Multi-objective layout optimization for sponge city by annealing algorithm and its environmental benefits analysis

Abstract

With the development of urbanization, cities are facing crises such as waterlogging, water pollution, and floods. In order to actually alleviate urban floods and other disasters, China has proposed the "sponge city" construction concept. A multi-objective optimization method of the minimization of rainfall runoff, pollutant discharge and construction and operation costs and the maximization of environmental benefit is proposed by Simulated Annealing (SA) algorithm in order to fulfill the planning and construction of sponge cities. Some Low-Impact Developments (LID) are optimized for the study area and the optimal underlying surface layout of sponge city is obtained. Results indicates that the optimal underlying surface layout of the study area satisfies Tianjin sponge city construction pilot implementation plan. For the study area, the annual runoff coefficient is 0.169 and the annual discharged pollutant mass of TSS, COD, TN and TP is reduced by 65.11 %, 62.06 %, 64.67 % and 80.94 %, respectively, which meets the requirements of annual runoff control coefficient (less than 0.22) and annual pollutant reduction rate (about 65 %) of sponge city construction pilot implementation plan. The optimal cost of the study area is about RMB 9.77*107 and the environmental benefits of the study area quantified by CO2 emission reduction is 1167 t.