Thousands fleeing New Orleans before Gustav

NEW ORLEANS (Reuters) - Thousands of people fled New Orleans on Saturday ahead of a likely evacuation order as Hurricane Gustav took aim at the Louisiana coast, reviving traumatic memories of Hurricane Katrina.

City Mayor Ray Nagin said if Gustav -- now a Category 4 storm with 150-mph (240-kph) winds -- holds to its current course, a city evacuation could start early on Sunday.

But one day after the third anniversary of Katrina, many already had decided to abandon the city, much of which lies below sea level.

Gustav was headed toward the Cuban mainland on Saturday and could hit the U.S. Gulf Coast as a Category 4 storm on the five-stage Saffir-Simpson scale of hurricane intensity, the U.S. National Hurricane Center said.

It could reach the central Louisiana coast by late Monday or early Tuesday.

In the Lower Ninth Ward, plunged under water by Katrina's flood waters, hundreds of residents packed belongings into cars and trucks and left. Some had returned home only a few months ago after fleeing Katrina.

"After Katrina, you've got to leave," said Ruby Hall, a longtime resident, pointing to the place on the timber frame of the porch where Katrina's waters rose. "I'm not going to chance it, not with my grandchild."

Katrina's massive storm surge broke through protective levees on August 29, 2005, and flooded 80 percent of the city. New Orleans degenerated into chaos as stranded storm victims waited days for rescue.

The hurricane killed about 1,500 people along the U.S. Gulf Coast and caused $80 billion in damages, making it the costliest U.S. natural disaster.

There was bumper-to-bumper traffic on highways leading out of the city, and six low-lying parishes -- the Louisiana equivalent of U.S. counties -- issued evacuation orders effective later on Saturday.

All major Louisiana interstates will allow only one-way traffic away from the coast starting at 4 a.m. CDT (0900 GMT) on Sunday. The last flight out of the New Orleans airport is scheduled to depart at 6 p.m. CDT (2300 GMT) on Sunday.

"This could be as bad as it gets," Louisiana Gov. Bobby Jindal said. "Our people need to take this storm extremely seriously."

In all, 11.5 million people are in the path of Gustav, according to the U.S. Census Bureau.

Hoping to avoid the 2005 spectacle of desperate city residents crammed into the New Orleans Superdome, the government has lined up hundreds of buses and trains to evacuate 30,000 people who cannot leave on their own.

Texas, which is set to host 10,000 low-income Louisiana residents, could see about 45,000 evacuees cross the border, Gov. Rick Perry's office said.

MEMORIES OF FLOATING BODIES

So far, about 1,200 people have left the city by bus, and another 1,500 by train, Nagin said, and about 20,000 people had requested evacuation assistance.

Many evacuees were issued wrist bands with bar codes that will allow city officials to track them.

Walter Parker, a security guard who was trapped for eight days in his apartment during the Katrina flooding, lined up outside the Union Passenger Terminal as families with bags packed and children in tow waited for transportation.

"I don't want to see another Katrina, with dead bodies floating in the water," Parker said. "I saw elderly people floating. I saw one body that really got to me, a child, floating, and it just made me sick."

Memories of the darkened, storm-battered Superdome were fresh on the minds of evacuees. But this time around, the mood was lighter, and evacuees were given water, cookies and misting tents to stay cool while they waited.

(Additional reporting by Jane Sutton in Miami)

(Editing by Chris Baltimore and Xavier Briand)