A. Falques, D. Calvete, H.E. de Swart, N. Dodd


A morphodynamic model is developed and analyzed to gain fundamental understanding on the basic physical mechanisms responsible for the characteristics of shoreface-connected sand ridges observed in some coastal seas. These alongshore rhythmic bedforms have a horizontal length-scale of order 10 km. It is found that the positive feedback between the topographic disturbances of a sloping bottom and the subsequent deflection of the mean coastal current is the main cause of the ridges. To be effective, this mechanism needs an averaged sediment transport mainly due to wave stirring during storms and an averaged current driven by pressure gradients rather than surface stresses. Even in the presence of significant tidal currents, their origin — related to the mean current instead of tidal oscillation — is essentialy different from that of tidal sand banks.


morphodynamics; shoreface-connected ridge

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