| The risk assessment of rainstorm disaster is one of the important parts of risk management,and it is also an important research content of human people to prevent natural disasters and reduce disaster risk.Global and local extreme precipitation events have occurred frequently in recent years due to climate change.As an extreme precipitation event,rainstorm has high frequency,great intensity and wide distribution,which often caused many casualties and property economic losses,bringing immeasurable impact.Therefore,analyzing the possibility of rainstorm disasters under different recurring periods,identifying the higher-level areas of rainstorm disasters,and assessing the risk of rainstorm disasters can provide a more favorable decision basis for rainstorm disaster warning and mitigation of losses caused by disasters.The present study takes the Bohai Rim as a case study,and uses daily precipitation data along with a copula joint function to calculate the probability of rainstorm occurrence in different return periods(5,10,20,and 50 years)as a means of analyzing the hazard levels of rainstorm disasters.The population density was selected to represent the exposure degree and the spatial distribution characteristics of the exposure degree were analyzed.The geographical mean GDP data was selected to measure the vulnerability and the spatial distribution characteristics of rainstorm vulnerability were analyzed.On this basis,according to the disaster risk assessment paradigm proposed by the United Nations office for disaster risk reduction(UNDRR),the risk of rainstorm disasters in the Bohai Rim under different return periods was analyzed.The conclusions are as follows:(1)Among the eight representative sites of humid and semi-humid,most sites of rainstorm single elements conformed to three or more edge distribution functions.According to the Pvalue size,the optimal edge distribution function was selected to fit the rainstorm elements.The three-dimensional combination of rainstorm multi-elements was carried out on the basis of the edge distribution of the single element of rainstorm.The optimal joint function of Fushun,Haiyang and Qinglong was Clayton Copula,and the optimal Copula function of Anshan,Dalian,Heishan,Yixian and Taishan was Frank Copula.(2)From the coastal areas of the Bohai and Yellow seas towards the northwestern area,the hazard levels of rainstorm disasters gradually decreased.As the return period increased,the range of the Low-and Lower-level areas gradually narrowed to the northwest until the 50-year return period,there were no Low-level and Lower-level areas in the Bohai Rim,while the Middle-level,High-level,and Higher-level hazard areas advanced towards the northwest.The Middle-level and High-level hazard areas showed a tendency to increase and then decrease,and the areas associated with a Higher-level hazard gradually expanded.(3)The Lower-level areas of population exposure were distributed in the northwestern and northeastern regions of the Bohai Rim,and were concentrated in areas northwestern regions of Hebei Province,western and northeastern regions of Beijing,eastern and western of Liaoning Province,and central and prefecture-level cities outside Shandong.The Higher-level and Highlevel areas were mainly distributed in the southeastern,and most areas are concentrated in urban areas of large cities and the centers of surrounding counties,such as Beijing,Tianjin,Shijiazhuang,Shenyang,etc.Most of the rest of the Bohai Rim region have low population exposure and medium-level areas.(4)Areas of Higher-level and High-level vulnerability were found to be concentrated in the eastern and southern,such as Shenyang,Beijing,Tianjin,and Shijiazhuang.Middle-level and Lower-level areas are scattered in the southeastern,concentrated in the central and southeastern regions of Liaoning Province,eastern and southern regions of Hebei Province,and western,northern and coastal areas of Shandong Province.The northwestern,that is,the northwestern regions of Hebei Province,the western regions of Liaoning Province,and the northern part of the region are low-level vulnerability areas for storm disasters.(5)The Lower-level risk of rainstorm disasters under different return periods in the Bohai Rim region was distributed in the northwestern region of Chaoyang,Liaoning,the northwestern region of Hebei,and the northwestern region of Beijing.The Low-level and Middle-level areas were concentrated in the southeast,concentrated in most of Liaoning Province,eastern and southern Hebei Province,Tianjin,Southeast Beijing,Shandong Province.The High-level and Higher-level were concentrated in the centers of large cities and outlying areas and county centers.From the southeastern coastal area to the northwestern area in the Bohai Rim,the rainstorm disaster risk levels gradually decreased under different return periods.As the return period increased,the Lower-level risk area narrowed 46% to the northwest,the Low-level area expanded 46% to the northwestern,the Middle-level and High-level areas decreased 0.14% to the northwestern,and the Higher-level area expanded 0.51% to the northwestern. |
