20世纪40年代初以来中国大陆沿海主要海湾形态变化

受气候变化和人类活动的影响,中国海岸带正在经历各种剧烈的变化,海湾形态变化是其中的一个重要方面.基于地形图资料与遥感影像提取20世纪40年代初至2014年7个时相的中国大陆沿海主要海湾的空间信息,进而分析海湾岸线类型结构,开发利用程度和空间位置的变化特征,以及海湾面积,形状和重心分布的变化特征.结果表明,20世纪40年代初以来,中国大陆沿海主要海湾的形态变化显著且复杂,主要体现为:海湾岸线的结构变化显著,自然岸线的长度和比例急剧减少;海湾岸线的开发利用程度持续增强;海湾岸线普遍背陆向海运动;海湾面积普遍大幅萎缩;海湾形状总体趋向复杂但个体间的差异在缩小;海湾重心分布位置普遍背陆向海迁移;海湾变化具有显著的时空差异性等.总的来说,以围填海为主的人类活动是导致海湾发生上述变化特征的主要原因.通过研究,指出应该对中国的海湾进行功能定位划分和分类管理,通过强化以海湾为基本单元的管理,促进中国海岸带综合管理能力的提高和管理目标的实现.

Shape changes of major gulfs along the mainland of China since the early 1940s

Impacted by climate changes and human activities, the coastal zone of China has undergone various dramatic changes, among which, shape change of major gulfs (including bays and estuaries) is one of the most important aspects. In this paper, spatial dataset of gulf shoreline and gulf shape in seven phases since the early 1940s was delineated based on topographic maps and remote sensing imageries, and a group of indices including the ratio of natural shoreline, the shoreline utilization degree, shoreline swing direction, gulf area, gulf shape index and gulf centroid were used to analyze the spatial-temporal characteristics of gulfs in detail. It turned out that: in general, shape changes of major gulfs in the mainland of China were significant and complicated during the past 70 years, specifically, visible changes of shoreline structure, especially the decreases in both length and ratio of natural shoreline took place; the shoreline utilization degree increased remarkably because more and more natural shoreline had been artificalized; the fact that shoreline seaward shift caused by sea reclamation occurred in the majority of gulfs; spatial size (area) decreased in most of gulfs due to the fast and extensive sea reclamation; the geometric shape of most gulfs had become more complicated while the discrepancies among all the gulfs were narrowed; the centroid of most gulfs moved toward the sea; gulf-shape variations exhibited remarkable spatio-temporal differences. It is obvious that human activities, especially sea reclamation, have become the key driving force of gulf shape change since 1990. Based on the above-mentioned findings, classification management strategy based on dominant-function oriented gulf classification is strongly recommended, and gulf-based management should be strengthen in order to improve the abilities of Integrated Coastal Zone Management (ICZM) practices in China.