comparison between simulation results and observed water level in rivers and investigated flooding and water-logging distribution shows that the generalization for this area in the model is reasonable, the characteristics of flood movement and inundation distribution under the integrated action of local rainfall,floods in upper reaches,influence of tidal level in lower reaches and complicated operating rules of flood control and drainage projects can be reflected. The simulation results are reliable and the model can provide support for flood hazard mapping and flood risk management in the case study area.