Migration of Intertidal Sandbanks, Bahia Blanca Estuary, Argentina

Abstract

Bahia Blanca is a mesotidal coastal-plain estuary characterized by a shore-connected ebb tidal delta closing the mouth of the Main Channel, an unusual feature in this kind of estuary. The study area comprises a series of banks and channels cut through the southern lobe of the ebb delta. The objective of the study is to determine the evolution of the banks in the last 160 years and to define their formation process.

To study the dynamic conditions of the area, a transport model was applied, considering the predominant tidal current. Seismic information was available to define the subsoil structure. Historical maps dated back to 1833 to present and currents were employed to determine the movement of the banks. The geoforms migrate toward the west up to the Main Channel where the stronger ebb currents prevent a westward transport of the sediments. The detected migration is only a local process. This observation rejects previous theory that supposed a large sand transport toward the west that might fill the estuary.