The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Claudia Wienberg - One of the best experts on this subject based on the ideXlab platform.
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acoustic seabed classification in a coastal environment outer weser estuary german bight a new approach to monitor dredging and Dredge Spoil disposal
Continental Shelf Research, 2005Co-Authors: Claudia Wienberg, Alexander BartholomaAbstract:Abstract Acoustic seabed classification provides a sophisticated technique to discriminate seabed characteristics and to map their distribution at high spatial and temporal resolution. In the present study, the seabed classification system QTC View/Impact was applied to investigate a 9- km 2 area at water depths between 6 and 20 m in the outer Weser Estuary (German Bight, southeastern North Sea). The survey area comprises parts of a routinely Dredged shipping channel as well as of a Dredge Spoil disposal site. The acoustic data, collected by means of a singlebeam 200-kHz echosounder combined with a QTC system, were classified into three acoustic classes. These classes are identified with (1) fine to medium sand, with a low content of shell fragments; (2) medium sand, with a moderate content of shell fragments; and (3) medium to coarse sand, with a high content of shell fragments. By comparing this point-related acoustic classification with sidescan sonographs, it can be convincingly demonstrated that the acoustic data obtained by the QTC system reflect more than simply sediment type distribution, but that rather the occurrence of bedforms also appears to be important. Furthermore, in a time series of three QTC surveys in a period of 14 months, it is apparent that dredging as well as the disposal of Dredge Spoil constitute a strong impact on the sediment distribution and seabed morphology of the study site.
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Impact of dumped sediments on subaqueous dunes, outer Weser Estuary, German Bight, southeastern North Sea
Geo-Marine Letters, 2005Co-Authors: Claudia Wienberg, Dierk HebbelnAbstract:The impact of Dredge Spoil disposal on asymmetrical large-scale dunes has been studied at a disposal site in a shallow subtidal area of the outer Weser Estuary (German Bight, southeastern North Sea). Between June and December 1998, this site was used for the disposal of ~3×10^6 m^3 Dredge Spoil. Repeated bathymetric surveys with a multibeam echosounder system reveal that the artificial supply of sediment provoked significant morphological changes in the dune field, including the infill of dune troughs and even the complete burial of individual dunes. However, even completely buried dunes began to regenerate within a few months. In addition, slow migration of the dunes toward the open sea was observed, indicating net seaward sediment transport in the survey area. Since the dumped sediment does not appear to have a persistent effect on the bedforms and, in all likelihood, will be exported from the estuarine system on medium- to long-term timescales, the investigated area constitutes a suitable disposal site.
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The fate of dumped sediments monitored by a high-resolution multibeam echosounder system, Weser Estuary, German Bight
Geo-Marine Letters, 2004Co-Authors: Claudia Wienberg, Jens Dannenberg, Dierk HebbelnAbstract:With the development of high-resolution multibeam echosounder systems (MBES) for surveying shallow-water areas a new tool is available to monitor rapid changes in seabed morphology as, e.g., caused by the dumping of Dredge Spoil in coastal waters. In this study, four data sets of repeated bathymetric surveys with a MBES were processed and analyzed. The data were collected in a 1.94-km^2 dumping site in the outer Weser Estuary (German Bight). Between June and December 1998, 2.6 million m^3 of Dredged sediment were deposited there. The bathymetric maps generated in the course of this study reveal features such as subaqueous dunes, scour holes, and mounds of dumped Dredge Spoil. The mean water depth decreased by about 1 m during the dumping period. Furthermore, difference grids showing changes in sediment volume allowed a calculation of the sediment budget for the monitored area. After a time period of only 5 months, 0.5 million m^3 of the originally dumped 2.6 million m^3 of Dredge Spoil had already been removed from the dumping site.
Dierk Hebbeln - One of the best experts on this subject based on the ideXlab platform.
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Impact of dumped sediments on subaqueous dunes, outer Weser Estuary, German Bight, southeastern North Sea
Geo-Marine Letters, 2005Co-Authors: Claudia Wienberg, Dierk HebbelnAbstract:The impact of Dredge Spoil disposal on asymmetrical large-scale dunes has been studied at a disposal site in a shallow subtidal area of the outer Weser Estuary (German Bight, southeastern North Sea). Between June and December 1998, this site was used for the disposal of ~3×10^6 m^3 Dredge Spoil. Repeated bathymetric surveys with a multibeam echosounder system reveal that the artificial supply of sediment provoked significant morphological changes in the dune field, including the infill of dune troughs and even the complete burial of individual dunes. However, even completely buried dunes began to regenerate within a few months. In addition, slow migration of the dunes toward the open sea was observed, indicating net seaward sediment transport in the survey area. Since the dumped sediment does not appear to have a persistent effect on the bedforms and, in all likelihood, will be exported from the estuarine system on medium- to long-term timescales, the investigated area constitutes a suitable disposal site.
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The fate of dumped sediments monitored by a high-resolution multibeam echosounder system, Weser Estuary, German Bight
Geo-Marine Letters, 2004Co-Authors: Claudia Wienberg, Jens Dannenberg, Dierk HebbelnAbstract:With the development of high-resolution multibeam echosounder systems (MBES) for surveying shallow-water areas a new tool is available to monitor rapid changes in seabed morphology as, e.g., caused by the dumping of Dredge Spoil in coastal waters. In this study, four data sets of repeated bathymetric surveys with a MBES were processed and analyzed. The data were collected in a 1.94-km^2 dumping site in the outer Weser Estuary (German Bight). Between June and December 1998, 2.6 million m^3 of Dredged sediment were deposited there. The bathymetric maps generated in the course of this study reveal features such as subaqueous dunes, scour holes, and mounds of dumped Dredge Spoil. The mean water depth decreased by about 1 m during the dumping period. Furthermore, difference grids showing changes in sediment volume allowed a calculation of the sediment budget for the monitored area. After a time period of only 5 months, 0.5 million m^3 of the originally dumped 2.6 million m^3 of Dredge Spoil had already been removed from the dumping site.
Jean-claude Dauvin - One of the best experts on this subject based on the ideXlab platform.
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What are the most suitable indices to detect the structural and functional changes of benthic community after a local and short-term disturbance?
Ecological Indicators, 2018Co-Authors: Jean-philippe Pezy, Stella Marmin, Aurore Raoux, Pierre Balay, Jean-claude DauvinAbstract:A one-year experimental study was conducted in 2012–2013 to assess the physical and biological impacts of dumping Dredge Spoil composed of muddy fine sand (1 million m3) in a benthic zone with medium-grained sands in the eastern part of the Bay of Seine. Previous study showed that the impact is local and the benthic habitats show a high degree of resilience after a short dumping phase and the recovery of the community is observed just after cessation of the disturbance. Moreover, during the deposition phase, Impacted and Influenced zones can be distinguished from a Non-impacted zone. A combination of indices (BO2A, AMBI benthic indices) and modelling tools were applied to study the dumping Dredge Spoil impact. Results highlighted that these different indices allowed detecting the dumping operations effects. In addition, results from the AMBI et BO2A indices revealed that the system showed a high resilience after a short dumping phase. Lastly, the macrofauna and demersal fishes appear to be stimulated in the Influenced zone during the dumping phase, thus supporting the Intermediate Disturbance Hypothesis.
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Dredge Spoil disposal (DSD) index.
Marine pollution bulletin, 2018Co-Authors: Jean-claude Dauvin, Noémie Baux, Jean-philippe PezyAbstract:(IF 3.78; Q1)International audienc
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An experimental study on Dredge Spoil of estuarine sediments in the bay of seine (France): A morphosedimentary assessment
Continental Shelf Research, 2016Co-Authors: Stella Marmin, Patrick Lesueur, Jean-claude Dauvin, Sandrine Samson, Patrice Tournier, Albert Gallicher Lavanne, Carole Dubrulle-brunaud, Coralie ThouroudeAbstract:Studies on the consequences of dredging on estuarine morphology and its sedimentary dynamics are common, but the impacts of dumping Dredge Spoil in coastal open settings are rarely found in scientific literature. An experimental study was conducted over the period 2012-2013 to monitor the physical impacts of Dredged material dumped at two adjacent sites (one million cubic metres at each) on the inner shelf of the Bay of Seine in France (eastern part of the English Channel, La Manche). As recently reinforced in the EU Marine Strategy Framework Directive (MSFD), knowledge on the location and intensity of human impacts (e.g. on marine ecosystems) is critical for effective marine management and conservation. So, two methods of disposition were tested to evaluate the impacts of dumping on the environment and thus propose recommendations for future dumping. The strategy is based on a Before-After-Control-Impact (BACI) approach, in which the spatio-temporal variability was studied by analysing the morphological and sedimentological characteristics over a period of 28 months, from November 2011 to April 2014, also including recovery of the seafloor after cessation of the dumping activities. The first experimental dumping operation (MASED) was carried out regularly for 8 months at a single point and generating a conical deposit of 5 m in height, while the second dumping (MABIO) lasted for 12 months involving four steps in the dumping process. In the second case, a wider area was covered, leading to the formation of a smaller deposit of 2 m in height. The dumped deposits consisted of muddy fine sand, whereas the inner shelf seafloor in this area is covered with fine to medium sand. As a result, muddy fine sand accumulated at or near the two dumping sites, with a maximum mud (i.e. particles4 Φ) content of 50% compared to
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an experimental study on Dredge Spoil of estuarine sediments in the bay of seine france a morphosedimentary assessment
Continental Shelf Research, 2016Co-Authors: Stella Marmin, Patrick Lesueur, Jean-claude Dauvin, Sandrine Samson, Patrice Tournier, Albert Gallicher Lavanne, Carole DubrullebrunaudAbstract:Studies on the consequences of dredging on estuarine morphology and its sedimentary dynamics are common, but the impacts of dumping Dredge Spoil in coastal open settings are rarely found in scientific literature. An experimental study was conducted over the period 2012-2013 to monitor the physical impacts of Dredged material dumped at two adjacent sites (one million cubic metres at each) on the inner shelf of the Bay of Seine in France (eastern part of the English Channel, La Manche). As recently reinforced in the EU Marine Strategy Framework Directive (MSFD), knowledge on the location and intensity of human impacts (e.g. on marine ecosystems) is critical for effective marine management and conservation. So, two methods of disposition were tested to evaluate the impacts of dumping on the environment and thus propose recommendations for future dumping. The strategy is based on a Before-After-Control-Impact (BACI) approach, in which the spatio-temporal variability was studied by analysing the morphological and sedimentological characteristics over a period of 28 months, from November 2011 to April 2014, also including recovery of the seafloor after cessation of the dumping activities. The first experimental dumping operation (MASED) was carried out regularly for 8 months at a single point and generating a conical deposit of 5 m in height, while the second dumping (MABIO) lasted for 12 months involving four steps in the dumping process. In the second case, a wider area was covered, leading to the formation of a smaller deposit of 2 m in height. The dumped deposits consisted of muddy fine sand, whereas the inner shelf seafloor in this area is covered with fine to medium sand. As a result, muddy fine sand accumulated at or near the two dumping sites, with a maximum mud (i.e. particles 4 Φ) content of 50% compared to<5% before dumping operations. Videos obtained from a LVB200 Seabotix ROV, highlighted the heterogeneity of the sea floor around the dumping areas. Due to hydrodynamic forcing (wave climate and tidal currents), about 50% (MABIO) and 75% (MASED) of the volume of Dredged material remained at the end of the dumping periods. After dumping ceased, a further 5% of material for MABIO and 20% for MASED, was transported out of the study area. For the latter, a spreading of fine particles was observed extending from the conical deposit towards the south west. To favour long-term exploitation, a more dispersive dumping over a wider surface area is recommended (e.g. MABIO)
Alexander Bartholoma - One of the best experts on this subject based on the ideXlab platform.
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acoustic seabed classification in a coastal environment outer weser estuary german bight a new approach to monitor dredging and Dredge Spoil disposal
Continental Shelf Research, 2005Co-Authors: Claudia Wienberg, Alexander BartholomaAbstract:Abstract Acoustic seabed classification provides a sophisticated technique to discriminate seabed characteristics and to map their distribution at high spatial and temporal resolution. In the present study, the seabed classification system QTC View/Impact was applied to investigate a 9- km 2 area at water depths between 6 and 20 m in the outer Weser Estuary (German Bight, southeastern North Sea). The survey area comprises parts of a routinely Dredged shipping channel as well as of a Dredge Spoil disposal site. The acoustic data, collected by means of a singlebeam 200-kHz echosounder combined with a QTC system, were classified into three acoustic classes. These classes are identified with (1) fine to medium sand, with a low content of shell fragments; (2) medium sand, with a moderate content of shell fragments; and (3) medium to coarse sand, with a high content of shell fragments. By comparing this point-related acoustic classification with sidescan sonographs, it can be convincingly demonstrated that the acoustic data obtained by the QTC system reflect more than simply sediment type distribution, but that rather the occurrence of bedforms also appears to be important. Furthermore, in a time series of three QTC surveys in a period of 14 months, it is apparent that dredging as well as the disposal of Dredge Spoil constitute a strong impact on the sediment distribution and seabed morphology of the study site.
R.j. Meijer - One of the best experts on this subject based on the ideXlab platform.
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natural radionuclides as tracers of the dispersal of Dredge Spoil dumped at sea
Journal of Environmental Radioactivity, 2001Co-Authors: L B Venema, R.j. MeijerAbstract:Monitoring large (underwater) surfaces, with rapidly varying composition, requires a sampling density which exceeds the capabilities of standard techniques. These techniques involve sample collection and a number of treatments and measurements in the laboratory; both steps are laborious, tedious and costly. This paper presents an in situ method in which a detector system is trailed over the surface and measures continuously the gamma rays emitted by the natural radionuclides in the sediment. Since each sediment component has its own characteristic set of activity-concentration values (radiometric fingerprint), the composition of the sediment can be deduced quantitatively. This paper shows the application of this technique for monitoring the dispersal of Dredge Spoil from Rotterdam harbour, dumped in the North Sea. In addition to a qualitative picture of Dredge Spoil dispersal, a mass balance equation has been used to quantitatively assess the Dredge Spoil transport with time.
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natural radionuclides as tracers of the dispersal of Dredge Spoil dumped at sea
Journal of Geochemical Exploration, 2001Co-Authors: L B Venema, R.j. MeijerAbstract:Monitoring large (underwater) surfaces, with rapidly varying composition, requires a sampling density which exceeds the capabilities of standard techniques. These techniques involve sample collection and a number of treatments and measurements in the laboratory; both steps are laborious, tedious and costly. This paper presents an in situ method in which a detector system is trailed over the surface and measures continuously the gamma rays emitted by the natural radionuclides in the sediment. Since each sediment component has its own characteristic set of activity-concentration values (radiometric fingerprint), the composition of the sediment can be deduced quantitatively. This paper shows the application of this technique for monitoring the dispersal of Dredge Spoil from Rotterdam harbour, dumped in the North Sea. In addition to a qualitative picture of Dredge Spoil dispersal, a mass-balance equation has been used to quantitatively assess the Dredge Spoil transport with time. (C) 2001 Elsevier Science Ltd. All rights reserved.
