Bottom Shear Stress Formulations to Compute Sediment Fluxes in Accelerated Skewed Waves

As waves travel and shoal towards a beach, their surface elevation becomes peaky (sharp crests) and asymmetric relative to the vertical. Within a wave period, the corresponding orbital velocity near the bottom shows a similar (time) variation and it is recognized that these nonlinearities are responsible for sediment transport. The resulting wave-induced bottom shear stresses are required for most sediment transport model computations. In this work, simple bottom shear stresses parameterisations for rough seabeds, under nonlinear waves, are analysed. The effects of the wave shape on the bottom shear stresses estimates is investigated by analysing a new set of experimental data, under accelerated skewed waves (SILVA et al., 2008). Results indicate a good agreement between all the formulations presented.