Case Study Downdrift Port Siltation Adjacent to a River Mouth: Effects of Mesotidal Conditions and Typhoon

The Zhuoshui River has one of the highest sediment yields in the world. The riverine sediment may have been transported away from the river mouth by strong tidal currents and deposited in a navigational channel and a harbor basin south of the Zhuoshui River. This study describes the dispersal of riverine sediments in mesotidal conditions, including transport processes of sediments via river plumes, initial deposition, resuspension, and long-term net accumulation. Our results revealed that the distribution of suspended sediment concentration (SSC) and the transport process of the river plume was markedly modulated by tidal currents in a north-south direction. Under high-discharge conditions, energetic winds and ocean currents interrupted the offshore propagation of the sediment-laden river plume with a high SSC to the ocean. The plume, induced by typhoon floods, was either propagated northward due to the Coriolis effect or was deposited near the river mouth. The sediments deposited within the inner shelf were resuspended by intensive tidal currents and transported through southward residual circulations to the navigation channel south of the river mouth.