By Tulane U., August 9, 2025
Credit: Shutterstock
New Orleans is slowly sinking — and in some spots, the drop is startling.
A Tulane University study using two decades of satellite radar data reveals parts of the city, its wetlands, and even billion-dollar post-Katrina floodwalls are losing up to two inches of elevation each year.
Sinking Threat to New Orleans and Its $15 Billion Flood Defenses
Parts of New Orleans and nearby wetlands are slowly sinking. While much of the city’s ground remains stable, new research from Tulane University indicates that some parts of the $15 billion flood protection system built after Hurricane Katrina may require ongoing upgrades to stay ahead of this gradual land loss.
Published in Science Advances, the study examined ground elevation changes across Greater New Orleans from 2002 to 2020 using satellite radar data. The analysis revealed that certain neighborhoods, wetlands, and even sections of floodwalls are sinking more than an inch each year, with some locations dropping as much as 47 millimeters (nearly 2 inches) annually.
Among the most troubling findings: some of the concrete floodwalls and levees built to protect the city after Katrina are themselves sinking. In a few cases, parts of the Hurricane and Storm Damage Risk Reduction System (HSDRRS) are losing elevation faster than sea levels are rising, reducing their capacity to block storm surges.
“These results are a wake-up call,” said co-author Prof. Mead Allison, also of Tulane. “We need ongoing monitoring and maintenance to ensure that our flood defenses don’t lose their level of protection beneath us.”
Uneven Ground Movement Across the Region
The study also found pockets of sinking around industrial sites, the airport, and newer residential developments — areas where soil compression and groundwater withdrawal are likely contributors. In contrast, some areas, such as parts of Michoud, showed modest land uplift, likely due to the halt of industrial groundwater pumping and recovery of the water table.
Wetlands east of the city, long known for their ecological importance, are also sinking rapidly in places. In some spots, the loss of elevation could transform marshes into open water within a decade if trend
s continue. This has implications not just for wildlife but also for storm protection, as wetlands help buffer storm surges.
Rising Seas, Narrowing Margins of Safety
New Orleans, much of which lies below sea level, relies on an elaborate system of levees, pumps and drainage canals to keep water out. As sea levels rise and the ground sinks, the margin for error narrows.
Experts say that without sustained monitoring, including satellite data and ground-based measurements, it’s difficult to know where to reinforce levees or how to plan for future storms.
“This research shows that land movement isn’t uniform, and understanding these patterns is crucial for protecting lives and property in a city where inches truly matter,” Fiaschi said. “However, it’s crucial to remember that our results still require careful ground-truthing. This is especially true for critical areas like the floodwalls, where on-site verification was not possible during this project.”
Global Lessons in Coastal Resilience
The study highlights the potential of satellite monitoring to guide infrastructure maintenance and urban planning, not just in New Orleans but in coastal cities worldwide facing similar challenges.
The Life of Earth
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