Research On Risk Zoning Of Urban Rainstorm And Waterlogging Hazard Considering Spatial Distribution Characteristics

With the global climate change and acceleration in urbanization process,as a result,rainstorm events in urban areas have increased a lot,and this disaster has already become one of the main natural disasters in cities,has a great impact on social and economic development of cities,peoples’ lives as well as property safety.Disaster risk assessment is one of the most important non-engineering measures to prevent and reduce the loss from disasters,its assessment results are helpful for disaster prevention and mitigation.And the assessment results usually displayed in disaster risk zoning maps to express the situation about spatial distribution characteristics and laws of regional disaster risk,but existing researches mostly only focus on the statistical characteristics of risk when selecting classification methods,ignoring the spatial characteristics of risk in study area.Consequently,the clarity in spatial distribution of disaster risk needs to be improved.Without a doubt an ideal classification scheme will help express risk’s spatial distribution in region.It’s also very significant for urban emergency management departments to quickly identify the spatial distribution of risk and make decisions.Because the spatial data analysis methods based on Laws of Geography has significant advantages in exploring the geographical elements’ spatial distribution and interaction relationship,it provides a feasible way for the related researches on spatial distribution characteristics of urban rainstorm and waterlogging disaster risk.In this paper,the Guangming District in Shenzhen City was taken as study area,and the disaster risk assessment index’s system and assessment model for urban rainstorm and waterlogging disaster was constructed to quantitatively calculate the risk index based on the laws of geography as well as the theories and methods of risk assessment.On basis of above,through the analysis of the difference between risk’s spatial distribution characteristics before and after the classification,an evaluation model of classification quality in urban rainstorm and waterlogging disaster risk was constructed to filter the optimal map classification method.On account of the best map classification method,the optimal zoning of the rainstorm and waterlogging disaster risk in study area was completed.It also provided a new idea for the selection of classification methods in risk’s zoning.The main research contents and conclusions were as follows:(1)Filtering the indices for urban rainstorm and waterlogging disasters considering the characteristics of geographical environment in study area.In order to filter the more suitable assessment indices for the study area,through referring the existing research results,the initial multi-indices were chosen.Considering the third law of geography to build a binary data set,the Boruta method and the Random forest method were utilized to identify the importance between multi-indices,and the extraction results of two algorithms were compared,the indices were also filtered by the qualitative evaluation threshold.The experimental results showed that filtered indices were not only more suitable to the geographical environment in study area,but also reduced the unnecessary data noise.(2)Calculating the risk of urban rainstorm and waterlogging disasters combing the assessment indices’ importance.In order to improve the accuracy in risk calculation results of urban rainstorm and waterlogging disasters,through combing the importance results of indices with AHP method,the calculation of disaster’s risk was completed.Finally,the experimental results showed that new CII-AHP method was better than traditional AHP method,it not only improved result’s accuracy,but also was more adaptive to the characteristics of geographical environment in study area.(3)Providing the classification method’s selection pattern of urban rainstorm and waterlogging disaster risk considering spatial distribution characteristics.In order to clarify the spatial distribution of rainstorm and waterlogging disaster risk in urban area,the spatial distribution characteristics of the rainstorm and waterlogging disaster risk before and after the classification were analyzed based on the first law and second law of geography.On basis of this,the evaluation model of classification quality in urban rainstorm and waterlogging disaster risk was constructed to attain the best map classification method.Eventually,the experimental results showed that the automatically recommended quantile method by evaluation model of classification quality had a better comprehensive classification effect while retaining the spatial distribution characteristics of the study area before risk classification.It not only improved the automation in the selection of risk classification methods,but also ensured the optimal zoning of rainstorm and waterlogging disaster risk in study area.