Ten years ago, Hurricane Katrina devastated New Orleans and other parts of the Gulf Coast. It wasn't the first storm to hit the Crescent City, but the failures of the city's protection systems were so dramatic that engineers have revamped the way they prepare for natural disasters.
That's essential, especially since New Orleans faces even greater risks in the future.
Most of the city is already below sea level, protected by an unreliable system of levees.
Flood risk will grow more severe as rising sea levels and sinking coastal land produce a local increase of at least four feet by the end of the century. And then there's the inevitable increase in major storm surges caused by extreme weather events.
We've created a guide to the crises ahead and the city's best hope for survival.