Roughly 80% of New Orleans flooded after Hurricane Katrina, but the damage was far from uniform. The worst flooding hit neighborhoods that sat below sea level and lay in the path of more than 50 levee breaches that opened up on August 29, 2005, and in the hours that followed. Some areas saw 10 feet or more of standing water, while a few higher-ground neighborhoods like the French Quarter stayed mostly dry.
How the Levee Failures Unfolded
Katrina made landfall as a Category 3 hurricane near the Louisiana-Mississippi border on the morning of August 29. The storm itself didn’t destroy the city. What destroyed the city was the failure of the flood protection system meant to keep storm surge out.
The first reported breach was on the Industrial Canal, near the line between Orleans and St. Bernard Parish. Surge from the canal poured directly into the Ninth Ward. Shortly after, the 17th Street Canal was compromised when a 400-foot section of its east floodwall gave way. Engineers later determined the wall failed when a gap formed between the buried sheet piling and the levee soil on the flood side, even though the water level was still about five and a half feet below the top of the wall. The London Avenue Canal then suffered two additional breaches. In total, more than 50 breaches opened across the levee system, and water moved into most of the city.
The Lower Ninth Ward
The Lower Ninth Ward became the most recognizable symbol of Katrina’s destruction, and for good reason. Floodwaters reached 10 feet and higher across the neighborhood. Two major breaches on the west side of the ward, one near Florida Avenue and another near North Claiborne Avenue, sent storm surge pouring in from the Industrial Canal. A large barge owned by the Ingram Barge Company was swept down the canal and over the levee near North Claiborne Avenue, leveling houses beneath it.
The flooding wasn’t limited to those two breaks. Several additional breaches formed along the Florida Avenue levee, and surge also came across the Main Outlet Canal on the neighborhood’s north side. The lowest-lying parts of the ward sit roughly 14 feet below sea level, and those areas were among the last to be pumped dry. Much of the neighborhood’s housing stock was completely destroyed, and recovery took years longer than in wealthier parts of the city.
Lakeview and the 17th Street Canal
Lakeview, a middle-class residential neighborhood on the north side of the city, flooded catastrophically when the 17th Street Canal floodwall collapsed. This was one of the most consequential single failures of the entire disaster. The canal runs along the neighborhood’s western edge, and most of the surrounding blocks are residential. Water poured through the breach and filled a vast bowl-shaped area that sits several feet below sea level. Parts of Lakeview saw six to ten feet of standing water that lingered for weeks.
The two breaches on the London Avenue Canal, which runs roughly parallel to the 17th Street Canal farther east, sent additional flooding into the Gentilly neighborhood and surrounding areas. Together, failures on these three outfall canals caused some of the most severe flooding in the entire city.
Broadmoor, Mid-City, and New Orleans East
Broadmoor sits in one of the deepest parts of the city’s natural bowl, at elevations roughly 4 to 13 feet below sea level (the elevation map shows much of this area in the lowest categories). When the levees failed, water naturally collected here. Broadmoor flooded to depths of four to eight feet, submerging nearly every home in the neighborhood. Mid-City, which shares similarly low elevations, experienced comparable flooding.
New Orleans East, a sprawling area on the city’s eastern side, also flooded extensively. Storm surge entered through breaches along the Industrial Canal and other waterways connected to Lake Borgne and the Gulf Intracoastal Waterway. Much of New Orleans East is low-lying reclaimed marshland, and water covered the area for weeks.
St. Bernard Parish, technically a separate jurisdiction but part of the greater New Orleans metro area, was almost entirely submerged. Surge funneled through a shipping channel known locally as “the funnel” pushed water deep into communities like Chalmette and Meraux.
What Stayed Dry
The areas that escaped flooding almost all share one trait: higher elevation. The French Quarter, the Central Business District, the Garden District, and the stretch along the natural levee of the Mississippi River sit at elevations ranging from about 3 to 8.5 meters (roughly 10 to 28 feet) above the lowest-lying neighborhoods. These areas were built on the original high ground along the river’s natural ridge, which is why they were settled first in the 1700s. Uptown, particularly the blocks closest to the river, also largely avoided flooding.
The Marigny and Bywater neighborhoods, just downriver from the French Quarter, mostly stayed dry as well, though blocks farther from the river and closer to the Industrial Canal saw some flooding. The pattern was consistent across the city: the closer you were to the river and the higher your elevation, the better your chances.
Why Elevation Determined Everything
New Orleans sits in a shallow bowl between the Mississippi River and Lake Pontchartrain. The highest ground follows the natural riverbank, where centuries of sediment deposits built up a ridge. Moving north toward the lake, the land drops steadily. Many neighborhoods developed in the 20th century, after pumping technology made it possible to drain swampland that sat well below sea level. Those neighborhoods, places like Lakeview, Broadmoor, the Lower Ninth Ward, and New Orleans East, depended entirely on the levee system and pumps to stay dry.
When the levees failed, water followed gravity into the lowest points and stayed there. The city’s pumping stations, designed to handle rainfall, were overwhelmed and in many cases lost power. Some areas remained underwater for more than three weeks before they could be fully drained.
Flood Protection After Katrina
The Army Corps of Engineers replaced the failed levee system with the Hurricane and Storm Damage Risk Reduction System, a $14.5 billion network of higher levees, stronger floodwalls, surge barriers, and pump stations. The system is designed to handle a storm surge with a 1% chance of occurring in any given year, commonly called “100-year” protection. The design factored in expected sea level rise, land subsidence, and possible increases in storm severity.
The failed I-walls on the 17th Street and London Avenue canals were replaced with stronger T-wall structures that are more resistant to the kind of soil separation that caused the original failures. Armoring was added to critical levee sections to reduce erosion from wave overtopping during storms that exceed the system’s design capacity. The new system is a significant upgrade, but it is built to reduce risk, not eliminate it. A storm larger than the design standard could still overwhelm the defenses.