Risk Assessment Of Typhoon Disaster In Hainan Island Based On GIS

Global warming and rising sea water temperature lead to the increase of frequency and intensity of typhoon.Typhoon and its secondary disasters caused more losses to the coastal provinces and cities in Southeast China.Due to its special geographical location,Hainan Island is particularly affected by typhoon.In order to better reveal the temporal and spatial evolution of the comprehensive risk of typhoon disasters in Hainan Island,71 typhoon data from 1980 to 2019 were used,a comprehensive evaluation system is established by coupling four factors,namely,the sensitivity of disaster pregnant environment,the risk of disaster causing factors,the vulnerability of disaster bearing body and the ability of disaster prevention and mitigation.Based on the typhoon data of Hainan Island from 1980 to 2019,the comprehensive risk assessment model of typhoon disaster in Hainan Island is constructed by using the combined weight method.The index and the comprehensive risk division of typhoon disasters in different periods are obtained by dividing the typhoon disaster into four periods in 10 years.The main research contents and results are as follows.(1)Six indicators,including terrain niche index,topographic index,degree of relief,drainage density,distance from southeast coast and vegetation coverage,were selected as the sensitive factors of disaster pregnant environment.Through data acquisition and comprehensive evaluation,the sensitivity zoning of disaster pregnant environment in the study area was obtained.The results show that:the spatial distribution of environmental sensitivity of pregnant disaster is gradually decreasing from the eastern and southwestern coastal areas to the inland;the high,medium and high sensitive areas are small aggregation distribution in the northeast,accounting for 4.33%and 16.6%respectively;the medium,low and low sensitive areas are large dispersion distribution,accounting for 30.4%,31.46%and 17.2%respectively.(2)The maximum wind speed,the maximum daily rainfall,the total rainfall and the typhoon path density during typhoon landing are selected as the disaster risk factors.Through data acquisition and spatiotemporal evolution evaluation,the disaster risk zoning of different periods in the study area is obtained.The results show that:(1)In the1980s,low and medium risk areas were dominant,with an area of 15512.63km~2and9951.15km~2respectively.In the 1990s,low and medium risk areas were dominant,accounting for 33.53%and 24.76%respectively.In the 21st century,low risk areas were dominant,with an area of 72.84%and 54.06%respectively.(2)Over time,the low-risk area has a rise-rise-fall model,the low-risk area,middle and high-risk area has a fall-fall-rise model,the high-risk area has a rise-fall-rise model.(3)The disaster risk level has a decreasing trend from coastal to inland.In the 1980s,it decreased from the eastern and western coasts to the inland.In the 1990s,it decreased from the southeast and southwest coasts to the inland to the northern coasts.In the 21st century,it decreased from the northeast and southwest coasts to the inland.(3)Five indicators such as population density,GDP per land,road network density,land use type and the proportion of primary industry output value were selected as the vulnerability factors.Through data acquisition and spatiotemporal evolution analysis,the vulnerability zoning of the study area in different periods was obtained.The results show that:(1)In the 1980s-1990s and the 2000s,low and medium vulnerability was the main,accounting for 77.71%,59.32%and 58.52%of the area respectively.In the2010s,low and medium vulnerability was the main,accounting for 12948.64km~2and14742.82km~2respectively.(2)Over time,the low,medium high and high vulnerable areas are rise-rise-rise model,low and low vulnerability is the fall-fall-fall mode,medium vulnerability is the rise-fall-fall model.(3)The vulnerability level of the disaster bearing body generally decreases from coastal to inland.In the 1980s,it was mainly distributed in a large area with low vulnerability,small aggregation with low vulnerability,and scattered distribution with medium high vulnerability.In the 1990s and the 21st century,it was obviously distributed along the road network,the medium vulnerability was mainly distributed along the island expressway network.The medium high vulnerability and high vulnerability were mainly distributed in the economic centers of cities and counties,and the low,medium and low vulnerability were mainly distributed in inland areas.(4)Five indicators such as the number of beds per capita,the number of medical care per capita,local fiscal revenue,rural per capita net income and the proportion of rural population were selected as the disaster prevention and mitigation capacity factors.Through data collection and space-time comparative analysis,the division of disaster prevention and reduction capacity in the study area is obtained.The results show that:(1)From 1980s to 1990s,low capacity areas dominated.In the 2000s,low,medium and low capacity areas dominated.In the 2010s,it was dominated by medium capacity areas.(2)With the development of time,the disaster prevention and mitigation capacity of all cities and counties in the study area showed an upward trend;Haikou and Sanya had the strongest disaster prevention and mitigation capacity,followed by Chengmai,Danzhou,Qionghai and Wuzhishan.(5)The comprehensive risk assessment index value of typhoon disaster in the study area is calculated by subjective and objective combination weight and linear weighted comprehensive assessment method,and the grades are divided according to the value.The results show that:(1)In 80’s and 90’s,medium risk was dominant,accounting for 40.85%and 39.68%of the total area respectively.In 00’s,medium and low risk was dominant,accounting for 14498.89km~2.In 10’s,low risk was dominant,accounting for 19194.03km~2.(2)With the change of time,the low risk is the rising mode,the middle and low risk is the rise-rise-fall mode,the medium and high risk is the falling mode,the high risk is the rise-fall-fall mode.(3)The comprehensive risk level of typhoon disaster in the study area has a decreasing trend from coastal to inland,and there is only spatial-temporal variation in the direction.In the 1980s and 2000s,it decreased from the East and southwest coast to inland.In the 1990s,it decreased from the southeast and southwest coast to the inland and the northern coast.From the northeast and southwest coast to inland in the 21st century.(6)The comprehensive risk of typhoon disaster in the study area is studied by using the average value and the maximum value.The results show that:(1)The average comprehensive risk value and the maximum comprehensive risk value have the characteristics of decreasing from coastal to inland in space,and the maximum standard partition can better reflect the comprehensive risk level of typhoon disaster.(2)The high,medium and high risk areas of the maximum comprehensive risk value division were mainly distributed in the eastern and southwestern coastal areas of the study area,with the number of towns accounting for 14.56%,21.84%and 23.79%respectively.The low and medium risk areas were concentrated in the central inland to the northwestern coastal areas,with the number of towns accounting for 13.59%and 26.21%respectively.(3)Over time,the overall risk level showed an upward trend,with a total of 40 townships,mainly concentrated in the northeast coast and southwest coast;there were 166townships with a downward trend,mainly located in the South and west of the central part of the study area.