Multi-objective Optimization Of Sponge City Based On SWMM Model And Urban Expansion Simulation

Rapid urbanization has resulted in a series of problems such as water ecological destruction,water security and water shortage.The concept of low-impact development of sponge city is considered to be able to effectively solve problems such as urban waterlogging,which has aroused extensive research by scholars at home and abroad.However,the traditional planning and design of sponge cities often ignore the dynamic development of the city itself,and usually fail to take into account the trade-off between multiple goals,which makes the overall planning of sponge city lack of foresight and overall.Based on the simulation analysis of urban expansion and land use change,this study evaluated the impact of urban dynamic development on the risk of waterlogging disaster,and put forward an analytical method of total runoff control objective from the perspective of urban expansion.Combined with the rainwater management model,intelligent optimization algorithm and regression analysis,Furthermore,the multiobjective optimization and comprehensive evaluation method system of economytechnology-environment synergy was constructed,and the optimal construction scheme of low-impact development under different scenarios was analyzed and decided.Firstly,the GeoSOS-FLUS software was used to build a prediction model of Changchun’s future land use,and the land use data of Changchun in 2034 was predicted.The total storage capacity of LID facilities needed to build a sponge city in Changchun in 2034 was analyzed and obtained.It was found that with the expansion of the city,the risk of urban waterlogging increased.The demand for the total storage capacity of LID facilities also increased accordingly.Changchun,secondly,based on the future land use data to sunken green,bioretention facilities and permeable pavement three LID facilities for the construction of the area of the decision variables,with LID facilities construction costs,volume capture ratio of annual rainfall,annual runoff pollutant reduction rate and environmental impact as the objective function,the multi-objective optimization model was constructed.The Pareto solution set was obtained by using NSGA-Ⅱ algorithm,and the tradeoff relationship among multiple objectives was analyzed.The optimal scheme configuration was calculated based on the comprehensive evaluation system: the construction area of sunken green,bioretention facilities and permeable pavement was 3030 ha,4709ha and 2351 ha respectively.Finally,taking a region of Nanhu in Changchun as an example,based on the future land use data obtained by urban sprawl simulation,the SWMM model was constructed to comprehensively analyze the regional hydrological characteristics.The results show that the drainage capacity of the regional drainage network is insufficient,runoff pollution is serious,and the risk of waterlogging is high.Based on the SWMM simulation results,the regression relationship between decision variables and control objectives was deduced,and three multi-objective optimization scenarios with different objective functions,different control objectives and different decision-making centers were constructed for comparative analysis,in order to provide reference and decision-making basis for the planning and design of sponge cities.