Sediment transport trend in an erosive sandy beach: the case of Matinhos Beach, south coast of Brazil

Abstract

Sandy beaches have different shoreline change rates (i.e., erosion/accretion rates). An erosive process on beaches poses risks for human-occupied areas. One example is Matinhos Beach (state of Paraná -Brazil), which has an average annual erosion rate of around 1.5 m yr -1 This study applied a methodology that combines in situ measurements and numerical modeling to simulate the physical processes in the coastal area of Matinhos during the 2018 Austral winter. Monthly DGPS surveys were carried out in the study area from June to September. The MOHID modeling system was applied to simulate hydrodynamics and sediment transport, considering waves and tidal forcing validated with in situ data. The WAVEWATCH III and SWAN models were applied in a nesting approach to simulate the waves at Matinhos Beach. The GFS was used to assess the wind conditions. The study period showed a dynamic evolution of accretion and erosion between monthly measurements with no clear pattern in most profiles. Significant sand accumulation was observed near the headland. Morphological changes were minor due to the predominance of low energy without significant storm events. The measured morphological changes are in line with the residual littoral drift obtained from the modeling results for the period. The residual current velocities were towards the southwest, with magnitudes ranging from 0.15 m s -1 to 0.2 m s -1 . A slight variation in the angle of wave incidence (10°) may change the direction (southwest or northeast) and intensity of the littoral drift. The applied methodology can reduce uncertainty and support effective coastal management. However, the seasonal scales of wave climate cannot be disregarded, nor can the need for coastal oceanographic data.