In the aftermath of the disaster, doubts have been raised as to the wisdom of rebuilding a city that lies 7ft below sea level. One Republican congressman, Dennis Hastert, has said it makes no sense to spend billions of dollars reconstructing a city that is so vulnerable to flooding, suggesting much of it "could be bulldozed".
Gordon Masterton, president elect of the UK's Institution of Civil Engineers, said: "Cities are like living organisms: they are good at repairing local damage. But the problem with New Orleans is, there has been a widespread failure of the whole infrastructure."
Yet he and other senior engineers believe measures can be taken to substantially reduce the city's vulnerability, noting that it was rebuilt once before after a major flood.
The city's system of flood barriers and levees - embankments of earth and concrete date back more than 150 years, and levees stretch along nearly 2,000 miles of the Louisiana coast and the Mississippi River. As an engineering project, it has been compared to the Great Wall of China.
The levees were breached before, in the great Mississippi river flood of 1927 when more than 26,000 square miles of land were flooded, forcing 600,000 people to flee their homes. Around 246 people died and the damage cost more than $230m.
The disaster provoked the Flood Control Act of 1928, under which upstream reservoirs were built on the Mississippi's major tributaries. More, and stronger, levees were constructed, as were waterways to divert floodwater. These defences protected the city during a flood on a similar scale in 1937.
But Dr Keith Eaton, chief executive of the Institution of Structural Engineers, says the flood defences have not kept pace with the growth of the city over the past century. Much of the city between the Mississipi and Lake Pontchartrain is now located below sea level.
"I visited New Orleans a few years ago and the river level was 20ft above the city, and I thought then: it's a catastrophe waiting to happen," Dr Eaton said.
"The first step in reconstruction will be to fill the breaches in the levees. From an engineering perspective, it's feasible to make the embankments even taller and stronger, and build them further upstream and all around Lake Pontchartrain, but it will cost billions of dollars and take years and years to complete. The Gulf of Mexico gets several major hurricanes a year, and other coastal towns will need protecting."
The US Army Corps of Engineers yesterday began work to fill the gaps in the levee system. Military helicopters dropped sandbags into the breaches, through which water from Lake Pontchartrain poured into the city.
Johnny Bradberry, head of the Louisiana department of transportation and development, said about 250 concrete road barriers would be dropped into the area to seal one spot where the waters had gushed over flood barriers.
Dr Eaton said the next step would be to pump the floodwater out of the city back into the Mississippi and Lake Pontchartrain so it could flow back into the sea, but he warned: "The logistics are huge."
Mr Masteron agreed that a major upgrade was necessary, noting that the pumping system was designed to cope with only one major breach in the flood defences. "But this time", he said, there have been several breaches, and even standby generators were partly disabled.
"An analogy is the failure of the World Trade Centre sprinkler system's failure to cope with the fire following the 9/11 attacks. The sprinklers were absolutely useless because they weren't designed to extinguish 1,000 gallons of aviation fuel."
In the longer term, both men believe the city will need to be re-zoned, with essential services relocated to areas that are less vulnerable to flooding. Dr Eaton said emergency services and administrative centres would need to be moved to higher ground, with their own water and power supplies. The safety of the city's neighbourhoods would have to be reassessed, and some may have to be abandoned, he warned.
Mr Masterton added that homes should be redesigned to minimise the risks of flood damage. "Many communities around the world build their homes on stilts," he said. "New houses should have their living quarters, gas, electric and water facilities above ground level."
In countries devastated by the tsunami that spread across the Indian Ocean last December, survivors have begun to rebuild housing on the coast, despite the risks. Alistair Burnett, senior Asia desk officer with the British Red Cross, said the Sri Lankan government had intended to impose a law banning construction within a 100-metre buffer zone around the coast, but the legislation had proved unworkable.
People wanted to return because they had traditionally lived by the coast, and the livelihoods of many depended on the sea, he said. Plans to move people further inland had also failed because the land was marshy and unsuitable for building.
Mr Masterton believes the relocation of New Orleans is unlikely for similar reasons: the surrounding land is either swamp or virgin territory, where new construction would raise major enviornmental concerns.
Dr Eaton added that in time it was likely that public awareness of the risk of another major flood would fade. He said: "After a disaster like this, people have an awareness of the risks, but that only tends to last about six months. I don't think people will want to go anywhere else.
"Every year after the floods in Bangladesh, people go back and rebuild their homes exactly in the same place."
