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Hydrodynamics and sediment dynamics of North Sea sand waves and sand banks

Hydrodynamics and sediment dynamics of North Sea sand waves and sand banks
Hydrodynamics and sediment dynamics of North Sea sand waves and sand banks
Seabed drag coefficients have been measured at a site within the Norfolk Banks and at a site within the sand wave field in the southern North Sea, using pressure sensors and moored current meters. At the sand banks site a seabed tripod measuring turbulent flows within 1 m of the bed was also used. The results are generally in agreement with values used in numerical models. At the sand banks site, the drag coefficient increases with wind conditions, but at the sand waves site there is a reduction during the highest wave conditions, attributed to the drag reduction caused by sand resuspension from the bed. This result suggests that sediment effects must be considered if wave/current interaction is included in numerical models of the region. The drag coefficient for reversing tidal flows over the asymmetric sand waves is found to be larger for flow towards the steeper face, suggesting a small form drag component. Studies of sand movement used bedform mapping, fluorescent sand tracing and photography of migrating ripples. There is evidence for the early stages of formation of a new bank between Broken Bank and Well Bank. At the sand waves site, ripple migration is found to be a useful estimator of bedload transport under conditions of negligible suspension. Over the sand banks, a definite correlation of surface water properties, notably the turbidity, with the topography of the banks was observed. The mechanism for this surface effect is not known but it is consistent with the observation of features, seen in satellite visible light images, which outline the shapes of the banks.

1364-503X
461-474
Huntley, D.A.
c0ae6ddd-cb02-432a-a3e8-f4e7dfe161e7
Huthnance, J.M.
320730a4-47f9-4a66-8a51-e746bbac606f
Collins, M.B.
3b70278b-0004-45e0-b3c9-0debdf0a9351
Liu, C.-L.
11bf6d58-26f0-428d-ad7e-775a6f4c4341
Nicholls, R.J.
4ce1e355-cc5d-4702-8124-820932c57076
Hewitson, C.
233893e2-e6a0-43f7-903e-a63a9a8f0c64
Green, M.O.
8cbee1d8-ea93-408d-a221-407d727534c8
Dyer, K.R.
2a824785-333e-4a16-90c0-e1a48a3a95dd
Jago, C.F.
411cd60d-b407-4fae-930e-234eaa5801c9
Huntley, D.A.
c0ae6ddd-cb02-432a-a3e8-f4e7dfe161e7
Huthnance, J.M.
320730a4-47f9-4a66-8a51-e746bbac606f
Collins, M.B.
3b70278b-0004-45e0-b3c9-0debdf0a9351
Liu, C.-L.
11bf6d58-26f0-428d-ad7e-775a6f4c4341
Nicholls, R.J.
4ce1e355-cc5d-4702-8124-820932c57076
Hewitson, C.
233893e2-e6a0-43f7-903e-a63a9a8f0c64
Green, M.O.
8cbee1d8-ea93-408d-a221-407d727534c8
Dyer, K.R.
2a824785-333e-4a16-90c0-e1a48a3a95dd
Jago, C.F.
411cd60d-b407-4fae-930e-234eaa5801c9

Huntley, D.A., Huthnance, J.M., Collins, M.B., Liu, C.-L., Nicholls, R.J., Hewitson, C., Green, M.O., Dyer, K.R. and Jago, C.F. (1993) Hydrodynamics and sediment dynamics of North Sea sand waves and sand banks. Philosophical Transactions of The Royal Society A, 343 (1669), 461-474. (doi:10.1098/rsta.1993.0059).

Record type: Article

Abstract

Seabed drag coefficients have been measured at a site within the Norfolk Banks and at a site within the sand wave field in the southern North Sea, using pressure sensors and moored current meters. At the sand banks site a seabed tripod measuring turbulent flows within 1 m of the bed was also used. The results are generally in agreement with values used in numerical models. At the sand banks site, the drag coefficient increases with wind conditions, but at the sand waves site there is a reduction during the highest wave conditions, attributed to the drag reduction caused by sand resuspension from the bed. This result suggests that sediment effects must be considered if wave/current interaction is included in numerical models of the region. The drag coefficient for reversing tidal flows over the asymmetric sand waves is found to be larger for flow towards the steeper face, suggesting a small form drag component. Studies of sand movement used bedform mapping, fluorescent sand tracing and photography of migrating ripples. There is evidence for the early stages of formation of a new bank between Broken Bank and Well Bank. At the sand waves site, ripple migration is found to be a useful estimator of bedload transport under conditions of negligible suspension. Over the sand banks, a definite correlation of surface water properties, notably the turbidity, with the topography of the banks was observed. The mechanism for this surface effect is not known but it is consistent with the observation of features, seen in satellite visible light images, which outline the shapes of the banks.

Full text not available from this repository.

More information

Published date: 1993
Additional Information: Deposited by J. Conquer

Identifiers

Local EPrints ID: 72276
URI: https://eprints.soton.ac.uk/id/eprint/72276
ISSN: 1364-503X
PURE UUID: 42088eff-0836-4135-ae81-11e21c0920ec
ORCID for R.J. Nicholls: ORCID iD orcid.org/0000-0002-9715-1109

Catalogue record

Date deposited: 04 Feb 2010
Last modified: 06 Jun 2018 12:44

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