Abstract:
To reveal the changes in the coastline of Hailing Island in the past 30 years in both alongshore and cross-shore directions and to explore the main factors causing these changes, the visual interpretation method was employed to extract five different types of coastlines using 25 periods of Landsat TM/OLI remote sensing image data from 1991 to 2021 in this study. Focusing on the evolution characteristics and driving factors of the coastline at this famous tourist island in the past 30 years, the proportion of coastline length, the amount of coastline advance and retreat, the rate of coastline change, and the linear/non-linear evaluation of the coastline evolution process was studied. Results show significant changes reached 23% in both the proportion of artificial and sandy coastlines and at least 7% of sandy coastlines have been transformed into artificial coastlines. On an interannual time scale, bedrock coastlines experienced minor changes, while sandy and muddy coastlines exhibited alternating erosion and deposition characteristics. Artificial coastlines display a “sudden change” behavior, and biological coastlines show rapid and prolonged deposition features. In the past 30 years, the rate of change for bedrock, sandy, and muddy coastlines mainly ranged between −0.5 m/a and 0.5 m/a, indicating relative stability. Artificial and biological coastlines were primarily characterized by deposition, with a maximum deposition rate of 37.4 m/a. Occasionally, the landing tropical cyclones caused significant short-term erosion or deposition in sandy and muddy coastlines, but the evolution of these coastlines was mainly a linear process, remaining relatively stable under long-term wave conditions. In contrast, the evolution of artificial and biological coastlines showed primarily a non-linear process, influenced by human activities such as reclamation for aquaculture, afforestation of tidal flats, salt pans, fishing ports, and seawall construction. This study reveals the evolution processes, characteristics, and potential driving mechanisms of different types of coastlines on Hailing Island, providing important insights for the development, utilization, management, and protection of island resources.