Exploring the bottom stress variability in the Venice Lagoon

A framework of numerical models has been implemented and applied to the Venice Lagoon. The models consist of a state of the art hydrodynamic model for shallow areas and lagoons and a last generation wave model. With these models the bottom stress distribution during typical strong meteorological situations is studied. Results show a good agreement of the computed bottom stress patterns and the empirical erosion and deposition rates found in the lagoon. The areas where wave action is responsible for sediment re-suspension are identified; they consist basically in the large shallow areas that are spread out all over the lagoon. This makes the wave action the most important erosion mechanism in the lagoon during typical strong winds. Three scenarios of future climatic changes are simulated: an increase in the amplitude of the tidal oscillation, a global sea level rise and the combination of both. The results show that the most vulnerable parts of the lagoon are the flat regions close to the deeper channels. The erosion of these channel borders could be the cause of the filling of the deeper channels that then would need artificial dredging.