Effect Of Climate Change And Urbanization On Urban Flood And Waterlogging Disaster Risk In Pearl River Delta

Climate change has changed the time-and-space of water cycle,which increases the probability and intensity of extreme hydrological events.Urbanization is an important expression of the influence of human activities on the water circulation.On the one hand,by changing the properties of the underlying surface,the characteristics of the surface runoff and the runoff are directly affected,and on the other hand,the regional rainfall characteristics are changed through the surface energy distribution and urban environmental factors,these influence the hydrological process of the surface.With the development of the economy,the economic loss caused by flood and flood risk is increasing along with time.Under two important factors of climate change and urbanization,the change of flood and flood is a common concern of many scholars in recent years.This have great significance to study the development trend and intensity change of the future flood and flood events under the condition of climate change and urbanization and to give the guidance in the decision-making of disaster reduction and so on.In order to study the effects of climate change and urbanization on urban flood in the Pearl River Delta region with frequent flood in China.The main conclusions of this dissertation are extracted as follows:(1)The spatial distribution of the rainfall in the Pearl River Delta region from 2013 to 2015 is analyzed and simulated based on the mesoscale meteorological model WRF coupled with the urban canopy model,and the influence mechanism of the change of the lower surface of the city on the summer rainfall in the Pearl River Delta region is explained.The results show that the lower surface of the city changes the distribution of energy,and the sensible heat flux is obviously increased,the latent heat flux is reduced,the change of energy increases the free convection height,the height of the lifting and the condensation,the height of the atmospheric boundary layer,and the better rainfall conditions are formed.The rise of the surface temperature causes the vertical wind speed to increase,and more water vapor is lifted to the upper air,and provides good water vapor condition for the rainfall process.The results show that the extreme rainfall intensity is significantly increased in the urban area,and the change of medium-intensity rainfall is not significant;and the extreme rainfall and the rainstorm frequency are rising.(2)The regional climate model RegCM4.6 one-way nested global climate model GFDL-ESM2 M has certain ability to simulate temperature and precipitation in the Pearl River Delta region from 1980 to 2000.In the future period(2030~2050),the average monthly air temperature in the Pearl River Delta region increases under the RCP4.5 and RCP8.5 scenarios,while the monthly rainfall shows greater spatial heterogeneity.Under the two emission scenarios,the extreme temperature index is increased in the whole region,while the extreme rainfall index is quite different in the whole region.For the extreme temperature index,the trend of temperature increase in the whole Pearl River Delta region under the RCP4.5 and RCP8.5 scenarios is obviously more significant under the RCP8.5 scenario.In both RCP4.5 and RCP8.5 scenarios,SU25 showed a significant upward trend in the estuary of the Pearl River Delta and the northern region,while the TXx,RCP4.5 increased significantly chaos in the area,while in the RCP8.5 scenario it increased significantly in the eastern region.For extreme rainfall indicators,RCP4.5 and RCP8.5 scenarios show great differences.Under the RCP4.5 scenario,the maximum daily rainfall(Rx1day)and maximum 5-day rainfall(Rx5day)showed a significant upward trend in the northwestern part of the Pearl River Delta,and in the RCP8.5 scenario.The maximum daily rainfall(Rx1day)and maximum 5-day rainfall(Rx5day)in the Pearl River Delta region increased significantly in the central region.(3)The risk assessment model of RCPs-Urbanization-SSPs in the future is constructed according to the hazard factors of the risk-forming mechanism system,the hazard inducing environment and the three large driving factors of the disaster-bearing body.The future scenario simulation shows that the high-risk areas have increased significantly,especially the RCP8.5-Urbanization-SSP5,with an increase of 90.80%,and the higher-risk areas are mainly in areas with large population density and less terrain,and the middle-risk areas are reduced under both emission scenarios.The results show that the risk of flood and flood is a serious challenge in the future,and it is necessary to prepare the related defense preparation for the danger zone,while the high emission scenario can directly increase the risk of flood and waterlogging in the highrisk area,and the increasing range is 10.44%-11.09%.The different socio-economic scenarios have different contributions to the flood risk,which the SSP5 will face a more severe flood risk in the future(4)The method of the short-duration rainfall in the future is put forward,and the influence of the climate change on the drainage system is quantitatively evaluated by using the InfoWorks ICM to build the pipeline,the river channel and the twodimensional ground coupling model.The results show that in the scenario of RCP4.5 and RCP8.5,the peak of rainfall intensity and the accumulated rainfall in the future are increased,and the number of the overflow node,the peak of the node overflow,the proportion of the full load of the pipeline and the maximum inundation depth are increased in the frequency of different design storm.The results show that the waterlogging disasters in the typical urban areas in the Pearl River Delta will be further exacerbated in the future.