Research Of Urban Flood Simulation And Optimization Under Complex Topographic Conditions

One of the effective ways to prevent and control urban flood disasters is drawing flood submergence map in advance by using urban rainfall-flood numerical model.Urban flood submergence map is a comprehensive result,which is affected by many factors.How to build a rainfall-flood model rapidly and accuracy has great significance to the development of urban flood research.A one-dimensional and two-dimensional coupled rainfall-flood model is used to analyse the effects of the urban topographic data,the generalization of surface features and the generalization of surface roughness on flood submergence maps.6-point Abbott-Ionescu scheme is used to discretize Saint-Venant equations and pursuit method is used to solve one-dimensional drainage network system.The implicit alternating direction implicit scheme is used to discretize two-dimensional shallow water equations and ADI progressive method is used to solve surface overflow.Weir flow equation and orifice equation are used to calculate flow exchange at inlets under different rainfall conditions.The model is verified by a historical urban flood event.The influence of each factor on flood submergence map was analysed under rainfall conditions in the recurrence periods of 2a and 10 a.The conclusions are as follows:(1)The submerged area of 70 m precision DEM data simulation is quite different from that of 17 m DEM data,and the common part of the submerged area is small.There are obvious differences in the process of flood and waterlogging at the observation points.The submerged area of 35 m precision DEM data is little different from that of 17 m precision DEM data,and the trend of flood and waterlogging process at the characteristic points is consistent.(2)The simulation results computing with manning coefficient and manning map fit well,the common part of submergence range is large,the flood evolution process is consistent,and the maximum water depth of submerged points is approximately equal.It shows that in the numerical simulation of urban flood,the reasonable comprehensive manning coefficient can replace the manning map to reflect surface resistance.(3)From the analysis of surface submergence distribution,submerged area and maximum water depth of submerged point,it can be found that the influence of buildings on shallow water flow in urban surface overflow simulation is much greater than that of urban surface road network.Once the buildings are not considered,the regression process of local waterlogging point will be significantly advanced.Building is more influential in generalization of surface features.