One big unknown is how much of the city's diaspora will return, and how many will find new homes and jobs elsewhere. A high percentage of its low-income residents were renters who don't have property to return to. Reducing its concentration of poor could ease some of New Orleans's social problems. At the same time, the city will need a wide range of workers and income classes to fill jobs at hotels and restaurants, as well as offices and stores.

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Now the New Orleans real-estate developer hopes that the study produced over the last year, dubbed Operation Rebirth, will become a road map to create the new New Orleans. The study, which seeks to reinvigorate rundown stretches of the city, envisions an "Afro-Caribbean Paris," with garden-lined boulevards, an African-American cultural district, a modern trolley system and 25,000 revitalized homes -- houses that were left to rot long before Katrina arrived.