The characteristics of sediment transport occurring in the nearshore region are mainly produced by the interaction of the coastal morphological evolution and nearshore hydrodynamics from waves, wave-driven-currents and tidal currents. In this study, we discussed how various seasonal marine conditions can influence the characteristics of sediment transport in spatial and temporal with filed observations near the estuary of Cho-Shui River. The spatial distribution of grain size is decreasing alongshore from the estuary during summer, and is decreasing offshore from shoreline but no significant changing alongshore during winter. Comparing with the numerical simulation with DHI MIKE-21, it shows that sands banked up at estuary caused by an excess of river sediments transport with smaller grain size in summer, and that estuarine erosion results from the interplay of less river sediment transport supplied and hydrodynamic forcing scoured with larger grain size by waves in winter. In this paper, the different characteristic associated from seasonal marine conditions, river sediment transports, and estuarine morphologies have been discussed, and the influence of typhoon also analyzed.
Coastal and estuarine morphological evolution results from the interplay of nearshore hydrodynamic forcing, geological settings and river sediment transports. Where the nearshore dynamics is significantly strong, as on the estuary of Cho-Shui River Located at the narrowest channel of Taiwan Strait, it is easily found large tidal range, strong tidal current, strong wind wave, strong winddriven- circulation and high river sediments transport as consequences of the forcing. For the requirement of coastal managements and appropriate developments in the feature, the establishment of the background environment database is very important. Field observations are an indispensable tool to quantify actual physical processes occurring in the nearshore region, such as wave transformation, tidal and nearshore current, sediment transport, and beach change.
