BY MICHAEL KUNZELMAN and STACEY PLAISANCE
NEW ORLEANS (AP) -- Newly downgraded Tropical Storm Isaac plodded its way across Louisiana on Wednesday, inundating parts of a mostly rural area southeast of New Orleans, while in the city, on the seventh anniversary of Katrina, levees were so far holding.
In hard-hit Plaquemines Parish, officials rescued dozens of people by boat after they became stranded by floodwaters. Authorities feared more could need help after a night of slashing rain and fierce winds that knocked out power to more than 700,000 households.
The hurricane also canceled commemoration ceremonies Wednesday for Katrina's 1,800 dead in Louisiana and Mississippi.
Louisiana Gov. Bobby Jindal said officials were considering using a backhoe to cut a hole in a levee on the east bank of Plaquemines Parish to relieve pressure on the structure, something they have during Katrina and Hurricane Gustav in 2008. Jindal said there was no estimate on when that decision would be made; it was still too dangerous to venture out.
Plaquemines Parish also ordered a mandatory evacuation for the west bank of the Mississippi River below Belle Chasse, affecting about 3,000 people in the area, including a nursing home with 112 residents.
Officials said they were worried more storm surge from Isaac would be pushed into the area and levees might be overtopped.
Joshua Brockhaus, an electrician who lives in the flooded area, helped rescue neighbors in his boat.
"I'm getting text messages from all over asking for help," he said. "I'm dropping my dogs off and I'm going back out there."
The hurricane's impact surprised him.
"We didn't think it was going to be like that," he said. "The storm stayed over the top of us. For Katrina, we got 8 inches of water. Now we have 13 feet."
Alvin Sylve, a disabled former long-distance truck driver, was preparing to get out. He lives on a street with rows of mobile homes in Jesuit Bend in Plaquemines Parish, an area outside the federal levee system where people were ordered to evacuate Wednesday as conditions worsened.
"We've never seen it this bad," he said. "The way this wind is shifting."
He was at a friend's double-wide with leaks springing in the ceiling.
"This double-wide is shaking, even though it's anchored down. You see another piece came off the roof," he said, pointing to a flying piece of roof tile. "It's falling apart!"
Meanwhile in New Orleans, Mayor Mitch Landrieu issued a curfew in part to make it easier for utility crews to restore electricity. Officials also warned they would make arrests for looting. So far, there had been only sporadic arrests.
Police cars had been patrolling the nearly empty streets since Isaac began bringing fierce winds and heavy rains to the city Tuesday night. The curfew was set to start Wednesday night and would last until further notice.
In Vermilion Parish west of New Orleans, Sheriff Mike Couvillon said a 36-year-old man had gone to help two friends move a vehicle from under a tree to get ready for the storm Tuesday evening, and fell to his death after climbing 18 feet up. Deputies don't know why the man climbed the tree.
Although Isaac was at Category 1 compared with a much stronger Katrina -- which peaked at Category 5 and made landfall at Category 3 -- the threat of dangerous storm surges and flooding from heavy rain was expected to last all day and into the night as the immense comma-shaped storm crawled across Louisiana.
Army Corps spokeswoman Rachel Rodi said the city's bigger, stronger levees were withstanding the assault.
"The system is performing as intended, as we expected," she said. "We don't see any issues with the hurricane system at this point."
There were initial problems with a few of several pumps not working at the 17th Street Canal, the site of a breach on the day Katrina struck, but it was fixed and there were no problems, Rodi said.
In Plaquemines Parish, a fishing community south of New Orleans, about two dozen people who stayed behind despite evacuation orders needed to be rescued.
"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."
As Isaac's eye passed overhead, authorities in armored vehicles saved a family whose roof was ripped off, Larpenter said.
Two police officers had to be rescued by boat after their car became stuck. Rescuers were waiting for the strong winds to die down before moving out to search for other people.
"The winds are too strong and the rain too strong," Plaquemines Parish
spokeswoman Caitlin Campbell said.
Water driven by the large and powerful storm flooded over an 18-mile stretch of one levee in Plaquemines Parish. The levee, one of many across the low-lying coastal zone, is not part of the new defenses constructed in New Orleans after Katrina.
After maintaining hurricane strength through the morning, Isaac weakened to a tropical storm Wednesday afternoon with 70 mph winds and was expected to continue losing strength. It came ashore at 7:45 p.m. EDT Tuesday with 80 mph winds near the mouth of the Mississippi River, driving a wall of water nearly 11 feet high inland and soaking a neck of land that stretches into the Gulf.
The storm stalled for several hours before resuming a slow trek inland, and forecasters said that was in keeping with the its erratic history. The slow motion over land means Isaac could be a major soaker, dumping up to 20 inches of rain in some areas. But every system is different.
Isaac's winds and sheets of rain whipped New Orleans, where forecasters said the city's skyscrapers could be subject to gusts up to 100 mph.
In the French Quarter near Bourbon Street, Jimmy Maiuri stepped outside his second-floor apartment to shoot video. Maiuri, who fled from Katrina at the last minute, stayed behind this time and had no regrets, though he was amazed at the storm's timing.
"It's definitely not one to take lightly, but it's not Katrina," said Maiuri, a bar owner. "No one is going to forget Aug. 29 forever, not here at least."
As hard wind and heavy rain pelted Melba Leggett-Barnes' home in the Lower 9th Ward, an area leveled during Katrina, she felt more secure than she did seven years ago.
"I have a hurricane house this time," said Barnes, who has been living in her rebuilt home since 2008. She and her husband, Baxter Barnes, were among the first to get a home through Brad Pitt's Make It Right program.
Her yellow house with a large porch and iron trellis was taking a beating, but holding strong. "I don't have power, but I'm all right," said Barnes, 56, a cafeteria worker for the New Orleans school system.
In Mississippi, the main highway that runs along the Gulf, U.S. 90, was closed in sections by storm surge flooding. At one spot in Biloxi, a foot of water covered the highway for a couple of blocks, and it looked like more was coming in. High tide was likely to bring more water.
In Pass Christian, a Mississippi coastal community wiped out by hurricanes Camille and Katrina, Mayor Chipper McDermott was optimistic Isaac would not deal a heavy blow.
"It's not too bad, but the whole coast is going to be a mess," he said.
The storm drew attention because of its timing ---- coinciding with the Katrina anniversary and the first major speeches of the Republican National Convention in Tampa, Fla. Republican presidential candidate Mitt Romney was considering whether to visit the Gulf Coast after Isaac.
Isaac promised to test a New Orleans levee system bolstered by $14 billion in federal repairs and improvements after the catastrophic failures during Katrina.
Contributing to this report were Associated Press writers Brian Schwaner and Cain Burdeau in New Orleans; Kevin McGill in Houma, La.; Holbrook Mohr in Waveland and Pass Christian, Miss.; Jeff Amy in Biloxi and Gulfport, Miss.; Jay Reeves in Gulf Shores, Ala.; Jessica Gresko in Mobile, Ala.; Erik Schelzig in Braithwaite, La.; and Curt Anderson at the National Hurricane Center in Miami.