AUTOMATIC SHORELINE EXTRACTION USING OPEN-SOURCE REMOTE SENSING TOOLS: A CASE STUDY IN HUNG YEN PROVINCE

Abstract

Coastline dynamics play a crucial role in coastal resource management and environmental monitoring, particularly in regions influenced by tidal processes, hydrodynamics, and climate change, such as the coastal zones of Vietnam. In this study, the authors propose a semi-automatic method for extracting shorelines from multi-temporal satellite imagery using open-source remote sensing tools, with a case study conducted in Hung Yen province for the period 2016–2024. The proposed approach focuses on improving the traditional Otsu thresholding algorithm by constraining the value range of the Automated Water Extraction Index (AWEI) and applying local thresholding to effectively reduce spectral noise caused by turbid water, wet soils, and cloud shadows. Quantitative analysis of shoreline changes during 2016–2024 reveals clear spatial variability: the northern sector remains relatively stable (±1 m/year), the central sector exhibits moderate fluctuations
(-2 to +2 m/year), and the southern sector shows significant dynamics, with erosion rates reaching -5 to -8 m/year and subsequent accretion of +4 to +6 m/year. These findings highlight the non-linear and heterogeneous nature of shoreline evolution in the study area. With advantages such as fully open-source implementation, low cost, and a high level of automation, the method is well suited for shoreline change monitoring in Vietnam and other regions with similar environmental conditions.