In this city still half-emptied from one of the worst floods in American history, one question provokes the ever present doubt.
Exactly how risky is it to live here?
Today, for the first time since Hurricane Katrina, U.S. officials offered some specific answers, the results of a landmark study of the flood threat.
After nearly two years of levee repairs, the chances are 1 in 500 that nearly all of the city will be flooded again this year with more than six feet of water, according to flood risk maps issued today by the Army Corps of Engineers.
There is a 1 in 100 annual chance that roughly one-third of the city will be flooded with as much as six feet of water. For dozens of city blocks, the chance of significant flooding is twice as high.
"If I were moving or returning to New Orleans, I'd have one of these flood maps in my back pocket," Donald Powell, the Bush administration's Gulf Coast recovery chief, said at a meeting to release to the information. "I'd want to be safe."
Meteorologists estimate that on average a storm like Katrina strikes once every 400 years.
Controversy of where to rebuild
The new flood-risk maps are expected to renew the controversy, sometimes racially charged, over what parts of the city ought to be rebuilt.
Although some experts have pressed for the most vulnerable neighborhoods to be closed at least temporarily, Mayor C. Ray Nagin has bowed to pressure from residents of those areas and insisted that every resident has the "right of return." He has said the free market, not planners, should dictate where the city is rebuilt.
In a statement, Nagin said "we need assurance that this is reliable data. . . . But even if this information is accurate, simply identifying the risk does not solve the problem. . . . These American citizens deserve the protection they were denied to begin with."
Said Powell: "Now you'll have science and political will all clashing. What will prevail? I don't know."
By 2011, the Corps of Engineers is supposed to finish its $7 billion levee construction project. That is expected to significantly reduce the flooding risks, though details regarding the added safety are not yet available.
In December, Corps officials are scheduled to present to Congress a menu of flood defense schemes of varying strength that could be provided beyond the $7 billion project. The cost estimates are expected to run into the tens of billions of dollars.
"We will never be able to say there's no risk," said Karen Durham-Aguilera, director of Task Force Hope, the levee project.
'Can we trust the Corps?'
The study of flood risks was conducted by the team of academic and private-sector engineers that issued an eight-volume report on the levee system's failures after Hurricane Katrina. It was led by Ed Link, a senior research engineer at the University of Maryland.
"There is a gnawing sense out there -- 'Can we trust the Corps?' " Powell said. "This team was independent."
The research team based its estimates of the flood risk on the odds of hurricane strikes and an assessment of the region's flood defenses, which consist of 350 miles of levees and flood walls, as well as pumping stations and flood gates.
One of the key findings of the group was a departure from the widely held idea that the flooding a hurricane can cause is almost entirely dependent on its intensity. Instead, the group found, the surge depends significantly on the hurricane's track and its radius.
The study showed that the levee work completed has significantly reduced the flood risks in some neighborhoods, particularly in Lakeview, the site of one of the catastrophic levee breaches caused by Hurricane Katrina. Elsewhere, only slight reductions in risk have been achieved.
Now they tell us?
In the neighborhoods where people are rebuilding, the immediate reaction to word of the new risk assessment was primarily: Now they tell us?
Dwight Carter, 55, a school maintenance worker, and his wife, Joann Carter, 53, a school cook, are among a handful of people who have rebuilt homes in their Gentilly neighborhood, which was wiped out by Katrina.
Following the federal guidelines at the time for rebuilding, the couple raised their home about three feet over the ground. But the new maps show that there is a 1 in 100 chance of having eight feet of water in the area, which sits below sea level.
"I wish they'd told us that," Joann said, shaking her head.
Then, like many others, they embraced the hope that another catastrophe is unlikely.
"I just don't see it happening again," Dwight offered.
"We're just going to have to trust in the Lord," Joann said.
It is unknown what effect the results of the study will have on those who have yet to rebuild -- a category that covers most of the people in the Carters' neighborhood and in many others.
A study of utility usage released in May by GCR & Associates, a city-hired research firm, indicated that only about 56 percent of the city's pre-Katrina population of 454,000 has returned.
Many of the hardest-hit neighborhoods are sparsely populated at best, desolate places where the streets are lined by empty, wrecked homes and high weeds. Portions of the Lower Ninth Ward remain nearly deserted.
According to the homeowner relief program run by the state, thousands of people have decided not to return or are undecided. But many have little financial choice but to try to rebuild their home.
"By now many people have picked their poison," said Angele Givens, a Gentilly homeowner and leader of a civic group. Many "are going to take the risk and pray."