Morphological evolutions in a 1D model for a dissipative tidal embayment

An idealized morphodynamic model of a tidal embayment is considered. It describes tidal water motions, sediment transport and bottom changes in a semi-enclosed rectangular channel with fixed coast-lines and an erodible bottom. The momentum equations contain terms due to horizontal pressure gradients and bottom friction. Using both analytical and numerical techniques bed form evolutions and equilibrium profiles are computed. For short channel lengths (compared to the frictional length scale) concave bed profiles are obtained. The difference with results reported earlier is due to the applied boundary condition for the depth-integrated sediment concentration at the landward side. Bed profiles become less concave if the channel length is increased, until a critical condition is reached for which no global morphodynamic equilibrium can exist. For very long channels the embayment will partly fill up at the landward side until a constantly sloping bottom profile is reached. The model predictions seem to be in qualitative agreement with observed bathymetries in the Wadden Sea, although these embayments are too deep for a strict application of the frictional dominance assumed in this paper.