Simulate And Analysis Of Surface Runoff Process On City Underlying Surface

With the rapid economic and social development, the urbanization process ofcontinuous expansion, surface characteristics of pad under the city change a lot. Due to theincrease of impervious area, resulting in increased surface runoff, peak flow increased, therunoff coefficient increased and the convergence Rainwater shortened. It gives the citytaken burden for prevent water-logging and easily lead to urban water-logging. In order toalleviate rainstorm waterlogging disasters,We must thoroughly study different underlyingsurface(sunken lawn, porous pavement) the influence on rainwater andconvergence.Therefore,in the present work,the residential district in Suzhou City was takenas an example,learn from the concept of low impact development(LID),the comprehensiveinvestigation on the mutual interaction among topographic and hydrologic properties wascarried out by means of in-site survey.After then, a comparative investigation on thetechniques’ functions was conducted in laboratory-scale.SWMM model was adopted tosimulate the storm-water of study area.First,baesd on the establishment of urban storm-water surface runoff model,this paperput forward the basic data processing,the subcatchment dividing and the setting of modelparameter.The Chicago Hydrograph Model(CHM) has been used to synthesize differentdesign return period(0.5a,1a,5a,10a)、the rainfall lasted for120mins and the rain peakmoment r=0.4hydrograph.Second, Based on the hydrological effects of urbanization after the SWMMsimulation,calculation and analysis the surface runoff and confluence,runoff coefficient,the amount of total flow capacity and infiltration.Results show that with the increase ofdesign return period, the total runoff, average runoff coefficient and the total flow capacityas also increase, but the infiltration volume basically no change.At last, this paper has a research the addition of sunken lawn, porous pavement andtwo measures of combination of city rainwater. Results show that in the same designstorm-water return period, compared with the present model scene and when sunken lawnwas adopted, it can reduce the total amount of runoff, average runoff coefficient and totalflow capacity, also can increase the infiltration volume. The total runoff decreased by30.6%,24.6%,24.6%,24.6%respectively, and the average runoff coefficient decreased by24.9%,22.6%,19.1%,18.6%respectively, and the total flow capacity decreased by 58.4%,43.1%,39.4%respectively, and the infiltration volume increased by18.6%,24.4%,42.8%,49.9%respectively; When taking the porous pavement measures, thetotal runoff decreased by24.7%、20.5%、15.4%、14.5%respectively, and the average runoffcoefficient decreased by30.2%,29.6%,27.2%,20.9%respectively, and the total flowcapacity decreased by88.5%,57.6%,49.5%respectively, and the infiltration volumeincreased by17.1%、20.4%、31.4%、36.1%respectively; When these two measures arecombined together, the total runoff decreased by46.3%,41%,33.9%,32.3%respectively,and the average runoff coefficient decreased by39.2%,37.9%,37.5%,28%respectively, andthe total flow capacity decreased by100%,83.9%,75.5%respectively, and the infiltrationvolume increased by31.9%、40.8%、68.8%、80%respectively.