Study On Performance Evaluation And Design Optimization Of LID In Urban Area

The process of urbanization reduced the permeability of the underlying surface and hindered the natural hydrological cycle process,resulting in frequent urban waterlogging disasters,confused life production activities,and losses of life and property.LID(Low Impact Development),as a decentralized small-scale rainwater control measurement,can effectively alleviate urban floods in source.For the complex land use structure and the limited development space of the city,a quantitative evaluation index of LID measures and a set of design optimization scheme are established in this paper.First of all,the LID concept was combined with the urban rainwater management system,as a surface control measure before the runoff into the rainwater drainage system,and a design planning framework of rainwater management in urban areas was established.This study used SWMM(Storm Water Management Model)as the auxiliary tool to construct the quantitative evaluation index of LID measures(Bio-retention,Porous pavement,Grass swale,Green roof)for hydrological simulation,which integrated the design rainstorm,the pre-development runoff coefficient,and the effective control range.The ELF(Effective Load Factor)was established as the LID performance quantitative indicator.And the removal of non-point source pollution was simulated according to the ELF.The data of the underlying surface of the study area were analyzed by GIS(Geographical Information System).The urban artificial structure information and hydrological analysis results are superimposed to divide the available construction range of LID measures in sub-catchments as the construction constraints of the optimization design;The WLCC(Whole Life Cycle Cost)was used to evaluate the long-term economic benefits of various LID measures,including the cost of initial investment,operation and maintenance in the whole design life cycle as the economic analysis index of the optimization design.Then,based on the ELF,the LID construction scales in each sub-catchment within the design area were calculated by LINGO(Linear Interactive and General Optimizer)with the optimization conditions such as the hydrological control andcapital optimization target,and the land construction constraints.In addition,this study took a comprehensive residential area in Tianjin as the research area,and established the DEM(Digital Elevation Model)of the research area through field measurement and design institute data.The quantitative evaluation index of LID measures and the set of design optimization scheme were used to calculate the construction scale of LIDs in each sub-catchment when the runoff coefficient was satisfied and the present value of WLCC was the lowest.