基于OPUT的城市LID设施防涝布设方法

Urban LID layouts for controlling waterlogging based on OPUT

近年来,极端暴雨增加导致城市内涝愈发严重,而合理布设低影响开发(low impact development,LID)设施可以有效地缓解城市内涝问题。该文提出了一种基于溢流点位上游追踪(overflow point upstream tracking,OPUT)的LID设施布设方法。运用暴雨洪水管理模型(storm water management model,SWMM)构建排水模型,模拟不同重现期管网溢流,采用OPUT方法确定需要布设LID设施的雨水子汇水区,与传统全范围等比例(traditional full range equal proportion,FREP)的LID设施布设方法结果进行对比。结果显示:从缓解内涝方面来看,OPUT方法和FREP方法节点溢流体积削减百分比在单位布设LID设施面积下均随着重现期增大而减小。从径流削减方面来看,在不同的重现期下,2种方法对径流体积和径流峰值流量的削减情况在单位布设LID设施面积下是不同的,OPUT方法对径流体积的削减在重现期较大时效果更好,对径流峰值流量的削减随着重现期的增大呈上升趋势并接近FREP方法。从经济方面来考虑,当2种方法对节点溢流的削减效果近似一致时,OPUT方法和FREP方法成本均随着重现期的增大而增加且OPUT方法的成本均小于FREP方法的。可见对于缓解内涝的LID设施布设需求,OPUT方法具有更佳的内涝缓解效果和经济性。

[Objective]With the continuous advancement in urbanization in recent years,the urban impervious rate has increased;hence,urban areas have to primarily rely on urban pipe networks for drainage.However,most of these pipe networks constructed in the early stages of cities cannot manage the extreme rainstorms caused by global warming,resulting in severe urban waterlogging.Low impact development(LID)facilities can effectively reduce urban waterlogging by increasing infiltration surface.However,the LID allocation method using the traditional full-range equal proportion(FREP)method,which is based on different land-use types,is usually adopted for determining the layout of LID facilities.The layout location of these facilities is determined by the distribution of land-use types.There will be no LID facilities in areas with severe waterlogging using FREP method,whereas more LID facilities will be available in areas with less overflow,thereby wasting LID facility resources.LID facilities can be fully utilized to better resolve waterlogging control effects if the layout of the waterlogging source is considered.Therefore,to address the above issue,this paper proposes the LID allocation method using the overflow point upstream tracking(OPUT)method.[Methods]OPUT method used storm water management model(SWMM)to build a drainage model,simulate pipe network overflow in different return periods,lock the overflow point,track the nodes of pipelines upstream of the overflow point layer by layer,and determine the corresponding catchment area level.LID facilities were laid on the catchment area depending on the land-use type.FREP method and OPUT method were compared from three aspects:runoff,waterlogging,and economy.[Results]The results obtained using the OPUT method show that in terms of relieving waterlogging,the reduction percentage of the overflow volume is 12.82%to 1.73%under design rainfall of 180 minutes(short-duration rainfall)with increasing return period and is 8.16%to 1.12%under design rainfall of 1,440 minutes(long-duration rainfall)for a unit LID area.Meanwhile,the FREP method yields reduction percentages of 1.87%—1.22%and 1.87%—0.83%under short-and long-duration rainfall,respectively.From the runoff reduction perspective,the reductions in runoff volume and peak runoff obtained using the two methods are different for LID per unit layout area under different return periods.The reduction obtained for peak runoff using the FREP method is always better than that of the OPUT method;however,as the return period increases,the reduction exhibited by the OPUT method is closer to that of the FREP method.For the reduction in runoff volume,the FREP method exhibits better results when the return period is small,whereas that of the OPUT method is better for a large return period.When the two methods have approximately the same reduction effect on overflow,under short-and long-duration rainfall,the cost for the layout requirement obtained using the OPUT method is 61.5—325 and 73.7—333 million yuan,respectively,as the return period increases.Meanwhile,with an increase in the return period,the short-and long-duration the costs for the layout requirement obtained using the FREP method are 66.1—423 and 137—423 million yuan,respectively.[Conclusions]The LID layout requirements obtained using the OPUT method exhibit a better reduction effect and economy for relieving waterlogging.