Oblique sand ridges in confined tidal channels due to Coriolis and frictional torques

The role of the Coriolis effect in the initial formation of bottom patterns in a tidal channel is studied by means of a linear stability analysis. The key finding is that the mechanism generating oblique tidal sand ridges on the continental shelf is also present in confined tidal channels. As a result, the Coriolis effect causes the fastest growing pattern to be a combination of tidal bars and oblique tidal sand ridges. Similar as on the continental shelf, the Coriolis-induced torques cause anticyclonic residual circulations around the ridges, which lead to the accumulation of sand above the ridges. Furthermore, an asymptotic analysis indicates that the maximum growth rate of the bottom perturbation is slightly increased by the Coriolis effect, while its preferred wavelength is hardly influenced.