Fifty years after World War II, something like the blitzkrieg returned to Nijmegen last week. Dutch soldiers swarmed around the city as low-flying helicopters thundered overhead. The scenes reflected the kind of combat the Dutch know best: struggling with the elements as an onslaught of water threatened to submerge vast tracts of the Netherlands' sub-sea-level terrain.
All across northwestern Europe an epic deluge was sloshing over the banks of rivers such as the Rhine, the Waal and the Meuse. Torrential rains had combined with prematurely melting Alpine snows to overload major waterways funneling into the Low Countries. The flooding provoked...