Navegando por Assunto "Praia da Romana - PA"

Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Avaliação experimental de métodos de armadilhas de sedimentos para determinação do transporte costeiro da praia da Romana, ilha dos Guarás (nordeste do Pará)
(2012) RANIERI, Leilanhe Almeida; EL-ROBRINI, Maâmar
The Romana Beach is ruled by waves, with an average height of 1,5 m, winds (average of 4,6 m/s) predominantly from the NE and semidiurnal meso-macrotidal (ranging from 4,3 m - march/2010; 3,4 m - august/2010). The methodology consisted of sediments samples with traps and intensity measurements of longshore currents and local winds during the months of january, march and august 2010. In the wind traps, the accumulated weight of sediments was very low, ranging from 0,02 g to 0,8 g (maximum occurred in August in the eastern sector, as well as the wind speed: 6,7 m/s). Larger quantities of sediment were collected from the eastern to the western sectors, coinciding with the prevailing wind direction (NE), whose maximum speed occurred in august (6.7 m/s in the eastern sector). In the portable traps, the minimum weight occurred in march (eastern sector, ebb tide: 0,74 g/h/m3), and the maximum in january (central sector, rising tide:139 g/h/m3). The intensity of the longitudinal currents ranged from 0,20 m/s (ebb tide) to 1,41 m/s (rising tide). It was concluded that the largest forcing of sediment transport on the beach is the flood tide current, which intensifies the longitudinal currents from the eastern to the west sectors. Secondly, the NE winds which minimize the loss of sediments on the beach, especially in the central and eastern sectors. Then the waves, maintain the direction of E-W transport because to their incidences on the coast with direction NE.
Acesso aberto (Open Access)
Morfodinâmica e transporte de sedimentos na praia da Romana, Ilha dos Guarás (Nordeste do Pará)
(Universidade Federal do Pará, 2011-03-03) RANIERI, Leilanhe Almeida; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429
Coastal processes, waves, tides, currents generated and winds, model the beach face shape and contribute in the transporte and distribution of sediments on beaches. Due to the performance of these procedures, conducting experiments is severely hampered by high levels of turbulence generated by breaking waves. In sand beach, the winds gain the function of the transporte and distribution of the sediments deposited by the spreading of the waves. In Romana Beach, progradational beach ridges oriented toward W indicate the predominant sediment transport in this direction. The main objective of this study is to analyze the dynamics of this transport on the beach. The Romana barrier beach is situated at the mouth of the Pará River, an area of high hydrodynamics, is dominated by waves (RTR <3) in the less rainy period, especially during the ebb tide, and dominated by waves and tides (> 3 RTR <7) in the rainy season, mainly by flood tidal currents. The tidal regime is dominant in macrotidal beach in the rainy season (height of 4,3 m - March 2010) and in the less rainy season mesotidal (height of 3,4 m - August 2010). The incident waves at Romana Beach (on average 1,5 m in height) are primarily Northeasterly winds as they arrive on the beach in this preferential direction. The currents generated by waves propagating to the direction W, as well as the dominant tidal current on the beach: flood tidal current. The methodological procedures were applied the second beach two sets: (a) experimentation of traditional methods and (b) of alternative methods for sediment transport. The first was applied in the submerged part of the beach, through the realization of cross-sections of beach areas in West, Central and East, and measurements of speed and direction of local winds in the high tide line of each profile. The second is the application of sediment traps in the high tide line (submerged part of the beach) and in the surf zone (the submerged part of the beach) of each sector of beach, and measuring the intensity of coastal currents, the height, period and angle of incidence of waves on the submerged part of each profile. Data acquisition occurred during four field campaigns, adopting the seasonal water cycle: (a) seasonal transition to the less rainy period during the rainy season (January 2010), (b) in the middle of the rainy season, in March 2010 (equinoctial tide day) and May 2010, and during (c) less rainy season (August 2010). Throughout the seasonal cycle studied, we obtained positive final volume of sediments in Sector West (409 m3/m) and negative in the Center Sector (-306 m3/m) and the Eastern Sector (-339 m3/m). The final coefficient of variation of beach width was 9,08% in Sector West, 7,43% in the Central Sector, and 13,33% in Sector East. Note the predominance of fine sand (> 2 phi to 3 phi) well sorted (0,35 phi to < 50 phi) and very well sorted (<0,35 phi) in viii Romana Beach. Data for application of granulometric statistical parameters in the emerged part of the beach indicate the predominance of sediment transport towards E-W, it was found that the values of Mean size are growing of East Sector (minimum value found: 2,31 phi in August 2010) to West Sector (maximum value obtained: 3,37 phi in August 2010), also implying the increase in the degree of skewness in that order (Sector East to Sector West), and the degree of sorting and kurtosis increases for the West Sector to East Sector. Larger wave heights (> 1,3 m), intensity of coastal currents (> 0,3 m/s) and larger amount of sediment retained in traps wind (> 0,02 g) occurred in Sector West, also indicating the predominance sediment transport in the direction E-W. During high tide, increasing the amount of sediment retained in sediment traps used in the surf zone, especially the finer sediment and in the background traps, as well as increases the intensity of longshore currents (maximum value in West Sector in January: 1,41 m/s) of wave height (maximum of 1,62 m in the Center Sector in August) and the intensity of the winds (7,5 m/s in Sector East in August). This is due to the influence of tidal currents to be greater than the flood currents ebb in Romana Beach. It was concluded that the most significant forcing acting in the study area corresponds to the flood tidal currents (flowing and intensifying East Sector to West Sector) and, secondarily, the winds flowing in the same preferred direction, keeping the sediment supply towards W.