Parts of the levee system installed in New Orleans by the United States Army Corps of Engineers after Hurricane Katrina appear to have performed as designed and helped spare the city from Hurricane Ida’s storm surge. 

Other parts of the city’s flood-protection system, however, remain untested as Ida’s storm surge did not reach them.

Ida made first landfall Aug. 26 near Port Fourchon about 60 miles south of New Orleans, and then again southwest of Galliano, Louisiana. 

The Hurricane and Storm Damage Risk Reduction System, which was built after Katrina inundated much of the city in 2005, protects Jefferson, New Orleans and St. Bernard’s parishes, said Kelli Chandler, regional director for the Southeast Louisiana Flood Protection Authority East.  

The authority manages 192 miles of levees and floodwalls along the east bank of the Mississippi River, she said.  

“It definitely did what it is supposed to do,” Ms. Chandler said. “It was very effective and performed as expected. It reduced the risk for the area for storm surge.” 

Reducing potential storm surge damages can improve an organization’s insurance exposure profile. 

FM Global insured properties that are protected by a levee that is adequately designed to contain a 500-year flood and is well maintained are rated as a reduced-hazard flood risk, said Katherine Klosowski, vice president and manager, natural hazards and structures at the insurer. 

“An adequately designed and maintained levee can prevent significant flood damage to businesses, to roadways, which are needed to move products and people to and from the business, and to the local community, where the local workforce often resides,” said Ms. Klosowski. 

FM Global has a team of engineers who specialize in evaluating levees, which are often large and complex structures that require regular inspection and maintenance, she said. 

Those parts of the system that were tested functioned well, but other areas went untouched and therefore untested. Elsewhere, levees that were not raised but only repaired after Katrina were overtopped. 

“Did it work? We really don’t know yet,” said Craig E. Colten, professor emeritus in the department of geography and anthropology at Louisiana State University in Baton Rouge.  

Mr. Colten said the part of the levee system that was “relatively new and highly modified … seemed to have suppressed storm surge and kept it from getting into the industrial canal. The surge barrier and the strengthening of those levees I think did help. It closed off the Mississippi Gulf Outlet. Two avenues for water to get in from the east side of the city were basically blocked.” 

Some parts of the system, however, did not see the same level of surge and were not forced to perform, he said. “There were improvements made in Jefferson Parish on what we call ‘The West Bank.’ Those portions were not really tested.” 

Elsewhere, down river, portions of the hurricane protection system that don’t offer the same level of protection were overtopped, Mr. Colten.

 said. “Those levees weren’t raised or elevated higher after Katrina, they were just repaired,” he said. 

The benefits of mitigating flood and water damages can be felt beyond the city limits of New Orleans because of its bustling global shipping activities. The Port of Louisiana ranks first in tonnage, according to the U.S. Bureau of Transportation Statistics. 

“It’s not just worth it for the city of New Orleans, it’s also worth it for the nation,” Ms. Chandler said, due to the port’s strategic role and its status as a major international shipping hub.  

“Economically, the flood protection for New Orleans is a wise investment,” said Sandy Rosenthal, founder of Levees.org, a public education nonprofit founded in 2005 after Katrina devastated New Orleans. “The flood protection for New Orleans protects a region with a high density of people, property and infrastructure,” as well as the port shipping operations. 

Ms. Rosenthal, author of “Words Whispered in Water: Why the Levees Broke in Hurricane Katrina,” published in August 2020, said levee construction costs were pushed higher due to the urgency given the project after Hurricane Katrina and the resulting compressed timeframe. The final cost of the project was about $15 billion.

“The reason the price tag was so high for the new system was because it had to be built really quickly. An entire metropolis was vulnerable,” she said. For comparison, the original system, which was authorized in 1965, was supposed to take 13 years to build at a cost of $85 million, Ms. Rosenthal said.