MORPHOMETRIC CHARACTERIZATION OF BANHO AND CAÚRA BEACHES IN THE MUNICIPALITY OF SÃO JOSÉ DE RIBAMAR, SÃO LUÍS ISLAND, STATE OF MARANHÃO, BRAZIL

The aim of the present study was to perform a morphodynamic and sedimentary characterization of Banho Beach and Caura Beach, which are located in the municipality of Sao Jose de Ribamar, state of Maranhao, Brazil (2°33'25"S - 2°33'52"S and 44°02'21"W - 44°03'13"W). Morphodynamic and geological studies were performed on both beaches in campaigns carried out in the dry season (October 2016). Sediment samples were collected along the beach profiles at both beaches for the determination of grain classification and permeability. The direction of the coastal drift current was determined using a red organic fluorescent tracer at Banho Beach. The results showed a greater width of sediments on Banho Beach, with a 624-meter foreshore, whilst Caura Beach had a width of 105 m, with the advance of the tide at several points, as well as a trough system, sand bar and cliffs. Regarding granulometry, medium-coarse sand was found at Banho Beach and fine sand predominated at Caura Beach. The sediment permeability test showed an inverse relation to particle size. In the foreshore region, Banho Beach had a lower permeability coefficient (k) and a higher textural class (medium sand), whereas Caura Beach had a higher coefficient (k) and lower textural class (fine sand). Mean granulometry at Banho Beach was predominantly in the range of 1.48 to 1.79 ɸ, which is classified a medium-coarse sand, whereas the sand at Caura Beach was classified as fine (2.31 ɸ). The coastal drift experiment at Banho Beach revealed flow parallel to the coastline at a speed of 0.10 ms -1 . A B S T R A C T The aim of the present study was to perform a morphodynamic and sedimentary characterization of Banho Beach and Caura Beach, which are located in the municipality of Sao Jose de Ribamar, state of Maranhao, Brazil (2°33'25"S - 2°33'52"S and 44°02'21"W - 44°03'13"W). Morphodynamic and geological studies were performed on both beaches in campaigns carried out in the dry season (October 2016). Sediment samples were collected along the beach profiles at both beaches for the determination of grain classification and permeability. The direction of the coastal drift current was determined using a red organic fluorescent tracer at Banho Beach. The results showed a greater width of sediments on Banho Beach, with a 624-meter foreshore, whilst Caura Beach had a width of 105 m, with the advance of the tide at several points, as well as a trough system, sand bar and cliffs. Regarding granulometry, medium-coarse sand was found at Banho Beach and fine sand predominated at Caura Beach. The sediment permeability test showed an inverse relation to particle size. In the foreshore region, Banho Beach had a lower permeability coefficient (k) and a higher textural class (medium sand), whereas Caura Beach had a higher coefficient (k) and lower textural class (fine sand). Mean granulometry at Banho Beach was predominantly in the range of 1.48 to 1.79 ɸ, which is classified a medium-coarse sand, whereas the sand at Caura Beach was classified as fine (2.31 ɸ). The coastal drift experiment at Banho Beach revealed flow parallel to the coastline at a speed of 0.10 ms -1 . Keywords: beach profile; granulometry, sediments; coastal drift.

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