11:39 AM CDT on Sunday, September 18, 2005

Matt Crenson / Associated Press

All it takes is cash and time. Given enough money, engineers agree that they could eventually build a system of levees and other flood control structures sufficient to protect New Orleans from another Katrina or even a stronger hurricane. But it would cost billions, and the work might not be completed for up to 30 years. The question is, and always has been, how much the federal government is willing to pay for that protection.

"New Orleans is what it is because the federal government made it that way," said Robert Hartwig, chief economist at the Insurance Information Institute. "And what it is today - underwater."

Much of New Orleans, especially the neighborhoods that were most severely flooded by Hurricane Katrina, would not be inhabitable at all without the ramparts that have been constructed around the city over the past 40 years. After Hurricane Betsy destroyed much of New Orleans in 1965, Congress authorized a massive construction project to ensure that such a storm would never threaten the city again.

The project began by raising the levees along Lake Pontchartrain on the city's north side, and linking them to the Mississippi River levees to form the "bowl" that encloses New Orleans. Over the years, Congress also approved levees to protect suburbs south and east of the city.

At 13 to 18 feet high those levees are high enough to handle another Betsy, but not a Katrina, a Category 4 hurricane.

"We tend to build for the last storm," said Craig Colten, a professor of geography and anthropology at Louisiana State University.

It isn't that nobody thought a storm more powerful than Betsy would ever strike New Orleans. The Army Corps of Engineers had looked into the prospect of building the city's levees up to Category 5 protection. But levee construction projects proceed over decades, and the last one isn't even close to finished. Some of the follow-up projects to the original 1965 effort, added during the 1980s and '90s, aren't scheduled for completion until 2018.

"The whole thing takes a long, long time," Colten said.

Now that Katrina has supplanted Betsy as the Crescent City's most recent catastrophic storm, the government is likely to embark on a new round of flood control construction. This time, experts say, the goal is likely to be Category 5 protection, achieved through a diversified approach that includes not just higher levees but storm gates and the abandonment of some low-lying areas.

"City and parish officials in New Orleans and state officials in Louisiana will have a large part in the engineering decisions to come, and the Army Corps of Engineers will work at their side to make the flood protection system stronger than it has ever been," President Bush said Thursday evening.

Bringing just the area of New Orleans along the Lake Pontchartrain shoreline up to Category 4 or 5 protection would cost $2.5 billion to $3 billion, according to the Army Corps of Engineers' latest estimates.

For comparison, the National Flood Insurance Program received approval this week to borrow $3.5 billion for the settlement of Hurricane Katrina claims. And the losses to the program could go higher than that, said Ed Pasterick, a senior adviser in the Federal Emergency Management Agency's mitigation division.

Bringing the whole city up to Category 5 protection would take about 30 years, Army Corps of Engineers project manager Al Naomi estimated before Hurricane Katrina. Parts of the project could be expedited, but it will be years before all of New Orleans is protected against the strongest storms.

Katrina may also generate the support needed to go ahead with Coast 2050, a plan to restore some of the marshes and swamps along the Louisiana coast that have disappeared since the 1930s. Those coastal wetlands help decrease the destructiveness of an incoming hurricane by slowing down, and thus spreading out, the storm surge it pushes ashore.

The cost of the Coast 2050 Project would be more than improving the levees - about $14 billion over 30 years, depending on how much of it was implemented.

"There are lots of ways of protecting the city," said Joannes Westerink, a civil engineer at the University of Notre Dame who builds computer simulations of hurricane storm surges for New Orleans and other parts of the U.S. coast.

Some experts recommend putting flood gates in the channels that funnel water toward the city, specifically in the Mississippi River itself and in the Rigolets, a narrow passage that connects Lake Pontchartrain and the Gulf of Mexico.

The gates would be left open under normal conditions, allowing water and ship traffic to pass unhindered. In the event of an approaching hurricane they would be closed to keep the storm surge from getting into Lake Pontchartrain or moving up the river.

London has a system of such gates in the Thames River. In the Netherlands, an extensive system of dams and gates protects the population from storm surges.

Within New Orleans itself, experts recommend improving the pumps that are used to remove rainwater from the city. Because the levees around New Orleans create a below-sea level bowl, every drop of rain that falls inside the barrier has to either evaporate or be pumped out.

There's no way that pumps could keep New Orleans dry in a Katrina-scale flood. But if they were elevated and had their own power generation, Colten said, the pumps might be able to pump the city dry in days rather than weeks.

It might also be possible to elevate some neighborhoods above flood level. Civil engineer Henry Petroski of Duke University has even suggested raising the entire city. The city of Galveston, Texas, used that approach after a hurricane washed over it in 1900, killing as many as 8,000 people.

Individual houses could be elevated as well. Many homes in New Orleans are already jacked up off the ground for flood protection, but since the 1950s the majority of them have been built directly on concrete slabs.

And it would be just as helpful to go down as up. New Orleans could create drainage basins inside the levee walls to collect floodwater that would otherwise flow into the lowest-lying neighborhoods.

Finally, some have suggested restoring some of the city's most vulnerable areas to the marshlands they once were. Neighborhoods that are up to 13 feet below sea level today got that way in part because they were built on marsh soils that compacted after being drained. The longer those areas are kept dry, the lower they will sink and the more flood-prone they will become.

Generally, the lowest parts of New Orleans lie in a belt just behind the high ground of the Lake Pontchartrain shoreline that stretches from the Ninth Ward in the east to Jefferson Parish north of Louis Armstrong International Airport.

"The lowest of the low areas probably shouldn't be redeveloped," Colten said.

There is plenty of time for the vocal debate that is bound to accompany such proposals. The Army Corps of Engineers estimates it will be next year before the Big Easy's flood protection is back up even to where it was before the storm hit.

"Certainly we're not going to be able to restore the levees back to their original protection before the end of hurricane season," said Col. Duane Gapinski, the commander of the U.S. Army Corps of Engineers task force responsible for pumping New Orleans dry.

That leaves vast swaths of the city vulnerable to even a relatively weak tropical storm. But as long as 80 percent of New Orleans remains damaged or destroyed by Katrina, another hurricane would add more insult than injury.

(Copyright 2005 by The Associated Press. All Rights Reserved.)