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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. [ABSTRACT FROM AUTHOR]

The mechanisms controlling sediment transport at river mouths and estuaries nearby ports are complicated interactions among waves, tidal currents, and river flows over complex bathymetry. Episodic river discharge triggered by large rainfall may contribute to significant sediment into the ocean. Over the last decade, the exposed riverine sediment from the Zhuoshui River, north of Mailiao Port, is one of the major sources of sediment supply in this region. Previous field observations shortly after the passage of a typhoon suggested fine-grained sediments settled rapidly near the river mouth, and tidal currents and strong wind-driven waves during winter were the mechanisms that transported sediment toward the navigational channel. Numerical simulations provide insights into the patterns of residual circulations for a range of spring-neap tidal forces and wave conditions. Model results show that extending North Jetty could be one of the engineering countermeasures to modify the circulation system between the port and the river mouth to mitigate the siltation problem. [ABSTRACT FROM AUTHOR]