Simulation And Risk Assessment Of Urban Rainstorm Waterlogging Of Tianjin

China is one of the countries with the most serious meteorological disasters in the world.Among them,the direct economic losses caused by floods and geological disasters account for the largest proportion of the losses caused by all of the natural disasters.The acceleration of urbanization also exacerbates the severity and loss of urban rainstorm waterlogging.Therefore,the forecast and prevention of rainstorm waterlogging can effectively reduce the influence of meteorological disasters.In view of this,this paper establishes a hydrodynamic mathematical model to calculate the runoff yield and confluence of heavy rain in the central part of Tianjin City.to solve plain waterlogging problems and puts forward a complete set of calculation schemes for early prediction and later risk assessment of regional rainstorm waterlogging.On the basis of a detailed summary of the scientific research progress in urban waterlogging models and flood disaster assessment at home and abroad,a rainstorm waterlogging model in the central part of Tianjin is established by using the finite volume method of unstructured grids with one and two-dimensional shallow water equation as the basic equation.In this process,the problem of false quantity of flow which often occurs in the confluence of water on steep slope and in thin aquifer is solved by using the method of integral correction of unit channel flow.The collation process and application mode of model geomorphological conditions,drainage conditions,geology and groundwater depth data are introduced in detail.The extraction process of model data is introduced in detail and the mesh generation method considering complex geomorphological features is presented.The qualitative and quantitative validation of two heavy rainstorms in Tianjin in 2016 and 2018 shows that the trend of the results is reasonable compared with the measured data.The absolute error of the maximum water depth is within 15 cm and the relative error is within 15%.Based on the above model,seven kinds of heavy rain of different recurrence period and four drainage schemes are simulated to simulate the rainstorm process of different recurrence period,and the effects on the depth of the water of four drainage modes,which are bank overflow,bank non-overflow,bank pump drainage and pump drainage while considering the effect of seepage,are compared.According to the results,combining the output value and population of the towns in the central part of Tianjin,this paper estimates the disaster caused by the rainstorm of different recurrence period,and divides the impact degree of the rainstorm by setting a threshold.Population,the disaster caused by heavy rain in the recurrence period is estimated,and the impact degree of heavy rain in towns is divided by setting threshold.In general,this mode of establishing a mathematical model considering complex geomorphological conditions to predict the possible inundation range,depth and duration,to identify the vulnerable points,and to quantitatively estimate the socio-economic impact of each region,and then setting a threshold to determine the extent of the impact of the disaster,is of practical significance for reducing the loss of flood disasters,as well as providing the basis for the building of sponge cities.