An aerial view of rebuilt elevated homes earlier this month along Waveland Beach in Mississippi, an area hard-hit by Hurricane Katrina 20 years ago. The catastrophic storm sent an approximately 30-foot-high storm surge into Waveland and destroyed or damaged nearly every home in the town. Nearly 1,400 people died across the Gulf Coast, and it remains the costliest storm in U.S. history at around $200 billion in today's dollars. (Getty Images)