Echo-bathymetry and acoustic characteristics of oceanic bottom in the Albardão channel region Rio Grande do Sul - Brazil

Abstract

The Albardão channel extends from the proximities of Punta del Este (Uruguay) to approximately the Albardão Lighthouse latitude (Rio Grande do Sul, Brazil), on mud depressions related to the ancient Plata River drainage channels. Bathymetric profiles with Bottom Surface Backscattering Strenght (BSBS) information were produced using hydroacoustic data collected on the southern continental shelf of Rio Grande do Sul, using a scientific echo-souder EK500 SIMRAD, operating at the nominal frequency of 38 kHz. The mean channel width in the region is 12,7 nautical miles (nm), and it´s length about 47 nm, occupying an area of approximately 670 nm2 (2.293,4 Km2). The statistical analysis indicates extremely significant differences between the average values of BSBS, inside (-16,04 dB) and outside (-9,96 dB) the channel, where lower values indicate softer bottom. A 3D surface of the channel shows it to be a continuous bathymetric feature, different from what is observed in the nautical chart No. 90 from DHN.