Sediment bank contribution to form a vortex and maintain a deep scour hole on tidal channel meander in the Bahía Blanca estuary, Argentina

Abstract

A wide range of processes determine the hydrodynamics and sedimentary balance in tide-dominated estuarine environments. Tidal channels can be subject to the most energetic processes. Therefore, changes in their geomorphology require continuous updates. Through oceanographic surveys, were collected in situ hydrodynamic, bathymetric, and sedimentological data in a section of the Canal del Medio in the Bahia Blanca Estuary (southwest of the Buenos Aires Province, Argentina) to examine the possible effect that the presence of a sediment bank can have on the tidal current pattern within a specific meander. An unusual elliptical deep scour hole was detected with a depth of 12.60 m in the thalweg of the meander (tidal range is about 3 m). Based on the data, it was found that the maintenance of the scour hole is possible because of a vortex forced by the presence of an elongated sandy bank connected to the tidal channel bank that acts as a hydrodynamic barrier to the currents, inducing the modification of the meander pattern.