A helicopter view of the devastation over the New Orleans area revealed people standing on black rooftops baking in the sunshine while waiting for rescue boats. A row of desperately needed ambulances was lined up on the interstate, water blocking their path. Roller coasters jutted out from the water at a Six Flags amusement park. Hundreds of inmates were seen standing on a highway because the prison had been flooded.

Sen. Mary Landrieu quietly traced the sign of the cross across her head and chest as she looked out at St. Bernard Parish, where only roofs peeked out from the water.

"The whole parish is gone," Landrieu said.

All day long, rescuers in boats and helicopters pulled out shellshocked and bedraggled flood refugees from rooftops and attics. Lt. Gov. Mitch Landrieu said that 3,000 people have been rescued by boat and air, some placed shivering and wet into helicopter baskets. They were brought by the truckload into shelters, some in wheelchairs and some carrying babies, with stories of survival and of those who didn't make it.

"Oh my God, it was hell," said Kioka Williams, who had to hack through the ceiling of the beauty shop where she worked as floodwaters rose in New Orleans' low-lying Ninth Ward. "We were screaming, hollering, flashing lights. It was complete chaos."

Frank Mills was in a boarding house in the same neighborhood when water started swirling up toward the ceiling, and he fled to the roof. Two elderly residents never made it out, and a third was washed away trying to climb onto the roof.

"He was kind of on the edge of the roof, catching his breath," Mills said. "Next thing I knew, he came floating past me."

Across Louisiana, Mississippi and Alabama, more than 1 million residents remained without electricity, some without clean drinking water. An untold number who heeded evacuation orders were displaced, and 40,000 were in Red Cross shelters, with officials saying it could be weeks, if not months, before most will be able to return.

Emergency medical teams from across the country were sent into the region, and President Bush cut short his Texas vacation Tuesday to return to Washington to focus on the storm damage.

Federal Emergency Management Agency director Mike Brown warned that structural damage to homes, diseases from animal carcasses and chemicals in floodwaters made it unsafe for residents to come home anytime soon. And a mass return also was discouraged to keep from interfering with rescue and recovery efforts.

That was made tough enough by the vast expanse of floodwaters in coastal areas that took an eight-hour pounding from Katrina's howling winds and up to 15 inches of rainfall. From the air, neighborhood after neighborhood looked like nothing but islands of rooftops surrounded by swirling, tea-colored water.