Study Maps Uneven Land Subsidence Across New Orleans, Highlighting Flood Protection Challenges

A recent study by Tulane University researchers has revealed that parts of New Orleans and its surrounding wetlands are gradually sinking, raising concerns about long-term flood protection.

Published on July 3, 2025

flood protection
Rustic stone bridge arching over the still water in City Park in New Orleans, Louisiana at dusk with palm trees and Cypress trees

A recent study by Tulane University researchers has revealed that parts of New Orleans and its surrounding wetlands are gradually sinking, raising concerns about long-term flood protection. Published in the journal Science Advances, the study tracked ground elevation changes in Greater New Orleans from 2002 to 2020 using satellite radar data.

The researchers employed Interferometric Synthetic Aperture Radar (InSAR), a remote sensing method capable of detecting millimeter-scale changes in land elevation over time. This technique produced the most detailed map to date of vertical land motion in the region, including data from wetlands that previously lacked reliable monitoring.

Findings show that while much of New Orleans remains stable, certain neighborhoods, wetlands, and parts of the post-Hurricane Katrina flood protection infrastructure are subsiding at rates exceeding one inch per year. In some locations, elevation loss reached up to 47 millimeters (nearly two inches) annually.

Key causes of this subsidence include natural soil compaction, groundwater extraction, industrial activity, and historical drainage of wetlands for urban development. The study identified significant sinking around industrial zones, the airport, and recent residential areas, with soil compression and groundwater withdrawal cited as likely contributors. Conversely, limited uplift was noted in areas like Michoud, attributed to reduced industrial groundwater use and subsequent water table recovery.

Notably, some components of the Hurricane and Storm Damage Risk Reduction System (HSDRRS), including floodwalls and levees built after Katrina, are themselves experiencing subsidence. In some cases, these structures are sinking faster than sea levels are rising, potentially compromising their ability to withstand storm surges.

Wetlands east of New Orleans are also subsiding rapidly. Continued elevation loss in these areas may convert marshland into open water within a decade, impacting both ecosystems and the natural storm surge buffer these wetlands provide.

Given New Orleans’ low elevation and reliance on levees, pumps, and drainage systems, the study emphasizes the narrowing margin for flood protection. The researchers advocate for sustained monitoring through both satellite and ground-based methods to identify vulnerable areas and inform future infrastructure planning.

While the satellite data offers detailed insights, researchers caution that ground-based verification is necessary, particularly for critical infrastructure like floodwalls where on-site assessments were not part of the current study. The findings underscore the potential of satellite technology to support urban planning and infrastructure maintenance in coastal regions facing similar subsidence and flood risks.

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