Morphodynamics of Sand Ridges on the Shelf: Modelling Effects of Waves, Wind and Tide

Abstract Shoreface-connected sand ridges (sfcr) and tidal sand ridges (tsr) are large-scale rhythmic bedforms found on many sandy continental shelves. Previous studies have not addressed the combined impact of waves, wind and tides on the evolution of these ridges. Furthermore, they were unable to simulate sfcr with wave-topography feedbacks. The objectives of this study are to 1) simulate sfcr in the presence of these feedbacks; and 2) to quantify the combined impact of waves, wind and tide on the evolution of shelf ridges. To this end, a morphodynamic shelf model (Delft3D + SWAN) is used in a setting representative of the Belgian shelf. The model successfully simulates sfcr in the presence of wave-topography feedbacks, producing ridges with characteristics consistent with observations. Regarding 2), a mix of two types of ridges develops on the shelf, which resemble the sfcr and tsr observed on the Belgian shelf. However, a notable difference is that observed tsr are located further offshore than modelled ridges.