Blacks and the poor were disproportionately affected by Katrina, according to the study led by Brown Professor John R. Logan. The analysis concludes that the difficulty in moving back to the city could mean a massive loss of population, overwhelmingly among blacks.

New Orleans was more than 65 percent black before Katrina hit in August, but it appears most of the estimated 135,000 residents who have been able to return are white. Mayor Ray Nagin recently apologized for saying New Orleans would remain a "chocolate city" as he tried to allay fears that blacks would not return.

The study found that if New Orleans' returning population was limited to the neighborhoods undamaged by Katrina, about half the white population would not return and 80 percent of its black population would not.

"There's very good reason for people to be concerned that the future New Orleans will not be a place for the people who used to live there, that there won't be room in New Orleans for large segments of the population that used to call it home," said Logan, who studies urban areas.

The study used maps from the Federal Emergency Management Agency that detailed flood and wind damage and compared them to data from the 2000 U.S. Census to determine who was affected and in what numbers.

It found the hurricane-damaged areas of New Orleans were 75 percent black compared to 46 percent black in undamaged areas of the city. It also found that 29 percent of the households in those areas lived below the poverty line, compared with 24 percent of households in undamaged areas.

More than half of those who lived in the city's damaged neighborhoods were renters, the analysis found. Those people were unlikely to have property insurance, and because so many are poor, would be unlikely to have the resources to return to the city.

"The odds of living in a damaged area were clearly much greater for blacks, renters and poor people," the study said. "In these respects the most vulnerable residents turned out also to be at greatest risk."

Along the Gulf Coast, about 46 percent of the population in damaged areas was black, compared with 26 percent in non-damaged areas. The study did not consider areas damaged if they reported just superficial problems, such as missing roof shingles.

By sheer numbers, the study noted there were almost as many non-Hispanic whites as blacks affected in damaged areas of the Gulf Coast region -- just under 300,000 of both populations. But it said that whites would be more likely to return to damaged neighborhoods.

"Whites are more likely to be homeowners," the study said. "But more important, they are much more likely to have the personal resources to reinvest in their homes or to find a new residence in a difficult housing market."

Some former residents may not be able to return to their old neighborhoods even if they wanted to, Logan said. Parts of New Orleans may close forever to development, renters can't necessarily return to homes they've left for months, and the housing market is tight. In addition, several large public housing complexes in the city have been closed since the storm and the federal Department of Housing and Urban Development has not offered specific details on how or when those projects may be restored or rebuilt.