Sonography and interferometric bathymetry of the Açù river estuary, Macau-RN

摘要

The objective of this work is the morphology characterization and identification of underwater textural patterns of the Açú river estuary. The estuary of the Açu river is located in the northern coast in the Rio Grande do Norte state, in the city of Macau, and geologically inserted in the Potiguar Basin. The 4600 multi-beam interferometric echo sounder, manufactured by Edgetech, was used for the acquisition of bathymetric and sonographic data, installed on the Spirit of Noronha vessel. The package data consisted of 21 sonographic and bathymetric profiles, resulting on the acquisition of approximately 16 million bathymetric points. The software used for the processing of sonographic and bathymetric data were Sonarwiz and Hypack, respectively. After filtering and processing of bathymetric and sonographic data the software ArcGis 10.1 and Surfer 11 were used to make a bathymetric map and Digital Elevation Model (DEM). Sonographic images indicate the presence of three underwater backscatter patterns in the Açú river estuary. Asymmetric underwater dunes with sinuous crest and ranging from small to large scale were also observed. The bathymetric data contributed to the morphological characterization of the estuary, such as the identification of sandy banks and channel locations. The sinuousity of the main channel is influenced by the flood and ebb phase tidal currents, as well as by the fluvial runoff. The ebb phase tidal currents and the river runoff act mostly on the main channel, on the other hand, the flood phase tidal currents are most important in the shallowest areas of the estuary.