Morphodynamics of the Tramandaí Lagoon inlet (RS, Brazil)

Abstract

The link of the lagoon bodies with the ocean occurs through of the inlets, which are also important ways to sediments exchange. The morphodynamics of this environment is controlled by a series of variables, such as tidal prism and channel geometry, amongst others. The interactions between these variables can cause a modification of the inlet geographical position. The knowledge of these parameters and interaction processes is extremely relevant for preservation and management of lagoon systems. This work analyzed the stability of the mouth of Tramandaí Lagoon, based on hydrodynamic, sedimentological and morphological data, integrated in a spatial and temporal analysis. The mouth of the lagoon is located between the beaches of Tramandaí and Imbé (north coast of Rio Grande do Sul) and is fixed by a rip-rap structure along its left margin. The methodology applied in this analysis consisted of bathymetry measurements, geoprocessing techniques and calculation of the empirical stability relations. It was possible to note that prior to fixing the left margin of the channel, the mouth migrated to the NE following of the predominant littoral drift. The analysis of the relations of physical stability allowed to conclude that the channel presented strong instability before the work of fixing the mouth. After the construction of the rip-rap, the minimum transversal section of the inlet has been fixed and there are no silting records.