Study On Stormwater Simulation In Convention And Exhibition City Of Yuelai Based On SWMM

With the acceleration of urbanization,impervious underlying surfaces such as urban buildings,roads and squares gradually replace the original green space and water area,which have changed hydrological and hydraulic characteristics of the underlying surface,reduced rainfall infiltration,increased total runoff and peak runoff,advanced peak runoff time,and caused severe urban storm water problems.At the same time,most urban construction in China still follows the traditional"centralized and fast-discharged"storm water management model,which not only ignores the resource utilization of rainwater,but also imposes a huge load on urban drainage systems.Under this background,the concept of low impact development?LID?has been proposed.By adopting multiple scale engineering measures such as source stagnation,midway guidance and terminal accumulation,the ability of underlying surfaces to penetrate,retard,store,purify and utilize runoff is improved,and the purpose to control urban storm water runoff and protect ecological environment is achieved.In this paper,Yuelai Exhibition City was selected as the research object in response to the increasingly prominent problem of urban storm water.According to the regional topography,planning layout,drainage system and rainfall data,the Storm Water Model of Yuelai Exhibition City was constructed on ArcGIS platform and SWMM software,and the inp.PINS software was used to couple the two.Based on the measured data,the sensitivity of model parameters was analyzed and calibrated.The calibrated model parameters were used to analyze the surface runoff process,node overflow and pipe section overload conditions,and discharge outlet runoff variation rule in different developing scenarios and return periods of rainfall,and evaluate the effect of LID measures on stormwater control.The main conclusions are as follows:?1?Based on the ArcGIS platform,Yuelai Exhibition City was generalized to 127subwater area,226 pipelines,and 227 nodes?including 7 outlets?,and the Storm Water Management Model of Yuelai Exhibition City was constructed by using the inp.PINS software.?2?The sensitivity of model parameters was analyzed by modified Morris screening method and multiple stepwise regression method.The results showed that Width-K showed high sensitivity to total runoff and peak runoff under different rainfall intensity;the Horton model parameters were insensitive when the rain intensity was weak,and the sensitivity significantly increased when the rain was heavy,which became the most sensitive parameter affecting the total runoff and peak runoff.?3?The measured rainfall data was selected to calibrate the model parameters and the suitable model parameters for the study area were determined.The feature width coefficient Width-K was 0.8,the Manning's rough rates N-imperv,Con-roughness and N-perv were respectively 0.018,0.18,and 0.011,and the sum-storage quantities Des-imperv and Des-perv were 2.5 mm and 5.5 mm,respectively.The Horton infiltration model parameters Max.Infil.Rate,Min.Infil.Rate,and Decay constant were 83.6 mm/h,2.5 mm/h,and 5 h^-1,respectively.?4?Under the conventional development scenario,as the return period increased,the amount of surface infiltration,surface water storage,and surface runoff in the study area increased,the number of overloaded nodes and overloaded pipe sections increased,the duration of node overflow and pipe section overload increased,the amount of total runoff and peak runoff gradually increased,and the peak runoff time accordingly advanced.For the return periods 0.5a,1a,2a,3a and 5a,the node overflow rates were0.44%,0.88%,1.76%,2.20%and 3.08%,respectively.Pipeline overload rates were0.44%,1.33%,2.21%,3.54%and 5.31%,respectively;compared with the return period of 0.5a,the total runoff of discharge PFK2 at return periods 1a,2a,3a and 5a increased by 28%,77%,104%and 139%,respectively,with peak runoff increased by 117%,201%,250%and 320%.and the peak time advanced by 1 minute,2 minutes,3 minutes and 3 minutes,respectively.?5?Compared with conventional development scenarios,the runoff coefficients of the study area decreased by 23%,19%,16%,14%,and 13%,respectively during the return period of 0.5a,1a,2a,3a,and 5a after implementing LID measures,and the decreasing amplitude gradually decreased with the increase of return period rainfall.?6?During low return period rainfall,LID measures played a very good role in reducing the drainage system load,total runoff and peak runoff,and delaying peak time of runoff.With the increase in the return period of rainfall,the effect of LID measures on storm water control gradually weakened.?7?After the implementation of LID measures in Yuelai Exhibition city,the annual total runoff rates of the PFK₂,PFK₃ and PFK₄ corresponding to the drainage area were77.59%,79.42%and 76.22%,respectively,which meet the requirements of the guideline for the total control rate of middle-aged runoff.The total control rate of annual runoff in the remaining drainage zones was less than 75%,and LID measures still needed to be further optimized.