The role of idealized storms on the initial stages in sand wave formation: A numerical modeling study

Sand waves are rhythmic bedforms observed in many shallow shelf seas. By adopting a process-based numerical morphodynamic model, Delft3D, the effect of the storm-related processes on the growth and migration of sand waves was studied systematically in this paper. In our model, the storm effect was included by adopting the shear stresses due to the nonlinear wave effect, wave-current interaction, and wind-driven current. A series of numerical experiments were performed, and it was found that accounting for the wave nonlinearity is important in predicting the growth rate. Moreover, the effect of wave-current interaction on sand wave growth and migration is significant. The asymmetric velocity of water particles induced by wave-current interaction leads to net sediment transport rates which resulted in the migration of sand waves. The wind-driven current effect can breach the symmetry of the tidal current and cause the migration of sand waves. In our specified cases, the effect of wind-driven current or wave action on the LFGM was not significant, while the combination of these two effects causes a larger wavelength of sand waves. The model results show that the storms influence sand wave dynamics in the formation stage significantly and are therefore important to account for in designing offshore engineering operations in sand wave fields. •Both wave nonlinearity and wave-current interaction play an important role in the evolution of sand waves in shallow water.•The modelled wavelength will become larger under the combined effect of wind and wave action.•In shallow continental shelf seas, storms significantly affect the evolution of sand waves.