Abstract: A two-dimensional numerical model is developed for investigating the effects of waves on sediment transport and bed morphology dynamics under different storm surge conditions. This work is based on an existing shallow water model coupling interactions between the flow, sediment transport, and bed changes. The SWAN model is adopted to simulate wave action, and its simulations of wave radiation stress are coupled into an existing sediment-flow model. Changes in the morphology of an idealized coast in different storm surge conditions are examined and compared. Results show that the wave effect decreases with the raising storm tide level. When the surge is weak, asymmetrical shoals are formed upstream and downstream of the tide inlet and a scour hole is formed at the entrance; at a high surge level, the asymmetry is weak, and the difference in morphological changes calculated with and without the wave effect is roughly 5% at the ratio of water depth to wavelength less than 0.15. Calculating the wave effects could double computational cost. This study also suggests that coupling waves and flows is important for modeling low storm surge tides.

Key words: numerical simulation, wave and flow interaction, sediment transport, storm surge, morphology change