Research On LID Scheme Of An Industrial Park Based On SWMM

With the continuous expansion of urbanization scale in China,the impervious area of urban underlying surface is increasing and urban waterlogging is easy to occur.In order to alleviate urban waterlogging,according to the concept and method of sponge city construction,it is of great significance and value to optimize and transform different schemes of existing built areas.The core concept of sponge city construction is LID（Low Impact Development）,which usually includes Green Roof,Sunken Greenbelt,rainwater regulating pool,rainwater garden,Wetland Park and other facilities.The research object was located in an industrial park in Hefei.According to relevant specifications and the actual elevation of the research area and the original pipe network information,the SWMM model was established by selecting 3-hour rainfall data under the conditions of P=3a,P=5a and P=10a respectively.According to the different methods of LID and the actual situation of research area,three LID facilities,i.e.sunken green space,green roof and rainwater regulating pool,were selected and brought into SWMM model to simulate the parameter changes of green roof,sunken green space,the impact of the position changes of rainwater regulating pool on water level and interaction between upstream and downstream LID facilities.The main research contents are as follows:（1）Made reasonable summary of the sub-catchment area in the study area,and divided the sub-catchment area in detail according to Arc Gis and the actual distribution of buildings and road direction.The whole research area could be divided into 38 sub-catchment areas and 80 nodes.（2）Current situation was simulated to analyze the reasons of node overflow in sub-catchment area: the impervious area in the upper and middle reaches was too large,the original drainage zoning did not conform to the actual situation,and the original LID facilities downstream only provided drainage in this area.（3）The rainwater outlet node of sub-catchment 7 and sub-catchment 30 were adjusted on the basis of original drainage zones,and node Y-21-2 and Y-23-4-1 were connected respectively.The purpose was to evenly distribute the drainage zones in the study area and to facilitate the drainage of the whole area.（4）This study simulated the Green Roof,Sunken Green belt and Water Storage poo.The results showed that the soil thickness should be controlled from 120 to 135 mm and the water conductivity should be controlled from 70 mm to 80 mm/h,which should not be too large.The impounding Greenland aquifer was controlled at 100 mm and the soil layer was controlled from 250 to 300 mm.The effect of setting a rainwater regulating basin near the flood prone point was more obvious than that of setting other places to reduce flood peak.（5）It was found from the research on the relationship between upstream and downstream LID that upstream LID measures could promote downstream LID measures to play a greater role.（6）After LID transformation,the number of nodes with moderate overflow decreased by 44.4%,the number of nodes with severe overflow decreased by 53.8%;the overflow time decreased by 14.9% or more.