Sediment Transport of Estuary Entrance Shoals and the Formation of Swash Platforms

ABSTRACT Sand shoals which extend seaward of Georgia estuary entrances are affected by a variety of sedimentary processes. Among these the interaction of waves and tidal currents appears to be most important to the sediment budget. As waves approach the shoreline they are refracted and wrap around the shoal margins. Wave crests interfer over the shoal surfaces and result in surges of water toward the shoreline. Waves also commonly "break" at points of interference and create wave bores which travel shoreward and interact with tidal currents. During the ebbing tide, this interaction is of particular importance to the sediment budget of the shoals. Sediment being transported seaward by tidal flow is diverted landward in gyral-paths by wave bores. The resultant "sediment gyres" are "dynamic sedim nt traps" which cause accumulations of sand in swash platforms. Swash platforms associated with shoals can be recognized by the sand-body geometry and characteristic internal structures.