By Alistair Leithead
BBC News, New Orleans
Thousands of people have congregated in the New Orleans convention centre - a spacious, largely dry building, where they have been told buses will arrive to take them out of the city.
Whole families lie on the floor with what few possessions they rescued from the flooding - toddlers, the elderly and people with disabilities.
Volunteers set up cots in Houston's Astrodome in preparation for evacuees from New Orleans
All say no-one is helping them.
Most are short of food and water and there is little sign of any organisation, let alone supplies to help those waiting to leave.
A lot of people here are criticising the authorities for not putting enough effort into the evacuation of the city.
The emergency services are split between the search and rescue operation, holding back more floodwater, and fighting gangs of looters.
It seems they have little time left for the survivors, who are becoming increasingly desperate.
It's very much the poorest people that are left here - those who didn't have the ability to get out with a car fast enough
I went down to the convention centre and I didn't see any officials providing people with aid. There was no water and no food supplies.
People are desperate to get out. Most of them have lost everything, except what they carry with them. They haven't got the supplies to last very much longer, and it is very difficult to leave.
I think all the food that could have been taken has been looted already.
I spoke to a man who used our phone and asked him how he was doing for food. He said that those in his apartment are working together to gather supplies.
They had to loot Wal-Mart and take what they could on the first day, he said.
"We hated doing it but we just know that we've got no food, we had to do it," he said.
But this man was clearly not a criminal. It's a very fine line between what people actually need and what people are doing out of the fact that they're poor and they want more.
It is very much the poorest people that are left here - those who didn't have the ability to get out with a car fast enough.
Some boarded up their homes, and came to stay in the hotels in the city. Those are perhaps the richer of the poor, if you like.
The rest are the bedraggled lot who've made their way from wherever they were when the storm struck.
Many of them waded through the water after being rescued from the roofs of houses, only to be told they've got to leave.
They are waiting desperately for buses to take them wherever it might be - anywhere where there are supplies of food, water, electricity.
These are old people, disabled people. I spoke to a single mother with eight-month-old twins, trying to change nappies amid the grime of a carpet on the floor of the convention centre.
It is amazing the number of people who are in a desperate situation and it is very, very difficult for the authorities to get everybody out fast - which is what they need to do.