New Orleans ? A long-awaited government projection on this city’s flood danger recommends that thousands of homes and businesses in areas ravaged by Hurricane Katrina be raised at least 3 feet, a requirement that clears the way for residents to decide how, or whether, to rebuild.

“This will enable people to get on with their lives,” said Donald Powell, the chief federal coordinator for Gulf Coast hurricane recovery.

The so-called flood advisories detail how high the water might rise in certain sections of the city during a once-in-a-100-year storm, and how well the levees would protect residents.

Property owners who ignore the guidelines risk losing out on government aid to rebuild and could miss an opportunity for lower flood insurance premiums. The flooding projections will also be key in planning the city’s overall reconstruction.

In drawing up the advisories, government experts took into account the increasingly active hurricane seasons, recent erosion of coastal land that acted as a buffer against large storms, and the sinking of land in parts of southern Louisiana.

The Federal Emergency Management Agency had delayed the release of the advisories several times since the start of the year as researchers incorporated new post-Katrina data.

A house n the Broadmoor area of New Orleans has been raised an additional 7 feet by its owners. The house was 3 feet above the ground and still sustained damage in the aftermath of Hurricane Katrina. After the work is done, the house will be more than 10 feet above the ground.

The government recommended that levee-protected homes damaged by flooding during Katrina be raised by 3 feet, but some residents may have to lift their homes higher, depending on the elevation and location of their property.

Federal aid is available to pay for raising houses, but many homeowners could still be stuck paying for a portion of the costs, which can be $40,000 for the first foot.

Powell and other officials declined to estimate how many homes would have to be raised. Powell described the recommendations as good news for homeowners, saying raising a house no more than 3 feet is “not that dramatic.”

But Timothy Riley, 44, said the guidelines would sharply increase the cost of repairing his home. “We’d have to tear our house down,” he said. “There’s no way we can jack the slab up to go any higher.”

Jeb Bruneau, president of a neighborhood association in the city’s Lakeview area, was relieved that the recommendations had been released.

“This will spur activity unbelievably,” he predicted. “A lot of people have been waiting for the advisory to come out so they’d have direction. A lot of people are looking at this as progress.”