To set their city above the tide, the master builders of medieval Venice pounded millions of alder posts into the muck of their lagoon. In succeeding centuries, they kept its storied churches and palazzos dry with a discipline so unforgiving that breaking the water laws could cost a man his life.

Today, saltwater and sewage swamp Venice as often as a hundred times a year. On a recent weekend, gondoliers ducked to pass beneath the bridges across the city's storm-swollen canals. In cafes and bars, the regulars sipped their espressos while wearing knee-high rubber boots in ankle-deep water.

Spurred by long histories of disastrous storms, the urban engineers of Venice, Tokyo and the Netherlands have been among the pioneers of modern flood control, building storm surge barriers and sea walls on the scale of the pyramids. Such structures could well be models for New York City in the wake of superstorm Sandy.