for National Geographic News
Almost a year ago the U.S. Army Corps of Engineers declared that it had restored New Orleans' levees and floodwalls to pre-Hurricane Katrina strength.
But the system is actually riddled with flaws, and a storm even weaker than Katrina could breach the levees if it hit this year, say leading experts who have investigated the system.
The unwelcome news comes as residents gird for what is predicted to be a "very active" Atlantic hurricane season, and as residents are still slowly rebuilding their homes and lives after Katrina.
During a recent inspection of the levee system with National Geographic magazine, engineering professor Bob Bea of the University of California, Berkeley, found multiple weak spots.
(See an interactive map of the weak spots).
The most serious flaws turned up in the rebuilt levees along the Mississippi River Gulf Outlet ship channel.
The channel's levees had failed in more than 20 places when Katrina's storm surge pounded them, leading to devastating flooding in the Louisiana city's Lower Ninth Ward and in St. Bernard Parish, which borders the city to the southeast.
Bea found several areas where rainstorms have already eroded the newly rebuilt levees, particularly where they consist of a core of sandy and muddy soils topped with a cap of Mississippi clay.
"It's like icing on the top of angel food cake," Bea said. "These levees will not be here if you put a Katrina surge against them."
Bea also found that decade-old gaps remain in the floodwalls lining the Orleans Avenue Canal. And hurricane-damaged sections of the walls along the London Avenue and 17th Street Canals have not been repaired or replaced.
Even more troubling, water appears to be seeping under the stout new floodwall erected along the Industrial Canal to protect the Lower Ninth Ward.
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