<b> Três Marias bank´s morphodynamics – Rio Grande bar </b>

Abstract

The shoreface near the West jetty of the Lagoa dos Patos inlet was surveyed detailly. Beyond the bathymetric data, sediment samples were collected. The data showed a scour hole near the head of the jetty, and a shoal located SW the structure. The shoal starts at isobath of 8 m and its crest is located at the isobath of 6 m. The feature is almost oval, its greatest axis (NNE- SSW) is almost 1600m long,123; the smallest is 1200m. The shoal was identified like what have been left from the ebb tidal delta that used to grow in the lagoon inlet. The scour hole presents high slope, starts at 8m and ends at 17m. We supposed it is generated by interaction of coastal currents and the jetty. The samples of sediment evidenced the different energy regimes in each environment. Fine and very fine sand at the shoal and the surf zone respectively showed a more energetic regime, and the mud in the scour hole highlighte d an low energy environment.