New Orleans is still at risk of serious flooding two years after Hurricane Katrina ravaged the city, a government report has found. While the levees and floodwalls that collapsed under Katrina's storm surge have been repaired, authorities have not yet raised the height of levees that were overtopped by the floodwaters.

That means that the risk of flooding in many neighborhoods remains virtually unchanged, said a report prepared by the US Army Corps of Engineers, the federal agency that oversees the country's flood control projects.

The report stops short of deeming any of the city's neighborhoods, many of which lie well below sea level, uninhabitable. Instead, it leaves the decision of whether to resettle some heavily damaged areas up to individuals and local officials.

"People are going to understand their risk, their personal risk," Lt. Gen. Robert Van Antwerp, newly installed chief of the corps, told the New Orleans Times-Picayune.

"You have a right to know what we know. And the other important part of that is truth well told. How do we translate this so everyone understands?"

Many people have already rebuilt their flood-ravaged houses, often right onto the slabs that the rushing waters left behind. Most refused to wait for official word on whether their street was safe and have been encouraged to return home by city officials who vowed to rebuild all neighborhoods.

Mayor Ray Nagin, who has vowed to rebuild all parts of New Orleans, said in a statement Thursday that the report is of limited use.

"Even if this information is accurate, simply identifying the risk does not solve the problem," he said. "We need to know what the Corps is doing to resolve the problem, because people are returning home and are rebuilding. These American citizens deserve the protection they were denied to begin with."

Katrina killed more than 1,500 people and flooded about 80 percent of New Orleans, forcing hundreds of thousands of residents from their homes.

Repairs to the 563-kilometer (350-mile) system of levees, floodgates, pumps and seawalls that protect the region are expected to be complete by 2011.

But many here have called for a stronger system that could protect the city from a Category 5 hurricane, an expensive and technologically challenging task that has yet to gain support from the Bush Administration or federal lawmakers.