NEW ORLEANS - Waves crashed high against flood walls Monday and New Orleans' rebuilt levee system survived its first hurricane in three years, but Gustav exposed weaknesses the Army Corps of Engineers won't plug any time soon.
Gustav was no Katrina. It was smaller, and the worst rain and wind missed New Orleans. Its storm surge - between 10 and 15 feet lower than Katrina's - entered New Orleans through navigation channels in the east and washed over the Industrial Canal.
The Industrial Canal has been characterized as the Achilles' heel in the system, and the corps is spending $700 million on a barrier at its mouth to stop surges. But the barrier won't be in place until at least 2011. On Monday, water overtopped parts of the canal's flood wall causing minor flooding in some parts of the Ninth Ward.
Another major weakness in the flood protection system is in the area known as the West Bank, where about 250,000 live. Gustav had been expected to seriously test those levees, but by Monday evening officials said water wasn't rising as much as was feared during Gustav's approach. Work on the West Bank is far from complete. The corps has repeatedly said it may be the city's weakest flank.
By Monday evening, however, the threat to most of New Orleans had subsided and levee officials felt confident the city would be spared flooding.
"All the walls have performed as they were designed to," said Maj. Tim Kurgan, a corps spokesman. "Scour protection has done what it was supposed to."
Scour protection - basically concrete pads behind floodwalls - is among a number of improvements in $2 billion in work to better protect New Orleans since Katrina flooded the city, bringing criticism and pressure on the corps.
Critics were quick to congratulate the agency.
"They did much better this time," said Ray Seed, a levee expert with the University of California-Berkeley who's studied the Katrina disaster and the city's levee system.
But Gustav barely tested some potential trouble spots as water levels in Lake Pontchartrain rose only moderately. Two of the canals - the 17th Street and London Avenue - were breached during Katrina and caused widespread flooding.
The corps' system of pumps and floodgates on the canals has been plagued with problems.
Any sigh of relief is premature and could even be risky, Seed said.
"The great danger is that people will become complacent," Seed said. "Gustav should be a lesson that tells us we have to keep moving."
New Orleans remains extremely vulnerable, said Paul Kemp, an oceanographer with the National Audubon Society.
"The fact that we have had in three years three of these storms, that threatened everybody in coastal Louisiana, shutdown all the offshore activities, it seems that this is a vulnerability that needs to be addressed more seriously," Kemp said.
In many ways, Katrina was a turning point for flood protection in southeastern Louisiana. Since Katrina, Congress has approved $14.8 billion in construction for New Orleans' levees. The corps says it will finish that work by 2011, making the city safe from severe hurricanes.
But for Louisianans, there is no time to waste. For the past century, south Louisiana has lost staggering amounts of wetlands - about 2,000 square miles. The loss of wetlands, marsh land and barrier islands has made the fragile delta a permanent disaster zone as the Gulf of Mexico gets closer with each passing hurricane season.
"We should have been building this system 30 years ago," said Sen. Mary Landrieu, D-La.