| With the development of global urbanization process,urban waterlogging and runoff pollution problems have occurred frequently,also socioeconomic activities have suffered losses.To alleviate this situation,best management practices,low impact development,and green infrastructure technologies came into being.In recent years,with the promotion of sponge city construction in China,low impact development(LID)with the core concept of"source governance and decentralized development"has launched nationwide research and construction.China has made obvious achievements in the promotion of LID theory,but in the actual construction process,more concerns are focused on the micro aspects such as rainwater treatment,applicability of technical measures and the construction of single LID facility.However,urban water environment and water ecology are system problems of different scales and regions,and also an interrelated and comprehensive problem.This requires us to take a macro view from the perspective of urban system,and the location and layout of LID facilities is an aspect that needs urgent research.The location and layout of LID facilities emphasize multiple concepts such as suitability,efficiency and economy.The optimization of the location layout of LID facility helps to achieve efficient and reasonable rainwater treatment in sponge city construction.The ArcGIS platform and SUSTAIN model provide decision support for the location,layout,type and cost of LID facilities.Based on the review of the connotation and target development process of stormwater management system both in China and abroad,the paper established a suitability evaluation index system,selected the northern drainage division of the urban drainage planning of Zhenjiang City as the research area,uesd the multi-factor weightiness analysis of GIS and AHP method to evaluate the suitability of the LID facility site selection,identified and extracted suitable areas for construction or modification.The paper based on the comparative analysis of the surface runoff under the pre-development and post-development scenarios without LID facilities,combined with the needs and conditions of Zhenjiang’s sponge City planning,took the annual total runoff control rate as the evaluation target,took the quantity and location of the plots with higher suitability as variables,and the NSGA-II algorithm of SUSTAIN model optimization module was used to optimize the calculation of each layout possibility and finally a series of optimal cost-effective layout schemes were obtained.The research results show that there are many suitable land for LID facilities construction in the study area,but the distribution of these land is uneven;the annual runoff output of the pre-development scenario is 113,470.1m~3,the annual runoff output of the basic scenario(i.e.no LID facilities are applied after development)is 351,682.4503m~3,and the increase of the impervious area is the main factor that produces runoff;all optimization schemes have 0.18%-8.11%change in the total annual runoff reduction effect,and there are also significant differences in cost input;By evaluating the total investment and reduction rate of each scheme,the most cost-effective optimization scheme that meets the characteristics of the study area is obtained:bioretention covers 43,464m~2,grassed swale covers 90,466m~2,green roof covers 107,762m~2,and porous pavement covers 32,433m~2.Optimized LID facilities account for 22.2%of the study area,and this scheme has a 86.95%runoff reduction rate and its engineering cost is about 92.3131 million yuan.The research took the suitability analysis and the cost-effective analysis based on the annual runoff reduction rate as the starting point,constructed the overall location and layout optimization research method of LID facilities,which enriches the methodological research field.It can not only solve the problem of land shortage in the current sponge city construction process,but also reduce the cost and difficulty of construction and bring out the best effect of LID facilities.Therefore,it has practical significance of providing new thinking,new perspective,scientific quantitative analysis support and decision-making basis for the study of sponge city planning and construction. |
