Addressing the effect of the Mo.S.E. barriers closure on wind setup within the Venice lagoon

A correct management of the mobile barriers that have presently been building at the three inlets of the Venice lagoon (Mo.S.E. project) is of paramount importance for the safeguard of the urban settlements located inside the lagoon. In this work, we compare, by means of a 2-D hydrodynamic model, the setup produced by intense winds during the period of closure of the mobile barriers to the pre-Mo.S.E. scenario, when the flow through the three inlets is not regulated. The analysis considers both some recent storm surge events and more systematically all the meteorological (i.e. wind speed, direction and duration) and hydrodynamic conditions (i.e. sea level and tidal amplitude). We demonstrate that the wind setup significantly increases when the gates at the three inlets are closed, up to exceeding four times the pre-Mo.S.E. scenario. This phenomenon will strongly affect the management of the Mo.S.E. barriers and their operating strategy when pursuing the goal of preventing the flooding at all the urban settlements of the lagoon. More precisely, it will impose to close the gates in advance with respect to what expected by considering only the safeguard of the city of Venice, which is not significantly affected by wind setup due to its central position within the lagoon. This would fatally increase the yearly period of closure of the lagoon, enhancing all the issues concerning long and repeated closures, such as, for example, lagoon water quality and port industry.