Study On Rainwater Infiltration Technology Optimization Based On Sponge City

With the expansion of urban scale,the underlying land surface attributes also change.The decrease of infiltration water and the increase of surface runoff affect the original hydrological cycle of the city.At the same time,the aging urban rainwater pipe network is difficult to adapt to the rapid development of urban drainage requir ements.It is lack of economy and feasibility to rebuild pipeline network.The traditional stormwater management model can not meet the requirements of urban drainage.Rainwater infiltration technology,dominated by natural infiltration,has begun to prevail in China.However,there is still a lack of research on the reasonable setting and the optimization of the design parameters of rainwater seepage technology.In order to make rainwater penetration technology play its most important role,it is necessary to optimize rainwater infiltration technology.In this study,the structure,function characteristics and main design parameters of typical rainwater infiltration technologies(permeable pavement,sunken green space and green roof)are summarized.And the theoretical formula of runoff reduction are also discussed.Secondly,the regional hydrological,hydraulic and rainwater infiltration technology model is constructed by using SWMM software,taking Kulangsu in Xiamen city as an example.Then,the influence of external conditions on runoff reduction effect of rainwater infiltration technique and its design sensitivity parameter is simulated.Compared with the high rainfall return period,permeable pavement,sunken green space and green roof have higher runoff reduction efficiency during the low rainfall recurrence period,and are recommended for solving the regional water accumulation caused by rainfall at2～10a.Finally,the optimized combination scheme is used to reconstruct the study area and analyze the effect of reconstruction.The following results are obtained:(1)Permeable pavement,sunken green spaces and green roofs are suitable for controlling runoff with low intensity rainfall.The back peak type of rainfall pattern is not conducive to runoff control of rainwater infiltration technologies.When the design rainfall pattern was the back peak type,increasing the setting parameters of rainwater infiltration technologies should be considered to improve the absorptive capacity of the runoff.Permeable pavement and sunken green spac e should not be set up in steep areas.(2)Through Morris screening method,the sensitivity analysis of design parameters of rainwater infiltration technologies are completed.It is concluded that the sensitive parameter of permeable pavement are the thickness of pavement layer,void ratio and surface roughness coefficient.The sensitive parameters of sunken green space are water storage depth of surface layer and surface roughness coefficient.The sensitivity parameter of green roof is vegetation coverage.(3)According to the sensitivity analysis and the orthogonal test,it is found that the sensitive parameters of permeable pavement are best for pavement thickness of 150 mm,void fraction of 0.2,and surface roughness coefficient of 0.1.The sensitive parameters of sunken green space are best for storage depth of 250 mm and surface roughness coefficient of 0.14.The sensitive parameters of green roof are best for vegetation coverage rate of 50%.(4)According to the optimized rainfall infiltration technologies,the scheme evaluation of easy waterlogging area in Kulangsu is carried out,which can provide theoretical guidance for planning and reconstruction of waterlogging prone area.