Severe flooding from Tropical Storm Isaac inundated the Gulf Coast early Thursday, but the multi-billion-dollar defenses built after Hurricane Katrina devastated New Orleans seven years ago held firm.
Officials ordered the evacuation of some 3,000 people in coastal Plaquemines Parish, the area hardest hit by the storm, with top winds still gusting at 50 miles per hour, hindering rescue efforts.
The National Hurricane Center said Isaac — which was downgraded from a hurricane to a tropical storm on Wednesday — would continue to weaken as it moved north into Arkansas but warned of further flooding.
"Life-threatening hazards from storm surge and inland flooding are still occurring," the Miami-based forecasters said in an 0600 GMT advisory.
Louisiana Governor Bobby Jindal said at least one American may have died as a result of Isaac, which made landfall as a hurricane late Tuesday.
Dozens of people were forced to huddle on roofs and in attics waiting hours for rescue from their homes after a massive storm surge spilled over levees in low-lying areas outside the stronger defenses built around New Orleans.
Isaac was nowhere near as strong as Hurricane Katrina, which struck exactly seven years ago, but has already caused significant damage to about 800 homes in Plaquemines Parish alone, Jindal told reporters.
Residents were urged to stay indoors, with officials warning it would be at least a day before winds calmed enough for crews to repair downed power lines.
Heavy rains — up to 25 inches in some areas — will continue through Friday, the NHC said, as the swirling vortex of cloud and storm-force winds moved slowly northward.
Isaac may wind up causing as much as $2.5 billion in damage in and around Louisiana and in the offshore oil sector in the Gulf of Mexico, according to early estimates from natural disaster modeler Eqecat.
More than a half million people were left without power in Louisiana, and tens of thousands more huddled in darkened homes in Alabama, Florida and Mississippi after Isaac snapped utility poles and downed power lines.
In New Orleans, Mayor Mitch Landrieu declared a dusk-to-dawn curfew after Isaac made landfall twice as a category one hurricane.
Plaquemines Parish president Billy Nungesser said damage from Isaac in some areas was worse than that wrought by Katrina, citing his own home as an example.
"Part of my roof is missing. The back wall has moved and the water is being pushed through the bricks into the house," he said Wednesday.
Across the state, more than 4,000 people were crammed into shelters.
Dozens of nursing home residents, many in wheelchairs, were among those taken to higher ground by the National Guard in high-water trucks.
Rescues were also underway in suburbs west of New Orleans late Wednesday after the storm surge swelled Lake Pontchartrain on the city's north side.
Claude Jones, 61, was trying to nap on a cot in the Belle Chasse high school gymnasium without much luck. He had spent two nights there already and — with his trailer home likely destroyed — could be there for many more.
"I'm worried about my family," he told AFP. "My cousin's still down there and they say they can't rescue him because the weather's so bad."
Sharon Sylvia said she spent the night trapped on her roof in the pounding rain, calling for help that did not arrive until morning.
"Water's over the top of the roof," she told WWL television. "We had to break through the ceiling and out through the attic. It's very bad down there. Very bad."
US President Barack Obama, who has been regularly briefed on the storm, late Wednesday declared a "major disaster" exists in Louisiana and Mississippi, paving the way for more federal aid to local authorities.
"We've got to make sure everybody's safe, then we'll start looking at what it'll take to recover," FEMA Administrator Craig Fugate said after surveying some of the damage on Wednesday.
Katrina left behind a devastating sprawl of destruction and death when it hit New Orleans on August 29, 2005, and a bungled response by then president George W. Bush's administration tarnished his second term in office.
Some 1,800 people were killed along the US Gulf Coast while thousands were left stranded for days on the roofs of their New Orleans homes after Katrina's storm surge smashed levees long-warned to be inadequate.