Study On Planning And Evaluation Of Low-impact Development Stormwater System In Ecological New Area Of Yongding River

With the accelerating pace of urbanization in China,the underlying surface with good permeability has been gradually hardened,and urban waterlogging events caused by extreme rainstorms are frequent.The problem of rainwater flooding caused by heavy rainfall can not be solved only by a single "gray" municipal rainwater pipeline system.The sponge city,a new concept of rainwater management with the characteristics of the times,is a good start for China to enter the field of rainwater scientific management.Sponge City-Low Impact Development Rainwater System is an integrated rainwater management system,which includes not only the infiltration and detention system of rainwater in the source site and the road,but also the municipal rainwater pipeline system in the middle and the storage and regulation system of rainwater runoff at the end of the downstream pipeline network.Link up to effectively alleviate the problem of rainwater and flood caused by urbanization.The purpose of this paper is to study the construction method of integrated rainwater management system.Taking the planning rainwater system of Yongding River Eco-cultural New Area as an example,the effect of rainwater runoff control under the comprehensive action of the rainwater system development,municipal rainwater pipeline system and drainage basin rainwater regulation and storage system with low impact on the plot and street level of the source site is analyzed.The model tool is used to simulate the rainfall processes in different recurrence periods,verify the control effect of LID measures on rainwater runoff in this study area,and optimize the planning scheme.Under the condition of 5-year rainfall,the runoff coefficient of rainwater drainage in the study area decreased from 0.52 to 0.32 after LID measures were adopted at the level of plot and street,which could meet the requirement of rainwater control in the new area where the runoff coefficient of rainwater drainage was not more than 0.4.For the 50-year rainwater exceeding the standard,LID measures(i.e.dry/wet)were added at the level of drainage basin.After the pond,the waterlogging control target of the regional rainwater self-absorption can be realized.The construction of integrated rainwater management system can not only realize the effective control of rainwater at the level of land and street,but also make full use of the role of storage space through reasonable vertical adjustment of roads,which is of great significance for regional waterlogging prevention and security.