Navegando por Assunto "Beach morphodynamics"

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Acesso aberto (Open Access)
Influência das oscilações climáticas tropicais na evolução da linha de costa atlântica do Pará-Brasil
(Universidade Federal do Pará, 2021-11-05) GUERREIRO, Juliana de Sá; SOUZA, Everaldo Barreiros de; http://lattes.cnpq.br/6257794694839685; https://orcid.org/0000-0001-6045-0984
Understand how the shoreline (LC) position dynamically changes in response to meteoceanographic processes and climate variability is essential to predict and mitigate the impact of future extremes on the Atlantic Coast of Pará (CAP). This thesis aimed to provide the first quantitative assessment of the relative influence of the El Niño-Southern Oscillation (ENSO) and Atlantic Meridional Mode (AMM) climate indices on meteoceanographic processes (wave climate, winds and precipitation) and on beach morphodynamics along the coast. In this study, the significant wave height (Hs), mean wave period (Tz), speed (Wspd) and wind direction (Wdir) of the Era-Interim data (1979-2017) together with in situ wave data measurements on a macrotidal beach were used to define wave climate and its variability. Spectral analysis was used to quantify the wave propagation energy towards the LC. The results indicate that in CAP there are 3 modes of wave variability: 1) North-Northeast (N-NE) swell waves (frequency band – 0.04 – 0.14 Hz) during the rainy season; 2) Waves formed by the action of winds (windsea) from the Northeast (NE) (frequency band 0.14 – 0.33 Hz); and 3) East-Southeast (ESE) wind waves (frequency band 0.14 – 0.33 Hz) each with distinct wave power signatures. The behaviour of meteoceanographic processes associated with the main tropical climatic indices was analysed through the composites, whose results indicated more energetic waves, longer periods, greater precipitation and less intense winds during the La Niña and positive phases of the AMM. Less energetic waves, shorter periods, less precipitation and more intense winds were observed during the El Niño and negative phase of the AMM. In order to understand how the LC positions (obtained through a spectral approach by the Modified Water Index by Normalized Difference) in the CAP respond to climate variability and meteoceanographic processes, correlations were made between climate indices and change distances of LC. Cross-correlation values between climate indices and LC indicate that there is significant climate forcing, as they showed that the effects of ENSO and AMM were found in the Tropical Atlantic Ocean after 3-12 months. Therefore, changes in coastlines are associated with periodic variations in atmospheric forcing as climatic indices that modulate the position of the ITCZ, altering seasonal patterns in rainfall and wind regimes and their effects on sediment transport processes. Keywords: meteoceanography; climatic variability; beach morphodynamics.
Acesso aberto (Open Access)
Mudanças morfológicas em praias da costa Leste da ilha do Marajó e os níveis de vulnerabilidade à erosão
(Universidade Federal do Pará, 2021-06-29) SOUSA, Maria Bárbara Pereira de; RANIERI, Leilanhe Almeida; http://lattes.cnpq.br/3129401501809850; https://orcid.org/0000-0002-9870-4879
The coastal zone is a transition area between the sea and the continent, being one of the most vulnerable geographic spaces on the planet. In view of this, the assessment of morphological changes and coastal vulnerability to erosion is essential, as it contributes to the planning of protective and mitigating actions against impacts that occur on the environment, whether natural or anthropic. Thus, the work aims to verify the morphological changes in beaches on the east coast of Ilha de Marajó/PA and their levels of vulnerability to erosion at different time scales. For this purpose, two field campaigns (dry and rainy seasons) were carried out at Barra Velha beach (municipality of Soure) and Praia Grande (municipality of Salvaterra). The methodology consisted of a semi-quantitative analysis, determined by parameters of human and natural occupation evaluated on the beaches. Remote sensing techniques (medium period data) and in situ data collection (short period data) were used. According to the results obtained, Barra Velha beach was classified as dissipative in the two periods studied and most profiles topographic showed an erosive trend from the dry to the rainy period. Praia Grande showed behavior of intermediate to reflective beaches in both the dry and rainy seasons. The sedimentary accretion phase of this beach occurred during the rainy season, reflecting an atypical pattern for beach morphodynamics. Barra Velha beach exhibited moderate erosion vulnerability in the northwest sector and high vulnerability in the southeast sector, mainly due to the high erosion rate over the 16 years studied. Praia Grande, on the other hand, presented a moderate degree of vulnerability to erosion, being considered a more stable beach, combined with coastal protection works. On both beaches, the coastal risk was low due to the low level of occupation close to the coastline. It is believed that the results of this research can contribute to future studies on the theme of vulnerability to erosion in areas that are little or very anthropized and, for possible actions of coastal management in the Amazon region, considering their environmental particularities.