[Undertoad]

Belmont Club points to this 2003 Civil Engineering Magazine article from 2003

Any concerted effort to protect the city from a storm of category 4 or 5 will probably take 30 years to complete. And the feasibility study alone for such an effort will cost as much as $8 million. Even though Congress has authorized the feasibility study, funding has not yet been appropriated. When funds are made available, the study will take about six years to complete. “That’s a lot of time to get the study before Congress,” Naomi admits. “Hopefully we won’t have a major storm before then."

Oops

For the most part, New Orleans does not have places for people to go. The American Red Cross no longer provides emergency shelters in the city because its officials cannot guarantee the structural integrity of the locations ... that could withstand the forces of a category 4 or 5 storm. ...

Most people would not wish to remain in the city if a category 4 or 5 storm were in prospect, but evacuating could be difficult. Experts say close to 400,000 people could be stranded in the city. There are an estimated 100,000 people without easy access to automobiles, and those who can drive may not be able to do so. ... Complicating the difficulty in New Orleans is the fact that each of the city’s three major evacuation routes is over or near water.

As Belmont Club says "they got that one right".