Research On The Design Method Of Building Rainwater Drainage System Adapted To The Utilization Of Rainwater Resources

The concept of Sponge City emphasizes the source and decentralized control of rainwater,as well as the utilization of rainwater resources.Rainwater on building roofs is one of the important sources of urban rainwater runoff.It is of great significance to study and improve the design methods of the existing building rainwater drainage system to adapt it to the purpose of rainwater utilization.At the same time,rainwater is intercepted and stored to reduce the pressure on the urban rainwater drainage system.This has important practical significance for alleviating the risk of urban waterlogging and improving the utilization of rainwater resources.Based on summarizing the composition and functions of the building rainwater drainage system,this paper systematically analyzes the adaptability of three technical measures of planting roof,rainwater flower box and vertical greening to the the purpose of utilization of rainwater resources.For these three technical measures,the division of roof rainwater catchment zones,the design of gutters and rainwater buckets were systematically studied,the corresponding design principles were clarified,and relevant design points,precautions and installation requirements were put forward.Based on the analysis of the design and calculation of the riser diameter combined with the planting roof,the calculation formula V=7q1F for the storage tank volume was established;According to the water balance basis of the drainage system combined with the rainwater flower box,the formula for calculating the total surface area of the rainwater flower box was obtained.A_f=（（A_dH_φ-Q_溢）d_f）/（60KT（d_f+h）+h_m（1-f₁）d_f+f₂d_f²）;The structure of a stagnant vertical greening planting pond was proposed,the rainwater drainage system diagram of the building was designed at the same time,and the detailed design method was clarified.Taking the R&D and production building projects located in the east of Fenghuang South Road and the south of Qingnian Road in Yancheng City as an example,the design methods of roof catchment zoning,gutter,rainwater bucket,downspout and other units combined with rainwater flower box proposed in this paper was applied to system design.Based on SWMM model,the effect simulation analysis was carried out.The analysis of runoff control rate showed that the reduction rates of total runoff in 10-year and 20-year return periods were 42.67% and 39.28% respectively after setting rainwater flower box and water storage tank.The reduction of runoff was mainly in the early stage of rainfall,and the reduction of peak runoff was not obvious.The analysis of rainwater reuse shows that the rainwater collection and reuse amount is 50.92m3 in the 10-year return period,which is limited by the regulation and storage capacity of the facilities.The rainwater collection and reuse amount remains unchanged in the 20-year return period.