Petrified Truth: Worst case scenario

September 14, 2004

Worst case scenario

With Hurricane Ivan bearing down on the Gulf Coast, the mayor of New Orleans and other officials issued a call for a voluntary evacuation on Monday.

The call by New Orleans city officials and those in the city's largest suburb, Jefferson Parish, fell short of a mandatory evacuation. But Mayor Ray Nagin and parish President Aaron Broussard both said the area faces strong winds and potential floods from Ivan.
"We're going to get hit," Broussard said during a news conference. "We don't know if were going to get a punch in the mouth or a kick in the knee. But we're going to get hit."

Mayor Ray Nagin got more specific Tuesday:

In New Orleans, Mayor Ray Nagin declared a state of emergency and strongly recommended that residents evacuate immediately.... Nagin said that as of Tuesday morning there was a 22 percent chance that New Orleans would take a direct hit from Ivan.
"The city basically sits like a bowl and most of the city is under sea level ... so if we get a storm like Ivan to hit us directly" there could be 12 to 18 feet of water in the city, Nagin said. If people can't get out of New Orleans, the mayor said, they should do a "vertical evacuation."

"Basically, go to hotels and high-rise buildings in the city," Nagin explained.

Is Nagin being alarmist or overly cautious? Hardly. Back in 2000, USA Today published an analysis of the potentially catastrophic results of a direct storm hit on New Orleans. Ivan could represent an end-of-the-world scenario for the Crescent City.

New Orleans, a city of nearly 1.4 million people, sits below sea level, as much as 8 feet lower than water in nearby Lake Pontchartrain and the Mississippi River and its delta, where it empties into the Gulf of Mexico. This in effect creates a "bowl" that floodwaters can settle into, like water headed for a stopped-up drain.
To combat this unique problem, a system of levees surrounds the city to hold back the waters of Lake Pontchartrain to the north and the Mississippi River to the south, says Joseph Suhayda, director of the Louisiana Water Resources Research Institute at Louisiana State University in Baton Rouge. The levee that holds back Lake Pontchartrain is 15 feet high while the one guarding against the Mississippi River is 20 feet tall.

Suhayda says the 15-foot levee will protect the city from a minimum hurricane of Category 1 or 2 intensity and at best a fast-moving Category 3 hurricane on the Saffir-Simpson hurricane intensity scale.

"A slow-moving Category 3 or any Category 4 or 5 hurricane passing within 20 or 30 miles of New Orleans would be devastating," Suhayda says.

The storm surge — water pushed into a mound by hurricane winds — would pour over the Pontchartrain levee and flood the city. A severe hurricane could push floodwaters inside the New Orleans bowl as high as 20-30 feet, covering most homes and the first three or four stories of buildings in the city, he says. "This brings a great risk of casualties."

In this type of scenario the metro area could be submerged for more than 10 weeks, says Walter S. Maestri, Director of Emergency Management for Jefferson Parish, which encompasses more than half of the city. In those 10 weeks, residents would need drinking water, food and a dry place to live.

Besides the major problems flooding would bring, there is also concern about a potentially explosive and deadly problem. Suhayda says flooding of the whole city could easily mix industrial and household chemicals into a toxic and volatile mix. Coupled with an estimated 100,000 tons of sediment, a cleanup could take several months. In the worst case scenario, the mix of toxic chemicals could make some areas of the city uninhabitable. "It could take several years for the city to recover fully, economically, from a strong hurricane," says Suhayda.

UPDATE: Now the Associated Press files a similarly apocalyptic report, "Direct hit by Ivan in New Orleans could mean a modern Atlantis."

People floating through a polluted stew to treetops, competing with fire ants for a dry perch — a direct hit here by Hurricane Ivan could be that horrifying, Louisiana storm damage experts say.
Surveys show about 300,000 of the city's 1.6 million metro-area residents would choose to risk staying inside the city's ring of levees.

Much of town would be inundated for weeks, meaning the hundreds of thousands who evacuated or could be rescued would have to stay with friends, relatives or in sprawling temporary shelters to the north for weeks.

The rescue operation, meanwhile, would be among the world's biggest since World War II, when Allied Forces rescued mostly British soldiers from Dunkirk, France, and brought them across the English Channel in 1940, van Heerden predicted.

Via Donald Sensing, who reports that he noted such predictions back in 2002, find related info from NPR here and here, as well as American RadioWorks:

Basically, the part of New Orleans that most Americans—most people around the world—think is New Orleans, would disappear.
Suyhayda agrees, "It would, that's right."

Just pray that this thing spares New Orleans.

UPDATE: In August 2005, the worst case scenario is back, thanks to Hurricane Katrina.

Posted by Alan at September 14, 2004 12:36 PM