Hurricane Ida is latest storm to test New Orleans' levees after Hurricane Katrina

Hurricane Ida peeled roofs off homes, flooded some communities and knocked out power to more than 1 million homes and businesses in Louisiana. 

But the New Orleans area's $15 billion federal hurricane protection system – a network of surge barriers, floodwalls and bolstered levees erected after Hurricane Katrina in 2005 – mostly did its job, sparing the area from widespread catastrophic damage, experts and engineers said. 

Though Ida's storm surge overtopped levees in low-lying areas such as Lafitte, 30 miles south of New Orleans, spurring rescue crews to retrieve trapped residents from attics Monday, the vast protection system held its ground, said Bob Jacobsen, a Baton Rouge consultant and engineer who has studied the area's flood protection system. 

Highway 51 is flooded Aug. 30 near LaPlace, La., after Hurricane Ida came ashore.

"Reports are that it held well," he said. "Water levels and waves were well within the design of the system."

Ida roared ashore Sunday near Port Fourchon as a Category 4 hurricane, with sustained winds of nearly 150 mph and gusts of more than 172 mph.

On Monday, rescuers in hundreds of boats made their way across southern Louisiana. New Orleans and several parishes said their 911 system experienced technical difficulties, leaving some trapped residents to seek help via social media. The Louisiana National Guard said it activated 4,900 personnel and lined up 195 high-water vehicles, 73 rescue boats and 34 helicopters. Local and state agencies brought in hundreds more. At least one death was reported. 

Ida was the latest major storm to hit near New Orleans since Katrina, a Category 3 storm that plowed ashore in Mississippi and easily overwhelmed federal levees, flooding more than 80% of New Orleans. More than 1,800 people died along the Gulf Coast in that storm's aftermath, many of them in New Orleans' Lower 9th Ward. Images of residents rescued from rooftops became searing reminders of the storm's cataclysmic aftermath and the government's lackluster response.

Ida hit land 16 years to the day after Katrina in New Orleans. It is tied for the fifth-strongest hurricane to strike the U.S. mainland.

After Katrina, Congress approved nearly $15 billion in projects to protect the greater New Orleans region, including massive floodgates, storm surge barriers, rebuilt flood walls and rearmored levees, as well as a mammoth pump station designed to carry massive amounts of water away from homes and into wetlands.

At least three major hurricanes have tested the system in varying phases of its completion – and each time, it's repelled storm surges and widespread flooding from the area's major urban areas. 

Craig Fugate, head of the Federal Emergency Management Agency under President Barack Obama, said the new levees appear to have worked.

A section of roof was blown off a building in the French Quarter by Hurricane Ida on Aug. 29 in New Orleans.

"It looks like everything inside of the levee protection systems built after Katrina is OK," he said. "The big problem in New Orleans was the wind that caused the power outages from the loss of those transmission lines. I wouldn't be surprised if they didn't get higher winds from this storm than from Katrina."

Fugate, 62, said the success of the New Orleans levees – and the apparent overtopping of ones closer to the coast – should reignite a debate that has echoed through southern Louisiana for decades: How much should the government help people rebuild damaged homes and buildings in storm-prone, flood-prone areas? 

He said the government has three ways to reduce risk in coastal areas prone to flooding: build bigger levees, raise buildings or pay people to move out and abandon communities.

"This is the eternal question: How much more do you build structures to protect these areas?" said Fugate, an independent consultant on disasters, flooding and climate change. "As we get through with the search and rescue, and we start talking about rebuilding, the question becomes, what are we going to do differently for the areas that are outside the protected areas?"

He said, "We are going to have more hurricanes. And building it back the way it was, we'll just end up with more devastation again. That's what we're facing: We're starting to have to have more and more uncomfortable conversations about where and how we build in coastal areas that are subject to these storms."

Sam Bentley, a geology professor at Louisiana State University who has consulted with state officials on coastal restoration strategies, agreed that the system performed well but said levees were not tested nearly as strongly as they were under Katrina. 

A tree blocks Nashville Avenue in the aftermath of Hurricane Ida in New Orleans on Aug. 30.

Ida entered the Gulf weak, then strengthened as it approached the coast; Katrina "came in like a buzzsaw," he said. Hurricane storm surges build because of a storm's winds and atmospheric pressure differences, and since Ida developed rapidly, it didn't have as much chance to shove water ahead of it, said Bentley, 58. 

Katrina's storm surge reached up to 28 feet in parts of Mississippi, according to federal estimates. Ida's surge was not forecast to be higher than 4 feet anywhere along the coast, though official measurements were still being compiled.

"Although the strength of Ida was higher at the time of landfall, Katrina was a larger storm, and the power of the surge, the extent of the surge is set about a day before the hurricane comes ashore," he said. "The winds and the atmospheric pressure gradient take time to pile the water up in front of the storm, and there just wasn't as much time for that with Ida."

He said there's reason to celebrate the New Orleans storm protection system: "It did well, and we should be proud of that."

Jacobsen, the Baton Rouge engineer, said the system did what it was designed to do: Protect private property and keep national flood insurance premiums down. 

That doesn't mean people should not evacuate as massive storms approach, he said. 

"This system functioned very well for its intended purpose: to reduce risk on property," Jacobsen said. "But there are other risks involved."

John Bacon contributed to this report. Follow Jervis and Hughes on Twitter: @MrRJervis, @TrevorHughes.