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Gustav May Overwhelm New Orleans Defenses, Experts Say

Willie Drye
for National Geographic News
August 29, 2008
 
As tropical storm Gustav continues its trek toward the U.S. Gulf Coast today—the third anniversary of Hurricane Katrina's Louisiana landfall—experts doubt New Orleans' levees can handle a direct hit from a major hurricane (Gulf Coast map).

As of this morning the National Hurricane Center predicts Gustav will be a Category 3 hurricane when it approaches the Louisiana coast Tuesday morning. Category 3 hurricanes have sustained winds of 111 to 130 miles (177 to 209 kilometers) an hour.

The latest forecast predicts the storm will make landfall about a hundred miles (160 kilometers) west of New Orleans.

Meteorologists caution that landfall predictions five days away can be off by as much as 300 miles (480 kilometers). Also, the National Hurricane Center advisory issued at 11 a.m. ET today noted that Gustav's path through the Gulf of Mexico is "rather uncertain" and that "landfall remains possible throughout the northern Gulf Coast."

(Special report: National Geographic magazine on New Orleans' hurricane vulnerabilities—full article, interactive map, videos, and more.)

Rapid Intensification

Keith Blackwell, a meteorologist at the University of South Alabama's Coastal Weather Research Center in Mobile, said conditions are in place for Gustav to undergo very rapid intensification during the upcoming Labor Day weekend.

The Caribbean Sea and southern Gulf of Mexico have very warm water to fuel the storm. And for the next couple of days there will be no wind shear—changes in upper-level wind speed or direction, which can weaken hurricanes—to inhibit Gustav's development, Blackwell said.

"Every component is coming together to produce a really big storm," Blackwell said. "I see a Category 3 easily. And conditions are there for it to become a Category 4 or 5."

A Category 4 hurricane has winds of from 131 to 155 miles (211 to 249 kilometers) an hour. A Category 5 storm's winds exceed 155 miles an hour.

Blackwell thinks Gustav's peak intensity will occur about 300 miles (480 kilometers) south of New Orleans. He adds that wind shear should pick up after the weekend, weakening the hurricane significantly as it gets closer to shore.

Levees Ready?

When Hurricane Katrina made landfall just south of New Orleans in August 2005, levees protecting the low-lying city from Lake Pontchartrain and the Mississippi River failed, causing catastrophic flooding in the city.

The U.S. Army Corps of Engineers has been repairing the levees since then. (See "New Orleans' Rebuilt Levees 'Riddled With Flaws'" [May 6, 2007].)

"If [Gustav] is a Category 3 that's going to central Louisiana [far west of New Orleans], we're fine," said Oliver Houck, a professor of environmental law at Tulane University in New Orleans.

The New Orleans levees have "more armor" than before Hurricane Katrina, Houck said. But that extra protection is mostly in the form of additional sandbags, he added.

"Clearly it's a stopgap measure," Houck said. "But stopgap measures ought to handle an indirect hit from a Category 3."

Still, Houck said, "I think the city would be wise to call for an evacuation, which I think is inevitable."

Yesterday, Louisiana governor Bobby Jindal called a mandatory evacuation, probably beginning no earlier than Saturday, "very probable," according to the New Orleans Times-Picayune.

Concerns Not Resolved

In May 2007 Bob Bea, an engineering professor at the University of California, Berkeley, was highly critical of the repairs that the Army Corps of Engineers had made to New Orleans since Hurricane Katrina.

The repaired levees would not withstand the impact of a storm similar to Katrina, Bea said at the time.

Asked this morning if his concerns from 15 months ago had been resolved, Bea said, "No."

He did say, however, that the levees would be less likely to fail if Gustav's center—with the storm's strongest winds—stays well to the west or east of New Orleans.

But Bea and Tulane's Houck agreed that if the eye comes ashore just to the west of New Orleans or goes directly over the city, the city will be in deep trouble.

A direct hit from a Category 3 hurricane could send water surging up the Mississippi River Gulf Outlet canal into New Orleans, Houck said. The narrowness of that waterway could cause the water to rise to as high as 17 feet (5 meters) as it rushes into the city, he said.

UC-Berkeley's Bea said, "If you directly challenge that flood-protection system today with a Category 3 storm surge, you can expect to see very, very significant breaching of the levees.

"That's why, if I lived in New Orleans, I'd get in my car and get out early and safely."


Willie Drye is author of Storm of the Century: the Labor Day hurricane of 1935, published by National Geographic Books.

HURRICANE BASICS




Hurricane Facts
Hurricane Safety Tips
Hurricane Photos
New Orleans' Faulty Levees (National Geographic Magazine)
Forecasting Killer Hurricanes (National Geographic Magazine)
 

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