A model to predict the migration of sand waves in shallow tidal seas

A model is presented to determine the wavelength, the height and, more importantly, the migration speed of sand waves (also named tidal dunes) in shallow tidal seas. The model is based on a linear stability analysis and predicts the growth and migration of the fastest growing mode of a random perturbation of the flat sea bed forced by tidal current and wind waves. The growth of the fastest growing mode is assumed to generate the sand waves and to have the same geometrical and kinematical characteristics of these bottom forms. The characteristics of the sand waves predicted by the stability analysis are found to be in fair agreement with field observations, even though the number of accurate quantitative and simultaneous measurements of sand waves and forcing tidal currents is small and does not allow an exhaustive comparison between theoretical results and field data.