Isaac was downgraded to a tropical storm late yesterday but storm surges and flooding unleashed by the weather system still posed a threat to life, the National Hurricane Centre said.
We had to break through the ceiling and out through the attic. It’s very bad down there. Very bad
The centre said the storm, located 80 kilometres southwest of New Orleans, had weakened from category one hurricane strength to a tropical storm with 110 kilometre-per-hour winds.
Officials warned, however, that heavy rains were to continue.
The upbeat assessment from the Army Corps of Engineers was surely little consolation for people whose homes were in fact deluged with water, left without power or forced to wait on roofs or attics for rescue.
As residents cowered in their homes, Isaac rolled slowly over Louisiana, dumping huge quantities of rain on a city known for its love of jazz, great food and easy-going lifestyle.
More than half a million people were left without power after the hurricane, packing winds of 130 kilometres per hour, snapped utility poles and downed power lines.
The National Hurricane Centre said the category one storm had forced a “dangerous storm surge” onto the northern Gulf Coast, with waters mounting to three metres in Louisiana and patches of coastal flooding.
Still, the flood defences built around New Orleans after Hurricane Katrina held up under the battering from Isaac, the US Army Corps of Engineers said.
The flood control system is “performing as designed. We are confident in the system,” the corps said in a statement.
The corps rebuilt the 133-mile system of levees, pump stations, floodwalls and surge barriers that surround New Orleans after levees failed during Katrina, seven years ago yesterday, swamping the city.
An elaborate €11.5 billion overhaul is still under way.
But storm-driven waters spilled over a levee south of New Orleans and inundated a residential area that had been ordered evacuated, a local official said.
The flooding in Plaquemines Parish, part of a tongue of land extending into the Gulf of Mexico south of New Orleans, saw water deluge over a levee on the east bank of that strip.
Even a relatively high-lying area that had never flooded in a hurricane is now under 1.5 metres of water, a local resident told National Public Radio. He said damage from Isaac in some areas was worse than that wrought by Katrina. He cited his home as an example.
“I stopped there to change clothes earlier. 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.
“I don’t know who is calling this a category one but this is no category one.”
About 65 people were stranded in Plaquemines, officials said.
Local TV station WWL spoke to a handful who were taken to dry land by boat. They looked shocked and exhausted. One man clutched a little dog.
“It’s horrible. Everybody’s house is gone. Nobody’s got a house in Braithwaite,” Cheryl Hicken said as she climbed out of the boat.
“The water is over my head.”
Sharon Sylvia said she had spent the night trapped on her roof, calling for help that didn’t arrive until morning.
“Water’s over the top of the roof,” she told WWL. “We had to break through the ceiling and out through the attic. It’s very bad down there. Very bad.”
More than 4,000 members of the Louisiana National Guard had been mobilised, with 48 boat teams deployed around New Orleans, according to the office of Governor Bobby Jindal, who had warned residents to prepare for the worst.