Research Of Rainwater Conflux Process Of Rainwater Garden System In Hilly Terrain

This paper selected the test site of a built rainwater garden system of Chengdu as the research area,measured and recorded data on rainfall and runoff rate in the area based on the survey results of the spatial and temporal distribution characteristics of rainfall and regional geomorphic characteristics in Chengdu,built a numerical model of rainfall and runoff and concentration process to test the parameter calibration and application,comparatively analyzed the difference in the characteristics of rainwater conflux process of rainwater garden system and obtained the following research results:(1)In accordance with the designed storm formula and observed rainfall process line of Chengdu,a typical rainfall process line of Chengdu was designed.As for the duration of rainfall,1h can be chosen.As for the recurrence interval,2 years are usually used.As for the position of storm peak,0.4 can be chosen.Analysis of observed rainfall process line,the rain type of unimodal,bimodal type proportion reaches 65%,which has certain relevance,with the typical rainfall process line of Chengdu.(2)The nonlinear reservoir-variable unit hydrograph method was used to simulate the rainwater conflux process at the catchment area within certain duration of raining.The model infinitely approached the actual flow curve by continuously changing the parameter value.The values of Smax,W0,Wm,?,fc and ? calibration results of 2#road section are respectively 11.5mm,35mm,130mm,1.3mim-1,0.245mm/min and 0.296 min-1;the values of Smax,W0,Wm,?,fc and? calibration results of 18#road section are respectively 7.7mm,44mm,104mm,1.3 min-1,0.310 mm/min and 0.311 min-1.(3)The parameter calibration results above were used for an application test of the mathematical model adopted.The test result shows:as for 2#road section,the relative error between the simulated peak flow and measured peak flow is 8.60%and the relative error between the simulated runoff volume and the measured runoff volume is 5.99%;as for 18#road section,the relative error between the simulated peak flow and measured peak flow is 1.12%and the relative error between the simulated runoff volume and the measured runoff volume is 2.92%.The relative errors of the model are within a reasonable range of project.Meanwhile,the model,which is rather correct in simulating the rainwater conflux process in the hilly terrain,is highly applicable.(4)Through the comparative analysis on the 2#road section parameter calibration result of the built rainwater garden system and the 18#road section parameter calibration result of the un-built rainwater garden system,the research shows:in the two areas with similar ground vegetation types and coverage,the maximum interception capacity of 2#road section is superior to that of 18#road section;in the two areas dominated by typical Chengdu yellow soil with the similar soil properties,the soil moisture holding capacity of 2#road section is superior to that of 18#road section;the soil infiltration capacity of 2#road section is inferior to that of 18#road section.According to the practical simulation and comparative analysis result of parameters,the 2#road section of the built rainwater garden system has obvious rainwater regulating and storing functions,compared with 18#road section of the un-built rainwater garden system.