北部湾海湾岸线时空变化特征研究

Temporal and spatial characteristics of the shoreline along the Beibu Gulf

人类活动对我国海湾生态环境的影响日趋严重,作为海湾变化的重要表征－海湾岸线自然成为陆海相互作用研究的主要内容之一.本文以西部大开发的前沿－北部湾海湾岸线为对象,利用Landsat系列影像反演1991、2005及2010年北部湾1595km的大陆岸线;选择1991～2010年间北部湾北部变化强烈的40个岸段,分析岸线的冲淤变化.结果表明：北部湾海湾曲折岸线的固有属性已发生改变,岸线平直化趋势明显;海湾岸线冲淤交互存在,相对遮蔽的岸段岸线积极向海推进,年淤积速率为23m/a,无防护地带的岸线以侵蚀为主,年平均侵蚀速率为24m/a;在不同类型的海湾岸线中,生物海岸与砂质海岸表现为向陆蚀退,年平均侵蚀14m/a,淤泥质海岸为向海淤积,年平均淤积速率为9m/a,基岩海湾岸线变化不大.

Anthropogenic activities have affected the ecosystem and environment of the Chinese gulf. The shorelineprovides an important reflection of geo-environmental changes in the gulf, and therefore land–ocean interaction in thecoastal zone is a focus of research attention. In the present study, the characteristics of the shoreline along the Beibu Gulfin 1991, 2005, and 2010 were examined by extracting and analyzing Landsat data using remote sensing and geographicalinformation system tools. A total of 40 shoreline segments of the studied area were selected to analyze the state of erosionand accretion of the shoreline. The analysis yielded the following conclusions. （1） There is an obvious straightening trend ofthe Beibu gulf shoreline over time, with the fractal dimension having decreased from 1.3375 in 1991 to 1.2615 in 2010. Thistrend may be a result of anthropogenic activities. （2） Deposition and erosion co-occurred during changes in the shoreline,whereby the accreting shoreline segments were located mainly in zone protected from the open ocean with a mean rateof accretion of 23 m/yr, and the eroding shoreline segments were located mainly in the zone exposed to the open oceanwith a mean rate of erosion of 24 m/yr. （3） Among the different types of shoreline, the biological coast and sandy coast bothretreated landward at a rate of 14 m/year. In contrast, the silt coast prograded at a rate of 9 m/yr, whereas the position of therocky coast remained static.