SEASONAL MORPHODYNAMIC BEHAVIOR OF ROMANA BEACH, GUARÁS ISLAND (NORTHEAST PARÁ), AS INDICATIVE OF COASTAL TRANSPORT IN THE AREA

Abstract

The Romana Beach is situated at the mouth of the Pará River, which gives it a high hydrodynamics, with winds (annual average of 4,6 m/s) and waves (annual average of 1,5 m) coming from NE, and semidiurnal meso-macrotidal (3,4 m – march, 4,3 m – august). It was found that this beach is dissipative, dominated by waves in the dry season (RTR < 3), and by waves and tides in the rainy season (> 3 RTR <7). The waves were higher than during the dry season (minimum of 1,49 m – eastern sector, maximum of 1,62 m – central sector). The angle of wave incidence (α) was higher in the west throughout the seasonal cycle, being increased by the rainy season (62° NE – January and 80 ° NE – March) for the dry season (85° NE – August ). In the central and western sector the angle did not vary much, being on average 20° NE and 25° NE, respectively. There was accretion of sediments 3 from the rainy season to dry season in the west sector (Vv end: 409 m /m), and erosion in central and 3 3 eastern sectors (Vv end: -306 m /m, -339 m /m, respectively). The coefficient of variation of the shoreline (CVYb) in the western sector ranged from 8,05% (March, the rainy season) to 9,08% (August, the dry season). In the central sector, this percentage has been decreasing: 8,30% (March) to 7,43% (August), as well as in the eastern sector: 16,43% in March to 13,33% in August. There was an almost standard behavior over the seasonal cycle for grain-size analysis: mean and asymmetry increasing from east to the west, and an increase in standard deviation and kurtosis of the western sector to the eastern sector. The beach is covered with fine sand (> 2 – 3 phi), preferably well selected and very well selected (<0.35 – <0.50 phi), and sediment transport is East to West.