Study On Urban Waterlogging Vulnerability Evaluation And Disaster Impact Model

Urban waterlogging refers to the internal accumulation of water in urban areas where runoff is formed during heavy rain or short-term heavy rainfall,and the terrain is low-lying and the drainage is not timely.In recent years,with the acceleration of the urbanization process,the size of city and the hardened ground surface have increased significantly,the urban impervious surface has increased sharply,and the probability of flooding in heavy rain has also increased.In Xi'an,heavy water has also caused waterlogging and waterlogging,which has a serious impact on the normal operation of the city and the production and life of residents.At present,urban waterlogging disasters have become one of the most common and most serious problems in cities and one of the hot research directions.Judging from the results of research on urban waterlogging at home and abroad,on one hand,according to the regional climate and hydrological characteristics,the existing urban waterlogging models are selected for calculation based on the principle of hydrological production and confluence;on the other hand,disaster monitoring and evaluation methods are carried out,using of GIS tools and statistical data to estimate the impact of urban waterlogging disasters.This paper addresses the problems of low extraction accuracy of urban impervious water surfaces,complicated method parameters of hydrological models,inadequate GIS model algorithms,inadequate urban flood internal vulnerability assessment system,and lack of systematic and quantitative research on urban flood effects,combined with the National Geographic Conditions Monitoring Project of the Ministry of Natural Resources and National Geographical and National Conditions Monitoring and Analysis of Key Technologies and Application Topics,it quantitatively researched on urban waterlogging vulnerability assessment and disaster impact model,achieved that joint methods extraction of impervious surface,dual-parameter multi-flow urban waterlogging submerged simulation,urban waterlogging vulnerability assessment system and evaluation system construction,discrete population and economic models construction,correlation relationship models construction of urban waterlogging influencing factors,indirect loss model construction of urban waterlogging and quantitative division of urban waterlogging impact,which can provide reference for the management decision of urban waterlogging.The main work and innovations of this paper are summarized as follows:1.Proposed a method for joint extraction of urban impervious surfaceThe surface classification of traditional remote sensing method only considers the spectral information,and due to the low brightness of shadow the confusion classification problem highlights,the overall classification accuracy is not high.In this paper,it fuses the spectral and texture features of the remote sensing image and considers the problem of shadow extraction and attribution,uses principal component analysis,gray level co-occurrence matrix method,supervised classification,gray scale mathematical morphology and other methods,surface classification and urban impervious surface extraction are completed.This method improves the accuracy of surface classification,and constructs the method system of surface impervious surface extraction.The result of the application in Xi'an is that the overall accuracy is 19.9%higher than that based on the spectrum only and without considering the shadow,and the Kappa coefficient is increased by 0.23,which can be used to extract the impervious surface.The average impervious rate of the fourth-phase urban area of Xi'an is above 65%,which is at a relatively high level,and showing a continuous growth trend.2.Constructed two-parameter multi-flow urban flood submerged simulation modelUrban waterlogging models such as STORM,UCURM,and SWMM based on the production confluence principle,required a large amount of real-time data and model parameters to support them.While the existing GIS simulation model is a single flow method and does not consider surface classification,drainage and infiltration,there are gaps in the situation and actual.In this paper,based on DEM,basic principles of hydrology,surface impermeability and drainage conditions,simulating the flow of water from high to low along the grid unit and distributing the flow in eight directions according to the slope ratio,generalizing the infiltration and drainage parameters,using the secondary development technology of ARCGIS,the water accumulation in the city under different periods and different rainfall intensity was simulated.This method realizes the urban waterlogging scenario simulation of large scenes.The simulation results of different rainfall intensities in Xi'an City are compared with the observation data of rainfall observation points in Xi'an City.The calculation amount of the model is simplified,the running time is shortened,and the operation efficiency is greatly improved.The waterlogging risk areas have a high degree of agreement and can be used for macroscopic simulation and monitoring of urban waterlogging.3.Constructed urban waterlogging vulnerability and evaluation systemAt present,there are many studies on the urban environmental carrying capacity evaluation system,the research on the risk study of urban waterlogging is mostly found in one aspect of external force and resilience.Comprehensive research and evaluation system of vulnerability are still rare.Based on these,this paper matches the PSR model with the hazard factors,disaster-preventing environment and disaster-bearing body of the disaster system theory,combines the city statistical yearbook data,selects evaluation indicators,uses the analytic hierarchy process to determine the index weights,and constructs the evaluation system and proposed a index UVI,which can effectively analyze and comprehensively evaluate the degree and change of urban waterlogging vulnerability.It quantitatively calculates,analyses and evaluates urban waterlogging vulnerability based on Xi'an statistical yearbook data in four years,and concludes that Xi'an city waterlogging vulnerability is generally low and the trend is stable.4.Constructed discretization models of population and economic dataPopulation and economic data are important urban flood disaster impact data,but these data is mostly in the form of statistical data,which is difficult to spatialize sciencely.The current isometric,equal frequency discretization model is not suitable for random and continuous data.In this paper,for this kind of problem,it based on the fixed distribution of population in the building and the negative correlation between the population and the normalized water index,the population of the image pixels of the residential area type is assigned and the number of high-rise buildings is higher than that of multi-layer buildings.The feature with a smaller normalized water index value is used to create a model,and the secondary development technology of ARCGIS is used to allocate population data to each pixel in a unit of area to achieve population dispersion,which overcomes the problem of average dispersion.Applying this model to the population data of various districts in Xi'an,the result is matched with the residential area of the geographic information data,and the coincidence is 90.50%.The economic data discrete model is created to simulate the sound wave attenuation,using the similarity of economic radiation attenuation and sound wave attenuation,taking the top ten commercial districts in Xi'an as the central point,based on the sound wave propagation theory to simulate the attenuation process of economic radiation,considering the economy intensity,it achieves economic dispersion in pixels used the Gini coefficient to adjust the attenuation and used the secondary development of ArcGIS 10,which overcomes the problem of average dispersion.Applying this model to the economic data of various districts in Xi'an,the result fits with the road network of the geographic information data,and the coincidence is 92.15%.5.Constructed urban waterlogging impact model and quantified the degree of impactAfter the occurrence of urban waterlogging,the quantitative assessment and evaluation of its impact has always been difficult.In this paper,based on multi-source data,combined with gray correlation,GM(0,N),least squares,fuzzy mathematics,gray clustering and other theoretical methods,it conducts research from three aspects:the horizontal correlation between urban waterlogging impact factors,the relationship between indirect and direct impacts and the classification of urban waterlogging levels,in order to realize the systematic and quantitative research on the impact of urban waterlogging,which has established a relatively complete frame.The correlation between rainfall and impact factors is calculated quantitatively;the horizontal impact of urban waterlogging disasters is constructed which has an accuracy of one level;the indirect effect model of urban waterlogging has been constructed which accuracy has reached one level,and the indirect impact has been quantitatively evaluated as same as direct loss,with an indirect coefficient of 1;comparing the whitening weight function of the center point triangle and the whitening weight function of the endpoint,it is found that the central point triangle whitening weight function is better,and it quantitatively divides the degree of urban waterlogging impact under different rainfall intensities.This method model is applied to Xi'an City,it concludes that the biggest impact of rainfall is the population factor;when the rainfall is 80mm-100mm in short duration,the comprehensive impact of Xi'an is mild;when the rainfall is above 120mm in short duration,the comprehensive impact of Xi'an is significant or extremely large.