Analysis Of The Temporal And Spatial Changes Of Population And Disaster Exposure In The Coastal Lowlands Of The Yangtze River Delta From 1990 To 2015

The coastal area of the Yangtze River Delta is located in the Yangtze River Delta,China's largest economic zone,and is the region with the largest coastal lowland area in China.The region is densely populated,economically developed,fragile ecological environment,frequent natural disasters,environmental risks,natural disasters nd climate change risks are increasing,and natural disasters such as floods,typhoons and storm surges are very serious.In recent years,due to the sustained and rapid economic growth and rapid urbanization in the Yangtze River Delta region,large-scale population has been attracted to this.As an important disaster-bearing body,population is the main target of disaster risk management and climate change adaptation.To this end,based on high-resolution population data,DEM data,administrative divisions and other data,this paper analyzes the spatial distribution and population spatial and temporal changes of the municipal-level administrative unit population in the low-lying coastal areas of the Yangtze River Delta from 1990 to2015,and explores the coastal lowlands of the Yangtze River Delta.The population distribution and changes from the coastline and different altitudes,combined with the Yihong District,storm surge-extreme water level data to calculate the extent of disaster exposure in different administrative regions and the physical exposure of the population,and analyze the changes in the exposure of the disaster population.The main work and main findings obtained are as follows:(1)Firstly,based on the DEM data and administrative division data,the actual range of the coastal lowlands in the Yangtze River Delta is determined,and the ratio of the low-lying area of each city in the coastal zone to the occupied lowland is calculated.It can be seen that the low-lying areas of the cities in the coastal areas of the Yangtze River Delta are very large.The difference is that more than 95% of Yancheng,Taizhou and Shanghai are located in coastal lowlands.(2)Using ArcGIS's classification area statistical module,statistics on the population and density of the coastal lowlands in the Yangtze River Delta in 1990,2000,2010 and 2015,and statistics show that the low-lying population of the coastal lowlands in the Yangtze River Delta for 4 years accounted for the total population of the administrative region.The proportion of the number is greater than 46%,indicating that while the overall population of the Yangtze River Delta is growing,thelow-lying population still maintains a high proportion.In 2015,there were 9 cities with a population of more than 2 million in the lowland.The population density per square kilometer in the lowland is greater than 1,000.There are also 9 cities in the lowland,and the population density in Shanghai is as high as 4,209 people per square kilometer.The population density in Ningbo is also low.Up to 3,153 people per square kilometer.(3)Using the Power function in Excel to analyze the lowland population changes from 1990 to 2015,mainly to analyze the changes in population size and population density,and to explore the relationship between lowland population changes and altitude and distance from the coastline.The results show that 25 years The coastal lowland population in the Yangtze River Delta has increased by a total of 15.337 million.There are 9 cities with an average annual population growth rate of more than1%,and 5 cities with more than 2%.At the same time,the population density per square kilometer in the lowlands of Jiangsu,Shanghai and Zhejiang increased by 46,1,879 and 375 respectively over the past 25 years.In the coastal lowlands of the Yangtze River in 2015,48.5% and 71.0% of the population were located below the altitude of 4m and within 40 km of the coastline,and the population within the region continued to change with time.Among them,the population within 3-4m above sea level and 0-20 km and 20-40 km from the coastline increased by 94.15 million,608.3and 6.749 million respectively in 25 years.(4)Using the data of the Yihong District and the flooding range of the storm tide-extreme water level data,respectively analyzing the exposures of different areas,and counting the population and density of the population within the inundation area,and finally analyzing the exposure of the disaster population in the coastal lowlands of the Yangtze River Delta.Variety.According to the analysis,in 2008,20.892 million people in the coastal lowlands of Shanghai were exposed to flood disasters.The exposed population accounted for 27.7% of the total population of the coastal lowlands in the Yangtze River Delta,accounting for 78% of the total population of Shanghai.In the past 25 years,the exposed population of low-lying floods in Shanghai and Suzhou has increased by 953.9 and 305.5 million respectively,with an average annual growth rate of 2.47% and 2.87% respectively.In the past 25 years,the number of exposed people with storm surges has increased by 1.757 million,but there are large differences in the low-lying population between cities.