Typhoon-induced sediment dynamics: Effects of extreme winds on resuspension and transport in Yeosu Bay, Korea

Typhoons significantly influence sediment resuspension through the mixing induced by strong winds, which alters the local current patterns and sediment dynamics. An acoustic Doppler current profiler was moored in Yeosu Bay from August 19 to September 20, 2022, to investigate the effects of typhoon on sediment transport mechanisms. Before the typhoon, the mooring station exhibited a strong stratification of water column caused by freshwater inflow from the Seomjin River. On September 6, 2022, Typhoon Hinnamor passed through the study area, disrupting the semi-diurnal current regime and associated sediment transport. Under the influence of the typhoon, the residual current profile transitioned from a two-layered structure to a fully mixed structure. Strong winds (~16 m s^–1) affected the stability of bed sediments and stratification, resulting in significant differences in suspended sediment concentration (SSC) during spring tides before (S_I) and after (S_II) the typhoon. Despite similar current-induced bed shear stress, the SSC during the S_II period reached up to 350 mg l^–1, which was about four times higher than during the S_I period (87 mg l^–1). Near-bed sediment fluxes controlled by tidal pumping increased during the S_II period (54%) compared to the S_I period (29%) and transport landward. This suggests that suspended sediments advected from the Seomjin River due to the typhoon settled in Yeosu Bay, resulting in the bed stability decrease. Along with suspended sediments, the typhoon led to an input of terrestrial nutrients from the Seomjin River, which could affect the biological productivity of Yeosu Bay. The results from this study indicate that Typhoon-induced disturbances of coastal currents could significantly affect sediment resuspension and transport, highlighting the complex interactions between meteorological forcing and sedimentary processes in coastal environments.