Monitoring And Analysis Of Spatial-temporal Changes Of Coastline In Hainan Island In Recent 30 Years Based On Remote Sensing

Hainan Island is located at the southernmost point of China,which has unique geographical position advantage and marine resource advantage,plays an important strategic fulcrum role in the construction of the "Maritime Silk Road",and bears duty-bound responsible in the South China Sea Strategy.With the development of the coastal economy,phenomena of coastal resources loss and coastline erosion and retreat appeared in the coastal zone of Hainan Province,and problems such as overexploitation of the coastal resources have become increasingly prominent.In order to explore the characteristics and causes of the change in coastlines of Hainan Island,and to well maintain the excellent resources and ecological environment in Hainan coastlines,this paper analyzes the temporal and spatial variation characteristics of the coastlines over the past 30 years based on the Landsat TM/OLI image of Hainan Island and using the combined method of remote sensing and GIS.Besides,by building the analysis model of the coastline change driving factors,this paper analyzes the status quo of the coastal development as well as the influence of human activities on coastline changes.The main research works are as follows:1.Coastline change analysis of Hainan Island:over the past 30 years,the total length of Hainan Island coastlines decreased first and then increased,and the length of the artificial coastlines significantly increased from 139.02km to 394.78km,with the length ratio increased from 8%to 24%,while the length ratio of the natural coastlines decreased from 91%to 76%.Among the natural coastlines,the length of muddy coastlines decreased most.The influence of human activities on the change in coastlines is becoming more and more prominent,and the comprehensive index of the coastline utilization degree is also continuously increasing.Under the influence of artificial development,the coastlines encountered erosion and silting,but the coastlines are expanding to the sea on the whole,leading to an increase in land area.2.Coastline change analysis of typical coastal segments:in this paper,in view of coastal segments with significant coastline change in Hainan Island,the temporal and spatial variation characteristics of the coastlines are expounded in detail:(1)the coastline change in Haikou is mainly concentrated in the Haikou Bay and Dongzhai Harbor,and the main causes include harbor construction,urban expansion and fish farming.As a provincial capital,Haikou has gotten rapid economic development after the reform and opening up,and people's rebuilding of the coastal zone is becoming increasingly intense.As a result,the utilization degree of coastlines in Haikou has increased and the conservation rate of natural coastlines has declined;(2)the areas with significant coastline change in Danzhou are located in the Danzhou Bay,and the main forms of coastline change include pond aquaculture and sea reclamation.Prior to the end of 1990s,the forms of human exploration of the coastal zone mainly included cultivation and salt pan construction,and the development of fish farming reduced the area of Danzhou Bay.After entering the 21st century,the development forms of the coastal zone are dominated by urbanization and industrialization construction,and the project of Yangpu Economic Development Zone has led to the expansion of the coastline to the sea;(3)the changes in coastlines of Qionghai City are mainly concentrated in Wanquan River of Bo'ao Town and the lagoon in Shamei enclosed sea.The form of the coastline changes is complicated,including the change of the estuary coastline position,the erosion and retreat of the sandy coastline,the increase of the aquaculture coastline caused by construction of fish ponds and the lagoon area lessening,and the above changes are most significant between 1995 and 2000.3.Analysis of the causes of coastline changes:accreted population,enhanced urbanization level and increased agricultural acreage exert a significant impact on the coastline changes of coastal cities.With the development of coastal economy,the impact of reclamation engineering,enclosing sea and cultivating and harbor construction on coastline length is becoming more and more prominent.In addition,because of the unique climate characteristics of Hainan Island,natural factors such as typhoons,storm surges and sea level rise are also aggravating the erosion of the coastlines.This study reveals the dynamic change characteristics and the changing causes of the coastlines in Hainan Island over the past 30 years,which can provide an information and technical support for promoting the rational utilization of Hainan Island coastlines,protecting the ecological environment of the coastal zone and driving sustainable economic development of the coastal zone.