Pathways for adaptation of Venice and its lagoon to sea-level rise

Abstract The substantial risks posed to Venice and its lagoon by ongoing and projected sea-level rise require unprecedented long-term adaptation strategies. With present insufficient greenhouse gas mitigation policies, the current open lagoon strategy, with mobile barriers and multiple accommodation measures, is likely to encounter hard limits within the current century. Follow-up strategies could be based either on ring-dikes, isolating the city from the rest of the lagoon, or on a closed lagoon with permanent coastal dams separating it from the sea. Relocation of monuments to a suitable inland area and abandonment of Venice would be the only remaining strategy for sea-level above 10-15 m. Indicative adaptation costs increase with sea level rise from less than 1 to more than 30Ge. Abandonment might become unavoidable in the 22nd century under current climate policies and an Antarctic ice-sheet collapse, a risk that could still be avoided by a rapid reduction of greenhouse gas emissions.