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De Oliveira, Allan De Oliveira. "CARACTERIZAÇÃO SEDIMENTAR E APLICAÇÃO DO DIAGRAMA DE PEJRUP PARA INTERPRETAÇÃO DA DINÂMICA EM UMA ENSEADA ESTUARINA NA LAGOA DOS PATOS/BRASIL / Sedimentary Characterization and Application of Pejrup Diagram to Interpret the Dinamics in a Small Cove of The Lagoa dos Patos/Brazil". Geographia Meridionalis 1, n.º 2 (18 de diciembre de 2015): 363. http://dx.doi.org/10.15210/gm.v1i2.6232.
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A partir da análise dos parâmetros estatísticos dos sedimentos de fundo de uma enseada estuarina e da aplicação do diagrama de Pejrup, foi possível caracterizar os processos dinâmicos e sedimentares que ocorrem em uma pequena enseada da Lagoa dos Patos. Os sedimentos que recobrem o fundo da área estudada são formados por areias finas a muito finas, com presença de material lamoso, preferencialmente silte, em direção à região central e margens da enseada. A hidrodinâmica da área é dominada pela circulação estuarina e correntes fluviais, bem como pela ação dos ventos que influenciam estas correntes. Esses fatores são responsáveis pelo transporte, redistribuição e deposição dos sedimentos na área de estudo.ABSTRACTFrom statistical parameters of the bottom morphology and of the application of the diagram of Pejrup it was possible to characterize the dynamic and sedimentary processes that occur in a small cove of the Lagoa dos Patos. The sediments that recover the bottom of the studied area are formed by fine to very fine sands, with the presence of muddy (silt) in the central region and marginal area. The hydrodynamic of the area is dominated by the estuarine circulation and fluvial currents as well, partly due the action of winds which influence these currents. These factors are responsible for the transport, redistribution and deposition of the sediments in the study area.Keywords: sedimentary characterization; hydrodinamics; estuarine cove.
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Jalón-Rojas, I., S. Schmidt y A. Sottolichio. "Turbidity in the fluvial Gironde Estuary (S–W France) based on 10 year continuous monitoring: sensitivity to hydrological conditions". Hydrology and Earth System Sciences Discussions 12, n.º 3 (10 de marzo de 2015): 2843–83. http://dx.doi.org/10.5194/hessd-12-2843-2015.
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Abstract. Climate change and human activities impact the volume and timing of freshwater input to estuaries. These modifications in fluvial discharges are expected to influence estuarine suspended sediment dynamics, and in particular the turbidity maximum zone (TMZ). Located in the southwest France, the Gironde fluvial-estuarine systems has an ideal context to address this issue. It is characterized by a very pronounced TMZ, a decrease in mean annual runoff in the last decade, and it is quite unique in having a long-term and high-frequency monitoring of turbidity. The effect of tide and river flow on turbidity in the fluvial estuary is detailed, focusing on dynamics related to changes in hydrological conditions (river floods, periods of low-water, inter-annual changes). Turbidity shows hysteresis loops at different time scales: during river floods and over the transitional period between the installation and expulsion of the TMZ. These hysteresis patterns, that reveal the origin of sediment, locally resuspended or transported from the watershed, may be a tool to evaluate the presence of remained mud. Statistics on turbidity data bound the range of river flow that promotes the TMZ installation in the fluvial stations. Hydrological indicators of the persistence and turbidity level of the TMZ are also defined. The long-term evolution of these indicators confirms the influence of discharge decrease on the intensification of the TMZ in tidal rivers, and provides a tool to evaluate future scenarios.
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Bogemans, Frieda, Mathieu Boudin, Rindert Janssens y Cecile Baeteman. "New data on the sedimentary processes and timing of the initial inundation of Lower Khuzestan (SW Iran) by the Persian Gulf". Holocene 27, n.º 4 (3 de octubre de 2016): 613–20. http://dx.doi.org/10.1177/0959683616670224.
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The early- and mid-Holocene deposits of the Lower Khuzestan plain at the north-eastern margin of the Persian Gulf have been investigated by means of facies analysis of sediment successions of undisturbed cores. Organic material and molluscs have been selected for dating by radiocarbon whereby possible contamination by hard-water effect is discussed. The results suggest that the Holocene transgression in Mesopotamia may have taken place later than generally accepted. Before ca. 7700–7900 yr cal. BP, the plain was characterized by mud-dominated fluvial systems. During the mid-Holocene, tides invaded the existing valleys, and the sedimentary environment shifted from fluvial to estuarine but not as extensively as has previously been suggested. The estuarine environments lasted for about 2000–2500 years until ca. 4850–5000 yr cal. BP when the seaward part of the plain was again characterized by widespread fluvial sedimentation.
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van den Berg, J. H., J. R. Boersma y A. van Gelder. "Diagnostic sedimentary structures of the fluvial-tidal transition zone – Evidence from deposits of the Rhine and Meuse". Netherlands Journal of Geosciences 86, n.º 3 (septiembre de 2007): 287–306. http://dx.doi.org/10.1017/s0016774600077866.
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AbstractIn mesotidal settings the transition of a coastal plain estuary to the river is marked by the change of a multiple ebb and flood channel configuration to a single channel system. At high river discharge fluvial processes operate, whereas in periods of low discharge the flow is complicated by a tidal component and a landward intrusion of the salt wedge. These hydraulic and morphological characteristics make the transitional zone different from the ‘pure’ fluvial and estuarine environment. Inspection of published and unpublished data from a number of outcrops of Recent and Tertiary deposits of the Rhine reveals that also in a sedimentary sense a transitional zone can be recognized. In order to separate this zone from the upstream fluvial and downstream estuarine environment a sedimentological definition of the fluvial-tidal zone is proposed being the part of river that lies between the landward limit of observable effects of tidal-induced flow deceleration on fluvial cross-bedding at low river discharge and the most seaward occurrence of a textural or structural fluvial signature related to the high river stage.
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Etcheber, H., S. Schmidt, A. Sottolichio, E. Maneux, G. Chabaux, J. M. Escalier, H. Wennekes et al. "Monitoring water quality in estuarine environments: lessons from the MAGEST monitoring programme in the Gironde fluvial-estuarine system". Hydrology and Earth System Sciences Discussions 7, n.º 6 (7 de diciembre de 2010): 9411–36. http://dx.doi.org/10.5194/hessd-7-9411-2010.
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Abstract. The Gironde estuary, one of the largest European ones, presents temporary low dissolved oxygen content in its fluvial section close to the Bordeaux urban area. In a context of population growth and of long-term environmental changes, the development of a high-frequency monitoring programme of the fluvial-estuarine system of the Gironde, called MAGEST (MArel Gironde ESTuary), had appeared essential to address current and future water-quality issues/evaluations. The objectives of the MAGEST survey programme are to establish a reference database to improve the knowledge of the Gironde estuary functioning, encompassing the aspects of hydrology, sediment dynamics and biogeochemistry. Through examples of results from intratidal to seasonal time scales, we demonstrate how such a time-series is of valuable interest to extract the main trends of its functioning and of the water quality in relation to external forcings (climatology, urban wastes, land use, ...) and to predict the future evolution of the Gironde estuary with global and environmental changes.
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Ralston, David K., W. Rockwell Geyer, Peter A. Traykovski y Nicholas J. Nidzieko. "Effects of estuarine and fluvial processes on sediment transport over deltaic tidal flats". Continental Shelf Research 60 (junio de 2013): S40—S57. http://dx.doi.org/10.1016/j.csr.2012.02.004.
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Nittrouer, Charles A., David J. DeMaster, Steven A. Kuehl, Alberto G. Figueiredo, Richard W. Sternberg, L. Ercilio C. Faria, Odete M. Silveira et al. "Amazon Sediment Transport and Accumulation Along the Continuum of Mixed Fluvial and Marine Processes". Annual Review of Marine Science 13, n.º 1 (3 de enero de 2021): 501–36. http://dx.doi.org/10.1146/annurev-marine-010816-060457.
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Sediment transfer from land to ocean begins in coastal settings and, for large rivers such as the Amazon, has dramatic impacts over thousands of kilometers covering diverse environmental conditions. In the relatively natural Amazon tidal river, combinations of fluvial and marine processes transition toward the ocean, affecting the transport and accumulation of sediment in floodplains and tributary mouths. The enormous discharge of Amazon fresh water causes estuarine processes to occur on the continental shelf, where much sediment accumulation creates a large clinoform structure and where additional sediment accumulates along its shoreward boundary in tidal flats and mangrove forests. Some remaining Amazon sediment is transported beyond the region near the river mouth, and fluvial forces on it diminish. Numerous perturbations to Amazon sediment transport and accumulation occur naturally, but human actions will likely dominate future change, and now is the time to document, understand, and mitigate their impacts.
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Duck, Robert W. "Pioneering, Scottish nineteenth century studies of sedimentary processes in fluvial, estuarine and coastal environments". Scottish Journal of Geology 47, n.º 1 (4 de abril de 2011): 81–87. http://dx.doi.org/10.1144/0036-9276/01-425.
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Lokhorst, Ivar R., Lisanne Braat, Jasper R. F. W. Leuven, Anne W. Baar, Mijke van Oorschot, Sanja Selaković y Maarten G. Kleinhans. "Morphological effects of vegetation on the tidal–fluvial transition in Holocene estuaries". Earth Surface Dynamics 6, n.º 4 (9 de octubre de 2018): 883–901. http://dx.doi.org/10.5194/esurf-6-883-2018.
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Abstract. Vegetation enhances bank stability and sedimentation to such an extent that it can modify river patterns, but how these processes manifest themselves in full-scale estuarine settings is poorly understood. On the one hand, tidal flats accrete faster in the presence of vegetation, reducing the flood storage and ebb dominance over time. On the other hand flow-focusing effects of a tidal floodplain elevated by mud and vegetation could lead to channel concentration and incision. Here we study isolated and combined effects of mud and tidal marsh vegetation on estuary dimensions. A 2-D hydromorphodynamic estuary model was developed, which was coupled to a vegetation model and used to simulate 100 years of morphological development. Vegetation settlement, growth and mortality were determined by the hydromorphodynamics. Eco-engineering effects of vegetation on the physical system are here limited to hydraulic resistance, which affects erosion and sedimentation pattern through the flow field. We investigated how vegetation, combined with mud, affects the average elevation of tidal flats and controls the system-scale planform. Modelling with vegetation only results in a pattern with the largest vegetation extent in the mixed-energy zone of the estuary, which is generally shallower. Here vegetation can cover more than 50 % of the estuary width while it remains below 10 %–20 % in the outer, tide-dominated zone. This modelled distribution of vegetation along the estuary shows general agreement with trends in natural estuaries observed by aerial image analysis. Without mud, the modelled vegetation has a limited effect on morphology, again peaking in the mixed-energy zone. Numerical modelling with mud only shows that the presence of mud leads to stabilisation and accretion of the intertidal area and a slight infill of the mixed-energy zone. Combined modelling of mud and vegetation leads to mutual enhancement with mud causing new colonisation areas and vegetation stabilising the mud. This occurs in particular in a zone previously described as the bedload convergence zone. While vegetation focusses the flow into the channels such that mud sedimentation in intertidal side channels is prevented on a timescale of decades, the filling of intertidal area and the resulting reduction in tidal prism may cause the infilling of estuaries over centuries.
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Shilla, D. "Fluxes and retention of nutrients and organic carbon in Manko estuary, Okinawa, Japan: influence of river discharge variations". Advances in Oceanography and Limnology 5, n.º 2 (4 de diciembre de 2014): 141. http://dx.doi.org/10.4081/aiol.2014.5354.
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Estuaries are often considered important filters for inorganic and organic nutrients, as they are located between the land and sea. This study reports on the fluvial fluxes and estuarine transformations and retention of dissolved nutrients (total oxidized nitrogen [TON = NO<sub>2</sub><sup>−</sup> and NO<sub>3</sub><sup>−</sup>]), NH<sub>4</sub><sup>+</sup>, PO<sub>4</sub><sup>3−</sup>, and dissolved organic carbon (DOC) in Manko estuary, Okinawa, Japan. The transport and transformation of dissolved nutrients and DOC varied widely among the eight conducted surveys due to variations in freshwater discharge and subsequent flushing times. Under high fluvial discharge, particularly during the May–June rainy season, the transport of nutrients and DOC accounted for up to 70%, 88%, 93%, and 53% of the annual transport of TON, NH<sub>4</sub><sup>+</sup>, PO<sub>4</sub><sup>3−</sup>, and DOC, respectively. The flushing times of river water into the estuary, which varied from 0.5 to 46 days, were important in determining the degree to which fluvial nutrients were transformed and retained within the estuary. The effect of long flushing times was evident during the dry months (December–March), when biological and geochemical processes within the estuary removed most of the fluvial nutrients and DOC.
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Fitch, Simon, Ken Thomson y Vince Gaffney. "Late Pleistocene and Holocene depositional systems and the palaeogeography of the Dogger Bank, North Sea". Quaternary Research 64, n.º 2 (septiembre de 2005): 185–96. http://dx.doi.org/10.1016/j.yqres.2005.03.007.
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Abstract3D seismic data from the Dogger Bank, North Sea, allow the mapping of Late Pleistocene and Holocene depositional systems in unprecedented detail. The data demonstrate that glacial processes resulted in the development of incised tunnel valley systems during the Weichselian and that these were subsequently modified by fluvial processes in a pro-glacial setting. Subsequently, the Dogger Bank formed an emergent plain during the Holocene with a complex meandering river system, associated tributary or distributary channels and lakes, dominating the region. Prior to the sea level rising sufficiently to submerge the Dogger Bank around 7500 yr ago, the meandering river system was replaced by a dendritic channel network of potential fluvial, estuarine or intertidal origin. As the Holocene depositional features bear no systematic relationship to the bathymetry this study demonstrates that previously published bathymetry-based models for the Holocene palaeogeographic development of the North Sea require modification.
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Mendes, Joana, Rui Ruela, Ana Picado, João Pedro Pinheiro, Américo Soares Ribeiro, Humberto Pereira y João Miguel Dias. "Modeling Dynamic Processes of Mondego Estuary and Óbidos Lagoon Using Delft3D". Journal of Marine Science and Engineering 9, n.º 1 (15 de enero de 2021): 91. http://dx.doi.org/10.3390/jmse9010091.
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Estuarine systems currently face increasing pressure due to population growth, rapid economic development, and the effect of climate change, which threatens the deterioration of their water quality. This study uses an open-source model of high transferability (Delft3D), to investigate the physics and water quality dynamics, spatial variability, and interrelation of two estuarine systems of the Portuguese west coast: Mondego Estuary and Óbidos Lagoon. In this context, the Delft3D was successfully implemented and validated for both systems through model-observation comparisons and further explored using realistically forced and process-oriented experiments. Model results show (1) high accuracy to predict the local hydrodynamics and fair accuracy to predict the transport and water quality of both systems; (2) the importance of the local geomorphology and estuary dimensions in the tidal propagation and asymmetry; (3) Mondego Estuary (except for the south arm) has a higher water volume exchange with the adjacent ocean when compared to Óbidos Lagoon, resulting from the highest fluvial discharge that contributes to a better water renewal; (4) the dissolved oxygen (DO) varies with water temperature and salinity differently for both systems. On the one hand, for Mondego Estuary during winter the DO levels mainly fluctuate with salinity. On the other hand, for Óbidos Lagoon, DO distribution is determined by both water temperature and salinity. During summer, the high residence time and water temperature limit the DO levels in both systems. The high transferability and superior stability of Delft3D make this model a foundation for realistic simulation and research of distinct estuarine systems, giving support to their maintenance and restoration.
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Deforce, Koen, Annelies Storme, Jan Bastiaens, Sofie Debruyne, Luc Denys, Anton Ervynck, Erwin Meylemans, Herman Stieperaere, Wim Van Neer y Philippe Crombé. "Middle-Holocene alluvial forests and associated fluvial environments: A multi-proxy reconstruction from the lower Scheldt, N Belgium". Holocene 24, n.º 11 (21 de agosto de 2014): 1550–64. http://dx.doi.org/10.1177/0959683614544059.
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Analyses of pollen, plant macrofossils (seeds, fruits, wood and mosses), molluscs, diatoms and vertebrate (mainly fish) remains allowed a detailed reconstruction of a middle-Holocene alluvial forest and its associated hydrological conditions. The use of multiple proxies resulted in a taxonomically more detailed and environmentally more comprehensive understanding of terrestrial as well as aquatic habitats. The results demonstrate possible biases in palaeoecological reconstructions of alluvial and estuarine environments drawn from single proxies. Many locally occurring woody taxa were underrepresented or remained undetected by pollen analyses. Seeds and fruits also proved to be inadequate to detect several locally important taxa, such as Ulmus and Hedera helix. Apparently brackish conditions inferred from diatoms, pollen and other microfossils conflicted strikingly with the evidence from molluscs, fish bones and botanical macroremains which suggest a freshwater environment. Brackish sediment (and the microfossil indicators) is likely to have been deposited during spring tides or storm surges, when estuarine waters penetrated more inland than usual. Despite the reworking and deposition of estuarine and saltmarsh sediment well above the tidal node at such events, local salinity levels largely remained unaffected.
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Chalov, R. S., K. M. Berkovich, G. A. Larionov y L. F. Litvin. "Study of erosion-channel systems and its components: theory, history, and practice". Geomorphology RAS, n.º 2 (26 de abril de 2019): 95–108. http://dx.doi.org/10.31857/s0435-42812019295-108.
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The article is dedicated to the 50th anniversary since the N. I. Makkaveev’s Scientific Research Laboratory for soil erosion and channel processes was organized at the Moscow University. The history of scientific school, created by N. I. Makkaveev, establishment is considered, as well as the discipline on integral erosion-depositional process and its evolution to the theory of catchment erosion-fluvial systems. The analysis of the fundamental researches performed by the Laboratory is submitted, and the application tasks in the area of soil erosion, gully erosion, channel and estuarine processes are outlined. Main directions of research are formulated, the prospects for their development are evaluated.
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Mathes-Schmidt, Margret, Denis Moiriat, Hervé Jomard, Klaus Reicherter y Stéphane Baize. "The Holocene sedimentary record of the flood plain of the Saint-Ciers-Sur-Gironde marsh (Gironde estuary, France)". Zeitschrift für Geomorphologie, Supplementary Issues 62, n.º 2 (1 de octubre de 2019): 295–322. http://dx.doi.org/10.1127/zfg_suppl/2019/0605.
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The Holocene sedimentary record of the flood plain of the Saint-Ciers-Sur-Gironde marsh was examined on sediment cores from the right bank of the Gironde estuary with regard to the evolution of the marsh and its potential to preserve high-energy deposits. Sedimentological, geochemical, geophysical and micropaleontological methods were applied. Radiocarbon ages in the central part of the investigation area reach back to 7,971 ± 44.5 BP. The sediments of the Saint-Ciers-sur-Gironde marsh reflect the condi- tions of a Holocene estuarine salt marsh before human activity and draining. The interpretation of the core data showed that the study area includes different facies during development from the pre-Holocene to recent times: tidal mudflats in the northwest at Mortagne and Beaumont, and a fluvial facies develop- ing into an estuarine facies in the southeast near Camp and Saint-Ciers-Sur-Gironde. The last stage is the formation of the saltmarsh. The changes in grain size reflect different transport mechanisms during the development from a fluvial environment to the recent marsh. First gravel, then sand and finally muddy sediments were deposited in the estuary and finally in the marsh area.. Below the salt marsh deposits in Mortagne-Sur-Gironde, there is some evidence of deposits from energy-rich events in tidal mudflats. The southern and central part, in which estuarine clays were deposited, was probably most of the time outside the range of storms. On the marshland surface, erosion, pedogenesis and bioturbation processes destroy storm relevant layers in a very short time.
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Parham, Peter R., Stanley R. Riggs, Stephen J. Culver, David J. Mallinson y John F. Wehmiller. "Quaternary depositional patterns and sea-level fluctuations, Northeastern North Carolina". Quaternary Research 67, n.º 1 (enero de 2007): 83–99. http://dx.doi.org/10.1016/j.yqres.2006.07.003.
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AbstractA detailed record of late Quaternary sea-level oscillations is preserved within the upper 45 m of deposits along an eight km transect across Croatan Sound, a drowned tributary of the Roanoke/Albemarle drainage system, northeastern North Carolina. Drill-hole and seismic data reveal nine relatively complete sequences filling an antecedent valley comprised of discontinuous middle and early Pleistocene deposits. On interfluves, lithologically similar marine deposits of different sequences occur stacked in vertical succession and separated by ravinement surfaces. Within the paleo-drainage, marine deposits are separated by fluvial and/or estuarine sediments deposited during periods of lowered sea level. Foraminiferal and molluscan fossil assemblages indicate that marine facies were deposited in a shallow-marine embayment with open connection to shelf waters. Each sequence modifies or truncates portions of the preceding sequence or sequences. Sequence boundaries are the product of a combination of fluvial, estuarine, and marine erosional processes. Stratigraphic and age analyses constrain the ages of sequences to late Marine Isotope Stage (MIS) 6 and younger (∼ 140 ka to present), indicating multiple sea-level oscillations during this interval. Elevations of highstand deposits associated with late MIS 5 and MIS 3 imply that sea level was either similar to present during those times, or that the region may have been influenced by glacio-isostatic uplift and subsidence.
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Braat, Lisanne, Thijs van Kessel, Jasper R. F. W. Leuven y Maarten G. Kleinhans. "Effects of mud supply on large-scale estuary morphology and development over centuries to millennia". Earth Surface Dynamics 5, n.º 4 (9 de octubre de 2017): 617–52. http://dx.doi.org/10.5194/esurf-5-617-2017.
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Abstract. Alluvial river estuaries consist largely of sand but are typically flanked by mudflats and salt marshes. The analogy with meandering rivers that are kept narrower than braided rivers by cohesive floodplain formation raises the question of how large-scale estuarine morphology and the late Holocene development of estuaries are affected by cohesive sediment. In this study we combine sand and mud transport processes and study their interaction effects on morphologically modelled estuaries on centennial to millennial timescales. The numerical modelling package Delft3D was applied in 2-DH starting from an idealised convergent estuary. The mixed sediment was modelled with an active layer and storage module with fluxes predicted by the Partheniades–Krone relations for mud and Engelund–Hansen for sand. The model was subjected to a range of idealised boundary conditions of tidal range, river discharge, waves and mud input. The model results show that mud is predominantly stored in mudflats on the side of the estuary. Marine mud supply only influences the mouth of the estuary, whereas fluvial mud is distributed along the whole estuary. Coastal waves stir up mud and remove the tendency to form muddy coastlines and the formation of mudflats in the downstream part of the estuary. Widening continues in estuaries with only sand, while mud supply leads to a narrower constant width and reduced channel and bar dynamics. This self-confinement eventually leads to a dynamic equilibrium in which lateral channel migration and mudflat expansion are balanced on average. However, for higher mud concentrations, higher discharge and low tidal amplitude, the estuary narrows and fills to become a tidal delta.
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Magalhães, A. J. C., C. M. S. Scherer, G. P. Raja Gabaglia, M. B. Bállico y O. Catuneanu. "Unincised fluvial and tide-dominated estuarine systems from the Mesoproterozoic Lower Tombador Formation, Chapada Diamantina basin, Brazil". Journal of South American Earth Sciences 56 (diciembre de 2014): 68–90. http://dx.doi.org/10.1016/j.jsames.2014.07.010.
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Lawler, D. M. "The importance of high-resolution monitoring in erosion and deposition dynamics studies: examples from estuarine and fluvial systems". Geomorphology 64, n.º 1-2 (enero de 2005): 1–23. http://dx.doi.org/10.1016/j.geomorph.2004.04.005.
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Leuven, Jasper R. F. W., Sanja Selaković y Maarten G. Kleinhans. "Morphology of bar-built estuaries: empirical relation between planform shape and depth distribution". Earth Surface Dynamics 6, n.º 3 (11 de septiembre de 2018): 763–78. http://dx.doi.org/10.5194/esurf-6-763-2018.
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Abstract. Fluvial–tidal transitions in estuaries are used as major shipping fairways and are characterised by complex bar and channel patterns with a large biodiversity. Habitat suitability assessment and the study of interactions between morphology and ecology therefore require bathymetric data. While imagery offers data of planform estuary dimensions, only for a few natural estuaries are bathymetries available. Here we study the empirical relation between along-channel planform geometry, obtained as the outline from imagery, and hypsometry, which characterises the distribution of along-channel and cross-channel bed levels. We fitted the original function of Strahler (1952) to bathymetric data along four natural estuaries. Comparison to planform estuary shape shows that hypsometry is concave at narrow sections with large channels, while complex bar morphology results in more convex hypsometry. We found an empirical relation between the hypsometric function shape and the degree to which the estuary width deviates from an ideal convergent estuary, which is calculated from river width and mouth width. This implies that the occurring bed-level distributions depend on inherited Holocene topography and lithology. Our new empirical function predicts hypsometry and along-channel variation in intertidal and subtidal width. A combination with the tidal amplitude allows for an estimate of inundation duration. The validation of the results on available bathymetry shows that predictions of intertidal and subtidal area are accurate within a factor of 2 for estuaries of different size and character. Locations with major human influence deviate from the general trends because dredging, dumping, land reclamation and other engineering measures cause local deviations from the expected bed-level distributions. The bathymetry predictor can be used to characterise and predict estuarine subtidal and intertidal morphology in data-poor environments.
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SCHETTINI, CARLOS AUGUSTO FRANÇA y ELÍRIO ERNESTINO TOLDO JR. "Modos de Transporte de Sedimentos Finos no Estuário do Rio Itajaí, SC". Pesquisas em Geociências 28, n.º 2 (31 de diciembre de 2001): 151. http://dx.doi.org/10.22456/1807-9806.20282.
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This paper presents an assessment about the modes of fine sediment transport in the Itajaí River estuary. ·The available information to approach a conceptual model is derived from three primary sources: (1) the river sediment delivery; (2) the distribution of salinity and particulate suspended mailer (MPS) along the estuary under influence of different river discharge conditions; and (3) near bed hydro-sedimentological processes. The river sediment delivery was achieved by daily monitoring the water and the suspended sediment discharge, since November 1998 at the Indaial lymnimetric station, which represents about 70 % of the drainage basin. The salinity and MPS distribution in the estuary were obtained through 47 weekly surveys along the estuary when vertical profiles of these variables were acquired every 1-1,5 km from the mouth to the upper limit of the salt intrusion. The surveys were carried out between November 1998 and November 1999, using an inflatable boat. The results allowed obtain the relationship between the salt wedge extension as function of the river discharge and the estuarine trapping efficiency. The near-bed hydro-sedimenlological processes were assessed through the deployment of an instrument tripod on the estuarine bed al the channel thalweg 4 km upstream from the mouth. The current speed, water level and MPS data were recorded hourly, 1 m above the bottom, from September to November 1999. Based on this data set, two main modes of fine sediment transport in the Itajaí River estuary were identified: a tidal driven and a fluvial driven mode. The tidal driven mode occurs when the river discharge is bellow 200 m3.s-1. Near bottom sediments arc in all erosion-deposition cycle following the semi-diurnal tides and the anomalistic cycle of spring and neap tides, with net sediment transport landwards. During such periods fine sediment is imported from the inner shelf. This mode occurs at time scales of weeks to months. The fluvial driven mode are fully developed when the river discharge exceeds 1,000 m3.s-1. accompanied by suspended sediment load as high as 10,000 ton.day-1. Fluvial advective process fully dominates the sediment transport resulting in zero trapping efficiency.
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CORRÊA, IRAN CARLOS STALLIVIERE. "Aplicação do Diagrama de Pejrup na Interpretação da Sedimentação e da Dinâmica do Estuário da Baía de Marajó-PA". Pesquisas em Geociências 32, n.º 2 (31 de diciembre de 2005): 109. http://dx.doi.org/10.22456/1807-9806.19551.
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From statistical parameters of the bottom morphology and of the application of the diagram proposed by Pejrup(1988) it was possible to characterize the dynamic and sedimentary processes that occur in the estuary of the Marajó bay. The sediments that recover the bottom of the studied area are formed by medium to very fine sands that grade to coarse to fine silt in direction to the continental shelf. The hydrodynamic of the area is dominated by the tidal and fluvial currents as well, partly due the action of winds which influence these currents. These factors associated with the estuarine circulation, are responsible for the transport, redistribution and deposition of the sediments in the study area.
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Serafin, Katherine A., Peter Ruggiero, Kai Parker y David F. Hill. "What's streamflow got to do with it? A probabilistic simulation of the competing oceanographic and fluvial processes driving extreme along-river water levels". Natural Hazards and Earth System Sciences 19, n.º 7 (16 de julio de 2019): 1415–31. http://dx.doi.org/10.5194/nhess-19-1415-2019.
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Abstract. Extreme water levels generating flooding in estuarine and coastal environments are often driven by compound events, where many individual processes such as waves, storm surge, streamflow, and tides coincide. Despite this, extreme water levels are typically modeled in isolated open-coast or estuarine environments, potentially mischaracterizing the true risk of flooding facing coastal communities. This paper explores the variability of extreme water levels near the tribal community of La Push, within the Quileute Indian Reservation on the Washington state coast, where a river signal is apparent in tide gauge measurements during high-discharge events. To estimate the influence of multiple forcings on high water levels a hybrid modeling framework is developed, where probabilistic simulations of joint still water level and river discharge occurrences are merged with a hydraulic model that simulates along-river water levels. This methodology produces along-river water levels from thousands of combinations of events not necessarily captured in the observational records. We show that the 100-year still water level event and the 100-year discharge event do not always produce the 100-year along-river water level. Furthermore, along specific sections of river, both still water level and discharge are necessary for producing the 100-year along-river water level. Understanding the relative forcing driving extreme water levels along an ocean-to-river gradient will help communities within inlets better understand their risk to the compounding impacts of various environmental forcing, which is important for increasing their resilience to future flooding events.
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Costa, Ana Maria, Maria da Conceição Freitas, Manel Leira, Susana Costas, Pedro JM Costa, César Andrade, Roberto Bao et al. "The role of climate, marine influence and sedimentation rates in late-Holocene estuarine evolution (SW Portugal)". Holocene 29, n.º 4 (28 de enero de 2019): 622–32. http://dx.doi.org/10.1177/0959683618824768.
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Estuaries are sensitive to changes in global to regional sea level, to climate-driven variation in rainfall and to fluvial discharge. In this study, we use source and environmentally sensitive proxies together with radiocarbon dating to examine a 7-m-thick sedimentary record from the Sado estuary accumulated throughout the last 3.6 kyr. The lithofacies, geochemistry and diatom assemblages in the sediments accumulated between 3570 and 3240 cal. BP indicate a mixture between terrestrial and marine sources. The relative contribution of each source varied through time as sedimentation progressed in a low intertidal to high subtidal and low-energy accreting tidal flat. The sedimentation proceeded under a general pattern of drier and higher aridity conditions, punctuated by century-long changes of the rainfall regime that mirror an increase in storminess that affected SW Portugal and Europe. The sediment sequence contains evidence of two periods characterized by downstream displacement of the estuarine/freshwater transitional boundary, dated to 3570–3400 cal. BP and 3300–3240 cal. BP. These are intercalated by one episode where marine influence shifted upstream. All sedimentation episodes developed under high terrestrial sediment delivery to this transitional region, leading to exceptionally high sedimentation rates, independently of the relative expression of terrestrial/marine influences in sediment facies. Our data show that these disturbances are mainly climate-driven and related to variations in rainfall and only secondarily with regional sea-level oscillations. From 3240 cal. BP onwards, an abrupt change in sediment facies is noted, in which the silting estuarine bottom reaches mean sea level and continued accreting until present under prevailing freshwater conditions, the tidal flat changing to an alluvial plain. The environmental modification is accompanied by a pronounced change in sedimentation rate that decreased by two orders of magnitude, reflecting the loss of accommodation space rather than the influence of climate or regional sea-level drivers.
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Sarna-Wojcicki, Andrei M., Charles E. Meyer, Harry R. Bowman, N. Timothy Hall, Paul C. Russell, Marta J. Woodward y Janet L. Slate. "Correlation of the Rockland Ash Bed, a 400,000-Year-Old Stratigraphic Marker in Northern California and Western Nevada, and Implications for Middle Pleistocene Paleogeography of Central California". Quaternary Research 23, n.º 2 (marzo de 1985): 236–57. http://dx.doi.org/10.1016/0033-5894(85)90031-6.
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Outcrops of an ash bed at several localities in northern California and western Nevada belong to a single air-fall ash layer, the informally named Rockland ash bed, dated at about 400,000 yr B.P. The informal Rockland pumice tuff breccia, a thick, coarse, compound tephra deposit southwest of Lassen Peak in northeastern California, is the near-source equivalent of the Rockland ash bed. Relations between initial thickness of the Rockland ash bed and distances to eruptive source suggest that the eruption was at least as great as that of the Mazama ash from Crater Lake, Oregon. Identification of the Rockland tephra allows temporal correlation of associated middle Pleistocene strata of diverse facies in separate depositional basins. Specifically, marine, littoral, estuarine, and fluvial strata of the Hookton and type Merced formations correlate with fluvial strata of the Santa Clara Formation and unnamed alluvium of Willits Valley and the Hollister area, in northwestern and west-central California, and with lacustrine beds of Mohawk Valley, fluvial deposits of the Red Bluff Formation of the eastern Sacramento Valley, and fluvial and glaciofluvial deposits of Fales Hot Spring, Carson City, and Washoe Valley areas in northeastern California and western Nevada. Stratigraphic relations of the Rockland ash bed and older tephra layers in the Great Valley and near San Francisco suggest that the southern Great Valley emerged above sea level about 2 my ago, that its southerly outlet to the ocean was closed sometime after about 2 my ago, and that drainage from the Great Valley to the ocean was established near the present, northerly outlet in the vicinity of San Francisco Bay about 0.6 my ago.
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Cicimurri, David J., James L. Knight, Jean M. Self-Trail y Sandy M. Ebersole. "Late Paleocene glyptosaur (Reptilia: Anguidae) osteoderms from South Carolina, USA". Journal of Paleontology 90, n.º 1 (enero de 2016): 147–53. http://dx.doi.org/10.1017/jpa.2016.16.
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AbstractHeavily tuberculated glyptosaur osteoderms were collected in an active limestone quarry in northern Berkeley County, South Carolina. The osteoderms are part of a highly diverse late Paleocene vertebrate assemblage that consists of marine, terrestrial, fluvial, and/or brackish water taxa, including chondrichthyan and osteichthyan fish, turtles (chelonioid, trionychid, pelomedusid, emydid), crocodilians, palaeopheid snakes, and a mammal. Calcareous nannofossils indicate that the fossiliferous deposit accumulated within subzone NP9a of the Thanetian Stage (late Paleocene, upper part of Clarkforkian North American Land Mammal Age [NALMA]) and is therefore temporally equivalent to the Chicora Member of the Williamsburg Formation. The composition of the paleofauna indicates that the fossiliferous deposit accumulated in a marginal marine setting that was influenced by fluvial processes (estuarine or deltaic).The discovery of South Carolina osteoderms is significant because they expand the late Paleocene geographic range of glyptosaurines eastward from the US midcontinent to the Atlantic Coastal Plain and provide one of the few North American records of these lizards inhabiting coastal habitats. This discovery also brings to light a possibility that post-Paleocene expansion of this group into Europe occurred via northeastward migration along the Atlantic coast of North America.
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Huggett, Rebecca D., Duncan A. Purdie y Ivan D. Haigh. "Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries". Estuaries and Coasts 44, n.º 1 (1 de julio de 2020): 54–69. http://dx.doi.org/10.1007/s12237-020-00776-3.
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AbstractSimple flushing time calculations for estuarine systems can be used as proxies for eutrophication susceptibility. However, more complex methods are required to better understand entire systems. Understanding of the hydrodynamics driving circulation and flushing times in small, eutrophic, temperate estuaries is less advanced than larger counterparts due to lack of data and difficulties in accurately modelling small-scale systems. This paper uses the microtidal Christchurch Harbour estuary in Southern UK as a case study to elucidate the physical controls on eutrophication susceptibility in small shallow basins. A depth-averaged hydrodynamic model has been configured of the estuary to investigate the physical processes driving circulation with particular emphasis on understanding the impact of riverine inputs to this system. Results indicate circulation control changes from tidally to fluvially driven as riverine inputs increase. Flushing times, calculated using a particle tracking method, indicate that the system can take as long as 132 h to flush when river flow is low, or as short as 12 h when riverine input is exceptionally high. When total river flow into the estuary is less than 30 m3 s−1, tidal flux is the dominant hydrodynamic control, which results in high flushing times during neap tides. Conversely, when riverine input is greater than 30 m3 s−1, the dominant hydrodynamic control is fluvial flux, and flushing times during spring tides are longer than at neaps. The methodology presented here shows that modelling at small spatial scales is possible but highlights the importance of particle tracking methods to determine flushing time variability across a system.
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Perignon, Mariela, Jordan Adams, Irina Overeem y Paola Passalacqua. "Dominant process zones in a mixed fluvial–tidal delta are morphologically distinct". Earth Surface Dynamics 8, n.º 3 (25 de septiembre de 2020): 809–24. http://dx.doi.org/10.5194/esurf-8-809-2020.
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Abstract. The morphology of deltas is determined by the spatial extent and variability of the geomorphic processes that shape them. While in some cases resilient, deltas are increasingly threatened by natural and anthropogenic forces, such as sea level rise and land use change, which can drastically alter the rates and patterns of sediment transport. Quantifying process patterns can improve our predictive understanding of how different zones within delta systems will respond to future change. Available remotely sensed imagery can help, but appropriate tools are needed for pattern extraction and analysis. We present a method for extracting information about the nature and spatial extent of active geomorphic processes across deltas with 10 parameters quantifying the geometry of each of 1239 islands and the channels around them using machine learning. The method consists of a two-step unsupervised machine learning algorithm that clusters islands into spatially continuous zones based on the 10 morphological metrics extracted from remotely sensed imagery. By applying this method to the Ganges–Brahmaputra–Meghna Delta, we find that the system can be divided into six major zones. Classification results show that active fluvial island construction and bar migration processes are limited to relatively narrow zones along the main Ganges River and Brahmaputra and Meghna corridors, whereas zones in the mature upper delta plain with smaller fluvial distributary channels stand out as their own morphometric class. The classification also shows good correspondence with known gradients in the influence of tidal energy with distinct classes for islands in the backwater zone and in the purely tidally controlled region of the delta. Islands at the delta front under the mixed influence of tides, fluvial–estuarine construction, and local wave reworking have their own characteristic shape and channel configuration. The method is not able to distinguish between islands with embankments (polders) and natural islands in the nearby mangrove forest (Sundarbans), suggesting that human modifications have not yet altered the gross geometry of the islands beyond their previous “natural” morphology or that the input data (time, resolution) used in this study are preventing the identification of a human signature. These results demonstrate that machine learning and remotely sensed imagery are useful tools for identifying the spatial patterns of geomorphic processes across delta systems.
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CORRÊA, IRAN CARLOS STALLIVIERE y MARCELO DEVENUTTE ÁVILA. "Sedimentação da Desembocadura do canal sul do Rio Amazonas". Pesquisas em Geociências 28, n.º 2 (31 de diciembre de 2001): 13. http://dx.doi.org/10.22456/1807-9806.20265.
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From statistical parameters of the bottom morphology and application of diagrams, as proposed by Sahu (1964), Passega & Beranjee (1969) and Pejrup (1988), the dynamic and sedimentary processes that occur in the Southern channel of the Amazonas river were characterized. The sediments that recover the bottom of the studied area are formed by medium quartz sand that grade, starting from the south river channel, to very fine silts in direction of the outlet of the Pará river, where happens a granulometric inversion. The hydrodynamic of the area is dominated by tidal and fluvial currents as well, partly due the action of winds which control these currents. These factors, associated with the estuarine circulation, are responsible for the transport, redistribution and deposition of the sediments in the Southern Amazonas river channel.
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Jay, David A., Amy B. Borde y Heida L. Diefenderfer. "Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: II. Water Level Models, Floodplain Wetland Inundation, and System Zones". Estuaries and Coasts 39, n.º 5 (26 de abril de 2016): 1299–324. http://dx.doi.org/10.1007/s12237-016-0082-4.
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Dubar, Michel y Edward J. Anthony. "Holocene Environmental Change and River-Mouth Sedimentation in the Baie des Anges, French Riviera". Quaternary Research 43, n.º 3 (mayo de 1995): 329–43. http://dx.doi.org/10.1006/qres.1995.1039.
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AbstractRiver mouths on the steep, high-relief coast of the French Riviera exhibit thick sequences of Holocene marine, estuarine, deltaic, and river channel-floodplain sediments that overlie basal fluvial Pleistocene gravel. Gravel is uncommon in most of the early to middle Holocene aggradational-progradational marine, estuarine, deltaic sediments, despite an ample supply from rock units in the steep adjoining uplands. River-mouth gravel is common only in late Holocene river channels and in barrier beaches perched on finer-grained nearshore sediments. Neither downslope grain-size fining on alluvial fans nor sediment stacking patterns during sea-level (base-level) rise readily account for the lack of early to middle Holocene gravel in the river-mouth sediment wedges. Holocene sea-level rise led to the storage of fine-grained sediments in shallow marine, estuarine, and deltaic environments in the present coastal zone. We infer that humid temperate conditions, a dense forest cover, landscape stabilization, and a regular quiescent river flow regime associated with the Atlantic climatic optimum limited gravel supply in the adjoining catchments and gravel entrainment downstream during the early Holocene. Sea-level stabilization in the middle and late Holocene coincided with a marked change in bioclimatic conditions toward the present Mediterranean-type regime, which is characterized by a less dense forest cover, soil erosion, and episodic catastrophic floods. The late Holocene was thus a time of downstream bedload channel aggradation, fine-grained floodplain and paludal sedimentation, and seaward flushing of clasts leading to the formation and consolidation of the gravel barrier beaches that bound the rivermouths and embayments.
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de Nijs, Michel A. J., Johan C. Winterwerp y Julie D. Pietrzak. "The Effects of the Internal Flow Structure on SPM Entrapment in the Rotterdam Waterway". Journal of Physical Oceanography 40, n.º 11 (1 de noviembre de 2010): 2357–80. http://dx.doi.org/10.1175/2010jpo4233.1.
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Abstract Field measurements are presented, which are the first to quantify the processes influencing the entrapment of suspended particulate matter (SPM) at the limit of saltwater intrusion in the Rotterdam Waterway. The estuarine turbidity maximum (ETM) is shown to be maintained by the trapping of fluvial SPM at the head of the salt wedge. The trapping process is associated with the raining out of fluvial SPM from the upper, fresher part of the water column, into the layer below the pycnocline. The dominant mechanisms responsible are baroclinic shear flows and the abrupt change in turbulent mixing characteristics due to damping of turbulence at the pycnocline. This view contrasts with the assumption of landward transport of marine SPM by asymmetries in bed stress. The SPM transport capacity of the tidal flow is not fully utilized in the ETM, and the ETM is independent of a bed-based supply of mud. This is explained by regular exchange of part of the ETM with harbor basins, which act as efficient sinks, and that the Rotterdam Waterway is not a complete fluvial SPM trap. The supply of SPM by the freshwater discharge ensures that the ETM is maintained over time. Hence, the ETM is an advective phenomenon. Relative motion between SPM and saltwater occurs because of lags introduced by resuspension. Moreover, SPM that lags behind the salt wedge after high water slack (HWS) is eventually recollected at the head. Hence, SPM follows complex transport pathways and the mechanisms involved in trapping and transport of SPM are inherently three-dimensional.
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Jay, David A., Keith Leffler, Heida L. Diefenderfer y Amy B. Borde. "Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: I. Along-Channel Water Level Variations, Pacific Ocean to Bonneville Dam". Estuaries and Coasts 38, n.º 2 (7 de junio de 2014): 415–33. http://dx.doi.org/10.1007/s12237-014-9819-0.
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Al-Masgari, Abd Al-Salam, Mohamed Elsaadany, Numair A. Siddiqui, Abdul Halim Abdul Latiff, Azli Abu Bakar, Sami Elkurdy, Maman Hermana, Ismailalwali Babikir, Qazi Sohail Imran y Teslim Adeleke. "Geomorphological Geometries and High-Resolution Seismic Sequence Stratigraphy of Malay Basin’s Fluvial Succession". Applied Sciences 11, n.º 11 (2 de junio de 2021): 5156. http://dx.doi.org/10.3390/app11115156.
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This study identified the Pleistocene depositional succession of the group (A) (marine, estuarine, and fluvial depositional systems) of the Melor and Inas fields in the central Malay Basin from the seafloor to approximately −507 ms (522 m). During the last few years, hydrocarbon exploration in Malay Basin has moved to focus on stratigraphic traps, specifically those that existed with channel sands. These traps motivate carrying out this research to image and locate these kinds of traps. It can be difficult to determine if closely spaced-out channels and channel belts exist within several seismic sequences in map-view with proper seismic sequence geomorphic elements and stratigraphic surfaces seismic cross lines, or probably reinforce the auto-cyclic aggregational stacking of the avulsing rivers precisely. This analysis overcomes this challenge by combining well-log with three-dimensional (3D) seismic data to resolve the deposition stratigraphic discontinuities’ considerable resolution. Three-dimensional (3D) seismic volume and high-resolution two-dimensional (2D) seismic sections with several wells were utilized. A high-resolution seismic sequence stratigraphy framework of three main seismic sequences (3rd order), four Parasequences sets (4th order), and seven Parasequences (5th order) have been established. The time slice images at consecutive two-way times display single meandering channels ranging in width from 170 to 900 m. Moreover, other geomorphological elements have been perfectly imaged, elements such as interfluves, incised valleys, chute cutoff, point bars, and extinction surfaces, providing proof of rapid growth and transformation of deposits. The high-resolution 2D sections with Cosine of Phase seismic attributes have facilitated identifying the reflection terminations against the stratigraphic amplitude. Several continuous and discontinuous channels, fluvial point bars, and marine sediments through the sequence stratigraphic framework have been addressed. The whole series reveals that almost all fluvial systems lay in the valleys at each depositional sequence’s bottom bars. The degradational stacking patterns are characterized by the fluvial channels with no evidence of fluvial aggradation. Moreover, the aggradation stage is restricted to marine sedimentation incursions. The 3D description of these deposits permits distinguishing seismic facies of the abandoned mud channel and the sand point bar deposits. The continuous meandering channel, which is filled by muddy deposits, may function as horizontal muddy barriers or baffles that might isolate the reservoir body into separate storage containers. The 3rd, 4th, and 5th orders of the seismic sequences were established for the studied succession. The essential geomorphological elements have been imaged utilizing several seismic attributes.
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Hijma, M. P., K. M. Cohen, G. Hoffmann, A. J. F. Van der Spek y E. Stouthamer. "From river valley to estuary: the evolution of the Rhine mouth in the early to middle Holocene (western Netherlands, Rhine-Meuse delta)". Netherlands Journal of Geosciences - Geologie en Mijnbouw 88, n.º 1 (marzo de 2009): 13–53. http://dx.doi.org/10.1017/s0016774600000986.
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AbstractThe aim of this paper is to reconstruct the evolution of the early to middle Holocene Rhine-Meuse river mouths in the western Netherlands and to understand the observed spatial and temporal changes in facies. This is achieved by constructing three delta wide cross-sections using a newly accumulated database with thousands of core descriptions and cone penetration test results, together with a large set of pollen/diatom analyses and OSL/14C-dates. Most of the studied deposits accumulated in the fluvial-to-marine transition zone, a highly complex area due to the interaction of terrestrial and marine processes. Understanding how the facies change within this zone, is necessary to make correct palaeogeographic interpretations.We find a well preserved early to middle Holocene coastal prism resting on lowstand valley floors. Aggradation started after 9 ka cal BP as a result of rapid sea-level rise. Around 8 ka most parts of the study area were permanently flooded and under tidal influence. After 8 ka a bay-head delta was formed near Delft, meaning that little sand could reach the North Sea. Several subsequent avulsions resulted in a shift from the constantly retreating Rhine river mouth to the north. When after 6.5 ka the most northerly river course was formed (Oude Rijn), the central part of the palaeovalley was quickly transgressed and transformed into a large tidal basin. Shortly before 6 ka retrogradation of the coastline halted and tidal inlets began to close, marking the end of the early-middle Holocene transgression.This paper describes the transition from a fluvial valley to an estuary in unprecedented detail and enables more precise palaeo-reconstructions, evaluation of relative importance of fluvial and coastal processes in rapid transgressed river mouths, and more accurate sediment-budget calculations. The described and well illustrated (changes in) facies are coupled to lithogenetic units. This will aid detailed palaeogeographic interpretations from sedimentary successions, not only in the Netherlands, but also in other estuarine and deltaic regions.
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Bomer, Edwin J., Carol A. Wilson y Dilip K. Datta. "An Integrated Approach for Constraining Depositional Zones in a Tide-Influenced River: Insights from the Gorai River, Southwest Bangladesh". Water 11, n.º 10 (30 de septiembre de 2019): 2047. http://dx.doi.org/10.3390/w11102047.
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The tidal to fluvial transition (TFT) of estuaries and coastal rivers is one of the most complex environments on Earth with respect to the transportation and deposition of sediment, owing in large part to competing fluvial and marine processes. While there have been recent advances in the stratigraphic understanding of the TFT, it is still unclear whether these findings are site-specific or representative of mixed tidal-fluvial systems worldwide. Yet, research from this depositional domain holds profound societal and economic importance. For instance, understanding the underlying stratigraphic architecture of channel margins is critical for assessing geomorphic change for fluvio-deltaic settings, which are generally vulnerable to lateral channel migration and resultant erosion. Findings would also benefit paleo-geographic reconstructions of ancient tide-influenced successions and provide an analog for hydrocarbon reservoir models. In the Ganges-Brahmaputra Delta of Bangladesh, the Gorai River is one of two Ganges distributaries actively connected to the Bay of Bengal. With fluvial input from the Ganges and meso-scale (2–4 m range) tides at the coast, the Gorai exhibits a variety of hydrodynamic regimes across its 350-km reach, providing a unique opportunity to investigate along-channel depositional patterns across the TFT. This study integrates multiple datasets—core sedimentology, river channel bathymetry, and remote sensing—to provide a process-based framework for determining the relative position of sedimentary deposits within the tidal-fluvial continuum of the Gorai River. The results of this investigation reveal coincident, abrupt shifts in river channel morphology and sediment character, suggesting the occurrence of backwater-induced mass extraction of relatively coarse sediments (i.e., fine sand). Despite being situated in an energetic tidal environment, evidence of tidal cyclicity in cored sediments is relatively rare, and the bulk stratigraphy appears strongly overprinted by irregularly spaced cm- to dm-scale sediment packages, likely derived from monsoonal flood pulses. Such findings differ from previously-studied mixed tidal-fluvial systems and underscore the site-specific complexities associated with this depositional domain.
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Fedorova, I., A. Chetverova, D. Bolshiyanov, A. Makarov, J. Boike, B. Heim, A. Morgenstern et al. "Lena Delta hydrology and geochemistry: long-term hydrological data and recent field observations". Biogeosciences 12, n.º 2 (19 de enero de 2015): 345–63. http://dx.doi.org/10.5194/bg-12-345-2015.
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Abstract. The Lena River forms one of the largest deltas in the Arctic. We compare two sets of data to reveal new insights into the hydrological, hydrochemical, and geochemical processes within the delta: (i) long-term hydrometric observations at the Khabarova station at the head of the delta from 1951 to 2005; (ii) field hydrological and geochemical observations carried out within the delta since 2002. Periods with differing relative discharge and intensity of fluvial processes were identified from the long-term record of water and sediment discharge. Ice events during spring melt (high water) reconfigured branch channels and probably influenced sediment transport within the delta. Based on summer field measurements during 2005–2012 of discharge and sediment fluxes along main delta channels, both are increased between the apex and the front of the delta. This increase is to a great extent connected with an additional influx of water from tributaries, as well as an increase of suspended and dissolved material released from the ice complex. Summer concentrations of major ion and biogenic substances along the delta branches are partly explained by water sources within the delta, such as thawing ice complex waters, small Lena River branches and estuarine areas.
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Weisscher, Steven A. H., Marcio Boechat-Albernaz, Jasper R. F. W. Leuven, Wout M. Van Dijk, Yasuyuki Shimizu y Maarten G. Kleinhans. "Complementing scale experiments of rivers and estuaries with numerically modelled hydrodynamics". Earth Surface Dynamics 8, n.º 4 (16 de noviembre de 2020): 955–72. http://dx.doi.org/10.5194/esurf-8-955-2020.
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Abstract. Physical scale experiments enhance our understanding of fluvial, tidal and coastal processes. However, it has proven challenging to acquire accurate and continuous data on water depth and flow velocity due to limitations of the measuring equipment and necessary simplifications during post-processing. A novel means to augment measurements is to numerically model flow over the experimental digital elevation models. We investigated to what extent the numerical hydrodynamic model Nays2D can reproduce unsteady, nonuniform shallow flow in scale experiments and under which conditions a model is preferred to measurements. To this end, we tested Nays2D for one tidal and two fluvial scale experiments and extended Nays2D to allow for flume tilting, which is necessary to steer tidal flow. The modelled water depth and flow velocity closely resembled the measured data for locations where the quality of the measured data was most reliable, and model results may be improved by applying a spatially varying roughness. The implication of the experimental data–model integration is that conducting experiments requires fewer measurements and less post-processing in a simple, affordable and labour-inexpensive manner that results in continuous spatio-temporal data of better overall quality. Also, this integration will aid experimental design.
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Stephens, Mark y James Rose. "Modern stable isotopic (δ18O, δ2H, δ13C) variation in terrestrial, fluvial, estuarine and marine waters from north-central Sarawak, Malaysian Borneo". Earth Surface Processes and Landforms 30, n.º 7 (julio de 2005): 901–12. http://dx.doi.org/10.1002/esp.1218.
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Kutluk, Hatice y Yuri Mazei. "Organic-walled Fossil Testate Amoebae Records (late Cretaceous–holocene) from the Neotethyan–mediterranean Region". Journal of Foraminiferal Research 48, n.º 2 (20 de abril de 2018): 121–41. http://dx.doi.org/10.2113/gsjfr.48.2.121.
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Abstract The significance of fossil testate amoebae having organic shells and their application for biostratigraphical and paleoecological studies are unexplored fields, although these organisms are extensively used as bioindicators in ecological studies of Recent and Holocene environments. Some taxa of fossil testate amoebae with organic (chitinous, pseudochitinous, or proteinaceous) shells were recovered in Turkey from a series of palynological samples, ranging in age from Late Cretaceous to Holocene. A total of 202 samples were processed from sediments from 11 sites representing fluvial flood-plain, lacustrine, estuarine, and peat-swamp as well as shallow and deep marine facies. Nineteen taxa of the genera Arcella, Centropyxis, Frenzelina, Microcometes, Nebela, Phryganella, Pyxidicula, and Sphenoderia were recorded from the Late Cretaceous, Lower−Middle Eocene, Lower Miocene, and Quaternary sediments. The literature on fossil organic-walled testate amoebae records was also reviewed and compared with the findings in this study.
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Ye, Fei, Wei Huang, Yinglong J. Zhang, Saeed Moghimi, Edward Myers, Shachak Pe'eri y Hao-Cheng Yu. "A cross-scale study for compound flooding processes during Hurricane Florence". Natural Hazards and Earth System Sciences 21, n.º 6 (2 de junio de 2021): 1703–19. http://dx.doi.org/10.5194/nhess-21-1703-2021.
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Abstract. We study the compound flooding processes that occurred in Hurricane Florence (2018), which was accompanied by heavy precipitation, using a 3D creek-to-ocean hydrodynamic model. We examine the important role played by barrier islands in the observed compound surges in the coastal watershed. Locally very high resolution is used in some watershed areas in order to resolve small features that turn out to be critical for capturing the observed high water marks locally. The wave effects are found to be significant near barrier islands and have contributed to some observed over-toppings and breaches. Results from sensitivity tests applying each of the three major forcing factors (oceanic, fluvial, and pluvial) separately are succinctly summarized in a “dominance map” that highlights significant compound effects in most of the affected coastal watersheds, estuaries, and back bays behind the barrier islands. Operational forecasts based on the current model are being set up at NOAA to help coastal resource and emergency managers with disaster planning and mitigation efforts.
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Fedorova, I., A. Chetverova, D. Bolshiyanov, A. Makarov, J. Boike, B. Heim, A. Morgenstern et al. "Lena Delta hydrology and geochemistry". Biogeosciences Discussions 10, n.º 12 (23 de diciembre de 2013): 20179–237. http://dx.doi.org/10.5194/bgd-10-20179-2013.
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Abstract. The Lena River forms one of the largest deltas in the Arctic; studying this delta has raised many questions regarding processes that occur there that remain open today. Comparing long-term hydrometric observational data of Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet) from the Khabarova polar station, located at the head of the delta not far from where the Lena River divides into its main branches, with field observations, which have been carried out since 2002 revealed new insights into the hydrological, hydrochemical, and geochemical processes within the delta. Three periods with various water volumes and intensity of fluvial processes were chosen from the long-term record of water and sediment discharge. The role of ice event (ice blockage and ice floating) during high water in reconfiguring branch channels and influencing the volume of sediment runoff was identified. Results were obtained quantifying the increase of water and sediment discharges in the middle part of the delta main branches. This increase is to a great extent connected with an additional influx of water, as well as an increase of suspended and dissolved material released from the ice complex. A range of major ion and biogenic element contents in the delta branches in summer is introduced, and differences specified between the hydrochemical composition of thawing ice complex waters, of small Lena River branches, and of estuarine areas. The conservative character of some dissolved substances was analyzed along the length of the river branches. The contents of carbon and geochemical substances in suspended and bottom sediments are reported.
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Patey, Géraldine, Catherine M. Couillard, Hilaire Drouineau, Guy Verreault, Fabien Pierron, Patrick Lambert, Magalie Baudrimont y Patrice Couture. "Early back-calculated size-at-age of Atlantic yellow eels sampled along ecological gradients in the Gironde and St. Lawrence hydrographical systems". Canadian Journal of Fisheries and Aquatic Sciences 75, n.º 8 (agosto de 2018): 1270–79. http://dx.doi.org/10.1139/cjfas-2017-0025.
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An international sampling program investigating the causes of the decline of American eels (Anguilla rostrata) and European eels (Anguilla anguilla) in the St. Lawrence (Canada) and Gironde (France) rivers systems provided the opportunity to compare early growth of eels of each species among habitats using back-calculated size-at-age from 1 to 5 years old. Our study supports previous studies showing that the early back-calculated lengths of A. anguilla were higher in downstream and more saline Gironde system habitats than in the upstream fluvial section and provides a new indication that length at 1 year old is twice higher than that reported 10 years earlier. However, our data contradict the current paradigm for A. rostrata by providing evidence that early size-at-age of eels from the upstream St. Lawrence system, most distant from the spawning area, exceeds those of eels sampled downstream, at less distant sites in the estuarine section. Overall, these observations are consistent with the hypothesis that the observed spatial variations in early growth rate of yellow eels sampled in the St. Lawrence and Gironde systems are the consequence of processes occurring in the first year of age, such as genetic selection and (or) genetically dependent habitat choice.
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Wibowo, Unggul Prasetyo, Anton Ferdianto, Nurul Laili, Dida Yurnaldi y Ruli Setiawan. "Vestige of The Ancient Estuarine of Cisaar Valley, Sumedang as One of the Pleistocene Fossil Bearing Site in West Jawa". PURBAWIDYA: Jurnal Penelitian dan Pengembangan Arkeologi 8, n.º 2 (29 de noviembre de 2019): 65–80. http://dx.doi.org/10.24164/pw.v8i2.302.
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Cisaar Valley is located on the east part of Sumedang Regency, West Jawa Province. It’s close to the boundary of Sumedang-Majalengka Regency. In this location the sandy and clay dominated sedimentary rocks are well exposed along the outcrops in the Cisaar Valley. These sedimentary rocks is inferred from Pliocene-Pleistocene deposits from Kaliwangu and Citalang Formation. Foraminifera microfossil that commonly used for interpretation of depositional environment is rarely found, whereas freshwater mollusk and vertebrate fossils often found in the sediment rocks of this area. This condition raises a question, what is the environment of this valley in the past? Data obtained from measured stratigraphic sections along Cisaar river and its tributary rivers in Cibengkung and Cirendang hamlets, Jembarwangi village. There are at least three depositional paleoenvironments which from old to young are: shallow marine, estuarine and fluviatil braided channel depositional paleoenvironment. Characteristics of the lower, middle and upper of the estuarine environment were found in this Cisaar Valley as the evidences of the oceanic regression processes was happened in the past in this area.
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Oliveira Novaes, Gabriela de, Sury de Moura Monteiro y Marcelo Rollnic. "Microplastics on the Fluvio-estuarine Beaches of Cotijuba Island, Pará River Estuary (Brazil)". Journal of Coastal Research 95, sp1 (26 de mayo de 2020): 780. http://dx.doi.org/10.2112/si95-152.1.
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Pinto, Álvaro José de Almeida, Leonardo Seabra Furtado y Aline Maria Meiguins de Lima. "The use of environmental indicators in the characterization and definition of wetlands in the Eastern Amazon". Revista Ibero-Americana de Ciências Ambientais 12, n.º 3 (13 de enero de 2021): 718–36. http://dx.doi.org/10.6008/cbpc2179-6858.2021.003.0057.
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Wetlands play a vital role in water quality, in addition to providing coastal stabilization and erosion control, aquifer recharge, they serve as important biological habitats, as nurseries for wildlife. The present study aimed to elaborate, based on environmental indicators, the characterization and classification of an estuarine fluvial plain in a humid area, considering a gradient of water bodies. The areas defined for the present study are located in the municipalities of Abaetetuba and Barcarena in Pará, which have an important and significant role, for the region and for the Amazon as a whole. The indicators used for characterization and classification, were altimetry, rainfall, hydrography and land use and coverage, and such information was processed in a GIS environment. Additionally, the Topographic Index of Wet Areas (ITU) was used, and the method of map reclassification was proposed in order to evaluate (altimetry, vegetation cover and precipitation) generating product through map algebra, defining areas with Potential Formation of Wet Areas ( PFAU). In general the region of the present study predominates low altimetric values less than or equal to 15 meters, the rainfall for the annual accumulated, varied between 3594 mm to 4844 mm, land use and cover, presented configuration where the vegetation represents 56% . Approximately 46.54% of the area has a strong potential for the formation of wetlands, being directly linked to the topographic processes and the main drainages. It is possible to demonstrate that the adoption of vegetation cover, altimetry and rainfall categories, with their respective parameters, proved to be effective for zoning AU's in the region. It is proposed that, based on this work, methodological procedures can be applied, in an expanded way in the region or in other Amazonian areas in order to confirm or indicate the classification as an AU, for different uses.
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Polyakova, Yelena I. y Ruediger Stein. "Holocene paleoenvironmental implications of diatom and organic carbon records from the southeastern Kara Sea (Siberian Margin)". Quaternary Research 62, n.º 3 (noviembre de 2004): 256–66. http://dx.doi.org/10.1016/j.yqres.2004.08.002.
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Diatom assemblages and organic carbon records from two sediment cores located within an estuarian bay of the inner Kara Sea trace changes in Yenisei River runoff and postglacial depositional environments. Paleosalinity and sea-ice reconstructions are based on modern relationships of local diatom assemblages and summer surface-water salinity. Approximately 15,500 cal yr B.P., rivers and bogs characterized the study area. When sea level reached the 38- to 40-m paleo-isobath approximately 9300 cal yr B.P., the coring site was flooded. From 9300–9100 cal yr B.P., estuarine conditions occurred proximal to the depocenter of fluvially derived material, and salinity was <7–8. Paleosalinity increased to 11–13 by 7500 cal yr B.P., following postglacial sea-level rise and the southward shift of the Siberian coast. Sharp decreases in diatom accumulation rates, total sediment, and organic carbon also occurred, suggesting the presence of brackish conditions and greater distance between the coast and study site. Maximum paleosalinity (up to 13) was recorded between 7500 and 6000 cal yr B.P., which was likely caused by the enhanced penetration of Atlantic waters to the Kara Sea. Stepwise decreases to modern salinity levels happened over the last 6000 cal yr.
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Ehn, Jens K., Rick A. Reynolds, Dariusz Stramski, David Doxaran, Bruno Lansard y Marcel Babin. "Patterns of suspended particulate matter across the continental margin in the Canadian Beaufort Sea during summer". Biogeosciences 16, n.º 7 (15 de abril de 2019): 1583–605. http://dx.doi.org/10.5194/bg-16-1583-2019.
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Abstract. The particulate beam attenuation coefficient at 660 nm, cp(660), was measured in conjunction with properties of suspended particle assemblages in August 2009 within the Canadian Beaufort Sea continental margin, a region heavily influenced by freshwater and sediment discharge from the Mackenzie River, but also by sea ice melt. The mass concentration of suspended particulate matter (SPM) ranged from 0.04 to 140 g m−3, its composition varied from mineral to organic dominated, and the median particle diameter determined over the range 0.7–120 µm varied from 0.78 to 9.45 µm, with the fraction of particles <1 µm in surface waters reflecting the degree influenced by river water. Despite this range in particle characteristics, a strong relationship between SPM and cp(660) was found and used to determine SPM distributions across the shelf based on measurements of cp(660) taken during summer seasons of 2004, 2008, and 2009. SPM spatial patterns on the stratified shelf reflected the vertically sheared two-layer estuarine circulation and SPM sources (i.e., fluvial inputs, bottom resuspension, and biological productivity). Along-shelf winds generated lateral Ekman flows, isopycnal movements, and upwelling or downwelling at the shelf break. Cross-shelf transects measured during three summers illustrate how sea ice meltwater affects river plume extent, while the presence of meltwater on the shelf was associated with enhanced near-bottom SPM during return flow of upwelled Pacific-origin water. SPM decreased sharply past the shelf break with further transport of particulate matter occurring near the bottom and in interleaving nepheloid layers. These findings expand our knowledge of particle distributions in the Beaufort Sea controlled by river discharge, sea ice, and wind, each of which is sensitive to weather and climate variations.
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Khan, Saeed, Hasley Vincent y Brent Wilson. "The qualitative and quantitative classification of modern clastic marginal-marine depositional systems, Trinidad". Journal of Sedimentary Research 91, n.º 7 (15 de julio de 2021): 710–34. http://dx.doi.org/10.2110/jsr.2020.119.
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ABSTRACT Trinidad's modern coastal depositional systems are for the first time documented by (traditional) descriptive and (modern) semiquantitative and quantitative classification methods. The processes controlling the morphology and distribution of these systems are also investigated. Google Earth™ satellite images, together with published basinal processes data (e.g., significant wave height, surface littoral currents, and tidal cyclicity) are used to describe system morphology, map depositional elements, and to determine the processes responsible for system distribution, respectively. Coastal depositional systems along Trinidad's east, south, and west coasts comprise deltas, estuaries, tidal-inlet complexes, strandplains, and tidal flats. Their distribution is controlled by the wave regime, although they are also influenced by tidal and fluvial processes. The wave regime changes from wave-dominated along the open east coast, to mixed-energy wave-dominated along the semi-sheltered south coast, and to mixed-energy tide-dominated along the sheltered west coast. Distribution of depositional systems related to this regime are such that the wave-dominated east coast sees the development of wave-dominated estuaries. The south coast has a series of wave-dominated, tide- and river-influenced deltas. The sheltered west coast is the most morphologically diverse with river- and wave-dominated deltas, strandplains, and tidal flats. The application of semiquantitative and quantitative classification methods on modern systems has showed their competence in classifying mixed-influence systems from their morphology and sedimentary record. Quantitative classification using depositional elements lends an appreciation to the morphological signatures of mixed-influence systems. Quantitative classification for sedimentary sections gives an appreciation of the preservation of mixed-influence physical processes. The combination of both allows the correlation of the impact of physical properties on morphology and sedimentary record (i.e., possible disparities between morphology and processes). The combination of semiquantitative and quantitative methods may also hold the key to unlocking the mixed-processes classification of depositional elements.
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Antunes do Carmo, J. S. "Environmental impacts of human action in watercourses". Natural Hazards and Earth System Sciences Discussions 2, n.º 10 (14 de octubre de 2014): 6499–530. http://dx.doi.org/10.5194/nhessd-2-6499-2014.
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Abstract. The economic, social and environmental conditions of various European river basins and estuarine systems have changed dramatically in the last decades as a consequence of anthropogenic effects, and they will go on changing in the years to come due to increasing human pressure. Particularly in Portugal, various river-estuary systems have undergone several human interventions, notably engineering works to restore considerable stretches of channels and river banks. Whenever the characteristics and natural evolution of a river are altered as a result of human intervention there is an environmental impact. In other words, it is understood that differences can be observed between any present situation that is the result of the evolution of an environment after human intervention, and the natural situation that would have existed if this type of intervention had not taken place, taking into account our previous knowledge of the situation. A thorough understanding of the fluvial processes and new strategies are needed to develop a multifunctional use structure, which must take into account the many-faceted aims of sustainable development. This paper provides a brief description of the nature and distribution of the direct and indirect types of impact arising out of building and operating large dams, as well as some specific points that should be taken into consideration. It also reflects on the way in which the problem of extracting inert material from water environments has been dealt with in Portugal and offers a brief technical contribution which, although qualitative, provides a basic record and explanation of the consequences of significant interventions in water environments that have not been properly assessed or have not taken other mitigating circumstances into consideration.