"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.
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 lifting 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 (0.9 meters) is "not that dramatic."
But homeowner 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."
Ignoring the recommendations could affect the value of homes because a new owner would have to pay substantially higher flood insurance rates or raise the structure to keep rates reasonable, said Gil Jamieson, FEMA's deputy director for Gulf Coast Recovery.
Most of the houses affected would be structures erected on ground-level slabs in the past 50 years, after much of the city's levee and canal systems were built.
In historic neighborhoods, many homes may not have to be raised at all, even if they flooded during Katrina, because they were built on foundations several feet above ground.
Raising a house typically involves lifting it with hydraulic jacks and constructing new wooden or steel supports.
The job can take one to two weeks and generally costs about $40,000 for the first foot, and $8,000 to $12,000 for each additional foot, said Phil Pieri, regional manager for a foundation-repair company that operates in 18 U.S. states.
Powell said the White House's new $2.5 billion request for flood protection, if approved by Congress, would pay to replace flood walls and raise levees surrounding 98 percent of the homes in the region.
The long-term work, which is expected to be completed by 2010, includes the replacement of 30 miles of flood walls, said Lt. Gen. Carl Strock of the Army Corps of Engineers.