scholarly journals Hydrodynamic and Sediment Transport Patterns in the Minho and Douro Estuaries (NW Portugal) Based on ADCP Monitoring Data: Part 1-Tidal Sediment Exchanges

Coasts ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 31-55 ◽  
Author(s):  
Ana Isabel Santos ◽  
Anabela Oliveira ◽  
José Paulo Pinto ◽  
M. Conceição Freitas
Keyword(s):  
River Flow ◽  
Acoustic Backscatter ◽  
Inner Shelf ◽  
Sediment Fluxes ◽  
Nw Portugal ◽  
Column Structure ◽  
Shelf Sediment ◽  
Tidal Variability ◽  
Transport Patterns ◽  
Sediment Export

The tidal variability of the Minho and Douro lower estuaries (NW Portugal) water column structure was assessed at the semi-diurnal and fortnightly time scales under two contrasting seasonal river flow scenarios during the summer of 2005 and winter of 2006. Sediment fluxes inferred from calibrated ADCP acoustic backscatter revealed that, during spring tides and low runoff conditions, both estuaries act as sinks instead of sources of sediments into the inner shelf. Sediment export occurred during neaps, in both estuaries, when the river flow values were high enough to counteract the effect of the entering flood. No evidence of coarse sediment export into the inner shelf that would eventually nourish the littoral system could be inferred from these datasets.

scholarly journals Hydrodynamic and Sediment Transport Patterns in the Minho and Douro Estuaries (NW Portugal) Based on ADCP Monitoring Data: Part 2—Statistical Interpretation of Bottom Moored Datasets

Coasts ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 56-72
Author(s):  
Ana Isabel Santos ◽  
Anabela Oliveira ◽  
Dora Carinhas ◽  
José Paulo Pinto ◽  
M. Conceição Freitas
Keyword(s):  
Sediment Transport ◽  
Clustering Analysis ◽  
River Discharge ◽  
Sandy Sediment ◽  
Statistical Interpretation ◽  
Nw Portugal ◽  
Transport Patterns ◽  
Sediment Export ◽  
Acoustic Responses ◽  
Effective Contribution

Exploratory statistical partitioning methods (K-means Clustering analysis) were applied to ADCP monitoring datasets collected inside the Douro and Minho estuaries. This analysis is aimed to discriminate ADCP acoustic responses according to the variations of the suspended particles within the ensonified medium. Based on the interpretation of the results, this work establishes general sediment transport patterns at both estuaries’ exits under continuously varying river flows and tidal amplitudes recorded during a summer dry seasonal scenario (September 2005) and winter high river discharge (January/February 2007) conditions. Results confirm the already known present scarcity of (sandy) sediment export from the Douro and Minho estuaries into the inner shelf and the consequent sediment depletion of the adjacent littoral, with no effective contribution of the Douro and some evidence of sand export observed at the Minho outlet during the winter of 2007.

scholarly journals Conceptualising and mapping coupled estuary, coast and inner shelf sediment systems

Geomorphology ◽  
2016 ◽  
Vol 256 ◽  
pp. 17-35 ◽  
Author(s):  
Jon French ◽  
Helene Burningham ◽  
Gillian Thornhill ◽  
Richard Whitehouse ◽  
Robert J. Nicholls
Keyword(s):  
Inner Shelf ◽  
Shelf Sediment

scholarly journals Marine and anthropogenic controls on the estuary of the Suriname River over the past 50 years

2016 ◽  
Vol 95 (4) ◽  
pp. 419-428
Author(s):  
K. Gersie ◽  
P.G.E.F. Augustinus ◽  
R.T. Van Balen
Keyword(s):  
Tidal Current ◽  
River Flow ◽  
Sediment Load ◽  
Anthropogenic Activities ◽  
Fluvial Systems ◽  
Sediment Fluxes ◽  
Fine Grained ◽  
The Past ◽  
The Impact ◽  
Strong Tidal Current

AbstractHumans have played an important role in fluvial systems because of the impact of their land-use activities, frequently leading to degradation of environmental conditions. Rivers, which are the primary agents in sediment transport, have thus been subject to changes in sediment fluxes. The Suriname River has been affected by anthropogenic activities since colonial times, and has experienced strong discharge and sediment-load changes since the construction of the Afobaka Dam in 1964. The river's estuary sediments largely consist of fine-grained sediments, originating, ultimately, from the Amazon River and transported by the strong tidal current. The influence of this tidal current is diminished at the head of the estuary, allowing the river flow to become dominant. Also remarkable is the interaction of the Suriname River and the westward-migrating mudbanks which is evident in the changing magnitude and volume of Braamspunt, a mudcape located at the mouth of the estuary. The regulated discharge of the river results in a change of the river's morphology, resulting, among other things, in the growth of river bars.

scholarly journals Unraveling The Impacts of Meteorological and Anthropogenic Changes on Sediment Fluxes Along an Estuary-Sea Continuum

2021 ◽  
Author(s):  
Florent Grasso ◽  
Eliott Bismuth ◽  
Romaric Verney
Keyword(s):  
Human Activities ◽  
River Flow ◽  
Morphological Changes ◽  
Large River ◽  
Fine Sediment ◽  
Global Changes ◽  
Anthropogenic Pressures ◽  
Estuarine Ecosystem ◽  
Anthropogenic Changes ◽  
Sediment Fluxes

Abstract Sediment fluxes at the estuary-sea interface strongly impact particle matter exchanges between marine and continental sources along the land-sea continuum. However, human activities drive pressures on estuary physical functioning, hence threatening estuarine habitats and their ecosystem services. There is an increasing societal need to better predict the potential trajectories of estuarine sediment fluxes resulting from natural and anthropogenic pressures, but the concomitance of human-induced and meteorological-induced changes makes the responses ambiguous. Therefore, this study explores a 22-year numerical hindcast, experiencing contrasted meteorological conditions and human-induced morphological changes (i.e., estuary deepening and narrowing), in order to disentangle the relative contributions of meteorological and anthropogenic changes on net sediment fluxes between a macrotidal estuary and its adjacent coastal sea. Our results highlight that intense wave events induce fine sediment (≤100 µm) export to the sea but coarser sediment (≥210 µm) import within the estuary. Remarkably, moderate to large river flows support mud import within the estuary. Over 25 years, the reduction of intense wave and river flow events reduces fine sediment export to the sea. In addition, the estuary morphological changes due to human activities increase fine sediment import within the estuary, shifting the estuary from an exporting to importing system. We propose a conceptualization of mud flux response to river flow and wave forcing, as well as anthropogenic pressures. It provides valuable insights into particle transfers along the land-sea continuum, contributing to a better understanding of estuarine ecosystem trajectories under global changes.

Nearshore—Inner Shelf Sediment Exchange on the NSW Central Coast

2001 ◽  
Author(s):  
Peter Evans ◽  
David Hanslow ◽  
Aaron Coutts-Smith ◽  
Zai-Jin You
Keyword(s):  
Central Coast ◽  
Inner Shelf ◽  
Shelf Sediment

scholarly journals SAND TRANSPORT AND COASTAL STABILITY, LANCASHIRE, U.K.

1974 ◽  
Vol 1 (14) ◽  
pp. 48
Author(s):  
William Reginald Parker
Keyword(s):  
Sediment Transport ◽  
Qualitative Description ◽  
Sand Transport ◽  
Residence Times ◽  
Coastal Evolution ◽  
Dune Erosion ◽  
Sediment Fluxes ◽  
Dune Stability ◽  
Transport Patterns ◽  
The Stability

The stability of an alluvial coast depends upon the local sediment budget. Along the shore, changes from erosion to accretion may reflect changing sediment fluxes, sediment residence times and patterns of sediment movement. Processes influencing these parameters, such as mud sedimentation or migration of intertidal channels will, through their influence on beach gradients and sediment transport patterns, affect the processes and rates of coastal dune erosion and the safety of the dune protected hinterland. A qualitative description of some of the various processes and phenomena linking foreshore and dune stability with sediment circulation and coastal evolution is presented.

Monitoring inner shelf sediment transport using fluorescent sand tracers: an example from the south coast of Portugal 

2021 ◽  
Author(s):  
João Cascalho ◽  
Rui Taborda ◽  
Marcos Rosa ◽  
Erwan Garel ◽  
Sebastião Teixeira ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Tracer Experiment ◽  
Current Data ◽  
Automated Image Analysis ◽  
South Coast ◽  
Inner Shelf ◽  
Shelf Sediment ◽  
Ongoing Work ◽  
Coated Sand

<p>The continuous need for beach nourishment requires a detailed understanding of the sediment transport characteristics at the shelf borrow sites, to assess their recovery rate and to evaluate the long-term sustainability of these operations. </p><p>The main objective of this work is to assess sediment transport conditions at an inner shelf borrow site exploited to nourish a beach located at the updrift boundary of the same sedimentary cell (Belharucas, Albufeira, south coast of Portugal).</p><p>The work is supported by a sand tracer experiment, where 600 kg of coated sand with fluorescent ink was deposited (August 2020) by divers at 11 m depth (referred to the mean sea level). Periodic sediment sampling using a Van Veen grab was performed using an adaptative sampling grid that accounted for tracer’s dispersion trough time. The samples were washed and dried in laboratory and tagged particles were automatically identified using an automated image analysis procedure based on ultraviolet lighting.</p><p>Preliminary results show that sediment transport is dominated by a eastward component,probably related with the energetic events from the SW. Ongoing work relates the tracer’s displacement with ADCP (wave and current) data measured nearby the borrow site during the experiment.</p><p> </p><p>The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – IDL and ECOEXA project (MAR-01.04.02-FEAMP-0016).</p><p> </p><p> </p>

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