Generation of nearshore oblique sand bars:: Sensitivity to sand transport formulation

A model is analysed that describes the initial formation of nearshore oblique bars as a result of inherent instabilities in the coupling between the wave-driven nearshore circulation and the erodible bottom. The aim is to gain fundamental knowledge about the sensitivity of bar generation to the formulation for sand transport. Three well-known transport formulas (Bailard bedload, Bailard suspended load and Engelund-Hansen total load) have been used in the limit of weak currents compared to wave orbital velocities. The differences in the cross-shore distribution of their wave stirring functions results in different characteristics of the fastest growing modes. Results are also sensitive to the angle between the net sediment transport and the net current: anisotropic transport causes bar shapes to change and growth rates to increase substantially.