Research On The Rainwater Drainage Law In Urban Area With Composite Slope And Plain

A series of reasons,such as accelerated urbanization,have led to a significant weakening of the ability of cities to cope with extreme rainfall,and many extreme rainfall events in recent years have led to heavy losses to human society.It is urgent to identify the main factors that cause the loss of drainage capacity of urban drainage systems during extreme rainfall,to summarize the changes in the urban pipe network system and road system,and to clarify the influence of river operation conditions on the drainage capacity of the system under mountainous urban conditions.In order to study the effects of rainfall conditions,stormwater inlet capacity,and pipe blockage on the drainage capacity of the system,and to clarify the role of river operating conditions on the drainage capacity of the system under mountainous urban conditions,this study takes the pipe network drainage system and road drainage system as the starting point,and uses the pipe network data,river data,DEM data,subsurface data,and rainfall monitoring data with the help of Info Works ICM.The two-dimensional drainage model of the Yuxiu River basin system is constructed to reflect the topographic and geomorphological characteristics of the study area,and to simulate the evolution of rainfall runoff,and the parameters of the twodimensional drainage model of the Yuxiu River basin system are rated and verified based on the flow process data of the Yuxiu River basin rainfall monitoring points.The model is used to analyze the influence of rainfall conditions on the pipe network system and road drainage system in the Yuxiu River basin.The main research contents and conclusions of this paper are as follows:(1)Rainfall factors significantly affect the pipeline drainage system as well as the road drainage system;the number of nodal overflows and the maximum nodal overflow volume increase with the increase of the recurrence period,and the time of maximum water accumulation appears earlier with the increase of the recurrence period.The number of pipes and the total length of pipes in different load states increase with the increase of the recurrence period;the trend of changes in the number of pipes and the length of pipes in both states remains consistent.The peak flow rate of the river outlet section increases with the increase of the rainfall recurrence period,and the larger the rainfall peak coefficient is,the later the peak time is.The number of network result points where the maximum water depth exceeds the threshold increases with the increase of rainfall peak coefficient and the increase of recurrence period,and is more significantly influenced by the recurrence period.The change in the number of result points of the road network with maximum flow rate exceeding the threshold is the same as the result points of the network with maximum water depth exceeding the threshold.(2)The larger the stormwater inlet capacity,the smaller the average water depth at the nodes,and in particular,the larger the recurrence period the more significant this effect is.There is no significant effect of stormwater inlet capacity on different pipe load states.The peak flow rate of river discharge outlet shows an overall irregularity,compared with the peak flow rate of river outlet cross-section,the total amount of river discharge increases with the increase of stormwater inlet capacity,but the change is relatively small.The effect of stormwater inlet capacity on the maximum water depth at the resultant point of the road network has three states of transition with the rainfall recurrence period.Rainfall inlet flow capacity from single grate to double grate,four grate,road system water depth * flow velocity basin maximum gradually decreased,but the maximum water depth * flow velocity occurred in the time distribution does not change with the rainfall inlet flow capacity changes.(3)rainfall recurrence period of 50 a,100a,the more serious the state of pipe blockage,the greater the node average water depth.The effect of different pipe blockage states on the river discharge flow is influenced by the rainfall recurrence period.The more serious the pipe blockage is,the larger the number of maximum water depth statistics at the network result point;meanwhile the larger the recurrence period is and the more backward the rainfall peak coefficient is,the more obvious this effect is.The pipeline blockage state at the connection between the pipeline system and the river gradually increases,and the number of maximum flow velocity statistics at the network result points exceeding the threshold value is larger.The pipe blockage status has a significant effect on the maximum water depth*flow velocity at the network result point and is not limited by the rainfall recurrence period.(4)The larger the peak river inflow,the longer the average duration of the pipe loading state and the earlier the average occurrence time.Different river inflow boundaries significantly affect the river outlet cross-sectional flow,and when the river inflow boundary changes from scheme 1 to scheme 2,the peak flow rate of river outlet cross-sectional flow increases significantly and the time of peak flow rate of river outlet cross-sectional flow is significantly delayed.When the return period is increased to 50 a and the river inflow boundary is changed from scheme 1 to scheme 2,the number of maximum depth network result points of the road drainage system increases significantly;the effect of the river inflow boundary on the maximum velocity network result points of the road drainage system is similar to the effect of the river inflow boundary on the maximum depth network result points of the road drainage system,and this effect is only obvious when the rainfall return period reaches 100 a.The effect of river inflow boundary on the maximum depth of road drainage system is similar to that of river inflow boundary on the maximum depth of road drainage system.The effect of the river inflow boundary on the maximum depth*velocity network result points of the road drainage system is consistent with its effect on the maximum velocity network result points.