1. When it was built, it was barely above sea level
The original part of the city, the French Quarter, was built on higher ground beginning in the early 18th century.
Settlers who got the best land were able to build only about 10 feet above sea level. Even from the beginning, the city was fighting an uphill battle as it expanded. New Orleans is mostly flat, and areas around the French Quarter are just a little lower.
But in this situation, every foot counts.
2. It was built on loose soil
As the city grew, architects chose to build shorter houses and structures, out of fear that the ground couldn’t support anything taller.
“Though a few [structures] climbed as high as three and sometimes four floors, most hovered around two or two-and-a-half stories, since builders feared that the town’s spongy soil couldn’t bear the added weight,” New Orleans historian Lawrence N. Powell wrote in “The Accidental City: Improvising New Orleans.”
3. A drainage system had unintended consequences
Without sediment and water to stabilize the ground, the “former marshes sunk as much as 8-12 feet,” and wetlands rapidly eroded, Campanella wrote in a study.
4. Sea levels are rising
That continual sinkage, combined with rising global sea levels due to the climate crisis, meant New Orleans would probably be between 2½ and 4 meters (2.73 to 4.37 feet) below sea level by 2100.