It is likely to be the largest demolition of a community in modern U.S. history -- destruction begun by hurricanes Katrina and Rita and finished by heavy machinery. A neighborhood tucked into a deep depression between two canals, railroad tracks and the Mississippi River, New Orleans's Lower Ninth has spent more of the past five weeks underwater than dry. Entire houses knocked off foundations. Barbershops and corner groceries flattened. Cars tossed inside living rooms. What remains is coated in muck -- a crusty layer of canal water, sewage and dirt. Mold is rapidly devouring interiors.

The question now is whether the Lower Ninth Ward, which was devastated 40 years ago by Hurricane Betsy, should be resuscitated again. The debate, as fervent as any facing post-hurricane New Orleans, will test this city's mettle and is sure to expose tensions over race, poverty and political power. The people willing to let the Lower Ninth fade away hew to a pragmatist's bottom line; the ones who want it to stay talk of culture and tradition.

The flooded sections "should not be put back in the real estate market," said Craig E. Colten, a geography professor at Louisiana State University. "I realize it will be an insult [to former residents], but it would be a far bigger insult to put them back in harm's way."

The notion is not without precedent. In the 1800s, cities such as New York, Boston and Chicago rebuilt on filled-in marsh. More recently, the federal government has paid to relocate homes destroyed by the Mississippi River floods of 1993; the Northridge, Calif., earthquake; and the Love Canal environmental disaster in Upstate New York.

Of the 160,000 buildings in Louisiana declared "uninhabitable" after Katrina, a majority are in the New Orleans neighborhoods that suffered extensive flooding. Mayor C. Ray Nagin, an African American who worked in the private sector before entering politics, has spelled out plans to reopen every section of the city -- except the Lower Ninth. Housing and Urban Development Secretary Alphonso Jackson told the Houston Chronicle he has advised Nagin that "it would be a mistake to rebuild the Ninth Ward."

Historic preservation advocates fear that the city will capitalize on a program run by the Federal Emergency Management Agency that pays to tear down damaged buildings but not to repair historic private properties.

New Orleans, with 20 districts on the National Register of Historic Places covering half the city, has the highest concentration of historic structures in the nation. That includes the Lower Ninth's Holy Cross section, with its shotgun houses and gems such as the Jackson Barracks, the Doullut Steamboat Houses and St. Maurice Church.

Although it is less than two miles northeast of the French Quarter, the Lower Ninth Ward is far removed from the money and clout pulsating through downtown. From the high ground along the banks of the Mississippi River, the ward gradually slopes down. Closest to the river, the flood was five or six or seven feet deep; farther down into the neighborhood -- away from the river -- the water lapped at rooftops.

Originally a cypress swamp, the community of 20,000 is overwhelmingly black; more than one-third of residents live below the poverty line, according to the 2000 census. The people of the Lower Ninth are the maids, bellhops and busboys who care for New Orleans tourists. They are also the clerks and cops now helping to get the city back on its feet. The ward is home to carpenters, sculptors, musicians and retirees. Fats Domino still has a house in the Lower Ninth. Kermit Ruffins -- a quintessential New Orleanian trumpeter whose band likes to grill up some barbecue between sets -- attended local schools. About half the houses are rentals.

Yet even some liberal activists, people who have worked to buoy the fortunes of the Lower Ninth, are beginning to talk favorably about clearing it away -- if residents are well compensated and given suitable housing elsewhere.

But scraping away the Lower Ninth would most certainly change the already delicate equations of racial and economic politics in one of America's poorest cities, a city that was 67 percent black but is likely to have a smaller black majority once it is resettled. LSU's Colten fears middle-class Gentilly and wealthy Lakeview -- just as prone to severe flooding -- will nevertheless be rebuilt, while the Lower Ninth is abandoned.

The temptation will be to "open up spaces where there has been a lot of poverty," similar to the urban renewal projects of the 1960s, he said: "Those were seen as a way of cleansing a problem. It didn't eliminate poverty; it just moved it."