Sandbanks in a tidal environment: Bottom features and sedimentary dynamics

Abstract

Tidal sandbanks are sedimentary features com monly found at the inlets of the tidal channels of Bahía Blanca Estuary (south Buenos Aires Province). To improve our understanding of the processes and mechanisms responsible for the formation and maintenance of the tidal sandbanks in estuaries, we carry out this study. We focus in a tidal sandbank located at La Lista channel mouth, denominated La Lista bank. It has an elongate shape with 4 km long. Bathymetric surveys, side-scan sonar records, grain-size characteristics of bottom sediment and bottom current measurements were used to define the hydrodynamics and sediment transport. Ebb-dominant current is the source of sand for this its south face is flood dominated, whereas the opposite face is ebb dominated, resulting in a clockwise residual transport. The rate of net bedload sediment transport estimated on the southern side of the sandbank is 0.00451 g cm^-1 sec^-1 in the flood direction and on the northern side is 0.02188 g cm^-1 sec^-1 in the ebb direction. Over the last years the shape of this bank have undergo several modifications and the accumulation of sand resulted in the lengthwise and elevation growth of it.