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In situ flume measurements of resuspension in the North Sea

In situ flume measurements of resuspension in the North Sea
In situ flume measurements of resuspension in the North Sea
The in situ annular flume, Voyager II, was deployed at three sites in the North Sea in order to investigate resuspension events, to determine the physical characteristics of the seabed, to determine the threshold of resuspension of the bed and to quantify erosion rates and erosion depths. These are the first controlled, in situ flume experiments to study resuspension in the North Sea, and were combined with long-term measurements of waves and currents. Resuspension experiments were undertaken at two muddy, and one sandy site: north of the Dogger Bank (DG: water depths not, vert, similar80 m, very fine, poorly sorted, very fine-skewed sediment experiencing seasonal thermal stratification of the water column along with oxygen depletion); the Oyster Grounds (OG: not, vert, similar40 m, similar bed properties, year round water column thermal stratification, Atlantic forcing); and in the Sean Gas Field (SGF: not, vert, similar20 m, moderately sorted, very coarse-skewed sand, and well mixed water column). The erosion thresholds of the bed were found to be 0.66–1.04 Pa (DG) and 0.91–1.27 Pa (OG), with corresponding erosion depths of 0.1–0.15 mm and 0.02–0.06 mm throughout the experiments.

Evaluation of a year of current velocities from 2007 indicated that at OG, resuspension of the consolidated bed was limited to on average not, vert, similar8% of the time as a result of tidal forcing alone for short (<30 min) durations, but would potentially increase during the winter as a result of wave influences. At DG, under similar conditions this would increase to 13%, and in the SGF, wave-induced resuspension events occurred throughout the year, with the potential exceedance of the threshold for suspension greater than 50% in January and March.

Resuspension of bed material and erosion rates were closely related to applied bed shear stresses, and eroded depths were significantly correlated with the physical properties of the bed. Therefore, while complex variations in biogeophysical factors affected the critical threshold of erosion, once exceeded, erosion rates were related to the nature of the sediment.
sediment, resuspension, North Sea, annular flume
0272-7714
77-88
Thompson, C.E.L.
2a304aa6-761e-4d99-b227-cedb67129bfb
Couceiro, F.
234f83a2-8265-4a21-81ad-5af41bcbd6ff
Fones, G.R.
5b71916c-4859-4a6f-b9ad-b6b1f541cbfa
Helsby, R.
d416fb20-05a6-44ab-91b9-2771b49ff08f
Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Black, K.
028f2582-68bf-40be-8431-0f3004db3898
Parker, E.R.
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Greenwood, N.
499b047b-f94d-4d8e-a5e9-79770c5d107d
Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Kelly-Gerreyn, B.A.
1434d5fd-49f7-4774-b5ff-ddf334a3dcc2
Thompson, C.E.L.
2a304aa6-761e-4d99-b227-cedb67129bfb
Couceiro, F.
234f83a2-8265-4a21-81ad-5af41bcbd6ff
Fones, G.R.
5b71916c-4859-4a6f-b9ad-b6b1f541cbfa
Helsby, R.
d416fb20-05a6-44ab-91b9-2771b49ff08f
Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Black, K.
028f2582-68bf-40be-8431-0f3004db3898
Parker, E.R.
1e7487cc-7ddf-4c56-9a6c-c6b1aafdaa3f
Greenwood, N.
499b047b-f94d-4d8e-a5e9-79770c5d107d
Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Kelly-Gerreyn, B.A.
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Thompson, C.E.L., Couceiro, F., Fones, G.R., Helsby, R., Amos, C.L., Black, K., Parker, E.R., Greenwood, N., Statham, P.J. and Kelly-Gerreyn, B.A. (2011) In situ flume measurements of resuspension in the North Sea. Estuarine, Coastal and Shelf Science, 94 (1), 77-88. (doi:10.1016/j.ecss.2011.05.026).

Record type: Article

Abstract

The in situ annular flume, Voyager II, was deployed at three sites in the North Sea in order to investigate resuspension events, to determine the physical characteristics of the seabed, to determine the threshold of resuspension of the bed and to quantify erosion rates and erosion depths. These are the first controlled, in situ flume experiments to study resuspension in the North Sea, and were combined with long-term measurements of waves and currents. Resuspension experiments were undertaken at two muddy, and one sandy site: north of the Dogger Bank (DG: water depths not, vert, similar80 m, very fine, poorly sorted, very fine-skewed sediment experiencing seasonal thermal stratification of the water column along with oxygen depletion); the Oyster Grounds (OG: not, vert, similar40 m, similar bed properties, year round water column thermal stratification, Atlantic forcing); and in the Sean Gas Field (SGF: not, vert, similar20 m, moderately sorted, very coarse-skewed sand, and well mixed water column). The erosion thresholds of the bed were found to be 0.66–1.04 Pa (DG) and 0.91–1.27 Pa (OG), with corresponding erosion depths of 0.1–0.15 mm and 0.02–0.06 mm throughout the experiments.

Evaluation of a year of current velocities from 2007 indicated that at OG, resuspension of the consolidated bed was limited to on average not, vert, similar8% of the time as a result of tidal forcing alone for short (<30 min) durations, but would potentially increase during the winter as a result of wave influences. At DG, under similar conditions this would increase to 13%, and in the SGF, wave-induced resuspension events occurred throughout the year, with the potential exceedance of the threshold for suspension greater than 50% in January and March.

Resuspension of bed material and erosion rates were closely related to applied bed shear stresses, and eroded depths were significantly correlated with the physical properties of the bed. Therefore, while complex variations in biogeophysical factors affected the critical threshold of erosion, once exceeded, erosion rates were related to the nature of the sediment.

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More information

Published date: 30 July 2011
Keywords: sediment, resuspension, North Sea, annular flume
Organisations: Ocean and Earth Science, Marine Biogeochemistry, National Oceanography Centre,Southampton

Identifiers

Local EPrints ID: 194859
URI: http://eprints.soton.ac.uk/id/eprint/194859
ISSN: 0272-7714
PURE UUID: e0b832f0-8e8a-42ff-8698-1bcec2334e84
ORCID for C.E.L. Thompson: ORCID iD orcid.org/0000-0003-1105-6838

Catalogue record

Date deposited: 11 Aug 2011 13:55
Last modified: 15 Mar 2024 03:05

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Contributors

Author: C.E.L. Thompson ORCID iD
Author: F. Couceiro
Author: G.R. Fones
Author: R. Helsby
Author: C.L. Amos
Author: K. Black
Author: E.R. Parker
Author: N. Greenwood
Author: P.J. Statham
Author: B.A. Kelly-Gerreyn

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