Navegando por Assunto "Morphodynamics"

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Acesso aberto (Open Access)
Evolução multitemporal (2010-2024) do canal de acesso do estuário do rio Amazonas (canal Norte - baía de Macapá - margem ocidental)
(Universidade Federal do Pará, 2025-02-27) SILVA, Eduardo Pantoja da; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429; https://orcid.org/0000-0001-7850-1217
The Amazon River, the world’s largest by water volume, has an average discharge of approximately 209,000 m³/s and exhibits a semidiurnal tidal range that varies from 0.3 m to 4 m during spring tides. Its vast watershed profoundly shapes the geomorphology of the Amazon Basin, driving sedimentary processes and directly affecting navigability. The economic importance of navigation within its estuary contrasts sharply with the challenges posed by both natural and anthropogenic alterations, which compromise the long-term stability of the channel. This dissertation analyzes the geomorphological evolution of the Amazon River’s northern channel and Macapá Bay from 2010 to 2024. It assesses the impacts of sedimentary dynamics on navigability and port management. The research methodology encompassed the analysis of bathymetric data, 38 Sentinel-1 radar scenes (captured between 2016 and 2024) processed via the Google Earth Engine platform, and historical hydrological records. Bathymetric processing was carried out in SURFER using the kriging method, while spatial analyses were performed with geostatistical tools in Python and QGIS. This included the delineation of sandbanks and the calculation of modification areas to identify erosion and deposition patterns. The study area is highly dynamic, influenced by tidal forces, river discharge, and sedimentation. These interacting processes drive the formation and migration of sandbanks and unstable channels, which directly affect bed depth and navigational safety. The findings indicate a reduction in the northern channel’s average depth from 26 m to 22 m, along with a noticeable east-northeastward migration. This shift is evidenced by erosion along the left bank and simultaneous deposition on the right bank. Three-dimensional analysis revealed that while the bed morphology was relatively homogeneous in 2011, by 2024 it had become more compartmentalized, reflecting a rate of change of 0.307 m per year. The study also highlights significant variations in the spatial extent of emerged areas within Macapá Bay. During El Niño years (2016, 2018, 2023), average accretion reached 8,326.93 km², whereas La Niña years (2017, 2020, 2021, 2022) experienced average erosion of -13,941.27 km². Linear regression analysis produced an adjusted R² value of 0.163, indicating that hydrological variability and human activity influence the region’s sedimentary dynamics. The observed geomorphological changes directly affect waterway management and the Santana port complex, underscoring the need for effective strategies to ensure ongoing navigability. Remote sensing has proven invaluable for monitoring these dynamic transformations, offering strategic insights to enhance port infrastructure planning and ensure the long-term sustainability of navigation in the region. This research reinforces the necessity of continuous monitoring and integrated hydrodynamic planning to maintain navigational safety and logistical efficiency. The combined use of geoprocessing and bathymetric techniques enables more accurate planning and the implementation of measures to mitigate sedimentation impacts, thereby preserving the viability of inland waterway transport. Ultimately, the results provide essential support for managing navigation in the Amazon River’s northern channel, promoting enhanced efficiency and safety.
Acesso aberto (Open Access)
Morfodinâmica de praias estuarinas da vila de Jubim (ilha do Marajó-Pa)
(Universidade Federal do Pará, 2025-04-25) RODRIGUES, Mayara de Souza; RANIERI, Leilanhe Almeida; http://lattes.cnpq.br/3129401501809850; https://orcid.org/0000-0002-9870-4879
The Brazilian Amazon Coastal Zone (states of Amapá, Pará and Maranhão) has environmental characteristics such as a humid tropical climate (high temperatures, low thermal and rainfall variation) and important oceanographic conditions (hyper to mesotidal), in addition to extensive mangroves and sandy beaches, including estuarine beaches. These are vulnerable to seasonal changes in river discharge, in addition to current climate change, the consequent rise in sea level and the resulting coastal erosion, which causes negative consequences for the goods and services originating from this coastal ecosystem. The objective of this study was to analyze the changes in the morphology and sediment dynamics of the estuarine beaches of Jubim and adjacent areas, during a complete seasonal cycle (March 2023 to March 2024). Jubim is a district located in the municipality of Salvaterra, State of Pará, on the east bank of Marajó Island, under oceanographic conditions of the Pará River estuary. Data collection was carried out on four specific beaches, namely: Salazar Beach, Meninas Beach, Baleia Beach and Curuanã Beach. To characterize the morphodynamic state of the beaches, the slope (β) and relative tidal variation (RTR) parameters, derived from the treatment of physical and topographic data (beach profiles), were used as reference. For granulometric analysis, surface sediment samples were subjected to dry sieving in order to obtain the average size, grain selection and sedimentary balance of the beaches. The results showed that the beaches of the village of Jubim have sedimentation ranging from medium to fine sand 1 ɸ and 2 ɸ, with moderately well-sorted grains. The beaches presented quite varied morphometric parameters: topographic elevation from 5.6 m to 2.7 m, and beach width ranging from 79 m to 550 m, thus classifying them into dissipative to intermediate morphodynamic stages (beach slope from 0.2° to 2.6°), with tidal dominance (RTR = 44). The seasonal sedimentary variation was both positive and negative, indicating that the variability index alternate along the beaches and climatic seasons, showing both erosive and depositional tendencies. Erosive processes were observed mainly in the rainy season and greater sedimentary deposition in the dry season. The morphological behavior of the beaches studied on the eastern shore of Marajó Island is directly influenced by estuarine hydrodynamics, where the distinct sedimentary changes are due to the interation that hidrodynamics with the differentiated geology along the coast, and the respective material that constitutes the substrate of the beaches and backwaters.