Morphodynamics of the Lagoa do Peixe inlet, south coast of Brazil

Abstract

The inlets morphology is a result of the environment in which they are, as well as all active physical variables. If the mouth is situated in coastal areas, the trend towards instability is amplified by the environment itself. This paper presents the results of a morphodynamic study of the communication inlet between the Lagoa do Peixe and the Atlantic Ocean, located in Lagoa do Peixe National Park, middle coast of Rio Grande do Sul, Brazil. It is also measured the variability of adjacent shoreline to the park. In order to determine the classification of the inlet and its natural dynamics, was used series of 47 years of Landsat images (1973-2009), rainfall data of the National Water Agency and equations. The interpretation of the time series and the calculation of averages precipitation allowed to describe the Lagoa do Peixe inlet as a tidal inlet, with silting morphodynamic mechanism, influenced by the rainfall regime. The results of the equations indicated as key factors to its occlusion tidal prism, sediment transport and deposition in front of the mouth, associated with the longshore bidirectional pattern of the study area. The inlet has intermittent character and is unstable on its position and geometry. The mobility of the adjacent shoreline to the Lagoa do Peixe National Park was verified by the method of extreme points, pixel by pixel, between two Landsat images of the same month, one of 1987 and other of 2009, erosion being found south of the mouth of the Lagoa do Peixe inlet and accretion to the north of it.