Research On The Exposure Of Rainstorm Disasters Under Different Social And Economic Development Scenarios In The Future

China is one of the countries most widely and frequently affected by rainstorm disasters.Extreme rainstorms often cause local or regional floods,which pose a great threat to people’s lives and property and the stable development of social economy.With the increasing trend of global warming,extreme precipitation events in China show an obvious increasing trend.The degree of social and economic exposure under extreme precipitation disasters determines the size of the disaster to a large extent.China’s social economy is in the stage of rapid and stable development.with the continuous change of external environment and national policies in the future,the development of social and economic scenarios should be multi-directional.there may be great differences in social population,economic development speed and land use under different scenarios,so to explore the spatio-temporal characteristics of rainstorm disaster exposure under different social and economic scenarios in the future.It can provide scientific reference for mastering the spatial distribution of high exposure population and economy,evaluating the risk of rainstorm disaster loss,carrying out rapid prediction of disaster loss,formulating regional disaster prevention and mitigation strategies and so on.In this paper,based on the daily precipitation data,30 meteorological stations in Qiantang River Basin,the occurrence frequency of rainstorm in 10-year,20-year,50-year and 100-year return periods is calculated based on information diffusion function,and the risk of rainstorm disaster in different return periods is analyzed.At the same time,the daily precipitation data averages : Phase 5 of Future Coupling Model comparison Plan(CMIP5)are selected that BCC-CSM1-1,BNU-ESM,GFDL-ESM2 G,IPSL-CM5A-MR and Can ESM2.The occurrence frequency of rainstorm under RCP4.5 and RCP8.5 scenarios is calculated,and analysis of the risk of torrential rain disaster in 2030 s and 2050 s.Comparing the distribution characteristics of population,GDP and land use disaster victims in 2030 and 2050 under different social and economic development scenarios.Analyzing and calculating the spatial distribution characteristics of comprehensive exposure degree of rainstorm disasters in Qiantang River Basin in the future.the main conclusions are as follows:(1)under different return periods,the spatial distribution of rainstorm hazard increases gradually from northeast to southwest,and with the increase of return period,the high risk area moves from southwest to northeast as a whole.The frequency of rainstorm increases with the increase of return period,and the frequency of rainstorm in the return period from 10 years to 100 years increases from 6.76 to 8.89.And the high value of rainstorm frequency is distributed in the western mountain area,which shows that not only the probability of rainstorm is high,but also the possibility of heavy rainstorm is very high.(2)The risk of rainstorm in Qiantang River Basin will increase with time under RCP4.5 and RCP8.5 scenarios in the future.Spatially,it shows a gradual increasing trend from northeast to southwest.In 2030 s,the average frequency of RCP8.5 rainstorm is3.76 times,and that of RCP4.5 rainstorm frequency is 3.85.There is little difference on the whole.The frequency of torrential rain in 2050 s under RCP8.5 scenario obviously increases to 4.37 times,which is much higher than 3.94 times under RCP4.5 scenario,and the spatial risk tends to move eastward as a whole.(3)Combined with land use remote sensing images and natural and social factor data of Qiantang River Basin in 2015 and 2020.Establish three different social and economic development scenarios based on inertia development,rapid economic development and ecological comprehensive development.Under the three scenarios,the simulation accuracy Kappa coefficient of Geo SOS-FLUS model is more than 0.8.the simulation effect is better.By comparison,it is found that the area demand of construction land under the comprehensive ecological development scenario is less than that of the other two scenarios,and the spatial pattern of land use is the best.(4)The spatial distribution pattern of future population and GDP exposure of rainstorm disaster in different return periods is basically the same,showing an increasing trend from southwest to northeast.Under RCP4.5 and RCP8.5 scenarios,the spatial pattern of future population and GDP exposure is consistent with the return period.Land use exposure under the scenario of comprehensive ecological development,the exposure area of construction land is the smallest and the exposure area is the lowest.In the same recurrence period,the population exposure increased first and then decreased,reaching the peak around 2030,and then decreased;GDP exposure increased with the increase of time.In the return period of 10 to 100 years and RCP4.5 and RCP8.5 scenarios,the population and GDP exposure showed an expanding trend.(5)The comprehensive exposure levels of rainstorm disasters under social and economic scenarios in the future are as follows:The comprehensive exposure of low(Ⅰ)grade is the largest,accounting for more than 90% of the watershed area,and the middle(Ⅱ)comprehensive exposure is scattered near the center of cities and towns in the eastern part of the basin.High(Ⅲ)comprehensive exposure is distributed in the areas with high rainstorm frequency in the west and economically developed areas in the northeast,and the comprehensive exposure of very high(Ⅳ)is the least.The comprehensive exposure in different scenarios increased gradually with time,but the increase was slightly different.Under different social and economic development scenarios,the comprehensive exposure level of ecological comprehensive development scenarios is the lowest.In the future urban planning,we should focus on the development of ecological comprehensive planning in order to reduce the comprehensive exposure of rainstorm disasters in the future.