Modeling the effect of nonuniform sediment on the dynamics of offshore tidal sandbanks

Pieter C. Roos*, Rik Wemmenhove, Suzanne J. M. H. Hulscher, Harry W. M. Hoeijmakers, N. P. Kruyt

*Bijbehorende auteur voor dit werk

    OnderzoeksoutputAcademicpeer review

    21 Citaten (Scopus)
    200 Downloads (Pure)

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    [1] 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.

    Originele taal-2English
    Artikelnummer02011
    Aantal pagina's11
    TijdschriftJournal of geophysical research-Earth surface
    Volume112
    Nummer van het tijdschriftF2
    DOI's
    StatusPublished - 3-mei-2007

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