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When the Army Corps of Engineers finishes rebuilding the east side of the Industrial Canal floodwall shattered by Hurricane Katrina to 15 feet by June 1, residents of the Lower 9th Ward and St. Bernard Parish will have the hurricane protection they were supposed to have before the storm hit.

The completion of that job, however, will have the unintended consequence of putting the rest of New Orleans in a more dangerous position than before Katrina, storm experts and engineers said.

That’s because the canal’s west floodwall — which protects most of the city from the canal waters — will remain only about 12.5 feet above sea level, the elevation to which it has subsided since being built.

The west wall isn’t scheduled to be raised to the authorized 15 feet until Sept. 1, 2007. Should a Category 3 storm like Katrina strike while that disparity exists during the next two hurricane seasons, storm modelers and engineers said, the lower west wall will be overtopped sooner and the volume of water pouring into the western section of the city from the canal will be greater and last longer than during Katrina.

“Any surge coming up the canal under this configuration will simply go over the west side much faster than before,” said Ivor van Heerden, deputy director of the LSU Hurricane Center and a member of the state team investigating the levee failures.

Bad news for the west

“If we get another storm like Katrina with (the walls like this) it’s bad news for the people on (the west) side.”

Col. Lewis Setliff III, commander of the corps’ levee rebuilding effort, said the agency is aware of the problems that disparities in the system may cause. “The water will follow the path of least resistance,” he said, acknowledging the higher east wall makes the west side more vulnerable. He said he did not know why both projects were not attempted simultaneously. “I don’t have an answer for that.”

Setliff added that the corps is taking some steps to increase the protection offered by the lower west wall by adding scour protection to the land side in case of overtopping. Corps and independent investigations have concluded the failure of the east wall happened when water rushing over its top eroded the supporting levee.

“We’ll be adding back-scour protection to (the west wall) to guard against catastrophic failure, and we’re confident it won’t breach if it’s overtopped,” Setliff said. “But gravity and the laws of physics can’t be stopped, so, yes, the west side would be more vulnerable to flooding.

“Our mission is to have the undamaged portions of the system back to the level of protection they provided before Katrina, and that’s what we expect to complete by June 1.”

Protection paradox

The paradox of the corps increasing the threat to one part of the city by improving protection to another is the result of its post-Katrina orders as well as its failure to resolve the subsidence problems that have plagued the system since its inception in 1965, corps officials and outside investigators said.

After the system failed catastrophically during Katrina, the Bush administration gave the agency a two-step mission for restoring protection to the metro area: rebuild by June 1 the destroyed or damaged sections of the system to the heights authorized by Congress when it passed the Lake Pontchartrain and Vicinity Hurricane Protection Plan in 1965; and have the rest of the system up to its authorized heights by Sept. 1, 2007.

Those involved in the project, from federal coordinator of Gulf Coast rebuilding Donald Powell to local corps officials, have repeatedly assured residents the system would be as strong as it was “before Katrina” by the start of hurricane season June 1. But the corps has known for more than 15 years that steady subsidence of the region’s deltas has left the levees and floodwalls below mandated levels of protection by as much as 2.5 feet. So while the system may be brought back to pre-Katrina heights, those heights in most cases are below what is deemed necessary to protect the city from a major storm. �

Outdated elevation info

Corps documents show that the agency chose in 1985 to use outdated elevation data for the official heights of the structures rather than go back and raise levees recently built, a practice that continued until 2000. The corps has since been struggling to compile accurate elevations of the system, said Ed Link, head of the Interagency Performance Evaluation Task Force, conducting an investigation of the system failure for the corps.

That task force recently concluded the Industrial Canal floodwalls, authorized for 15 feet, were no higher than 12.5 feet in most places when Katrina struck. Similar deficiencies were recorded at the sites of other catastrophic breaches. The London Avenue canal floodwall that failed was no higher than 12.8 feet although it was designed to be 14.4 feet. Sections of the 17th Street Canal floodwall that breached were no higher than 12.4 feet when they were supposed to be 14 feet.

In recent years the development of highly accurate satellite-based measuring technology has greatly reduced the cost and time required to get accurate elevations, even on the constantly subsiding coastal Louisiana landmass, engineers said.

“The corps was actually in the process of doing the work to get the right elevations, which is a very long and expensive process, when we came along,” Link said. “We had a lot of money to throw at this (after Katrina) and get it done quickly.”

Link said teams working on the investigation had measured the heights of the entire system using the latest technology. The results of that work should be published in the next month, he said. Local corps officials said an effort launched the past two weeks to inspect “every inch” of the system will include getting accurate elevations for all levees and floodwalls.

(Bob Marshall can be reached at rmarshall@timespicayune.com or (504) 826-3539.)