The National Hurricane Center has issued a report stating that Katrina was a Category 3 hurricane when it swamped New Orleans.
Katrina was thought to have been a Category 4 storm at the time it made landfall. New Orleans' levee system was supposed to withstand a Category 3 hurricane.
Others have offered evidence of Katrina's less-than-thought strength before, but this is the definitive statement on the subject.
Before you start booking your French Quarter reservations for next summer, just think for one minute about what a real Category 5 storm would do to that city. Why, exactly, do we need to rebuild New Orleans?