Simulation And Optimization Of The Control Effect Of Urban Stormwater Management Measures Based On SUSTAIN Model

With the rapid development of urbanization,the urban impervious area gradually expands,which increases the total amount of runoff generated in the process of rainfall and leads to the continuous occurrence of urban stormwater.Urban stormwater management measures,as the main means to regulate urban stormwater,which play a crucial role in urban planning and construction.However,the current research rarely focuses on the impact of the internal connection between stormwater management measures on the effect of stormwater regulation.In this study,four scenarios of connection schemes of stormwater management measures were constructed.By designing different rainfall return periods,with the help of the SUSTAIN model,the impact of four planning scenarios(Series connection,Parallel connection,Series and parallel connection1,Series and parallel connection2)on the effect of urban stormwater in Xiaozhai area of Xi’an City was considered.After selecting the optimal planning scenario based on the simulation results,analyze the influence on the carbon emissions of the research area after the layout of the scenario.The main research results are as follows:(1)This paper summarizes the advanced rainwater management measures in the word,selects indicators from four aspects of regional applicability,economic benefits,environmental benefits and social benefits by using AHP,establishes the evaluation system of stormwater management measures,and finally obtains four rainwater management measures with the highest comprehensive scores: green roof,bioretention ponds,grassed swales and rain barrels,which provides reference for future scenario planning.(2)Simulated the effect of different scenarios on the control of urban stormwater.According to the simulation results,we can see that under the condition of low return period rainfall(1a、5a),the reduction capacity of all four planning scenarios for peak flows is ranked as follows: scenario 3(Series connection)> scenario 2(Series and parallel connection2)>scenario 1(Series and parallel connection1)> scenario 4(Parallel connection).When facing the condition of high recurrence period rainfall(10a、20a、50a),because the stormwater management measures connected in parallel with Scenario 4((Parallel connection))can make full use of the detention capacity of each stormwater management measure,its reduction effect on peak flow is higher than the other three planning scenarios,and the order of reduction ability is: Scenario 4(Parallel connection)>Scenario 1(Series and parallel connection1)>Scenario 2>Scenario 3(Series connection).The reduction rates of the four planning scenarios to the flood peak delay and total runoff of all rainfall return periods are:Scenario 3(Series connection)>Scenario 2(Series and parallel connection2)>Scenario 1(Series and parallel connection1)>Scenario 4(Parallel connection).(3)Analyzed the water quality(COD,SS)reduction ability of four planning scenarios under different rainfall conditions.From the reduction effects on COD and SS,the reduction rates for COD and SS for all four planning scenarios ranged from 41.85% to 87.11%,scenario3(Series connection)has the best performance in reducing pollutants,and the reduction ability of SS of each planning scenario is stronger than that of COD.(4)Evaluated cost benefit scenarios for different planning scenarios.By analyzing the cost-benefit curve of the simulated four planning scenarios,it can be concluded that the planning scenario 3(Series connection)is finally selected as the optimal solution,According to the distribution ratio of various rainwater management measures in the planning scenario3(Series connection),calculate the carbon sequestration of green space,carbon sequestration of runoff reduction,carbon sequestration of building energy saving,carbon sequestration of rainwater purification of each stormwater management measures the carbon emission can be reduced by 189.70 t a year.Through the analysis of the effects of different connection modes of different rainwater management measures on the regulation of stormwater,selecting the most suitable stormwater management measures planning scenario for urban construction can not only alleviate the problem of urban stormwater,but also avoid investment waste,maximize resources and benefits,provide decision-making basis and support for urban construction and planning,and also provide reference for sponge construction in other cities.