Co-author Prof. Mead Allison emphasized the critical need for ongoing monitoring and maintenance of flood defenses to ensure they continue to provide adequate protection against storms.

A recent study from Tulane University has revealed alarming findings about New Orleans' $15 billion flood protection system, which is sinking at a rate of up to 28 millimeters per year, nearly ten times the rate of sea level rise.

The research also found that newly constructed concrete floodwalls are sinking at rates over seven times faster than the current sea-level rise of approximately 3.6 millimeters annually.

Using satellite-based Interferometric Synthetic Aperture Radar (InSAR), researchers created a detailed map of vertical land motion, showing that some floodwalls and levees constructed after Hurricane Katrina are sinking faster than sea levels are rising, thereby reducing their effectiveness.

As New Orleans relies heavily on a complex system of levees, pumps, and drainage canals, the risks posed by rising sea levels and sinking ground highlight the necessity for improved monitoring strategies.

The study pointed out that ongoing geological challenges contribute to subsidence, including natural sediment compaction and human activities such as groundwater pumping and wetland drainage.

Specific areas identified as sinking include regions around industrial sites, the airport, and newer residential developments, while some locations, like Michoud, are experiencing slight land uplift due to reduced groundwater pumping.

The area surrounding Louis Armstrong International Airport is particularly affected, showing the most severe subsidence at a rate of 27 millimeters annually, largely attributed to recent construction activities.

The study analyzed ground elevation changes in Greater New Orleans from 2002 to 2020, revealing that some neighborhoods are sinking by more than an inch per year, with certain areas experiencing nearly 2 inches of elevation loss annually.

Lead author Simone Fiaschi noted that even minor drops in elevation can significantly heighten flood risk in a city like New Orleans, which is already precariously close to sea level.

The findings underscore the importance of understanding land movement patterns for effective urban planning and infrastructure maintenance, suggesting that satellite monitoring could be beneficial for coastal cities facing similar challenges.

Published on June 27, 2025, in Science Advances, the study calls for additional investments to sustain the flood protection capabilities of New Orleans.