Enhanced settling velocity and floc formation in response to dredging-induced plumes: In-situ observations from a coastal sand mining site

초록

In-situ observations were conducted to investigate suspended sediment dynamics within dredging-induced plumes at a sand mining site in Gyeonggi Bay, Korea. Combined acoustic and optical measurements captured the spatiotemporal variability in suspended sediment concentration (SSC) and settling velocity (W-s) during and after the dredging. Overflow discharge generated near-surface plumes with SSCs up to an order of magnitude higher than background levels, which were rapidly dispersed within one hour of dredging cessation. Particle size distributions revealed the formation of large flocs (>100 mu m) during active dredging, accompanied by increased Ws of 0.46-0.63 mm s(-1) . Post-dredging conditions showed reduced floc sizes and Ws (<0.1 mm s(-1)), indicating rapid floc disaggregation. Flocculation was enhanced by high cohesive sediment supply and organic matter under calm hydrodynamic conditions. The findings from this study provide essential insights for assessing the environmental impacts of dredging on marine systems and serve as a valuable foundation for developing sustainable sediment management strategies.

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