As evacuees continue to stream out of New Orleans, engineers work to repair the levee system -- the massive barriers that protect the city and that collapsed on Tuesday, flooding the city. The questions now to be answered: When will the breeches be closed? And when and how can the water be pumped out of the city?

Even before Hurricane Katrina struck, experts were warning that the network of earthen, steel and concrete barriers that protected the sub-sea level city was inadequate.

On Tuesday, a day after Katrina stormed ashore, sections of two levees broke, spilling water into the streets, and flooding nearly the entire city.

Levees like this surround New Orleans protecting it from the Mississippi River and Lake Ponchartrain. Katrina's rain and storm surge created enough pressure to break through the barriers.

The Commander of the Army Corps of Engineers, Lt. General Carl Strock, says since the 500 kilometers of barriers were only built to withstand a category 3 hurricane officials knew a category 4 storm, like Katrina, could spell disaster.

"And that is exactly why the mayor and the governor ordered the evacuation of New Orleans, because they knew that if a Category 4 or 5 hurricane were to strike New Orleans, that this levee system could not be relied upon,? said the general. ?And that is why we evacuated the city."

This type of disaster has been anticipated for years, ever since Hurricane Betsy hit in the 1960s. Newspapers, hurricane experts, and even members of Congress returning from the tsunami zone have warned this type of damage was inevitable.

Bobby Jindal, a Republican Congressman from Louisiana lobbied hard for preemptive action.  "One of the arguments we made is we have to invest now or it's going to be more expensive in human lives and dollar terms later."

While some steps were taken to shore up the levee system, tight budgets made it impossible to undertake a major upgrade of the barriers.

Chip Groat, with the U.S. Geological Survey, says decisions like that are short sighted.  "It's going to get worse with time because we've got nature working against us."

Once engineers close the levee breaches in the next few days, General Strock hopes nature will work with them in drying out the city.

"The plans call for breaching the levees on the Lake Pontchartrain side and really letting gravity take control to move the water out of the city. That is the most effective and efficient way to do that," he said.

Pumps will then be used to remove the remaining water. General Strock says it will take weeks to drain the city, a necessary step before any reconstruction can begin.