南昌市城区暴雨积水的数值模拟

Numerical Simulation of Storm Sewer Discharge in Nanchang Urban Region

论述了南昌市城市暴雨积水仿真系统的数学原理和开发成果,并应用实况降水对该系统的模拟精度进行测试。结果表明：大多数（62.6%）模拟计算结果的绝对误差在10 cm以内,只有极少数（2.4%）实际积水与模拟结果的误差超过30 cm。暴雨积水等级试验结果表明,中度以上暴雨积水地段的预报准确率达98%,轻度积水和无积水地段的预报准确率达92%。总体来看,暴雨积水趋势（等级）预报基本准确,定量（积水深度）预报有误差,平均相对误差为6%,模型的预测结果与实况基本相符。通过人工给定不同强度的雨量来模拟南昌市两个重点积水地段的积水过程,得到结论：当降水强度达到20 mm/h时,开始产生积水,降水强度超过30 mm/h时将产生严重积水;两个积水点因排水条件不一样,退水时间差异较大。排水条件差的地段,中—大雨需要15 h退完,暴雨需要24 h以上才能退完;在不同降水强度和排水条件下,最大积水深度出现的时间有明显区别;在暴雨情况下,绝大部分（76%）积水点的最大积水深度出现在2～3 h内。此外,讨论了模拟误差产生的原因。

The mathematical principles and development achievements of the storm sewer discharge simulation system of Nanchang urban region designed by the authors,are elaborated in this paper.The observed precipitation and flood data are used to examine the precision of the model,and the results indicate that the absolute error is less than 10 cm in most simulations（about 62.6 %）,and above 30 cm in only a few simulations（2.4 %）.According to various stormwater flood grade simulation experiments,the forecast accuracy can reach 98 % in moderate or severe flood regions,92 % in gentle or light flood regions.In general,flood trend（grade） forecast is basically accurate in most of the times,but the quantitative forecast（flood depth） still has some errors,with the average relative error being about 6 %.The model forecast results are basically in accordance with the actually situation,suggesting that the model can be applied in city stormwater flood forecast.In addition,the flooding processes of two key blocks in Nanchang urban region are also simulated through artificially assigning different precipitation rates,and the results show that flood starts when the precipitation rate reaches 20 mm/h,with the increasing of precipitation rate to 30 mm/h,flood becomes more severe.The draining duration is obvious different between the two blocks with different drainage conditions.In the block with poor drainage conditions,it is about 15 hrs/24 hrs required for accumulated stormwater to be completely drained off in a moderate-heavy/terrential rain process,respectively.The timing of maximum flood depth,which is 2—3 hours after the beginning of rainstorm in most blocks,also varies evidently with different precipitation rates and drainage conditions.The cause of error is also analyzed.