| Flooding is one of the most damaging natural hazards,and its negative impacts have markedly increased in many regions of the world during the last decades.The variation of flood exposure which refers to people,infrastructure,housing,production capacities,and other human assets that are located in floodplains is increasingly considered as a major driver of disastrous flood consequences.China is one of the countries that most suffer from disastrous floods.On the other hand,China has been experiencing unprecedented socioeconomic development since the late 1970 s,with a rapid increase in population and bulit-up area.The dynamic sand complex human-water interactions embedded within the process,which are more vulnerable to flood risk when settling close to river.Therefore,the dynamics of population and bulit-up area in floodplain of China and its spatial relationship with water bodies are of great significance for understanding the risk of flood disasters.The quantitative analysis of its spatial and temporal changes can help to fully understand the exposure of floods in China and provides a basis for strengthening flood risks.However,a national-scale study of the dynamics of population in floodplain and the relationship between bulit-up area exposure and water with are still to be accomplished in China.Here we present the first quantification of Chinses population and bulit-up area and its spatial relationship with water based on newly-available population datasets for years 1990,2000,2010,and 2015,bulit-up layer for years 1990,2015,water dataset and on a flood map.The followings are the main conclusions of this study:1.This research investigated the spatial distribution of Chinese population in floodplain.The Chinese population in floodplain was accounted 33.0% of the total population,with a population density 3.6 times higher than outside floodplains.The population in floodplain shows high spatial heterogeneity.A majority of the national population in floodplain is located in the Eastern Costal and the Middle Yangtze River of China and further concentrated in the three primary urban agglomerations.2.This research analyzed the changes of Chinese population in floodplain between 1990 and 2015.Firstly,the population in floodplain increased by 1.3% annually,overwhelmingly faster than elsewhere.A rising proportion of the population in floodplain resided in flood zones deeper than 2 m.Secondly,A majority the national population in floodplain growth occurred in the Eastern Costal and the Middle Yangtze River of China with a higher annual growth rate and further clustered in the three primary urban agglomerations with a significantly higher significantly higher than national average and other area.Finally,Demographic changes in China's floodplain showed a heterogeneous trends during the last decades.It grew faster in 1990 s and 2010 s than in 2000 s.A high growth rate of the population in floodplain across all the three periods in the three primary urban agglomerations.3.This research explored the bulit-up lands in floodplain distance to water in China.The average distance between China's bulit-up lands in floodplain and water was 5.41 km.62% of the bulit-up lands in floodplain distributed within 3 km of a water bodies.The bulit-up lands in floodplain distance to water shows large spatial variations across the country.The average distance between bulit-up land in floodplain and water bodies shows a short distance in Southwestern of China while a long distance in Northwest.A trend that the bulit-up land in floodplain has become farther away from the upper and the lower of the water bodies and the proportion of bulit-up land in floodplain near the water bodies has decreased with increasing distance.showed in China's three major rivers—the Yangtze River,the Yellow River,and the Pearl River.4.This research quantitatively calculated the temporal and spatial variation characteristics of the distance between Chinese bulit-up land in floodplain and water,and the changes in the area of bulit-up land in floodplain within different distances of the water bodies.During 1990 and 2014,the bulit-up in floodplain in China increased by 81%,the proximity to water was decreased 169 m.57% of the bulit-up land in floodplain is growing within 3 km of the water body,and the newly added area shows an exponential decrease trend with the increased of the distance from the water body.The bulit-up land in floodplain in the Eastern region has grown rapidly and is generally far from the water.In Southwestern and Northwestern regions,the percentage of bulitup land in the floodplain within 3 km increased by 1.58 percentage points and 7.61 percentage points respectively,which was generally close to the water body.5.This research revealed the difference and indication significance of the relationship between bulit-up land in Chinese floodplain and outside.The distance from bulit-up land to water bodies outside the floodplain in China is 10.44 km,which is much father than that in floodplain(5.41 km).During 1990 and 2014,bulit-up land outside the floodplain in China was close to 223 m to the water body,more than 169 m above the floodplain.Compared with the bulit-up land outside the floodplain,the bulit-up land in floodplain area will increase in frequency and flood deaths as close water bodies and its increased area.The above results showd that exposed populations and the spatial relationship between bulit-up land and water bodies in China shows different trends in time and space.In general,China's floodplain has a dense population distribution,most of which are distributed in eastern China and are clustered in three major urban agglomerations.The population in floodplain has grown rapidly and shows a difference trends during last decades.It has has grown rapidly in East and maintained rapid growth in the three major urban agglomerations.The distance from bulit-up land to water bodies in floodplain of China is shorter than that outside the floodplain.The bulit-up land in Chinese floodplain is generally close to the water bodies,and it has the largest area growth near the water body.The bulit-up land in the floodplain of the Western region is close to the water body.a majority of the newly appeared bulit-up land in floodplain distributed close to water bodies within 3 km.The temporal and spatial variation characteristics of the exposed population of China's floods and the relationship between exposed bulit-up land and water bodies shows the dynamic characteristics of flood exposure in China,which has important scientific significance for understanding the flood risk dynamics in China. |
PDF Full Text Request