Morphodynamics of estuarine beaches on the east coast of Maraj Island, Eastern Amazon

The coastal zone is one of the most vulnerable geographic spaces on the planet, especially due to current climate changes. This research aimed to verify the seasonal morphological changes in beaches on the Amazonian coastal zone, located on the largest fluviomarine island on the planet (Ilha de Marajo). The methodology consisted of collecting topographic data on Barra Velha (municipality of Soure-PA) and Praia Grande (municipality of Salvaterra-PA), sampling of surface sediments from them and the classification of beach morphodynamic stages. Barra Velha beach was classified as dissipative beach (beta < 2), with fine sand (2 to 3 Phi) and an erosive tendency from the dry to the rainy season. The opposite was obtained for Praia Grande, whose morphodynamic state was intermediate to reflective beach (beta > 3), with medium sands (1 to 2 Phi) predominant. On this beach, the seasonal sediment variation ranged from-48 to 77 m(3)/m, showing alternating sedimentation in the upper and lower parts of the beach. On Barra Velha, sedimentation was more uniform (-30 to 48 m(3)/m). It is concluded that there was less mobility in the width of Praia Grande (Delta Yb: 18 m), compared to Barra Velha (Delta Yb: 38 m). It is believed that the results of this research can contribute to the understanding of morphosedimentary particularities in equatorial estuarine beaches.