Roughly half of metropolitan New Orleans sits below sea level. The other half, concentrated along the natural ridges nearest the Mississippi River, remains above it. The below-sea-level portions aren’t just slightly lower than the waterline: some neighborhoods sit 6 to 12 feet below sea level, making the city one of the most topographically unusual in the United States.
How Far Below Sea Level Different Areas Sit
New Orleans is not uniformly low. The city’s elevation varies dramatically over short distances, and the difference between a neighborhood that flooded catastrophically during Hurricane Katrina and one that stayed dry can come down to a few blocks and a few feet of elevation.
The French Quarter, the city’s most iconic neighborhood, is entirely above sea level, in some spots by more than 10 feet. The Garden District, Uptown, and the Bywater corridor along the river also sit on relatively high ground, generally 10 to 12 feet above mean sea level at their peaks. These neighborhoods developed first precisely because they occupied the natural levee ridges built up over centuries by Mississippi River flooding.
Move inland from the river and the ground drops quickly. Parts of Broadmoor sit 3 to 6 feet below sea level. Lakeview and Gentilly, closer to Lake Pontchartrain, range from 5 to 8 feet below. The lowest areas, including sections of Metairie and New Orleans East, dip 6 to 12 feet below sea level. These neighborhoods were developed in the 20th century after the city built drainage systems powerful enough to keep them dry under normal conditions.
Why the City Keeps Sinking
New Orleans wasn’t always below sea level. The city was built on a river delta, a thick stack of loose sediment deposited by the Mississippi over thousands of years. That sediment naturally compresses under its own weight, a process called subsidence. In a natural delta system, periodic flooding deposits fresh sediment on top, offsetting the sinking. But levees built to protect the city from river floods also cut off that sediment supply, so the ground compresses with nothing to replace it.
The problem accelerated in the early 1900s when the city installed powerful drainage pumps to dry out swampy land for development. Removing water from the organic, peaty soils caused them to shrink and oxidize, dropping the surface further. Groundwater pumping for drinking water and oil and gas extraction added to the effect.
Today, parts of the city are sinking at rates up to 20 millimeters per year, roughly three-quarters of an inch annually. Some flood protection walls built after Hurricane Katrina are sinking even faster, at rates up to 28 millimeters per year. Near the international airport, rates reach 17 millimeters per year, and in vegetated areas east of the city, subsidence has been measured at up to 34 millimeters per year. These numbers may sound small, but over a decade they add up to inches of lost elevation in a city where inches determine whether a neighborhood floods.
How the City Stays Dry
Living below sea level requires constant mechanical intervention. New Orleans operates one of the world’s most extensive urban drainage systems: a network of canals, levees, floodwalls, and massive pumping stations that move water uphill and out of the city’s low-lying basins.
The Hurricane and Storm Damage Risk Reduction System, completed after Katrina, surrounds the metro area with upgraded levees and floodwalls designed to handle storm surges from a hurricane with a 1-in-100 chance of occurring in any given year. The system’s design accounts for expected sea level rise, ongoing subsidence, and potential increases in storm intensity. At key drainage canals, enormous pump stations push water out of the city. The station at 17th Street Canal alone can move 12,600 cubic feet of water per second. The London Avenue station handles 9,000 cubic feet per second, and the Orleans Avenue station adds another 2,700. Together, just these three stations can pump the equivalent of a large river.
Armoring on levee surfaces provides additional resilience if storm surges overtop the walls, reducing erosion that could cause a breach. But the system requires constant maintenance and monitoring, particularly because the structures themselves are sinking along with the ground beneath them.
Disappearing Wetlands and Storm Surge
The land between New Orleans and the Gulf of Mexico is vanishing. Louisiana loses 25 to 35 square miles of coastal land every year, an area larger than Manhattan, to a combination of subsidence and rising seas. Since the 1930s, the state has lost roughly 1,900 square miles of coastal marshland.
This matters directly for the below-sea-level portions of New Orleans because coastal wetlands act as a buffer against hurricane storm surge. Every mile of healthy marsh can reduce storm surge height by several inches. As that buffer disappears, storm surges travel farther inland with more force, reaching the city’s levee system with greater energy. Louisiana’s barrier islands, the outermost line of defense, have been the focus of beach restoration projects, but the overall trend of land loss continues to outpace restoration efforts.
What Sea Level Rise Means for the City
The Gulf Coast faces some of the fastest rates of relative sea level rise in the country, roughly 10 to 15 centimeters higher than the national average, because global ocean rise compounds with local land subsidence. NOAA projections estimate that the western Gulf Coast will see about 0.59 meters (nearly two feet) of relative sea level rise by 2050 compared to 2000 levels, with a likely range between 0.51 and 0.67 meters. The eastern Gulf, which includes the Louisiana coast, projects about 0.48 meters.
For a city where half the population already lives below sea level, even modest increases in baseline water levels reduce the margin of safety that levees and pumps provide. A neighborhood currently sitting 5 feet below sea level effectively sits deeper relative to the water pressing against the flood protection system. Heavier rainfall events, which climate projections also anticipate, add further strain to drainage infrastructure that must pump harder and longer to keep those basins dry. The city’s geography is not static. It is actively getting worse, and the engineering required to keep New Orleans habitable grows more demanding with each passing decade.