In a nutshell
- New Orleans’ $15 billion flood protection system is sinking up to 28 millimeters per year—nearly 10 times faster than sea level rise
- The Louis Armstrong International Airport area shows the most severe land subsidence at 27 millimeters annually due to recent construction
- Satellite monitoring reveals that newly built concrete floodwalls are sinking faster than older earthen levees that were simply raised
NEW ORLEANS — Nearly $15 billion bought New Orleans what many believed was the gold standard in hurricane protection: 350 miles of state-of-the-art levees and floodwalls designed to withstand the worst storms nature could throw at them. But there was one thing engineers didn’t fully account for: the ground beneath these massive structures won’t stop moving. New research reveals that parts of this critical infrastructure are sinking more than an inch per year.
Using advanced satellite technology, Tulane University scientists have discovered that sections of New Orleans’ Hurricane and Storm Damage Risk Reduction System (HSDRRS) — the massive network of levees and floodwalls built after Hurricane Katrina — are dropping by as much as 28 millimeters (about an inch) per year. Some parts of the city itself are sinking nearly as fast, losing up to 20 millimeters annually.
As these structures sink relative to sea level, they become less effective at keeping floodwaters out during major storms. This poses a serious threat to the long-term effectiveness of defenses designed to withstand once-in-a-century storm surges.
Satellites Reveal Hidden Infrastructure Problems
Researchers led by Simone Fiaschi, a former researcher with Tulane’s Department of River-Coastal Science and Engineering, used Interferometric Synthetic Aperture Radar (InSAR) to measure tiny changes in ground elevation across Greater New Orleans. This satellite-based method can detect movements as small as a few millimeters by comparing radar images taken at different times…