(CBS/AP) NEW ORLEANS - Isaac is drenching Louisiana and Mississippi but is weakening as it trudges roughly north over land and should lose its tropical storm status by Thursday night.
The U.S. National Hurricane Center says Isaac's wind strength should drop below 39 mph to become a tropical depression as the storm's center heads for Arkansas and Missouri on Friday.
Isaac's center bypassed New Orleans and its newly fortified levees as a hurricane Wednesday but flooded areas to the city's north and south, where people had to be evacuated or rescued.
Isaac had top sustained winds of 45 mph early Thursday as its center moved over southern Louisiana. It was still packing heavy rains that threatened lowland flooding through Friday in Louisiana, Mississippi, southwest Alabama and Arkansas.
A fallen tree blocks all the lanes along a downtown road in New Orleans, Aug. 29, 2012 in Louisiana.
(Credit: Getty)In New Orleans, the biggest problems seemed to be downed power lines, scattered tree limbs and minor flooding. Just one person was reported killed, compared with 1,800 deaths from Katrina in Louisiana and Mississippi. And police reported few problems with looting. Mayor Mitch Landrieu ordered a dusk-to-dawn curfew just to be sure.
President Obama signed declarations of disaster in Louisiana and Mississippi and has authorized federal aid to help those states impacted by Isaac, according to statements issued by the White House on Wednesday.
But in Plaquemines Parish, a sparsely populated area south of the city that is outside the federal levee system, dozens of people were stranded in flooded coastal areas and had to be rescued. The storm pushed water over an 18-mile levee and put so much pressure on it that authorities planned to intentionally puncture the floodwall to relieve the strain.
Earlier, Louisiana Gov. Bobby Jindal said as many as 40 people are reportedly in need of rescue in the area. CBS affiliate WWL-TV reports that 75 people were rescued from flooded homes and rooftops from Braithwaite, La., and that dozens people were still reportedly awaiting rescue on the parish's east bank on rooftops and in attics.
. "I'm getting text messages from all over asking for help," said Joshua Brockhaus, an electrician who was rescuing neighbors in his boat. "I'm dropping my dogs off, and I'm going back out there."By midafternoon, Isaac had been downgraded to a tropical storm and the Louisiana National Guard wrapped up rescue operations in Plaquemines Parish, saying they felt confident they had gotten everyone out and there were no serious injuries.
"That should be everyone," National Guard spokesman Capt. Lance Cagnolatti said. "We're pulling out."
Even at its strongest, Isaac was far weaker than Hurricane Katrina, which crippled New Orleans in 2005. Because Isaac's coiled bands of rain and wind were moving at only 5 mph -- about the pace of a brisk walk -- the threat of storm surges and flooding was expected to last into a second night as the immense comma-shaped system crawled across Louisiana.
"We didn't think it was going to be like that," Brockhaus said. "The storm stayed over the top of us. For Katrina, we got 8 inches of water. Now we have 13 feet."
In Plaquemines Parish, about two dozen people who defied evacuation orders needed to be rescued. The stranded included two police officers whose car became stuck.
"I think a lot of people were caught with their pants down," said Jerry Larpenter, sheriff in nearby Terrebonne Parish. "This storm was never predicted right since it entered the Gulf. It was supposed to go to Florida, Panama City, Biloxi, New Orleans. We hope it loses its punch once it comes in all the way."
At left, watch video of a levee in Plaquemines Parish being overtopped as filmed by storm chaser Jeff Piotrowski
The storm knocked out power to as many as 700,000 people, stripped branches off trees and flattened fields of sugar cane so completely that they looked as if a tank had driven over them.
Plaquemines Parish ordered a mandatory evacuation for the west bank of the Mississippi below Belle Chasse because of worries about a storm surge. The order affected about 3,000 people, including a nursing home with 112 residents. In Jefferson Parish, the sheriff ordered a dusk-to-dawn curfew.
