Study On Stormwater Runoff And Pollutants Reduction Of Sunken Green Space

With the urbanization process speeding up and people's living standards improving, city size expands and population density increases, a lot of impervious surface replaced by pervious surface results in increased surface runoff and peak flow, ahead of the peak runoff and increased runoff coefficient; meanwhile, constantly increasing population density leads to the large accumulation of pollutants, these pollutants washed by stormwater are discharged into rivers by urban rainwater pipe network, and it causes serious non-point source pollution, the quality of receiving water becomes worse. As an important part of urban ecological system, urban green space can not only reduce the stormwater runoff but also have a good effect on the removal of pollutants from the runoff. This thesis focuses on the actual situation of Suzhou, determining sunken green space as the comprehensive controlling measure of stormwater runoff and pollutants reduction through experimental studies.The characteristics of the historical rainfall events and runoff water quality in Suzhou are investigated firstly, and the runoff water quality in Suzhou area is analyzed by the project team, what mentioned above provides a theoretical basis for the configuration of the experimental water. Then improve the soil of Suzhou green percolation layer, the removal efficiency of stormwater runoff and its pollutants is studied by simulating the urban green space system and rainfall system. Finally, using the SWMM model to contrast the effect of the reduction of the runoff and its pollutants before and after sunken green space applying in the studied area. And it provides theoretical basis for the planning and construction of green space in Suzhou City.The experiments' conclusions are following:1.Three types of green space system have good reduction effect on stormwater runoff, the original soil backfill, the ceramsite improved soil and the zeolum soil sunken green space have a consistent reduction effect under the condition of different designed storm recurrence periods. Three types of green space system have a good effect on the rainfall events of low rainfall intensity. The designed storm recurrence period is two years, with the increase of rainfall time, the stormwater runoff removal rate of three types of green space system increases gradually.2.With the increase of designed storm recurrence period, the average removal rates of COD,SS,TN,TP and other pollutants of three types of green space decrease gradually. With the rainfall time increases, the removal rates of COD,SS,TN,TP and other pollutants of three types of green space decrease gradually in the process of rainfall. When the pollutant concentration of rainfall runoff is low,medium and high, with the concentration increases, the removal rates of different pollutants have a gradually increasing trend. The ceramsite improved soil sunken green space has a good reduction effect on TP. The zeolum soil sunken green space has a good reduction effect on TN.3.Using the SWMM model to stimulate and analyze the studied area, it can effectively reduce the total amount of surface runoff and the peak flow, shorten the duration of the runoff and delay the peak time of the runoff when substituting the flat green space with sunken green space.