Evaluation Of Stormwater Regulation Benefits Of Nanjing Jinling Primary School Under Different LID Planning Scenarios

The rapid urbanization development is accompanied by the continuous expansion of population and scale,leading to multiple adverse effects on the hydrologyof the city.Traditional urban drainage system,which is dominated by fast drainage,can no longer meet the requirements of modern urban development Therefore,after long-term research,scholars at home and abroad have proposed new models of urban stormwater management that can efficiently reduce the risk of urban flooding and turn rainwater into resources,among which Low impact development(LID)has been increasingly attracting wide attention and become an important part of China's sponge city construction.Currently the research on LID mainly focuses on the analysis of rainwater flooding effects of single or combined LID measures.Whereas the planning layout and the evaluation of rainwater flood control benefits at the lot scale level of LID has been much less studied.Lacking reference in setting up LID measures leads to poor improvement of the ability of the project's storm flood control.Therefore,constructing a cost-benefit optimal LID planning scheme at the lot scale level is of high necessity and demand.In addition,"Sponge Campus",as a subsystem of sponge city,not only enables teachers and students to get closer to nature,but provides a better understanding and insghts of the construction of the sponge city.In this paper,taking Nanjing Jinling Primary School as the designated research area,the current situation scheme and seven LID plannings are compared based on different surface runoff feature perspectives by the effects of stormwater flooding,employing LID module of the SWMM model under five different rainfall scenarios.At the same time,according to the Life Cycle Assessment(LCA),the life cycle cost of seven LID planning programs is quantitatively analyzed with the STEP-LID-TOOL tool.Finally,the optimal cost-benefit LID planning scheme for rainwater flood control for the study area is discussed,which provides a reference for LID planning and "Sponge Campus" construction in the lot scale areas in Nanjing and other cities.The results of this study are as follows:1)Based on the relationship between the effect of LID measure rain flood regulation effect and rainfall characteristics,the effect of LID measures on rainwater flood control is affected by changes in rainfall characteristics.Therefore,it is more reasonable to set up different rainfall scenarios and generate the storm flood control analysis with different surface runoff characteristics in the experimental simulation.2)To achieve the optimization of cost-benefit for rainwater control in the study area,it is necessary to conduct reasonable LID planning for the study area according to local conditions and to strengthen factors such as ecology,sustainability,and economy.Besides,LID measures and landscape planning as a whole and the relationship between layout and infrastructure construction should be considered.3)Under different rainfall scenarios,seven LID planning schemes are superior to the current situation scheme for storm flood control.Besides,there are significant differences in the effects of rain-flood regulation for different LID planning scenarios.The comparative analysis found that in the five rainfall scenarios,the optimal solution for the total runoff reduction is the scenario S7(green roof,rain garden and rain barrel).4)According to the 30-year life cycle cost-efficiency and return on investment of the integrated LID planning program,the S1(green roof)is the best cost-efficient solution for the total runoff reduction effect in the study area.Under different rainfall scenarios,30 years Life Cycle Cost-Efficiency of different LID planning schemes were analyzed base on the life cycle cost and total runoff reduction effect based on the actual rainfall data for a year in the study area.At the same time,by estimating the construction cost of traditional grey infrastructure,the pay-back on investment of 30-year life cycle for different LID planning schemes was obtained.Due to the differences in the functional characteristics of different LID measures,it is appropriate to deploy green roofs in this study area.Considering the effects of rainwater flooding such as infiltration,water storage,and cutting peak water flow,a small number of other types of LID measures can be appropriately configured.It is beneficial to the study area to better achieve different effects of rain flood control.In addition,considering the above factors comprehensively,when this rainwater flood regulation benefit evaluation method is applied in other urban site-scale areas,it is necessary to pay attentions to whether there is space condition or economic condition for runoff control.Under certain circumstances,a lower total runoff control target can be selected.At the same time,excessively high total runoff control objectives may affect the virtuous circle of the water system and cause problems such as excessive scale of LID measures and investment waste.This study also provides analytical ideas and research methods of a layout of LID measures,storm flood control effect analysis,LID planning schemes(including individual LID measures),life-2cycle cost calculations,stormwater control cost-efficiency evaluation,and "Sponge Campus" construction on the lot-scale area in other cities.The whole thesis contains about 33810 words,56 pictures and charts.