Study On The Simulation And Risk Assessment Of Rainstorm Waterlogging Disaster In The Main Urban Area Of Xi’an City

With the rapid urbanization process and frequent extreme rainstorm events,urban waterlogging has increasingly become the main factor restricting the healthy development of cities.It is an important non-engineering means to effectively control urban waterlogging disaster to obtain the physical process of waterlogging caused by rainstorm through numerical simulation,and to comprehensively assess the risk of urban waterlogging disaster with multiple information sources.Therefore,in order to reduce the loss of life and property caused by urban waterlogging disasters,this article took the main urban area of Xi’an City as the study area,simulated the waterlogging process of different rainfall scenarios in the city through a one-dimensional and twodimensional coupled rain flood model,and comprehensively evaluated the risk of urban waterlogging based on multi-source fusion information.The main results obtained are as follows,(1)In order to accurately simulate the waterlogging process in the main urban area of Xi’an City,a one-dimensional and two-dimensional coupled rain flood model was constructed.The model parameters were calibrated using historical measured data and the reliability of the model was verified.The relative error between the measured water depth and the simulated water depth at five waterlogging points in the current rainfall scenario was calculated,and the maximum relative error was not more than 10%.Therefore,it indicates that the model can accurately simulate the waterlogging process in the main urban area of Xi’an City.(2)By using this model to simulate the process of waterlogging depth and waterlogging flow velocity in rainfall scenarios of 5a,10a,30a,50a,and 100a,and evaluating the spatial distribution of risk levels for two hydraulic indicators,it was found that the proportion of low-risk areas is the highest for the two indicators and the proportion of high-risk areas is the lowest.Among them,under each rainfall return period,the proportion of low-risk areas with waterlogging depth indicators ranges from 72.97%to 82.21%,and the proportion of high-risk areas ranges from 2.15%to 7.29%;The proportion of low-risk areas in the waterlogging flow velocity index ranges from 91.44%to 95.62%,while the proportion of high-risk areas ranges from 0.11%to 0.46%.(3)In order to systematically and comprehensively evaluate the risk of waterlogging disasters in the main urban area of Xi’an City,a waterlogging disaster risk assessment index system was constructed using the natural and social factor assessment framework,with waterlogging depth,waterlogging flow velocity,terrain elevation,and terrain slope as natural factor indicators,and population density,road network distribution,building density,disaster rescue capacity,and urban lifeline engineering as social factor indicators.And the weight of the indicators was determined using Analytic Hierarchy Process,the risk level of the indicators was divided using Natural Discontinuity Method,and the multi-source information was fused using Linear Weighted Comprehensive Evaluation Method.Finally,the spatial region division of the risk of waterlogging disasters in the main urban area of Xi’an City was obtained.Unlike a single indicator of waterlogging depth or waterlogging velocity,in the comprehensive assessment results of waterlogging disaster risk in the main urban area of Xi’an City,the proportion of areas with different risk levels during different rainfall return periods is characterized by the highest proportion of areas in medium risk areas and the lowest proportion of areas in high risk areas.Among them,under each rainfall return period,the proportion of medium risk areas in the comprehensive assessment of waterlogging disaster risk in the main urban area of Xi’an City is between 55.14%and 66.17%,and the proportion of high risk areas is between 1.80%and 5.29%.The difference in the proportion of risk level area between a single hydraulic element and the comprehensive risk assessment of waterlogging disasters reflects the importance of comprehensive risk assessment of urban waterlogging.