Quantifying shear stress due to wind waves and tidal currents in the Venice lagoon

A numerical model that combines wind waves with tidal fluxes in a tidal basin is presented and validated. The model couples a hydrodynamic finite element module based on the shallow water equations with a finite volume module that accounts for the generation and propagation of wind waves. The wave module solves the wave action conservation equation on the same triangular mesh used in the hydrodynamic module, thus efficiently reproducing the physical relationships between waves and tide propagation. The combined wind wave-tidal model is applied to the Venice lagoon. The highly irregular bathymetry of this tidal environment, characterized by deep channels, emergent salt marshes, and extensive tidal flats, suggests the introduction of ad hoc hypotheses that simplify the governing equations with a noteworthy increase in efficiency and robustness of the algorithm. Simulations of wave fields generated under specific wind conditions are presented and discussed. The model results are compared, with good agreement, to field data collected in different stations inside the lagoon of Venice. Finally, evidence of the effect of tidal currents and wind waves on sediment resuspension is presented using the results of different simulations.