The 12th International Conference on Scour and Erosion (ICSE 2025)

104 / 2025-04-24 12:56:06

Examining how environmental factors affect suspended sediment plumes in coastal seas

sediment plume; salinity; river discharge; wind stress

Sediment plumes form when low-density waters with elevated suspended sediment concentrations (SSC) from tidal estuaries enter coastal regions and continental shelves. This study numerically examined the influence of environmental factors on suspended sediment plumes on the continental shelf near the Danshuei River estuary using the unstructured-grid three-dimensional hydrodynamic model (SCHISM) coupled with a suspended sediment (SS) module. The SCHISM-SS model was calibrated and validated with in situ measurements from 2016, accurately replicating water levels, velocities, salinities, and suspended sediment concentrations. The model was then used to assess the impact of various environmental factors on the dynamics of suspended sediment plumes from the estuary to adjacent coastal seas, including tidal forcing, salinity, river discharge, and wind stress. Results showed that tides significantly influence sediment plume dynamics, with a larger plume flux under tidal motions extending its distance. Additionally, sediment concentration offshore was higher during neap tides compared to spring tides. Salinity differences were found to affect density current movement and plume spread, extending the plume’s reach due to residual circulation. Extreme river flows, such as those caused by typhoons, increased water discharge, expanding the sediment plume further offshore. Prevailing wind directions had a minor influence on sediment plume behavior.