Risk Evaluation Of Rainstorm Waterlogging Disaster In Nanjing Urban Area

In recent years, with the development of China’s urbanization improved continuously, urban rainstorm waterlogging disasters’frequency, intensity and the resulting loss has increased year by year, it has become one of the major weather disasters affect China’s national economic development in urban areas. Main city of Nanjing affected by the monsoon climate, in the summer, it usually has a faster and fierce rain, especially it has a higher frequency of a wide range of persistent heavy rains or a concentration of heavy rain weather phenomenon. It is not only affecting the industrial and agricultural production, but also may endanger the lives of the people, and cause serious economic losses. Risk evaluation of rainstorm waterlogging disaster in urban as a very urgent basis, has get more and more attention of people. Scientifically evaluating the urban rainstorm waterlogging disaster risk has a great significance for ensuring the harmony and stability of social life, and promoting the sustainable development of the national economy.From the viewpoint of disaster science, climatology, hydrology, geography and environmental science, this article used the Nanjing Statistical Yearbook information, basic geographic information data, land use data, and historical disaster data, combined with GIS technology, applied the principle of weighted comprehensive evaluation method and the Analytic Hierarchy Process calculating factor weights,then built urban rainstorm waterlogging disaster risk assessment model. At last, this paper assessed the risk of Nanjing urban area rainstorm waterlogging disasters, the main conclusions of this study are obtained listed as follows:(1) This article used numerical simulation method to quantitatively determine the spatial distribution of the Nanjing urban area rainstorm waterlogging disaster threshold in the light floods, the floods, heavy floods and extreme floods waterlogging scenarios. Overall, the hazard thresholds of Xiaguan and Gulou are lower than Jianye, and Baixia, Qinhuai, Xuanwu three zones hazard threshold are between the former two.(2) Constructing urban rainstorm waterlogging disaster risk assessment model which contained hazard risk, sensitivity of hazard environment, vulnerability of hazard bearing body, and the disaster prevention and mitigation capacity, and assessing the risk with GIS. In accordance with natural breakpoint law, the risk regionalization of rainstorm waterlogging disaster in Nanjing urban area are classified into five grades, including the lowest risk, the lower risk, medium risk, the higher risk and the highest risk. High-risk areas distribute in the periphery of the main city along the Yangtze River and southeast of urban area. Southerly areas of the urban center and south of Xiaguan belong to the higher risk and the medium risk areas. The higher risk, the medium risk, and the lower risk areas occupied the most part of the urban area. The lowest risk areas include the north of Gulou and the hill in urban area. This assessment results match with the Nanjing disaster reality quite well.Urban storm waterlogging disaster risk assessment provides timely, accurate and scientific basis for governments at all levels and relevant departments to the development of disaster prevention and mitigation plans and countermeasures, in order to minimize the losses caused by the rainstorm waterlogging disasters, and effectively prepare before the disaster occurred.