近15年洞头五岛海岸线时空变化分析

Analysis on the Spatial and Temporal Change of the Five Islands in Dongtou District from 2002 to 2017

洞头五岛相连工程连接的5个海岛的变化是洞头区发展的缩影,2002—2017年洞头五岛形态处于快速发展阶段。文章收集了2002年、2010年和2017年3期Landsat系列卫星影像,结合2010年、2014年两期0.5m分辨率DOM和2017年实地调查数据,采用RS和GIS技术提取3个时相海岛岸线,并分析了其15年来的时空变化特征。研究表明:2002—2017年海岛不断外扩,五岛面积增加约1290.8hm2;岸线日趋平直,平均曲折度由2.7变化为2.2,长度减少约12692m;自然岸线和人工岸线此消彼长,自然岸线保有率由90.3%降低到54.2%,新增人工岸线长约41927m,类型以道路和海堤为主;2002—2010年海岛形态及岸线人工化速率较2010—2017年快;岸线外推区内土地利用率不断提高,填筑形成的土地逐渐转化为建筑物、交通用地、人工绿化用地和水系等城市设施。

The five islands in Dongtou district are in a stage of rapid development from 2002 to 2017.Remote sense images of Landsat TM,ETM+ and OLI in the year of 2002,2010 and 2017,aerial photo with high-resolution in 2010 and 2014,field investigation data were processed to extract coastlines and landcover in the region formed by the coastlines of different phase based on RS and GIS technology.The results showed that: Affected by marine development activities,from 2002 to 2017 the five islands of Dongtou district had expanded outward at 6.4 m/a averagely,the area was increased by 1 290.8 hm 2,the length of coastline was reduced by 12 692 m,the average crooked degree of coastline reduced from 2.7 to 2.2.The area growth and coastline decrement of Dongtou were both the greatest in the five islands,the second was Zhuangyuanao;The natural coastline ratio decreased from 90.3% to 54.3%,and the artificial coastline increased by 41 927 m from 2002 to 2017.The new artificial coastline was dominated by seawall and road,accounted for 15.4% and 13.8% respectively in 2017.The type of seawall were mainly distributed in Dongtou and Zhuangyuanao where had large reclamation project,road was distributed in each island and mainly in Niyu and Dongtou.There was 8.6% of the total coastline in 2017 still under construction;With the continuous development of the five islands,the rate of natural coastline development slowed.The shape change and coastline artificialization speed of the five islands of Dongtou in 2002-2010 were all higher than 2010-2017 in this study;The land use rate of the new area was increasing and the land formed by reclamation projects was gradually transformed into urban facilities such as building,road,greening area and water from 2002 to 2017.The landcover change matrix between 2010 and 2017 for the region formed by coastline extrapolation from 2002 to 2010 showed that the landcover area of road,harbour,building and green area in the same area were more and more.The focus of local construction was shifted from land expansion to urban construction.By 2017,the road and water system had been basically formed in the reclamation region excepting southern of Zhuangyuanao.