Environment: Dams for Venice

Venice, as every visitor learns, is built on low islands in a huge, protected lagoon. When exceptionally high tides strike—which occurs about 25 times a year—the charming Italian city is flooded. Last week for instance Venetians had to cross the Piazza San Marco on wooden gangplanks; the great square was once again ankle-deep in sea water. Though floods have plagued Venice for centuries (one was recorded in A.D. 885), lately they have been getting worse. Main reason: to permit the passage of large ships, the Italians have widened and deepened the three channels through the 38-mile-long barrier beach that protects...