Numerical Investigation of Sea-Bottom Morphological Changes by the Interaction of Tidal Flow and Idealized Coastal Geometries

Different idealized geometries, resembling shallow tidal-dominated seas with different geographical features like bays, islands, and headlands, were investigated by applying a two-dimensional hydrodynamic-numerical and morphological model. The geometries were exposed to fast oscillatory tidal velocities and unbounded sediment availability. The interaction between the oscillatory tidal flow and the seabed, in all the experiments, generated vorticity and small bed perturbations that evolved to incipient shoals or bed forms. The reversing tidal regime created asymmetric sediment transport, which in turn triggered sediment accretion at specific areas. The flow, residual circulation, and vorticity produced by mixed tides, and, in the presence of coastal morphological features like headlands, bays, and islands, also triggered the generation as well as the enhancement of asymmetric shoals. Experiments applying only one tidal component revealed a more symmetric pattern of vorticity and sediment accretion. Satellite images of areas of the Gulf of California including an island, bay, and headland were compared with the predicted tidal morphodynamics. They reflected quite well, in all cases, accretion areas located in sites similar to those predicted in the present numerical investigation.