厦门岛海岸线分形特性演变规律的研究

Fractal Characteristics Evolution of Coastline of the Xiamen Island

滨海城市海岸线的空间特征演变规律及其影响因素对于陆海统筹的空间规划具有重要的研究意义。将改进的归一化水体指数(Modified Normalized Difference Water Index, MNDWI)和Canny边缘检测法相结合,从Landsat遥感影像中提取了厦门岛1976-2018年共九景海岸线,并对其进行分形分析。采用自主编写的图像分形维数计算程序计算了研究期间厦门岛海岸线的盒维数,总结分析了其变化趋势以及变化原因。结果表明:厦门岛的海岸线具有分形特性,其盒维数的变化范围为1.098 9~1.118 1,先后经历降低、增加、再降低和最后缓变四个阶段,总体呈现下降的趋势;进一步分析,发现厦门岛在快速发展进程中,海洋工程对海岸线空间形态复杂性有显著的影响,其中,填海造陆工程的实施导致海岸线盒维数降低,而港口、码头建设却导致盒维数增加。盒维数的变化程度间接反映了海洋工程对海岸带的改造程度。本研究对厦门海岸线分形特征的分析,可为该区域资源开发、生态保护和城市规划提供有价值的参考依据。

The spatial evolution characteristics of coastal cities are of great significance to spatial planning. This study combined the Modified Normalized Difference Water Index(MNDWI) and the Canny operator to extract the coastlines of the Xiamen Island from 9 landscapes of Landsat remote sensing images between 1976 and 2018. Then we developed a program to calculate box-counting dimension. The results show that the coastlines of Xiamen Island have fractal characteristics. During the study period, the box-counting dimension varies from 1.098 9 to 1.118 1, which has experienced the stages of evolution: decreasing, increasing, decreasing, and then keeping steady. Further analysis shows that the evolution of coastline box-dimension is closely related to the ocean engineering during different periods. The implementation of land reclamation project leads to the decreasing of box-dimension, while the construction of ports and wharfs increases box dimension. This study might provide valuable information for resource exploration, ecological protection, and urban planning in coastal cities.