Rugosity as a metric for seabed morphodynamics: Insights from a sand mining site in Gyeonggi Bay, Macrotidal Yellow Sea, Korea

초록

Marine sandpit morphodynamics have focused on broad-scale morphometrics like slope and depth changes, while finer-scale metrics such as rugosity, a dimensionless index used to quantify variations in seabed roughness, remain underexplored. This study examines the evolution of a sand mining site through rugosity, with specific objectives to: (1) characterise anthropogenic and natural bedforms, and (2) evaluate the relationship between rugosity and depth changes. The study site, located in Gyeonggi Bay, experienced sand extraction between 2019 and 2022. Bathymetric data (2017–2024) from the Korea Hydrographic and Oceanographic Agency were used to construct digital elevation models of the mining site (Site Z) and two adjacent control sites (X and Y). Depth and rugosity changes were quantified relative to a 2019 baseline, and spatial patterns were analysed using continuous wavelet transform and coherence analyses. The results show that mining at Site Z induced substantial morphological changes, with the pit expanding to a perimeter of 6281.18 m and a depth of 25.25 m, whereas the control sites exhibited minimal changes. Wavelet analysis revealed stable dominant wavelengths (∼75 m and ∼140 m) at control sites, but Site Z showed a shift from 142 m pre-mining to 310–490 m during mining, indicating the formation of large anthropogenic bedforms. Coherence demonstrated a morphodynamic association between rugosity and depth change, with synchronous interactions driven by sandwave migration at the control sites and mining at Site Z. These findings establish rugosity as a robust metric for assessing seabed morphodynamics under anthropogenic and natural forcings. © 2026 Elsevier Ltd.

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