Transport and retention characteristics of floating debris in the Han River Estuary

• Published in: Marine pollution bulletin Vol. 222; no. Pt 2; p. 118670
• Main Authors: Do, Hyewon, Kim, Jong Wook, Woo, Seung-Buhm, Song, Yun Ji, Yoon, Byung Il, Lim, Chaewook
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2026
• Subjects: Drifter; Freshwater discharge; Han River estuary; Retention; Spring-neap variations; Drifter; Spring-neap variations; Han River estuary; Retention; Freshwater discharge
• ISSN: 0025-326X; 1879-3363; 1879-3363
• DOI: 10.1016/j.marpolbul.2025.118670

The Han River estuary is subject to strong tidal transformations due to its complex topography and shallow depth, making it a potential hotspot for the retention of floating marine debris. However, research in this region remains limited due to restricted access as a designated military protection zone. This study quantitatively analyzed the movement, retention, and seaward exit of GPS-tracked drifters in response to seasonal variations in freshwater discharge and tides in the coastal waters near Ganghwa Island. A total of 49 drifters were deployed at three stations over a six-month period, and their trajectories were assessed in relation to changes in discharge and tidal conditions. Most drifters remained confined within the narrow channels near Ganghwa for over a month due to tidal influence and repeated grounding–refloating cycles. Only about 12 % exited the estuary, primarily during periods of high freshwater discharge (top 5 %), through the northern Ganghwa channel. During lower discharge periods, drifters tended to stay near intertidal zones or became immobilized after grounding. Drifter movement was most active during spring tides or during transitions to neap tides, with current velocities nearly twice as high during spring tides. Notably, seaward exit also occurred under neap tide conditions when intertidal exposure was reduced. These findings suggest that the transport and retention of marine debris are governed by the combined effects of freshwater inflow, tidal cycles, and geomorphology. The results provide a scientific basis for modeling debris dynamics and inform environmental management strategies for the Han River estuary and surrounding areas. •Drifter residence exceeds one month due to flow reversal and grounding.•Over half of grounded drifters refloat within 3 days as tide rises.•Drifter escape occurs when daily discharge ranks in top 5 % from rivers.