| dc.description.abstract | Estuaries and tidal rivers are the primary conduit between river and coastal ocean. Estuaries are the semi-enclosed coastal water body which connects with the open sea, and they have the characteristics of inland river, such as flood and dry seasonal variations due to runoff. They also exhibit the characteristics of ocean, such as the flood and ebb tides. Therefore, the hydrodynamics and salinity characteristics of the estuary and tidal river are extremely complicated, and they also affect the transport processes of suspended sediment. The Danshuei River system is the largest estuary system in Taiwan and consists of three major tributaries: Tahan Stream, Hsintien Stream and Keelung River. In this study, the measured salinity and suspended sediment data including slackwater and intense surveys were collected in the periods of 2002 to 2004. The measured stations along the Danshuei River to Tahan Stream and Danshuei River to Keelung River were conducted, respectively, from 2002 to 2003, and in 2004.
A real-time, three-dimensional Hydrodynamic-Eutrophication Model (HEM-3D) was performed and applied to simulate salinity distribution and transport of suspended sediment distributions in Danshuei River estuarine. The boundaries of upstream (i.e. the Tahan Stream, Hsintien Stream, and Keelung River) are specified with constant freshwater discharge, salinity (with zero), and suspended sediment concentration. The downstream boundary is extended to the adjacent coastal sea and specified with tidal elevation, salinity, and suspended sediment concentration. Governing Equations are formulated in curvilinear-orthogonal horizontal coordinates and a sigma vertical coordinate. The comparisons of simulated result and field measurement in salinity and suspended sediment distributions were used to investigate and analyze the salinity stratification phenomenon and estuarine turbidity maximum (ETM) in the estuarine system. Moreover, the model sensitivity analyses were used to identify the vital parameter in the suspended sediment transport model. Finally, the numerical experiments were conducted with no saline effect, no sediment supply from the sediment bed, wind stress effect, and the influence by mean freshwater discharge to comprehend the influence on residual current and suspended sediment distribution in the Danshuei River estuarine system. | en_US |