|Tidally-averaged currents and bedload transport over the Kwinte Bank, southern North Sea|
Garel, E. (2010). Tidally-averaged currents and bedload transport over the Kwinte Bank, southern North Sea. J. Coast. Res. SI 51: 87-94
In: Journal of Coastal Research. Coastal Education and Research Foundation: Fort Lauderdale. ISSN 0749-0208, more
sandbank; short-term dynamics; dredging
The short-term dynamics of a dredged tidal sandbank (the Kwinte Bank, southern North Sea) are examined, on the basis of field measurements and 1D sediment transport modelling. The field measurements include current data from shipborne Acoustic Doppler Current Profiler (ADCP) and from moorings (ADCP and electromagnetic S4), collected across the bank during a nominal (spring) tidal cycle, and during 7 tidal cycles, respectively. The dynamics of the bank are described in terms of tidally-averaged (residual) currents and (net) bedload transport. The results indicate a predominance of ebb flow during the period of study. Convergence of (net) bedload transport is predicted, from both flanks towards the crest of the bank. The exact location of the sand transport convergence zone varies, in the short-term, according to the prevailing tidal currents. The observation of clockwise veering of the peak ebb and flood currents over the bank indicates that this sediment transport pattern relates, at least partially, to tidal rectification of the flow. In relation to dredging, the present study suggests that the presence of a (dredged) depression at the crest of the bank influences locally the short-term hydrodynamics. The currents are channelised, and the across-bank peak (near-bed) flow is enhanced towards the crest. Net erosion of the depression is predicted, over the tidal cycle considered. More data are needed to evaluate the morphological evolution of the trough over the long-term.