The effect of wind-waves and tidal currents on sediment resuspension in shallow microtidal basins.

Observational evidence and mathematical modeling have demonstrated the crucial role of wind waves on sediment resuspension in shallow microtidal basins, where tidal fluxes alone are unable to mobilize tidal flat sediments. Carniello et al. [2005] presented a mathematical model for shallow microtidal basin which combines wind waves with tidal fluxes under the assumption of constant wave period. A detailed analyses of field data shows that the wave period varies as a function of wind speed and flow depth, and its variation has a non-negligible impact on wave heights and wave induced bed shear stresses. We therefore re-formulate the model by introducing a variable wave period through a suitable empirical power law relating the wave period to the wind speed and flow depth. The improvement obtained by introducing such an estimation of the local wave period is emphasized by the results of a number of simulations, carried out considering different storm events recently occurred in the Venice lagoon. The new formulation of the wind wave-tidal model provides a better description of the wind-wave field and, therefore, reflects favourably also on the estimation of the sediment re-suspension, as clearly shown by the comparison of turbidity measurements with the results obtained with a sediment transport model coupled with the wind wave-tidal model.