Research On Model-based The Sponge Optimization Design Of Three-dimensional City

With the rapid growth of urban population,the speed of urbanization is accelerating and the shortage of land resources is becoming more and more serious,which brings about a series of problems.The "three-dimensional city" realizes the three-dimensional integration of the functions of housing,employment,entertainment,culture and other functions in the central area of the city without expanding the boundary of urban land and without evacuating the core functions and population of the city,and the above-ground and underground space can be fully utilized.Faced with the current situation of urban expansion in China,the concept of "three-dimensional city" is very forward-looking and revolutionary.However,in the three-dimensional overhead development mode,the rainwater falls to the roof of the overhead floor,and is discharged through the drain pipe.The underlying surface is almost equivalent to impervious.The urban rainwater runoff increases and the risk of waterlogging increases.At the same time,the underlying surface blocks the exchange of rainfall and groundwater,hindering the natural hydrological cycle,resulting in the loss of rainwater resources,intensified non-point source pollution,and the urban heat island effect.In this form,it is urgent to find suitable construction methods to alleviate a series of problems caused by urban rainwater runoff."Sponge City" means that the city is like a sponge.When it rains,it stores water to avoid standing in the water.When needed,it can be used for greening and watering.Since the pilot work of sponge city was carried out in 2015,China has accumulated some experience in the construction of sponge city,but there is still no case to follow on how to carry out the construction of sponge city under the three-dimensional city model.Firstly,the paper analyses the research progress of stormwater management at home and abroad,and based on the simulation results of the background of the Huizhou Xincheng area in the South Station,puts forward the annual total runoff index value of sponge city construction in the study area.This paper analyzes the types of facilities available for sponge city construction under the three-dimensional city development mode,the implementation paths of various facilities,and the problems that should be paid attention to in the process of application.In the construction of sponge city under the aerial mode,the vertical greening design of three-dimensional city and the aerial greening are fully utilized,and the ideas of "stagnation,storage,purification,utilization and drainage" are combined to separate and retain rainwater and make proper use of it.SWMM model(Storm Water Management Model)is used to analyze the implementation effect of sponge city.Through simulation analysis,it can be concluded that retaining a certain area of green space in the study area,setting up appropriate sponge facilities to absorb and infiltrate rainwater can effectively alleviate the impact of large-scale hardening underlying surface changing urban hydrological cycle.Urban non-point source pollution is one of the important causes of river and lake water pollution.By setting up the source of sponge facilities and optimizing the types of sponge facilities,non-point source pollution in the study area can be controlled.Under the construction mode of sponge city,the reduction rates of SS,COD and ammonia nitrogen in non-point source pollutants are all over 40%,and non-point source pollution is effectively controlled.