New Orleans has been there for 200 years, and the levee system was developed over time. Changing the levees would be a challenging project.

In Utah, levees are like the dikes along the Provo River in Heber Valley, or beside a reservoir — relatively small structures. "But along the Mississippi River, their levees are potentially 100 feet high and a quarter of a mile across. They're massive structures," Zundel said.

Levees are "very successful when floods are small in scale or moderate in scale," said Marek Matyjasik, associate professor of geosciences at Weber State University.

But in extraordinary events like huge hurricanes, he said, "the levees are more likely to fail, because they're not designed to sustain extreme water pressure."

He stressed that he does not know any of the details about the New Orleans levee failure, other than news reports. But sometimes, he said, levees fail because they are overtopped with water, causing them to erode, or because uncontrollable leaks burrow through the levee material.

When a levee starts to leak, it can create "an artificial river inside the levee," he said. "Then it's almost impossible to stop."

The flow can happen even if there's water on both sides, when water pressure is higher on one side. Water eats through the levee's fill in a process called piping, and as it continues the opening grows. Material inside the levee, often sand or other fill, erodes more swiftly, he said.

The process is hard to monitor, according to Matyjasik. "We don't see the first symptoms on the surface, because the damage is more likely to be created somewhere at the base of the levee.

"As the process continues the flow velocity increases, and it's more difficult to stop it."

Eventually the levee can fail. Sometimes water knocks over or rotates a section. At times, a section of levee can slide away, he said.

"The sea surge of 20 or 25 feet creates enormous pressure. . . . What I heard in the news is those levees were not necessarily designed to sustain a hurricane of Category 5."

Tom Cova, associate professor of geography at the University of Utah, noted that New Orleans has levees both along the gulf and Lake Pontchartrain, and the levee broke.

"They've always had pumping stations because they have to deal with this (flooding) after heavy rain," he said. "They have a huge, sophisticated pumping situation."

This time, of course, the lake poured into the city and pumps were helpless. As soon as the breach is patched, he said, "they can pump the streets dry."

But the Army Corps of Engineers needs to plug the holes somehow, he said in an interview this past week.

Meanwhile, bodies floating in New Orleans' streets pose public health threats. Officials are "worried about cholera and typhoid," Cova said.

New Orleans isn't the only city that was built in a dangerous zone, he noted. "We have development in hazard areas all around the country." Utah's Wasatch Fault, which runs through Salt Lake City, is likely to experience a disaster because of a large earthquake, he said.

Everyone knew that someday a hurricane would score a direct hit on New Orleans, he said. "Someday the Wasatch Fault is going to have an earthquake that kills thousands of people. . . . If it happens in a hundred years, there will be that many more millions of people living here."

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