One of America's most destructive natural disasters has presented an unprecedented challenge for those who must rebuild the New Orleans conurbation for its half-million population. These are some of the problems that must be addressed:
Power Restoring electricity to a city that has languished under 20ft of contaminated floodwater for days is probably the toughest task ahead. Power is essential to operate the pumps that must clear the floodwater. Executives from Entergy, which supplies power to 1.1 million customers in New Orleans and parts of Mississippi, say it will take a month or more to restore service to some of the hardest hit areas. The city's mayor, Ray Nagin, said six weeks was an optimistic expectation and other experts fear it could be 12 weeks or longer.
To avoid damaging its equipment, Entergy shut down two power plants on the Mississippi River before the storm moved in, so power generating is not the problem, but fixing the tens of thousands of fallen electricity poles and miles of spaghetti-like power cables will be. Entergy has called on thousands of workers from power companies in neighbouring states for help.
Health The Federal Emergency Management Agency (Fema) has set up 40 field hospitals in and around the city but longer-term solutions will be provided by the US navy, which has dispatched the support ship USNS Comfort to the Mississippi. It has full hospital facilities, operating rooms and hundreds of beds, and will probably have to serve as the city's primary emergency health centre until Charity Hospital and Tulane University Hospital are serviceable again.
Water supplies The city has no running water. The Carrolton water purification plant operated by the the New Orleans sewage and water board, draws water from the Mississippi river. It failed early in the storm and raw sewage has been floating along the streets. The plant is under water and cannot be operated again until electricity is restored.
Food supplies Fresh food is next to impossible to find. Most routes into the city are impassable and until they are fixed officials must find other ways of re-establishing a supply line. The national guard is considering air drops of food.
"You have to have supplies in for the rescue workers before anything else," said Dr Nicole Dash, a disaster researcher at the University of North Texas. "Food and water are critical." Roads and transport are another long-term operation. Once the initial flooding subsides, construction experts will have to conduct surveys to assess the extent of damage to and safety of existing structures, flyovers, underpasses before they can be reopened to traffic.
Emergency housing Fema is preparing to house "at least tens of thousands of victims for literally months on end", according to its executive director, Michael Brown. As in the aftermath of Hurricane Andrew, which ravaged parts of south Florida in 1992, Fema will pay for and provide mobile homes for families left homeless, and the military, probably the national guard, will set up interim tented cities for victims, and supply food and water.
Looting Expected to be addressed as national guard troops and the New Orleans police department begin to make their presence felt, and aid organisations increase the supplies of food and water. Most of the looting that has taken place so far has been for essential supplies.
"We've seen desperate people walking out of shops with diapers, food, water and so on," Dr Dash said. "I don't deny there are some inappropriate things going on but I don't think we should be arresting people for taking food and water. They're not looting, they're surviving."
Nevertheless, police have said they intend to stamp out looting "by whatever means necessary".
Prisons inmates at the Orleans Parish prison were reported to have rioted and taken a prison officer hostage, and others tried to escape, according to the service's commissioner, Oliver Thomas. Prisoners from another flooded jail were marched out on to a highway and watched over by national guardsmen who could have been helping the rescue efforts.