Much of New Orleans was flooded by Hurricane Katrina
Building bigger, stronger levees in New Orleans will not be enough to save the US city from another Hurricane Katrina, a report has said.
The risks of severe flooding in the city could "never be fully eliminated", said an independent panel of experts.
The report said the authorities should consider raising the level of buildings and even abandoning flood-prone areas.
More than 1,800 people died in the devastating 2005 hurricane, and about 80% of the city was flooded.
New Orleans has about 563 km (350 miles) of barriers, levees and other structures intended to protect the city.
But in August 2005, large sections of this system failed and much of the city was inundated by the storm surges brought by Katrina.
The report, from the National Academy of Engineering (NAE) and the National Research Council (NRC), said the disaster had exposed the "many weaknesses in the hurricane protection and preparedness systems" for New Orleans and surrounding areas.
It said there had been "undue optimism" about the ability of the protection systems to withstand the impact of a storm on the scale of Katrina.
FLASHBACK TO KATRINA
Katrina struck US Gulf Coast in August 2005 as a Category Three storm, killing more than 1,800 people
New Orleans was 80% flooded after storm surge breached protective levees
US government was blamed for slow, botched response that exacerbated disaster
Hundreds of thousands of people were displaced
The report said improvements made to the flood protection system since Katrina had "reduced some vulnerabilities".
But, it said that "the risks of inundation and flooding never can be fully eliminated by protective structures, no matter how large or sturdy those structures may be".
The authors advised that as there can be no absolute protection against storm surges and flooding, the authorities should consider encouraging people to move away from areas at risk.
Where this is not possible, "significant improvements in flood-proofing measures will be essential".
This would include raising the standard height for ground floors of properties, strengthening critical infrastructure such as power and telecommunications and improving evacuation plans.
The report also found that there had been "limited understanding and appreciation of the risks of living behind levees".
It advised that these risks needed to be communicated more clearly and consistently to those in affected areas.
Hurricane Katrina was one of the deadliest storms in US history, causing billions of dollar of damage and leaving tens of thousands of people homeless.
The US government was heavily criticised for the extent of the damage and for what was perceived to be a slow response to the disaster.