Urban Flood Simulation Based On Hydrodynamic Model And The Traffic Impact Dynamic Evaluation

In the context of global climate change,with the development of urbanization and the increasing impact of human activities on the environment,the frequent occurrence of urban floods in recent years has caused a serious influence on the normal work of cities and people’s life,has become a major problem constraining the development of city.Thanks to the rapid development of computer technology,numerical modeling method has become an important technical means to analyze urban flooding problems,playing an irreplaceable role in urban flood prevention,flood drainage,early warning and other fields.Facing the increasingly serious urban flooding problems,based on the actual requirements of urban flood management,this study establish a research framework of urban flood impact evaluation on traffic.Firstly,this study based on the previous researches builds a one-dimensional and two-dimensional hydrodynamic coupling model that could fully simulate the urban flood inundation process.A series of analyses on urban flooding processes were studied by using this model.And then the simulation results were applied to the field of transportation,the analysis of traffic congestion caused by waterlogged roads under extreme rainfall conditions has important research significance and practical value.Some valuable research results were obtained,which are helpful to provide some technical supports for urban disaster prevention.The main findings are as follows.(1)The basic principles of the urban flood hydrodynamic model are introduced,and the model’s computational accuracy and simulation results are verified.Based on the well-developed TELEMAC-2D module and EXTRAN module,the basic principles are introduced of the coupled model,including the rainfall-runoff flow module,over land flow concentration module,pipe-network flow concentration module and the coupling implementation method,and the one-and two-dimensional coupled hydrodynamic model of urban flooding is built.In order to verify the computational accuracy and performance of this coupling model,a general theoretical case in the field of hydrodynamics was used for the analysis.The case results showed that the urban hydrodynamic model constructed in this paper performed well,and the two simulation indicators,node depth and coupled flow,were basically consistent with the model results of the same case in the literatures.Another,the coupling model constructed in this paper had good stability and convergence.(2)Urban flood simulation without pipe network data was studied based on the equivalent drainage method and road network methods.This study analyzed the principles of the equivalent drainage method and road network method in depth,and urban flooding models were constructed based on these two methods.The simulation accuracy of the model was verified by comparing the location of the waterlogging points with those related reports in the network news.In the process of analysis,the simulation process was divided into rainfall process and after-rainfall process,with the total amount of waterlogging and the area of waterlogging as indicators,the Xiamen Island case was studied in depth.The results showed that:comparing with the equivalent drainage method,the road network method had larger total amount of waterlogging and area of waterlogging in the rainfall stage,and the greater decreasing rate in total amount of waterlogging and area of waterlogging in the after-rainfall process;under the 50-year and 100-year extreme rainfall scenarios,comparing with road network method,the total amount of waterlogging of equivalent drainage method was reduced by about 23.9%and 19.6%respectively,and the area of waterlogging of equivalent drainage method was reduced by about 27.8%and 17.6%respectively.(3)Based on the results of the scenario simulations,the impact of waterlogged roads on traffic due to urban flooding was analyzed and evaluated.The results of urban flood simulation are applied in the field of transportation,by using OSM road data as traffic roads distribution and BaiduMapAPI technology to obtain real-time road network information.The impact of waterlogged roads on the interruption of different road grades was studied using the example of 50-year and 100-year extreme rainfall;the attenuation of road network speed under the influence of extreme rainfall and the length of the affected road sections were studied for typical moments of traffic peak periods and traffic flat periods as examples.The results of the Xiamen Island case showed that comparing with the 50-year extrema rainfall scenario,the length of road disruptions in 100-year scenario on expressways,primary roads,secondary roads,tertiary roads and feeder roads increased by 25.2%,48.0%,26.4%,22.4%and 32.1%,respectively;during traffic peak period,the length of affected roads accounted for 21.91%and 22.42%of the total length of roads under the 50-year and 100-year extreme rainfall scenarios,respectively,and average speed decreased by 48.7%and 49.6%compared with the clear roads;during the traffic flat period,the length of affected roads accounted for 10.3%and 10.9%of the total length of roads under the 50-year and 100-year extreme rainfall scenarios,respectively,and average speed decreased by 30.9%and 31.9%compared with the clear road.