The Effect Of Urban Rainwater Garden Storage Process On Rainwater Runoff Reduction

With the rapid development of urbanization of our country,the cities are on construction of city roads on a large scale,city road is mainly adopted impervious surfaces,changed the original surface structure,make the path surface rainfall runoff and infiltration process of the destruction,prone to flooding and surface water environmental pollution and other issues.This topic built a rainwater garden system as a field test,first analysis of the test area landform characteristics in Chengdu,through the test area rainfall measured rainfall data collection and sorting out and analyzing space-time distribution characteristics,according to the water system structure characteristics of the test area and the surface runoff of networks theory,simulate the actual situation of runoff process.The surface confluence process adopts the isocurrent method,which divides the catchment area into two parts.most of them are directly connected to the rainwater pipe network,and the small part is transferred into the rainwater garden and then remitted to the rainwater pipe network.Pipe network confluence process adopts the method of solving the saint venant equations,the rainwater garden storage process completely water balance method,combining the storage process with the runoff process to analyze the cut effect of the storage process on the rainwater runoff.Taking the rainwater garden as the research object,the change of water level in the rainwater garden was analyzed,the critical water level of rainwater garden storage system is 0.38 m.However,when the input amount of rainwater garden is greater than the critical volume,the rainwater begins to flow into the rainwater pipe network along the discharge pipe,because the velocity and discharge flow rate of the internal liquid level of rainwater garden is relatively smooth,the calculation of the flow rate of the pipe network is not significant.According to area rainfall runoff process simulation experiment,the measured flow process line and the simulation flow process line,the fitting degree between the results show that the runoff error between 2.3% ~ 17.4%,the total amount of runoff of peak error is between 0.6% ~ 13.1%.By comparing the 18 # and 2 # roads and road during a rainfall peak runoff,runoff amount of each water wells input differences and 2 # road well stand-up rainwater runoff,built the rain garden system road conclusion: cut effect to the peak runoff,cutting efficiency is about 32%;The effect of rain water runoff was reduced by 39%,and the average efficiency of runoff was 64.39%.