The Value of Protecting Venice from the Acqua Alta Phenomenon under Different Local Sea Level Rises

Venice (Italy) is built on several islands inside a lagoon. It undergoes a periodical �ooding phenomenon, called "Acqua Alta" (AA). A system of mobile dams, called Mo.S.E., is currently under construction to protect it. When needed, several fl�oodgates will be lifted to separate the lagoon from the Adriatic sea. AA, whose length and height has been increasing in recent years, is a random phenomenon, correlated with local sea level rise (LSLR). Several possible LSLRs can be assumed as consequences of different global warming scenarios. We investigate here the cost-bene�t of Mo.S.E. under different possible LSLRs. First, we simulate the future patterns of AA for the next 50 years under alternative LSLRs. Then, we calculate the bene�t of Mo.S.E., converting each avoided AA episode into an economic value (avoided cost). We show that the bene�ts are just at the level of the costs, when a low LSLR is assumed and increase with LSLR, provided that it does not reache a catastrophic (yet unpredictable) extreme level.