Navegando por Assunto "Erosão de praias"

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Acesso aberto (Open Access)
Análise das variações da linha de costa na Ilha de Mosqueiro- PA ao longo de 17 anos
(Universidade Federal do Pará, 2019-05-24) BRAGA, Carlos Alberto Oliveira; OLIVEIRA, Francisco de Souza; http://lattes.cnpq.br/8386440288477782
The average rates of coastline variation are one of the best indicators to determine the trend of the oscillatory behavior of any part of the coastline over time. The multi-temporal study of the coastline dynamics of the beach segments of Mosqueiro Island, PA, using the Landsat and Sentinel series of satellite imagery, the United States Geological Survey (USGS) and the European Space Agency (ESA) with the aid of the Digital Shoreline Analysis System (DSAS), demonstrated that during the period from 2001 to 2018, the total linear mean change for all beach segments was -81.3 m at a rate of -9.67 m / year. The average linear retreat was - 160.77 m, while the average linear advance was 79.47 m, indicating a clear erosion tendency of the Mosqueiro Island coast. From the 11 beach segments analyzed (Baia do Sol, Paraíso, Marahú, Carananduba, São Francisco, Ariramba, Murubira, Porto Arthur, Bishop / Praia Grande, Bitar), in the western part of the Island, 06 (São Francisco, Ariramba, Murubira, Porto Arthur, Bishop / Praia Grande and Bitar) showed a trend of retreat of their coastlines, presenting average rates of variation from -1.00 m / year to -3.31 m / year, the highest rate belonging to the Bishop segment /Big beach. The segments of Baía do Sol, Paraíso, Marahú, Carananduba and Farol / Chapéu Virado were the only ones that presented a tendency to advance in their coastlines, presenting values of average rates varying from 0.30 m / year to 1.74 m / year. In addition to the study of the behavior of the coastline of the western part of Mosqueiro Island, the classification of the physical vulnerability to the coastal erosion of the Island was carried out. In general, the coastal zones of the island bathed by Guajará Bay, Furo das Marinhas and Furo do Maguari were classified as "high to very high", with the exception of some sectors located in the northwest, northeast and southeast of the island. were classified as "low to moderate" vulnerability. The most localized areas in the center of the island not directly impacted by oceanographic variables were classified as "very low to moderate"vulnerability, in addition to some contiguous areas that were classified as "high" vulnerability.
Acesso aberto (Open Access)
Morfodinâmica costeira e o uso da orla oceânica de Salinópolis (Nordeste do Pará)
(Universidade Federal do Pará, 2014-12-15) RANIERI, Leilanhe Almeida; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429
The morphodynamic aspects related to erosion or accretion of the coastline are some of the topics analyzed in the management of coastal zones being discussed around the world in order to monitor and protect these zones. This thesis aims to analyze the behavior of the coastal morphodynamics of the Salinópolis, relating to the use of ocean margin. The study area was compartmentalized into three sectors: Western (Corvina and Maçarico beaches), Center (Farol Velho beach) and Eastern (Atalaia beach). The methodology consisted of: (a) acquisition and processing of multi-temporal images (1988-2001-2013) of the Landsat 5 TM, 7 ETM and 8 OLI; (b) application of interviews/questionnaires with bathers, (c) acquisition of field data during the rainy season (April 26th, 27th and 28th, 2013) and less rainy (045.5) prevailed at these beaches, but with the occurrence of the the longshore bar and trough state (4.7 <Ω <5.5) in the western sector. The macrotidals in the study area showed maximum height of 5.3 m (Center Sector during the less rainy season) and a minimum of 4 m in the same sector during the rainy season. The longshore currents were more intense in the eastern sector (> 0.45 m / s) during the two seasons of the year. The wave heights were also higher in the eastern sector (maximum of 1.05 m during the flood tide in the less rainy season) and wave periods were shorter (<4.5 s) in the western sector. The mean grain size obtained from sediments collected on the beaches had more frequent scale between 2.6 to 2.8 phi, indicating the predominance of fine sand. The predominant degree of sorting of sediment was 0,2 to 0,5 phi (very well sorted and well sorted), and asymmetry was positive (0.10 to 0.30) and nearly symmetrical (-0.10 to 0.10). The degree of kurtosis ranged from very platykurtic (<0.67) to very leptokurtic (1.50 to 3.00). Sediment accretion events were observed of the rainy season to less rainy season. From 07/22/1988 to 08/28/2013 (25 years) also predominated accretion, where the average linear advancement of the coastline was 190.26 m. The average linear retreat obtained for the entire study area was -42.25 m. The eroding areas are point: currencies from the beaches of Corvina and Maçarico, and Farol Velho and Atalaia. Portable traps indicated a greater quantity of sediment transported longitudinally in the less rainy season (minimum 280 g/m3: flood, west sector; maximum 1098 g/m3: ebb, east sector). In the traps applied in the swash zone, the balance of sediment entering and leaving the beaches was lower in the center sector (minimum 80 g/m3: ebb, maximum 690 g/m3: flood; less rainy season). The coastal sediment movement is derived mainly from effect of the tides, which are oriented toward the direction of the ebb and flow of the estuary crossing the coast. The data indicate the longshore transport of sediment from the Atalaia island and Sampaio River to the west sector and the beaches margins.