Parts of New Orleans are flooded with up to six feet of water Monday after some of the pumps that protect the low-lying city failed under the onslaught from Hurricane Katrina, Mayor Ray Nagin said.
Nagin said the Lower 9th Ward of New Orleans, on the east side of the city, was under five to six feet of rising water after three pumps failed.
WGNO reporter Susan Roesgen, who is with the mayor at the Hyatt hotel, said New Orleans police had received more than 100 calls about people in the area trapped on their roofs.
Katrina crashed ashore around 6 a.m. in southeastern Louisiana as a Category 4 storm with winds topping 140 mph. By 11 a.m., winds had fallen to 125 mph as it moved inland.
To the east, Katrina was hammering Biloxi, Gulfport and other communities along Mississippi's Gulf of Mexico beaches, where CNN correspondent Gary Tuchman reported from Gulfport that the storm was "dismantling" the area.
"There is intense damage," Tuchman said. "We are watching the dismantling of a beautiful town."
CNN's Rob Marciano reported extensive damage in Biloxi, east of Pascagoula. "Just a few minutes ago, the wind, surely over 100 mph, peeled roofs off, hurling 6-by-8 sheets of plywood into our parking lot, blowing out the windows of SUVs," he said.
And further to the east in Alabama, Mobile Bay topped levees and spilled into downtown Mobile, where winds gusts approaching hurricane strength were reported.
Levees have been overtopped in the New Orleans area, the National Weather Service said.
"Levees overtopped in Orleans and St. Bernard parishes," the NWS said in a hurricane local statement. It also said "extensive and life-threatening storm surge flooding" was occurring along the Louisiana and Mississippi coast. The weather service reported "total structural failure" in some parts of metropolitan New Orleans, where Katrina brought wind gusts of 120 mph. While it offered no details, it said it had received "many reports."
New Orleans was prepared for a catastrophic direct hit from the powerful storm. About a million people fled the area, and about 10,000 people who couldn't leave hunkered in the mammoth Louisiana Superdome.
While the counterclockwise spin of a hurricane usually leaves the worst damage on its eastern edge, CNN meteorologist Chad Myers cautioned that "there's not really an easy side of a Category 4 storm" on the Saffir-Simpson scale.
CNN's John Zarrella said that the wind was howling through the buildings in downtown New Orleans, ripping off chunks of debris and causing whiteout conditions. (See video of near whiteout conditions and debris-filled winds)
He said that water was rushing down the street and had risen up to the wheel wells of parked cars.
Earlier, reporter Ed Reams from affiliate WDSU told CNN that Katrina ripped away a large section of the Superdome's roof. (See video of conditions within the darkened Superdome)
"I can see daylight straight up from inside the Superdome," Reams reported.
From a vantage point nearby, CNN's Jeanne Meserve reported that the parts of the roof of the massive building was hanging "in shreds" from the top.
"Incredible rain, punishing, punishing wind," Meserve reported.
National Guard troops moved people to the other side of the dome. Others were moving beneath the concrete-reinforced terrace level.
About 70 percent of New Orleans is below sea level and is protected from the Mississippi River by a series of levees. (Full story)
NHC deputy director Ed Rappaport told CNN that New Orleans could expect a storm surge of 15 to 20 feet.
That surge wouldn't top New Orleans' levees, but CNN's Myers noted that "there may be a 20-foot surge, but there may be a 20-foot wave on top of that."
Louisiana Gov. Kathleen Blanco said it was too soon to feel any sense of relief.
"We don't know yet," she said. "We still have a long way to go throughout this day. We are watching. We are worried of course."
At 11 a.m. ET, the storm was centered about 35 miles east-northeast of New Orleans and 45 miles west-southwest of Biloxi, Mississippi. Hurricane force winds extended about 125 miles from the storm's center.
The storm was moving north at 16 mph.
Authorities in Gulfport told CNN that 10 feet of water cover downtown streets.
"We are watching these building deteriorate and break down before our eyes," Tuchman said. "Because the water is so deep, boats are floating up the street. There is extensive damage here. This is essentially right now like hell on earth."
In Biloxi, Marciano reported that wind gusts topping 100 mph were starting to pull the roofs off of nearby buildings. (Watch video report from Biloxi, Mississippi)
Isolated tornadoes were possible Monday across southern portions of Louisiana, Mississippi, Alabama and the Florida Panhandle, forecasters said.
Three residents of a New Orleans nursing home died Sunday while being evacuated to Baton Rouge, said Don Moreau, chief of operations for the East Baton Rouge Parish Coroner's Office.
The 23 residents were supposed to stay at a church, where one of the bodies was found. The other body was found on a school bus and a third person died at a hospital, Moreau said.
The others were found to be suffering from various forms of dehydration and exhaustion, he said.
Moreau did not know whether authorities would term the deaths storm-related. "These people are very fragile," he said. "When they're loaded up on a school bus and transported out of New Orleans ..."
One person died in similar circumstances during evacuations from Hurricane Ivan, he said.
Katrina is blamed for at least seven deaths in Florida, where it made landfall Thursday as a Category 1 hurricane. As much as 18 inches of rain fell in some areas, flooding streets and homes.
Category 5 is the most intense on the Saffir-Simpson scale. Only three Category 5 hurricanes have made landfall in the United States since records were kept. Those were the Labor Day hurricane of 1935, 1969's Hurricane Camille and Hurricane Andrew, which devastated the Miami area in 1992. Andrew remains the costliest U.S. hurricane on record, with $26.5 billion in losses.
Camille came ashore in Mississippi and killed 256 people.