Research On Waterlogging Simulation And Risk Assessment Based On 1D-2D Coupled Hydrodynamic Model

With the continuous expansion of urbanization,the problem of waterlogging has become more and more prominent,and the frequent occurrence of domestic floods has seriously affected the normal operation of the city and the daily life of society.There are countless losses caused by urban waterlogging disasters.In order to reduce the losses caused by urban waterlogging as much as possible,it is necessary to establish scientific methods to quantify various flood risks and provide technical support for urban flood risk management.Based on a case study in City H,this thesis constructs a one-and two-dimensional coupled hydrodynamic model,studies the drainage capacity of the existing pipe network system under various rainfall scenarios,and analyzes the characteristics of surface water.In the risk assessment,the expected average annual loss（EAD）is calculated based on the flood inundation volume,and the flood risk quantification of the existing drainage system is realized.Finally,two adaptive scenarios are proposed and evaluated,their effects on reducing urban flood volume and waterlogging risk are compared,and the benefits of the two adaptive measures are calculated.The results show that from the perspective of one-dimensional pipeline network,the design return period standard of the pipeline network in the study area is low,and most pipelines do not meet the one-year design return period standard.From a two-dimensional perspective,under torrential rains with different design return periods,most of the accumulated water in the study area is below 0.15 m,accounting for more than 90%.However,due to the large range,pedestrian traffic will also be blocked.Combined with the location of the overflow point and the inundation characteristics of flood areas,these areas are prone to waterlogging and have high risks,which can be given priority during reconstruction.The risk assessment results show that the current drainage system in the study area has weak anti-risk ability and high EAD index.Due to the low return period standard of the design of the pipeline network in the study area,a large amount of flood inundation will be generated in the event of a heavy rain of more than 2 years,and the probability of occurrence is high,so the flood risk is mainly concentrated in the small amount of about 2 to 5 years.return period.Further,we can conclude that in order to minimize the risk of rainstorm and waterlogging,and also reduce the cost of renovation,the renovation of the pipe network system should make it meet the design return period standard of once in 2 to 5 years.The two adaptive measures proposed in the study can effectively reduce the amount of system floods and reduce the risk of flooding,and the reduction ratio of EAD relative to the current system is more than 80%.Among them,the expansion of pipeline diameter has a more significant effect on flood control than lowimpact development measures（LID）.Therefore,when carrying out the transformation of the pipe network system,the transformation cost should be comprehensively considered.Under normal circumstances,when the economy is more constrained,priority is given to the transformation of pipelines.When the area is limited,LID transformation can be added.Combining the advantages of the two can better achieve the goal of preventing waterlogging disasters from the source.The evaluation results can provide a reference basis for the implementation of urban flood risk management policies,and put forward feasible reference suggestions for the future drainage system reconstruction planning in the study area.