By Paul Reynolds
World Affairs correspondent, BBC News website
The breakdown of the relief operation in New Orleans was the result of multiple failures by city, state and federal authorities.
Evacuation at last, but why so late?
There was no one cause. The failures began long before the hurricane with a gamble that a Category Four or Five hurricane would not strike New Orleans.
They continued with an inadequate evacuation plan and culminated in a relief effort hampered by lack of planning, supplies and manpower, and a breakdown in communications of the most basic sort.
On top of all this, there is the question of whether an earlier intervention by President Bush could have a made a big difference.
Before Hurricane Katrina struck, the Federal Emergency Management Agency (Fema) was confident that it was ready. Its director, Michael Brown, said: "Fema has pre-positioned many assets including ice, water, food and rescue teams to move into the stricken areas as soon as it is safe to do so."
Mr Brown even told the Associated Press news agency that the evacuation had gone well. "I was impressed with the evacuation, once it was ordered it was very smooth," he said.
Yet on Saturday 28 August, the day before the evacuation was ordered, Mr Brown did not say that people should leave the city. All he said was:
"There's still time to take action now, but you must be prepared and take shelter and other emergency precautions immediately."
It might not be his constitutional role to order evacuations yet he felt able simply to tell people to take shelter.
This has made Fema appear complacent in the period immediately before the hurricane arrived. If it did not expect the worst, it would not have prepared for the worst.
The Brown statement went out on the same day that the National Hurricane Center was warning that Katrina was strengthening to the top Category Five. (In fact I have double checked this and find that on the Saturday evening the forecast was for a strengthening to Category Four. It went up to Five on Sunday. But the point remains -- the danger was there. The difference between a Four and a Five is the difference between being hit by a truck and a train.) A Fema exercise last year called "Hurricane Pam" had looked at a Category Three, and that was bad enough.
It was announced at a news conference by the Mayor Ray Nagin on Sunday 28 August, less than 24 hours before the hurricane struck early the next morning.
The question has to be asked: Why was it not ordered earlier?
The Louisiana Governor Kathleen Blanco said at the same news conference that President Bush had called and personally appealed for a mandatory evacuation.
The night before, National Hurricane Director Max Mayfield had called Mayor Nagin to tell him that an evacuation was needed. Why were these calls necessary?
School buses still lined up after the hurricane
Again, as with Fema, the New Orleans mayor would or should have known that on the Saturday, Katrina was strengthening.
It was already clear on the Sunday that the evacuation would not cover many of the poor, the sick and those who did not pay heed.
The mayor said people going to the Superdome, a sports venue named as an alternative destination for those unable to leave, should bring supplies for several days. He also said police could commandeer any vehicle for the evacuation.
But how much support was there at the Superdome? And how much city transport was actually used? There is a photo showing city school buses still lined up, in waterlogged parking lots, after the hurricane.
Update: a reader has pointed out that there are detailed plans for Louisiana and the City of New Orleans for an evacuation and these make it clear that buses should be used to transport those without cars.
There are questions for the mayor, dubbed heroic by some, to answer.
The relief operation
The scenes which most shocked the world were at the Superdome and the Convention Center. Yet it turns out that neither Mr Brown nor his boss, Homeland Security Secretary Michael Chertoff, knew about the crisis at the Center until Thursday. And they should have known about the Superdome all along as it was the designated shelter.
This, despite numerous television reports from the scene. It was not until Friday that the first relief convoy arrived.
"The very day that this emerged in the press, I was on a video conference with all the officials, including state and local officials. And nobody, none of the state and local officials or anybody else, was talking about a Convention Center," Chertoff told CNN. Note how he blames local officials.
Nor did he know about the significance of the breach in the floodwalls until a day later.
"It was midday Tuesday that I became aware of the fact that there was no possibility of plugging the gap, and that essentially the lake was going to drain into the city," he said on NBC.
update: it is possible of course that the engineers had not themselves concluded that before Tuesday but the potential could have been realized.
Other, more successful operations, notably the airlift by the Coast Guard, should be acknowledged.
And in a disaster area the size of Great Britain, resources were stretched.
But ironically the failure at the Convention Center would have been fairly easy to put right. Reporters drove there without problems. One took a taxi.
What, one wonders, was Fema/the mayor's office/the governor's office doing while all that was played out on live TV?
One lesson agencies might want to learn is that someone senior should do nothing but monitor TV.
Some of this might explain why people at the Superdome and the Convention Center had to wait so long. It does not explain why communications were not better.
Another sign of slowness was that the Department of Homeland Security did not issue the first ever declaration of an "incident of national significance" until the Wednesday. Such a declaration allows the federal government a greater role in taking decisions.
In fact, the arguments between federal and state authorities about who was able to do what is another part of this story.
The Department of Homeland Security said the local authorities were inadequate. The locals responded that Fema had been obstructive - it had, for example, stopped three truckloads of water sent by the store Wal-Mart. And so on.
It took days to sort out who should send troops and from where.
Indeed, the intricacies of the various responsibilities of state and federal authorities do not always allow for quick decision making, though that did not stop rapid action in New York City on 9/11.
Nor does Governor Blanco escape criticism. It took until Thursday, for example, for her to sign an order releasing school buses to move the evacuees.
The president's response
Mr Bush has been blamed for failing to rise to the occasion. His critics argue that he took too long to get back to Washington and did not provide the inspirational leadership needed at such a time. Nor, it is said, did he intervene early enough to get things moving.
Washington Post correspondent Dan Balz concluded:
"Anger has been focused on Bush and his administration to a degree unprecedented in his presidency. Senator Mary Landrieu [a Louisiana Democrat] said in an ABC News interview that aired Sunday that she would consider punching the president and others for their response to what happened there. Local officials, some in tears, have angrily accused the administration of callousness and negligence."
The president's defenders point out that it was he who urged an evacuation of New Orleans (he has no legal power to order one) and that he did acknowledge the "unacceptable" pace of the relief effort. Further, they say that aid is now flowing and reconstruction will take place.
Another issue for Mr Bush is why Michael Brown was appointed director of Fema. He had previously been its deputy and had been hired as its general counsel by the director Joe Allbaugh, George Bush's chief of staff when he was Texas governor. Mr Brown, a lawyer from Oklahoma, played a role in studying the government's response to national emergencies. Before that he had run the Arab horse association.
Senator Hillary Clinton has said that Fema should be removed from the Homeland Security Department and made an independent agency again.
When Hurricane Camille, a rare top Category Five storm, hit Mississippi in 1969, just missing New Orleans, the levees around the city were strengthened - but only enough to protect against a Category Three hurricane.
The gamble was taken that another Category Five would not threaten New Orleans anytime soon. This attitude prevailed among successive administrations.
Lt General Carl Strock, the Army Corps of Engineers commander, admitted that there was a collective mindset - that New Orleans would not be hit. Washington rolled the dice, he said.
After flooding in 1995, the existing system was improved. However, the sums were relatively small. About $500m was spent over the next 10 years.
From 2003 onwards, the Bush administration cut funds amid charges from the Army Corps of Engineers that the money was transferred to Iraq instead. The latest annual budget was cut from $36.5m to $10.4m.
A study to examine defences against a category Four or Five storm was proposed, at a cost of $4m. The Times-Picayune quoted the Army Corps of Engineers project manager Al Naomi as saying: "The Iraq war forced the Bush administration to order the New Orleans district office not to begin any new studies."
But in any event, there was no plan for a major strengthening. This would have taken billions of dollars and many years.
And an Army Corps of Engineers spokeswoman, Connie Gillette, said there had never been any plans or funds to improve those floodwalls which had failed.
Update: a reader has pointed out a quote in the New York Times indicating that the failed floodwalls had in fact previously been strengthened.
'"Shea Penland, director of the Pontchartrain Institute for Environmental Studies at the University of New Orleans, said [it] was particularly surprising because the break was "along a section that was just upgraded."
"It did not have an earthen levee," Dr. Penland said. "It had a vertical concrete wall several feet thick."'
It is a long and complex chain of responsibility.
All these issues, and many more, will now be the subject of congressional and other inquiries.