The Calibration And The Influence Factor Analysis Of Runoff Coefficient Of Rain Garden

Accelerated urbanization process With the construction of urban roads,the original terrain and soil structure changes,impermeable pavement increased.At the same time with the frequent occurrence of extreme weather,Short-duration and heavy rainfall of local occur frequently,causing serious urban waterlog.Design lag is the main cause of urban waterlog,and runoff coefficient is the basis for estimating the net flow of rainfall data,and also the important parameters of rainwater flow calculation.The current value of the runoff coefficient in the design of rainwater pipe network is mainly based on the provisions of "Outdoor Drainage Design Code"(GB50014-2006)and "Design Code for Building Water Supply and Drainage"(GB50015-2003),and the design runoff The coefficient is the empirical value determined by the type of ground cover,and not from the practical point of view,the rainfall duration,rainfall intensity,geomorphology and other factors into account.In this paper,the experimental base of the rain garden of Xinjin County,Chengdu,China,and there is a comparative study between the#2 road with rainwater garden and the 18#road without rainwater garden.Collect the rainfall data,and analyze the rainfall type,the rainfall duration,the rainfall intensity etc.Study the rainfall-runoff-confluence process through the water balance principle and isometric time-line method.Combining with the measured outflows data of the two roads,find the optimal fitting model,calibrating the runoff coefficient and analyze the influence factors.Which provides design parameters for the design of drainage network in practical engineering construction,and provides theoretical reference for urban flood control theory research and practical engineering design and application.The research results show that the rainfall data collected during the experiment covers a variety of rain patterns,there are different rainfall intensity,rainfall duration,the test area involves four different underlying surface,mainly asphalt road,sidewalk,green belt,Raw slopes.The above factors have an impact on the runoff coefficient of the test area.From the runoff coefficient of 2#and 18#which is determined by the rainfall and outflow rate on September 5 can be seen,the runoff coefficient of the front is much less than the behind.It is suggested that the road with rainwater garden has a better effect on the flood control.It has positive significance to control the city waterlogging.At the same time,the results show that the runoff coefficient is different in different test areas,the runoff coefficient of the asphalt road and pavement surface is lager than the runoff coefficient of the green land and the slope.That is the slope has a strong retention effect on rainfall;When the underlying surface is on the same,runoff coefficient are affected by factors such as rainfall,rainfall duration and rainfall intensity.The runoff coefficient and rainfall duration and rainfall intensity are positively correlated with the increase of rainfall duration,and with the increase of rainfall intensity Increase.The runoff coefficient obtained by the study rate is different from the runoff coefficient in the design specification,This shows that the actual regional environmental runoff coefficient is affected by the complex factors,large fluctuations in the engineering design needs comprehensive consideration of local conditions.