基于高分遥感的西沙群岛珊瑚礁沙洲稳定性评估

珊瑚礁沙洲是珊瑚岛形成的前一地貌类型，大多无植被生长，易受气候条件和水文动力条件的影响，位置不稳定，形态多变。本研究利用2005－2020年多期高分辨率遥感影像，分析了西沙群岛珊瑚礁沙洲的大小、形状变化以及平面位置移动过程，评估了珊瑚礁沙洲稳定性，并对其影响因素进行了初探。结果表明:（1）北沙洲、中沙洲、盘石屿和筐仔北岛相对稳定，而西新沙洲、三峙仔、全富岛和银屿仔尚不稳定；（2）珊瑚礁沙洲稳定性是沙洲沉积物供应、海洋动力环境条件和珊瑚礁地形地貌综合作用的结果，在相同的季风浪和台风浪作用下，各个沙洲由于在礁坪中所处位置和岸滩沉积物类型等不同，在不同的水动力作用下，形成了8个沙洲不同的演变过程和稳定状态；（3）建议在相对稳定的北沙洲、中沙洲、盘石屿和筐仔北岛上人工种植抗风、抗盐碱的植被（如木麻黄），促使其更快地由珊瑚礁沙洲发育成为珊瑚岛。西沙群岛珊瑚礁沙洲监测与评估结果可为南海珊瑚礁沙洲发育研究和西沙群岛岛礁建设与保护管理提供数据支撑。

Assessing the stability of coral reef sandbanks in the Xisha Islands using high-resolution satellite images

Coral reef sandbanks are the former landforms of the formation of coral islands. Most of them have no vegetation growth and are easily affected by climatic and hydrodynamic conditions. They are unstable in position and changeable in area and shape. Using the high-resolution remote sensing images from 2005 to 2020, the area and shape changes as well as the movement process of the horizontal position of coral reef sandbanks in the Xisha Islands were analyzed, the stability of the sandbanks was assessed and its influencing factors were discussed. The results show that: (1) Bei Sandbank, Zhong Sandbank, Panshiyu and Kuangzaibei Island are relatively stable, while Xixin Sandbank, Sanzhizai, Quanfu Island and Yinyuzai are yet in an unstable stage. (2) The stability of the coral reef sandbanks come from the integrated effect of sediment supply, marine dynamic environmental conditions and coral reef topography. Under the same monsoon wave and typhoon wave, each sandbank is affected by different hydrodynamic forces due to the different position of each sandbank in the reef flat and the different beach sediment types, resulting in individual evolution process and stable state of eight sandbanks. (3) It is suggested that the wind and salt resistant vegetation (e.g. Casuarina equisetifolia) can be planted on relatively stable Bei Sandbank, Zhong Sandbank, Panshiyu and Kuangzaibei Island, so as to accelerate the development of coral reef sandbanks into coral islands. The monitoring and assessment results of coral reef sandbanks in the Xisha Islands can provide data support for the study on the development of coral reef sandbanks in the South China Sea and the construction and protection management of islands and reefs in the Xisha Islands.