BY amy wold
Advocate staff writer
September 21, 2012
BELLE CHASSE – A post-Katrina surge barrier built along the Inner Harbor Navigation Canal that fronts Lake Borgne appears to have saved New Orleans from possible flooding from Hurricane Isaac, judging by high water marks on the barrier, officials say.
The high water mark hit 13.6 feet at the surge barrier, which protects floodwalls nearer to New Orleans, such as those along the Industrial Canal between the Bywater District and the Lower 9th Ward in New Orleans, said Col. Ed Fleming, commander of the U.S. Army Corps of Engineers New Orleans district.
In comparison, the storm surge at the same location during Hurricane Katrina in 2005, before the surge barrier was built, was 15.5 feet, he told the Coastal Protection and Restoration Authority during a meeting of the group in Belle Chasse on Wednesday.
Since floodwalls on the Industrial Canal are between 11 and 12 feet high, it’s likely they would have been overtopped by the storm surge from Isaac, he said.
“Hurricane Isaac was probably the first significant test of the system,” Fleming said. “Largely, the system performed as designed.”
Although much work has been done over the past seven years to construct what Fleming prefers to call a hurricane risk reduction system around the greater New Orleans area, there were still some areas, including eastern Plaquemines Parish, that flooded.
“People have a baseline of Katrina and say ‘I didn’t flood for Katrina, why did I flood this time,’ ” Fleming said. “You have to recognize that every storm is different.”
Some areas, such as St. James Parish, received a large amount of flooding and raised questions about whether the post-Katrina improvements to the New Orleans levee protection system contributed to that flooding. The corps is currently doing computer modeling looking at what the storm surge did with the added components of the levee system and preliminary results should be available by the end of October, Fleming said.
When those results are ready, Fleming said, the corps will brief local officials and hold public meetings.
Garret Graves, chairman of the state Coastal Protection and Restoration Authority, said the loss of 1,900 square miles of coastal wetlands in Louisiana contributed to flooding problems.
“It’s no longer a situation where you have miles of wetlands between the Gulf of Mexico and our people,” Graves said. “You cannot have loss and not have an increase in flooding.”
Another concern, he said, is that many people weren’t prepared for the extent of flooding from Hurricane Isaac because it was only designated a Category 1 storm.
The Saffir-Simpson scale that defines hurricanes by a category number scale reflects wind speed but doesn’t take into account size of a storm, its forward speed, rainfall, barometric pressure or a host of other factors that help determine a storm’s damage potential, Graves said.
“I think people stopped listening when they heard Category 1,” Fleming agreed.
The state Coastal Protection and Restoration Authority voted to send a letter to the National Weather Service asking for a better way to convey a storm’s strength to the public that is based on more than just wind speed.
The discussion echoed a similar one held at a CPRA meeting in 2009 when Ken Graham, meteorologist in charge at the National Weather Service in Slidell, told the authority the National Weather Service was trying to move away from the scale.
Authority members at the time acknowledged that is was going to take time to get people to stop judging hurricanes solely on their category designation.