Modeling the effect of non-uniform sediment on the dynamics of offshore tidal sandbanks

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Abstract

Tidal sandbanks are large-scale bed features present in many shallow shelf seas. Here we investigate the effect of nonuniform sediment on their dynamics, with a particular aim to explain observed surficial grain size variations over tidal sandbanks from a process-based modeling perspective. To this end, we use a linear stability analysis that describes the positive feedback mechanism between hydrodynamics, sediment, and the seabed responsible for sandbank formation on a horizontal shelf. In this model the sediment transport and bed evolution modules are extended by introducing an active layer and a bimodal sediment mixture. We include a dynamic hiding/exposure description of sediment transport, enhancing the transport of coarse grains and inhibiting the transport of finer grains. The model results show that for symmetrical tidal conditions, coarse grains tend to accumulate at the bank crests. Moreover, the growth rates of the perturbations increase compared to the case of uniform sediment, while the preferred wavelength and bank orientation remain unchanged. For asymmetrical tidal conditions we find a spatial phase shift between topography and the mean grain size fraction, indicating an accumulation of coarse grains on the lee side of the bank. The model results qualitatively agree with observations from banks on the Belgian continental shelf.
Original languageEnglish
JournalJournal of geophysical research
Volume112
Issue numberF02011
DOIs
Publication statusPublished - 2007

Fingerprint

sandbank
Sediments
sediments
sediment transport
Sediment transport
shelves
sediment
modeling
beds
grain size
Linear stability analysis
positive feedback
active layer
feedback mechanism
shelf sea
continental shelves
stability analysis
Phase shift
Topography
continental shelf

Keywords

  • IR-60091
  • METIS-229793

Cite this

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title = "Modeling the effect of non-uniform sediment on the dynamics of offshore tidal sandbanks",
abstract = "Tidal sandbanks are large-scale bed features present in many shallow shelf seas. Here we investigate the effect of nonuniform sediment on their dynamics, with a particular aim to explain observed surficial grain size variations over tidal sandbanks from a process-based modeling perspective. To this end, we use a linear stability analysis that describes the positive feedback mechanism between hydrodynamics, sediment, and the seabed responsible for sandbank formation on a horizontal shelf. In this model the sediment transport and bed evolution modules are extended by introducing an active layer and a bimodal sediment mixture. We include a dynamic hiding/exposure description of sediment transport, enhancing the transport of coarse grains and inhibiting the transport of finer grains. The model results show that for symmetrical tidal conditions, coarse grains tend to accumulate at the bank crests. Moreover, the growth rates of the perturbations increase compared to the case of uniform sediment, while the preferred wavelength and bank orientation remain unchanged. For asymmetrical tidal conditions we find a spatial phase shift between topography and the mean grain size fraction, indicating an accumulation of coarse grains on the lee side of the bank. The model results qualitatively agree with observations from banks on the Belgian continental shelf.",
keywords = "IR-60091, METIS-229793",
author = "Roos, {Pieter C.} and Rik Wemmenhove and R. Wemmenhove and Hulscher, {Suzanne J.M.H.} and Hoeijmakers, {Hendrik Willem Marie} and Kruyt, {Nicolaas P.}",
year = "2007",
doi = "10.1029/2005JF000376",
language = "English",
volume = "112",
journal = "Journal of geophysical research",
issn = "0148-0227",
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Modeling the effect of non-uniform sediment on the dynamics of offshore tidal sandbanks. / Roos, Pieter C.; Wemmenhove, Rik; Wemmenhove, R.; Hulscher, Suzanne J.M.H.; Hoeijmakers, Hendrik Willem Marie; Kruyt, Nicolaas P.

In: Journal of geophysical research, Vol. 112, No. F02011, 2007.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Modeling the effect of non-uniform sediment on the dynamics of offshore tidal sandbanks

AU - Roos, Pieter C.

AU - Wemmenhove, Rik

AU - Wemmenhove, R.

AU - Hulscher, Suzanne J.M.H.

AU - Hoeijmakers, Hendrik Willem Marie

AU - Kruyt, Nicolaas P.

PY - 2007

Y1 - 2007

N2 - Tidal sandbanks are large-scale bed features present in many shallow shelf seas. Here we investigate the effect of nonuniform sediment on their dynamics, with a particular aim to explain observed surficial grain size variations over tidal sandbanks from a process-based modeling perspective. To this end, we use a linear stability analysis that describes the positive feedback mechanism between hydrodynamics, sediment, and the seabed responsible for sandbank formation on a horizontal shelf. In this model the sediment transport and bed evolution modules are extended by introducing an active layer and a bimodal sediment mixture. We include a dynamic hiding/exposure description of sediment transport, enhancing the transport of coarse grains and inhibiting the transport of finer grains. The model results show that for symmetrical tidal conditions, coarse grains tend to accumulate at the bank crests. Moreover, the growth rates of the perturbations increase compared to the case of uniform sediment, while the preferred wavelength and bank orientation remain unchanged. For asymmetrical tidal conditions we find a spatial phase shift between topography and the mean grain size fraction, indicating an accumulation of coarse grains on the lee side of the bank. The model results qualitatively agree with observations from banks on the Belgian continental shelf.

AB - Tidal sandbanks are large-scale bed features present in many shallow shelf seas. Here we investigate the effect of nonuniform sediment on their dynamics, with a particular aim to explain observed surficial grain size variations over tidal sandbanks from a process-based modeling perspective. To this end, we use a linear stability analysis that describes the positive feedback mechanism between hydrodynamics, sediment, and the seabed responsible for sandbank formation on a horizontal shelf. In this model the sediment transport and bed evolution modules are extended by introducing an active layer and a bimodal sediment mixture. We include a dynamic hiding/exposure description of sediment transport, enhancing the transport of coarse grains and inhibiting the transport of finer grains. The model results show that for symmetrical tidal conditions, coarse grains tend to accumulate at the bank crests. Moreover, the growth rates of the perturbations increase compared to the case of uniform sediment, while the preferred wavelength and bank orientation remain unchanged. For asymmetrical tidal conditions we find a spatial phase shift between topography and the mean grain size fraction, indicating an accumulation of coarse grains on the lee side of the bank. The model results qualitatively agree with observations from banks on the Belgian continental shelf.

KW - IR-60091

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DO - 10.1029/2005JF000376

M3 - Article

VL - 112

JO - Journal of geophysical research

JF - Journal of geophysical research

SN - 0148-0227

IS - F02011

ER -