Urban flooding is increasingly pervasive, with the decreasing water area in cities and the dreadful impact on people. Therefore, it is necessary to carry out a quantitative evaluation of the area of urban water and analyze the threshold of the reasonable water ratio under different drainage scenarios. In this research, simulations were performed by using the Personal Computer Storm Water Management Model (PCSWMM), and the model parameter calibration method was based on the runoff coefficient as a contribution to meeting the data-poor urban areas. Then, urban flood control standards were divided into four classes, and the rainfall scenario once in 200 years and historical maximum were selected to build future extreme inundation scenarios in the case study. Simultaneously, methods for the reasonable water area ratio estimation were decided. The cost-effectiveness of all possible solutions was examined across the two scenarios based on the assessment method. The results show that the range of reasonable ratios of the water area under traditional planning is 5.78–6.02% to meet the standard of urban drainage. Similarly, the range of reasonable ratios of water area under the LID (low impact development) plan combined with the sponge city concept is 5.63–5.88%.

随着城市水域面积的减少以及对人们的可怕影响，城市洪水泛滥。因此，有必要对城市用水面积进行定量评估，并分析不同排水情景下合理水比的阈值。在这项研究中，使用个人计算机雨水管理模型（PCSWMM）进行了仿真，并且模型参数校准方法基于径流系数，以应对数据贫乏的城市地区。然后，将城市防洪标准分为四类，并选择200年一次的降雨情景和历史最高值，以建立未来的极端淹没情景。同时，确定了合理的水面积比估算方法。根据评估方法，在两种情况下检查了所有可能解决方案的成本效益。结果表明，按照城市规划的排水标准，传统规划中合理的水面积比范围为5.78％〜6.02％。同样，在LID（低影响开发）计划下结合海绵城市概念，合理的水面积比率范围为5.63-5.88％。