Temporal and spatial variation of coastline using remote sensing images for Zhoushan archipelago, China

The acquisition of dynamic information on the coastline is of great significance for the Zhoushan archipelago. However, a large amount of suspended sediments, a tortuous coastline, numerous tidal flats, and so on have brought many challenges to research involving coastline extraction and the analysis of the spatial–temporal dynamics. This study has developed a method for extracting coastline information using multi-temporal remote sensing images based on tasseled cap transformation and mathematical morphology, allowing the temporal and spatial evolution of the coastline to be analyzed. The results showed that the proposed method can effectively attenuate the influence of suspended sediments, winding coastline, and shoals on the extraction of coastline information, and allow researchers to extract the spatial position of the coastline more accurately. The total coastline length of the Zhoushan archipelago increased by 327.36 km during the study period from 2000 to 2018, the average growth in length was 18.19 km, and the average growth rate was 0.72% over the 19-year period. The total area enclosed by the coastline of the Zhoushan archipelago increased by 112.26 km2 during the study period from 2000 to 2018, the average growth in area was 6.24 km2, and the average growth rate was 0.49% over the 19-year period. Construction, reclamation, and ocean engineering are the main causes of changes to the coastline of the Zhoushan archipelago. This study is useful for accurate coastline information extraction using remote sensing images in a complex marine environment and for protecting coastal resources in the archipelago.