不同空间布局下LID设施径流控制效果模拟研究

Simulation Study of the Runoff Control Effects of LID Facilities with Different Spatial Placement Strategies

城市流域尺度上的低影响开发(LID)可有效缓解城市洪涝问题,但目前研究主要集中在LID设施的规模占比、布设位置、设计参数等不同布局方案对城市洪涝风险削减的综合影响上,对于不同空间布局下LID设施径流控制效果却鲜有研究。以重庆市秀山海绵示范区为例,将城市排水系统(UDS)根据汇水区域划分为上、中、下游3个区域,利用SWMM模型将雨水花园(RG)、生物滞留带(BRC)和透水铺装(PP)3种典型LID设施以不同比例进行空间布设,评估不同降雨重现期下LID设施空间布局方案对径流的控制效果。研究结果表明,3种LID设施均可显著减少地表径流量和洪水总量,但对径流峰值的削减效果较差,总体性能为RG>BRC>PP;对于不同空间布局下LID设施组合布设时,其中均匀布设方案可最大程度减少城市洪涝,而其他布设方案仅在较低降雨重现期(P≤5 a)才可实现较好的径流峰值削减效果。此外,LID设施空间布局对城市洪涝的缓解效果受管网溢流节点分布显著影响,当LID设施布设于内涝点附近时,可最大程度降低城市洪涝发生几率,并可有效降低UDS转移至其他区域的水力负荷。

With the acceleration of global warming and urbanization,the frequency of urban impervious surfaces and extreme rainstorms has increased,resulting in frequent urban floods.Recent studies have indicated the effectiveness of low impact development(LID)at urban catchment scale in preventing urban flooding.Most of the past researches have mainly focused on the comprehensive impact of different configurations on urban flood risk reduction,such as the footprint ratio,placement location,and design parameters of LID facilities.However,there are few studies on the effectiveness of runoff control of LID facilities under different spatial placement strategies.A practical Urban Drainage System(UDS)of Xiushan Sponge City Demonstration Area in Chongqing is chosen as a case study and divided into three sections(upstream,center,and downstream)according to the catchment area.A combination of three typical LID practices,rain gardens(RG),bioretention cell(BRC),and permeable paving(PP),is installed on one of these sections or the entire catchment under different rainfall scenarios.The SWMM model is used to evaluate the influence of spatial distribution effects of LID facilities on runoff control and the impact on the formation process of UDS urban flood points under different rainfall return scenarios,and improve the ability of sponge city construction to cope with urban flood risks.The results show that surface runoff and flooding volume were reduced significantly,while poor reduction on peak runoff was observed when laid out with individual LID practices,and the overall performance of LID practices was RG>BRC>PP.Results also confirm the combination distribution of LID facilities under different spatial placement strategies.Uniform placement strategy proves to be the best among the four strategies because of the maximum potential for flood mitigation.Other investigated spatial distribution scenarios have relatively potential for peak runoff mitigation under a low rainfall return periods(P≤5 a).Furthermore,the mitigation effect of LID spatial distribution on urban flooding is significantly influenced by the distribution of pipe overflowing nodes.The placement of LID facilities nearer to the flooded locations maximizes the benefits in terms of urban flood alleviation and also reduces the probability of transferring hydraulic load to other parts of UDS.Therefore,factors such as the topology and hydraulic characteristics of UDS,the distribution of overflow nodes,and the design standards of LID facilities should be fully considered when the optimal location and proportion of LID facilities in the construction of sponge cities are determined.