Navegando por Assunto "Praias amazônicas"

Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Caracterização dos padrões morfodinâmicos em cristas de praias na costa amazônica
(Universidade Federal do Pará, 2023-09-29) ROSÁRIO, Edineuza dos Santos; SANTOS, Valdenira Ferreira dos; http://lattes.cnpq.br/1395198888623953; HTTPS://ORCID.ORG/0000-0002-5038-4191; RANIERI, Leilanhe Almeida; http://lattes.cnpq.br/3129401501809850; https://orcid.org/0000-0002-9870-4879
Knowledge of beach environments requires an integrated morphodynamic approach using different spatio-temporal scales, in order to understand the role of coastal and marine processes in modifying beach morphology. There are some important peculiarities about these processes on the beaches of the Amazon region, such as the large hydro-sedimentary discharge from the estuaries, high rainfall rates and the high amplitude and intensity of the tidal currents, which shape the often complex beach systems, such as beach ridges. The objective of this research was to analyze the morphological dynamics of a beach ridge segment located north of the mouth of the Amazon River, in Goiabal (city of Calçoene), in the coastal ocean sector of the state of Amapá.The hypothesis is that the morphological changes in the segment of beach crest under study are influenced by the hydrosedimentary dynamics of the Amazon River. The research methodology was based on three stages: (1) determining the morphology of beach ridges and their changes (beach profile variation, sedimentary deposits and beach classification); (2) analysis of morphosedimentary processes (physical coastal agents such as tides, waves and currents, and sediment supply such as sediment plumes; (3) data integration (correlation between the processes analyzed in stage one and two). The results indicate significant average variations in the morphosedimentation of the Goiabal beach ridge system, with seasonal migration (~24 to ~42 meters) towards the mainland. Erosion and deposition on the ridges and subsequent channels averaged less than 0.30 m along the beach profiles during the seasonal cycle. The oceanographic parameters indicate an average wave height of 0.25 m and an average tidal range of 5 m. Coastal currents are directed west-southwest and there is a predominance of ebb tide currents during the rainy season. The sediment plume of the Amazon River was closer to the study area during the rainy season (~15 to 25 km), with a predominance of ebb tide currents. Thus, it can be concluded that the segment of beach crest studied has a greater influence from the Amazon River sediment plume during the rainy season, intensifying the deposition of fine sediments. The displacement of beach ridges and the supply of sediment have a strong relationship with tidal dynamics in the region.
Acesso aberto (Open Access)
Geoindicadores de vulnerabilidade à erosão em praias estuarinas, costa amazônica, Pará.
(Universidade Federal do Pará, 2022-04-19) NOVAES, Gabriela de Oliveira; RANIERI, Leilanhe Almeida; http://lattes.cnpq.br/3129401501809850; https://orcid.org/0000-0002-9870-4879
The coastal zone (CZ) is a region responsible for various ecological functions, and also object of concern due to its uses and anthropic pressures, which affect its balance and environmental integrity. The beach is one of the most important environments in CZ, due to its intense use by the human population, having ecological function for many organisms and being a natural protection against physical forcers (waves, tides and chains). The anthropogenic occupation on a particular beach can aggravate coastal erosion (natural process of the morphological amendment of the environment, due to the interaction with physical agents). This occurs on the island of Mosqueiro, object of study of this work, where erosive processes have been intensified in recent decades, combined with urbanization. Observing this problem, the present research aims to analyze vulnerability to erosion on the Amazonian estuarine beaches of the Mosqueiro Island, well as evaluating the degree of coastal risk to which they are exposed. Using geoindicators, index and classification of local vulnerability were obtained. Being the index composed of coastal variables: morphology and granulometry of the beach, sedimentary swing, variation of the coast line, cliffs, natural barriers; and continental variables: land elevation, vegetation, coastal engineering structures, percentage of occupation and soil permeability. Then it was carried out: (a) collection of topographic data and sealing samples on 16 beaches; (b) observational analysis with Checklist of geoindicators of coastal erosion in loco and through satellite images; c) treatment of data collected in the field and by remote sensing; d) Use of the coastal vulnerability index to evaluate erosion on the beaches; and, e) identification of risk degree in these beaches. The results demonstrate that 8 of the 16 analyzed beaches are classified with high vulnerability (IVC: 5,0-7,4) and accentuated coastal risk, and that the presence of active cliffs, wall of arrimation and high occupation next the beaches stood out as favoring ones for this result. The data indicated high human occupation (> 70% on most beaches), since several forms of land use are frequent on the island, whether for homes or establishments (shops, restaurants, inns), which raises local risk for the occurrence of damage caused by erosion. In general, the adapted method of this study for Amazonian estuarine beaches, proved to be an interesting tool to be used in urban planning and to minimize future impacts of coastal erosion. It provides information that can aid in decision-making focused on coastal management and choosing which mitigatory measures can be carried out. Thus, the importance of this analysis and continuous coastal monitoring is reinforced through the use of geoindicators.