With Hurricane Isaac's arrival, New Orleans will get its first glimpse of the effectiveness of $14.5 billion in improved levees, pumps, flood walls and other protections built after Hurricane Katrina.
Although the area will probably see heavy rain and flooding, experts say the improved hurricane protection — including what's billed as the largest drainage pump in the world, capable of emptying an Olympic-size pool in four seconds — will prevent the loss of life and widespread damage caused by the storm surge that followed Katrina in 2005.
"There's really no such thing as complete and total flood protection. The best we can do is reduce the risk," said Richard Campanella, a geography professor at the Tulane School of Architecture in New Orleans who stayed in town to ride out the storm.
He cautioned that even if the levees held and were not overtopped by the storm surge, the bowl-shaped New Orleans area would have to cope with flooding because of heavy rain likely to overwhelm drainage systems.
Campanella said that despite contentious negotiations between the U.S. Army Corps of Engineers and local officials concerning levee improvements in recent years, the revamped Greater New Orleans Hurricane and Storm Damage Risk Reduction System would probably withstand an expected storm surge of 6 to 12 feet above sea level.
"The Army Corps, like so many agencies around here, learned a painful lesson seven years ago: The levee system was a system in name only," Campanella said, calling the pre-Katrina levee system "shoddy" and disorganized.
After the corps got approval to start work on the levees in 2006, he said, they "fast-tracked about 30 or 40 years of work," completing the new system this year with "massive, Netherlands-style barriers erected on eastern and southern portions of the metropolis," 130 miles of reinforced flood walls and levees.
Aiding the system will be reduced water levels along the lower Mississippi River due to the drought farther north, he said. That will force some of the storm surge to effectively flow uphill, slow down and "swell in place" within the river.
"If there's going to be flooding in the streets, it's going to come from the sky," Campanella said, possibly enough to block streets and engulf cars in this city built "like a series of bathtubs," half below sea level. But any flood was expected to fall short of that from Katrina, which made landfall seven years ago Wednesday. Its rising water enveloped houses and claimed more than 1,800 lives, mostly in Louisiana.
"People don't generally drown in rainwater flooding here," he said. "They drown in surge flooding."
In preparation for Isaac, New Orleans Mayor Mitch Landrieu, a Democrat, helped corps staff close for the first time what he called the Great Wall: a new $1.1-billion, 1.8-mile-long, 26-foot-high wall protecting New Orleans East and St. Bernard Parish from surrounding waterways.
Elsewhere in New Orleans, Republican Sen. David Vitter embedded himself with the corps while Gov. Bobby Jindal, also a Republican, checked on the 17th Street canal pumps.
Some officials in Jefferson Parish were negotiating late Tuesday to close a floodgate in the Intracoastal Waterway to protect local businesses once waters rose 2 feet above sea level, but corps officials wanted to wait until water rose closer to 3 feet.
It would be the first time the gate was closed since its completion this year, said Susan Maclay, president of the board of directors of the Southeast Louisiana Flood Protection Authority West. She said closing the gate and managing the flow of water into the Intracoastal Waterway were complicated.
"That's going to require serious choreography," Maclay said.
In the four-parish New Orleans area, 78 water pumps have been upgraded since Katrina. But in New Orleans proper, drainage systems can handle only an inch of water in the first hour of the storm and half an inch each hour thereafter — probably not enough to avoid flooding, said Landrieu's sister, Sen. Mary L. Landrieu.
"Everybody outside thinks you build a levee and keep the water out. But rain is a big factor in these storms — water can fill up the bowl," said Mary Landrieu, a Democrat. "It's not just a few poor neighborhoods in New Orleans at the bottom of the bowl. The whole region is at the bottom. We live on a delta."
Mary Landrieu, whose parents' home was flooded during Katrina, said local officials were especially concerned about heavy rain.
"Hurricanes can be Category 1 and 2, but if they drop rain over an area like this for too long, that can turn into a pretty desperate situation," she said.