The proposed flood gates will have to close much more frequently in the future than now, given sea level rise. That closure will hinder navigation, and create a major pollution hazard. So those issues will have to be tackled, and solved.
But if we can tackle and solve those problems, for example by moving the port traffic elsewhere and sewering Venice, let us begin to plan to do so now. In the meantime we can solve 90 per cent of the flooding problems with the small-scale flood works that are being constructed.
Then the gates will only prevent damage from the rarer large floods, which will in any case be less serious now than in 1966, because Venetians have moved upstairs. But their cost is excessive for this role: no rational comparison of costs and benefits would lead to their implementation.
What Venice needs is a broader perspective and an enduring solution. It is inevitable that the lagoon will have to be isolated progressively from the Adriatic but this needs a permanent scheme, not movable gates. Until now the gates have been seen as "the only solution". They are not.
Professor of Geography
University of Middlesex