Study On Rainwater Pipe Network With SWMM Model And Sponge City Concept

In recent years due to the rapid development of economy and the increase of population,the development of the town is on.Along with the rapid urbanization,urban development is facing huge pressure to environment and resource,and outward expansion has been hard to go on.Due to surface hardening and narrowing of urban lake,short duration storm caused some urban waterlogging occurs,which cause serious damage to people’s daily travel and work.However the sponge city construction by rainwater infiltration,hysteresis,storage can to a great extent,prevent waterlogging phenomenon,therefore,across the country have been promoted.In order to improve the phenomenon of "city to see the sea",people also gradually pay attention to on construction of drainage pipe network,application of SWMM model also gradually accepted by some of the domestic water supply and drainage experts applications,the domestic experts have carried out some practical application of the SWMM model in Beijing,Tianjin and other places,and achieved good results.In this paper,the application of SWMM model to the northern suburbs of xi ’an area of storm runoff simulation calculation,and then combined with the results of the analysis to discuss the measures of sponge city construction,the main research content for the following four aspects:(1)According to xi ’an stormy formula and Storm Pattern to calculate the design return period respectively 1,2,3,5,10,20 and 50 years of 2 h rainfall intensity time sequence table;Combined with the land use map and all kinds of land use types of impervious rate reference table is calculated for each sub catchment area impervious rate;According to the regional characteristics and other references to determine the rest of the parameters.(2)Use SWMM model by different rainfall return period of simulation can be obtained:In design return period is 1 year,only for 4 node Y4-12 in the overflow,pipeline G4-12 overloading,the rest of the nodes and the pipeline is in normal state,the velocity is less than 5 m/s,in the range of specification;Again for 2 years,node Y3-6 and pipeline G3-6 such as individual node and pipeline in the overflow and overload phenomenon;Design again for 3,5 years,has a small number of nodes and pipelines in the overflow and overload phenomenon,its velocity within the normal range;When design again for 10 years and above,each area appear different degree of node overflow and pipeline overload phenomenon,its velocity is normal.Aiming at these problems,corresponding to analysis the cause of the problem is: due to factors such as surface hardening impervious rate is bigger,the earth’s surface produce large flow;Bear the catchment of sub area is too much,that heavy drainage task;Small design return period when the choice,part of small diameter or slope slower lead to poor drainage.(3)When the return period is 3 years,because of the catchment area of impervious rate is large,the node Y3-6 overflow,through recessed green space,green roofs,the permeable pavement sponge city transformation methods,such as reducing surface runoff;Due to smaller diameter of the downstream pipeline nodes appear overflow,Y2-1,Y3-2 and Y4-12 can be adjusted in diameter at the same time the permeable pavement and other measures to ease the drainage pressure;Because the catchment area of too much lead to node Y1-9,Y2-9,Y3-9,Y4-6 and Y4-9 has overflow,but through the way of the overflow upstream node,such as buildings,landscape water body implement sponge city transformation for rainwater infiltration or delay storage.(4)When design return period of 50 years,according to the results of simulation to calculate the need to regulate the flood volume of 220606 cubic meters,build storage pool volume is 222900 cubic meters,the average per hectare to build storage facilities volume of 136.33 cubic meters.In order to ensure the drainage capability,should dredge flood discharge channel,at the same time according to the concept of sponge city,to modify river,combining wetland,the initial rainwater treatment facilities etc.measures to enhance the capacity of water to flood peak and pollutant control.