Tests confirm effectiveness of post-Katrina upgrades
NEW ORLEANS — The entire 133-mile perimeter of the Greater New Orleans hurricane protection system will be completed by the year’s end, the result of state and federal action and funding since Hurricane Katrina in 2005, a U.S. Army Corps of Engineers official said Tuesday.
The corps ran an annual systemwide test for some of its larger structures, including the Gulf Intracoastal Waterway West Closure Complex, the Inner Harbor Navigation Canal Seabrook Floodgate Complex and the 17th Street Outfall Canal Interim Control Structure.
One of the newer structures is the Seabrook floodgate which, for the first year, has gates that can close off storm surge from Lake Pontchartrain into the Inner Harbor Navigation Canal. It will operate in conjunction with the surge barrier that prevents storm surge from the west, and a lock structure to prevent water from the south, said Col. Ed Fleming, commander of the corps’ New Orleans District.
During Katrina, storm surge pushed through Lake Pontchartrain and Lake Borgne to converge into the Inner Harbor Navigation Canal, where elevated water levels contributed to floodwall failures and extensive flooding.
However, now the surge barrier between Lake Borgne and the Gulf Intracoastal Waterway will be closed first because water in Lake Borgne is higher than in Lake Pontchartrain, Fleming said. As the water drains through the system to Lake Pontchartrain, the Seabrook gate at Lake Pontchartrain will be closed as late as possible, he said.
The surge barrier change will help create a reservoir inside the system to better handle rain and any overtopping at the Lake Borgne structure, Fleming said. That structure is lower than the surrounding levees because the idea is that any overtopping would go into the wetland basin rather than into St. Bernard Parish, he said.
Although the flood walls along the Inner Harbor Navigation Canal have been closed off from direct storm surge now, they have also been strengthened as a secondary line of defense, Fleming said.
“In total, 69 miles of levees and floodwalls that previously served as first line of defense have now been relegated to the second line of defense,” Fleming wrote in the corps’ newsletter.
The Seabrook floodgate joined other structures Tuesday that are in place now, but were not last year, including structures at Bayou Segnette, Bayou Verret and the Inner Harbor Navigation Canal-Lake Borgne Surge Barrier.
Although these structures were not completed last year, the Greater New Orleans areas has had protection through temporary measures. There are 500 feet of “construction openings” at six locations in the system where it has not been closed, primarily to allow continued construction, Fleming said.
The operation of the entire system also involves better personnel and agency interaction than before Katrina, Fleming said. For example, when the gates on the outflow canals that take water from inside the system to Lake Pontchartrain are closed, a corps official will stay with the Sewerage and Water Board of New Orleans, he said.
The water board is responsible for internal drainage, so communication between the corps and the board about water levels in the canals and pump activity can happen more quickly, Fleming said. In addition, corps members also co-locate with local parish officials to help with communication during storm events, he said.
The exercises Tuesday of operating flood gates and turning on pumps at various locations provides confidence that the system is working and allows workers to get experience operating the equipment, Fleming said.
“And it helps give the public confidence that the gates do work and the pumps do work,” Fleming said. Corps staff who act as liaisons with the state or other agencies during tropical storms also have a chance to see the structures working so they have a better idea of the system, he said.
After Katrina, the phrase that came out of the aftermath investigation was that the New Orleans area hurricane protection system was a system in name only, Fleming said. There was criticism after Katrina that the system was just pieces of protection that were never integrated to work together but that has changed, he said.
“This is no longer a system in name only,” Fleming said.