The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

The transport processes of suspended sediment from river sources to ocean sinks are crucial for the global material cycle. This study investigates the wind and wave effects on hydrodynamics and riverine sediment transport over a continental shelf during a typical year, utilizing the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) model. Through meticulous calibration, the model accurately replicates various marine environmental parameters observed during the study period. Key findings indicate significant riverine sediment retention near the estuary (~62%), primarily riverine sediment transport along a southwestward pathway, and deposition in the Beibu Gulf, supported by previous studies revealed by gravity core sediments, surface sediment samples, and seismic survey data. During the wet summer season, when winds and waves are relatively calm, riverine sediments are initially carried by the river plume and deposited near the estuary. Conversely, in the dry winter season, stronger winds and waves resuspend and transport previously deposited sediments. Diagnostic analyses unveil the significant influence of winds and waves on surface/bottom boundary layers and shelf circulation. These alterations intensify riverine sediment resuspension and elevate the nearshore suspended sediment concentration (SSC). Additionally, intensified cross-shore gradients of water level and density enhance westward geostrophic flow and thermal wind vertical shear, facilitating the riverine sediment transport to distant regions, and the westward flux in the wind and wave scenario is three times as much as that of the no wind or wave scenario. This study provides valuable insights into the complex relationship between winds, waves and riverine sediment dynamics on continental shelves.