How long the Mo.S.E. barriers will be effective in protecting all urban settlements within the Venice Lagoon? The wind setup constraint

The last IPCC report highlights that, along the present century, sea level rise driven by climate change will exacerbate the flooding frequency in coastal areas. Among others, the Venice Lagoon is one of the most vulnerable because of the presence of worldly famous historical urban settlements. To face this, a mobile flap gate system (Mo.S.E.) is nearly completed and has already raised across the lagoon inlets under testing phase to protect Venice from flooding. However, relative sea level rise and the wind setup effect during the closure of the lagoon, pose relevant management challenges such as timing and frequency to operate the barriers. In the present work, we first highlight some issues related to the management protocol currently adopted. We suggest a new strategy that optimizes the gate operation by identifying the shortest duration of closure that simultaneously prevents the flooding of all urban settlements within the lagoon. The new strategy is then used to estimate the Mo.S.E. management considering the last 20-year-long tidal record, but also for investigating different scenarios of relative sea level rise. The analysis we propose proves that the enhanced wind setup constraint will lead the Mo.S.E. system to fail in controlling all flood events starting from a relative sea level rise of +0.40 m. In addition, wind setup will increasingly often produce long and repeated closures, requiring further measures to combine flood protection, port and industrial activities and the conservation of the lagoon ecosystem.