The nation's capital is not exactly a beach town. But the cherry-tree-lined Tidal Basin, fed by the Potomac River, laps at the steps of the Jefferson Memorial. And, especially since Superstorm Sandy, officials in Washington have a clear idea of what would happen in a worst-case storm scenario.
"The water would go across the World War II memorial, come up 17th Street," says Tony Vidal of the U.S. Army Corps of Engineers. "And there are actually three spots where the water would come up where we don't have ... a closure structure right now."
Florida — especially South Florida — is very flat and very low, and in places like Miami Beach and Key West, buildings are just 3 feet above sea level. Scientists now say there may be a 3-foot rise in the world's oceans by the end of the century.
Since the 1930s, Louisiana has lost roughly as much land as makes up the state of Delaware.
"If you put the state of Delaware between New Orleans and the ocean, we wouldn't need any levees at all," says John Barry, vice president of the Southeast Louisiana Flood Protection Authority-East. "There is this large buffer of land that has disappeared, and that buffer makes New Orleans much more vulnerable to hurricanes."