Key infrastructure like roads and hospitals may also be far lower than previously believed, putting them at greater risk of future flooding, Dokka said.
What's Causing New Orleans to Sink?
While scientists agree that parts of New Orleans are sinking, they don't agree on the rates or the root causes of the subsidence.
"There is a raging debate on rates of subsidence, how you measure it, and what's really happening," said University of Texas at Austin geologist Charles Groat, former director of the U.S. Geological Survey.
Groat explains that understanding this process is critical, but answers have proven elusive.
Subsidence has been attributed to geological processes, the weight of aboveground development, and the withdrawal of oil, gas, and water from shallow underground reservoirs.
"Members of the scientific community have squared off against each other in polite and not-so-polite terms," Groat said.
Areas built on reclaimed marshland, like much of New Orleans, may be particularly susceptible to continued subsidence, he explained.
"All [scientists] are in agreement that the subsidence issue is a huge one. Combined with sea level rise, it's a supreme challenge in low-lying coastal areas and a key part of any future plans for the [Gulf] Coast."
The study's authors hope that their findings will cast more light on a critical issue.
"There's an interagency group studying why the levee system failed, and a [National Academy of Sciences] report that came out, but neither of these really dealt with subsidence in any meaningful way," Dokka said.
"Engineers need to understand more about geology. Maybe this will help them."
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