Research Of Stormwater Drainage System Modification Plan Control Effect On Rain-flood Under Extreme Weather Conditions

With the accelerating development of China’s urbanization,expanding building area leads to an increase in impervious surface,and waterlogging occurs frequently in urban area.How to solve waterlogging is one of the most important issues in today’s cities.In order to solve the problem,the idea of"Sponge City"was put forward as newest concept of city flood management.Low Impact Development(LID)is key part of Sponge City,which not only can control flood effectively,but also can make rainwater reuse efficiently.LIDs can better meet the requirement of China flood management in new era.This thesis selects 3 universal LID counter measures(green roof,vegetative swale and permeable pavement)and 2 gray infrastructure mitigations(Large diameter tube&reservoir)to design 9 types of storm water drainage system modification plan in Fuzhou University.According to different duration rainfall events,SWMM model were used to analyze flood control effect of different plan in 3 different extreme weather conditions,including runoff depth,node and pipeline.The main results in the thesis are listed as follows:(1)Modified Morris Screening Method was used for the sensitivity analysis of SWMM model parameters,and integrated runoff coefficient was chosen to calibrate the parameters.Flood simulation was carried out within the 3 different duration rainfall events in study area.(2)The simulation results of current land layout under 3 different rain scenarios showed that:with the increasing of rainfall return periods,the rainfall amount,infiltration amount,runoff depth and number of waterlogging node increased constantly.When rainfall return periods P=0.5a,the number of waterlogging node reached half.Central of the study area was selected as key region to study storm water drainage system modification plan further.(3)The control effects of different storm water drainage system modification under short duration and strong rainfall indicated that:except single gray rain infrastructure,the other plan with LID all had obvious control effect.Combination of 3 LIDs had best control effect;the permeable pavement had best control effect within unit area,the combination of LID and gray rain infrastructure(Large diameter tube)is best on node flood control,and it had distinct effect on cutting flood flow and duration.The combination of LID and gray rain infrastructure had best control effect in the pipeline control.The combination of LID and large tube diameter had resulted in shortest time of pipe full flow,and the combination of LID and reservoir made the peak time postponed.(4)The control effects of different storm water drainage system modification plan under middle duration and strong rainfall indicated that:three LID combinations have best control effect in the control depth,and the combination of LID and gray rain infrastructure placed 2nd.The permeable pavement is best one in all single measures.On the node flood control aspect,3 combinations of LID and large tube diameter together with 3 LID combinations are best,and the study area never occur waterlogging under this scenario.On the pipe flood control aspect,all modification plan had no obvious difference,while the combination of LID and large tube diameter and LID combination work well in control of pipe full flow time.The pipe full flow time of LID combination is 0 that is best result,and the pipe full flow time of three LIDs and large tube diameter is close to 0.(5)The control effects of different storm water drainage system modification under long duration and strong rainfall indicated that:3 LID combinations have best control effect in the control depth,the permeable pavement had best control effect within unit area.On the node flood control aspect,3 LID combinations and large tube diameter could shorten maximum depth duration,and it will not take place flood phenomenon.On the pipe control flood aspect,the LID combination have the longest peak flow time and shortest pipe full flow time,and its control effect is best.(6)The research results of the flood control effects of different storm water drainage system showed that:on the node flood control aspect,the combination of 3 LIDs and large tube diameter is best due to its integration of infiltration,retention and quick drainage,and other control measures were ineffective.On the pipe flood control aspect,the LID combination had a certain effect on full flow and peak flow time.The short duration had the minimum full flow time and peak flow time,middle duration had no distinct difference,and long duration had the maximum full flow and peak flow time.