NEW ORLEANS - Five years after Hurricane Katrina flooded more than 80 percent of this city, the Army Corps of Engineers says billions of dollars of work has made the city much safer and many of its defenses could withstand a storm as strong as the deadly 2005 hurricane.

Surprisingly, many locals - even the vocal critics of the Army Corps - say its assessment of work done on the levee system is not far off the mark.

Since Katrina flooded New Orleans on Aug. 29, 2005, and killed more than 1,800 people, New Orleans has become a round-the-clock construction site and Congress gave the Army Corps more than $14 billion to fix and upgrade the levees and other defenses. Numerous breaches in the hurricane protection system led to the flooding that devastated the New Orleans area. The corps says about half of the work is complete, and the rest should be finished by next summer.

"The good news is that the Corps of Engineers has done an about-face in its sense of urgency," said Sandy Rosenthal, the executive director of Levees.Org, a citizens group formed after Katrina that's waged numerous battles with the corps. "By their actions, words and deeds, it looks like they are doing everything they can to meet their deadline."

The threat of flooding from another storm remains a top concern in the city, which has a population that's about 80 percent of what it was before Katrina.

The corps has given itself until June 2011 to make the city safer from big storms, and says it will meet the deadline. Once the upgrades are complete, the corps says very little of the city would flood if a storm like Katrina were to hit again.

The corps' brass say that even if such a storm were to hit tomorrow, the city would be in much better shape.

"This could handle Hurricane Katrina's storm surge if Hurricane Katrina followed the same path it did during 2005," said Col. Robert A. Sinkler, the corps official in charge of levee work, as his boat cruised by a massive dam-like wall being built across two miles of open water and marsh near New Orleans' Lower 9th Ward.

The massive $1.3 billion, 26-foot-high structure is meant to keep storm surge out of the Industrial Canal, long considered the "Achilles' heel" in New Orleans' levee system.

The agency likes to call a 23-mile stretch of levee and floodwall it's building along St. Bernard Parish the "Great Wall of St. Bernard." The levee-and-wall structure will include enough steel to build 28 Eiffel Towers. The agency plans to complete two miles of the 30-foot high structure every month.

The work is critical to protect St. Bernard, a parish where nearly every building was flooded in Katrina. Fewer than 60 percent of its structures have been rebuilt, and its population is still down by about 35 percent.

Victor B. Zillmer, the corps engineer overseeing work on the storm surge barrier, said the wall was rock solid. He said enough concrete was used in it to "fill a football field 93 feet high."

He added: "It's kind of like an iceberg too. You see about 10 percent of it up here. Most of it is actually down below."

"All in all, it's better protection than we had in the past. Whether or not it's enough, who knows," said Tom Jackson, a past president of the American Society of Civil Engineers and commissioner with the Southeast Louisiana Flood Protection Authority-East, a state panel formed after Katrina to oversee levee work in New Orleans.

Jackson agreed that the levee system should be able to handle a Katrina-like storm once upgrades are done. Still, he said there are many lingering concerns - including signs of corrosion on some of the new flood walls.

Many unknowns rermain because the new system has yet to be tested by a major storm.

"It's like combat: Defend your perimeter. Where are my weakest points on my perimeter? Water will find the weakest point," said J. David Rogers, an engineer and levee expert at the Missouri University of Science and Technology in Rolla, Mo.

Rogers said Katrina exposed numerous weak points - floodgates that did not close, porous ground and sewer lines that undermined defenses.

Rogers said that while "everybody's attention is focused on what failed the last time," the next major storm could expose new weak points.

Despite the uncertainties, residents are feeling better about their chances.

David Warino, a 46-year-old operations manager at a shipyard in Avondale, La., said he bought a two-story house next to the site of a breach on the 17th Street Canal in New Orleans because he felt confident.

"This seemed like a safe spot," Warino said. "We're on high ground. The corps rebuilt the wall here."