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Carbajal, N.; Montaño-Ley, Y.; Páez-Osuna, F.; Soto-Jiménez, M., and Tuxpan, J., 2020. Numerical investigation of sea-bottom morphological changes by the interaction of tidal flow and idealized coastal geometries. Journal of Coastal Research, 36(5), 981–991. Coconut Creek (Florida), ISSN 0749-0208. 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. [ABSTRACT FROM AUTHOR]

The interaction among tidal currents, sediment transport, and long-term changes of the sea bottom in the Colorado River Delta have been investigated applying a two dimensional nonlinear hydrodynamic-numerical finite differences model. The system was forced by the dominant M 2 tidal component at the open boundary. We carried out calculations to study the morphodynamics of the actual bathymetry caused by the bedload sediment transport. To investigate the origin of actual morphological features, we performed experiments using a smoothed bathymetry, in which the islands Montague, Gore, and Pelícano were eliminated. Under the imposed tidal hydrodynamics, the results indicate that the bedload transport contributes significantly in the genesis of sandbanks and in the formation and maintaining of the Montague and Gore Islands. [ABSTRACT FROM AUTHOR]

Applying a two-dimensional, non-linear hydrodynamic numerical model in combination with a semiempirical equation for bedload sediment transport, the influence of geometry on the formation of sandbanks is investigated. In the first experiment, the formation of sandbanks in an ideal rectangular basin, resembling the Taylor’s problem, was calculated. Sandbanks occur in a small area at the closed boundary. Similar experiments were carried out for a range of wavelengths of the incident Kelvin wave. The results reveal that large wavelengths favor the generation of sandbanks. In subsequent calculations, the basin was modified by introducing new geographical features like bays and peninsulas. The numerical experiments show that geometry is a fundamental factor to determine the position where groups of sandbanks appear. The results suggest that in regions where the Kelvin wave is diffracted, the formation of sandbanks occurs. An experiment, in which we applied an ideal geometric configuration representing that of the Southern Bight of the North Sea, generated sandbank patterns resembling those observed in the region. [ABSTRACT FROM AUTHOR]

The present investigation focused on solving the significance of tidal currents in the sediment resuspension process revealed by satellite imagery in the tidal basin of the Colorado River Delta, located in the northernmost part of the Gulf of California. A depth-integrated finite difference hydrodynamic model, coupled with a suspended sediment transport module, has been applied to calculate the velocity field and potential suspended sediment changes in the delta region. Prescribed values of tidal harmonics were used to force the model at the open boundary of the model domain. The experiments revealed that sediment plumes are generated by the interaction of the tidal flow and the seabed, exposing a remarkable agreement between the crest of sandbanks existing in the delta and the potential sediment resuspension. Close to spring tides, the instantaneous potential transport of sediment in suspension reaches values up to 0.05 m3, integrated over each cell of 280 m × 280 m. The calculations showed that in the shallow coastal area at the gulf's head, sandbank presence is critical for the energy dissipation processes. The crests of sandbanks dissipate much of the energy. The simulated processes are strong evidence that the frictional effect of tidal flow during the initial stages of the spring tides contributes significantly to the sediment's picking up from the seabed going into suspension. These processes shape the plumes of suspended sediment, which extended in the same direction as the sandbanks. Comparison between satellite imagery and modeled distribution of sediment revealed a good agreement between observed and modeled finger-like plumes of sediment. The undulating topography's effect is reflected in the horizontal distributions of energy dissipation, current speed, and kinetic energy. • Sediment resuspension process in the Colorado River Delta. • Interaction between topography and strong tidal currents. • Formation of extensive sediment plumes in the cycle neap-spring tides. • Agreement between results of numerical modeling and satellite images. [ABSTRACT FROM AUTHOR]