04:40 PM CDT on Tuesday, September 14, 2004

Brett Martel / Associated Press

People floating through a polluted stew to treetops, competing with fire ants for a dry perch -- a direct hit here by Hurricane Ivan could be that horrifying, Louisiana storm damage experts say.

With New Orleans' saucer-shaped topography that dips as much as nine feet below sea level, there's nowhere for water to go if a storm surge is strong enough to top levees ringing the city.

"Those folks who remain, should the city flood, would be exposed to all kinds of nightmares from buildings falling apart to floating in the water having nowhere to go," Ivor van Heerden, director of Louisiana State University's Hurricane Public Health Center, said Tuesday.

And that's not all. Flood waters, in addition to collecting standard household and business garbage and chemicals, would flow through chemical plants, "so there's the potential of pretty severe contamination," van Heerden said.

LSU's hurricane experts have spent years developing computer models and taking surveys to predict when hurricanes could flood the city and how many people would choose to wait out the storm at home. Both results paint grim pictures.

Surveys show about 300,000 of the city's 1.6 million metro-area residents would choose to risk staying inside the city's ring of levees.

Computer models show a hurricane of a strong Category 3 or worse (wind speeds of around 120 mph or more), hitting just west of New Orleans, would push storm surges from the Gulf of Mexico and Lake Pontchartrain over the city's levees. New Orleans would be under about 20 feet of water, higher than the roofs of many homes here.

Much of town would be inundated for weeks, meaning the hundreds of thousands who evacuated or could be rescued would have to stay with friends, relatives or in sprawling temporary shelters to the north for weeks.

The rescue operation, meanwhile, would be among the world's biggest since World War II, when Allied Forces rescued mostly British soldiers from Dunkirk, France, and brought them across the English Channel in 1940, van Heerden predicted.

As far as draining flood water out, once the storm passes, if levees have trapped water above sea level, the U.S. Army Corps of Engineers would cut the levees.

"The real big problem is the water from sea level on down because it will have to be pumped and restoring the pumps and getting them back into action could take a considerable amount of time," said John Hall, the Corps' spokesman in New Orleans.

Hall was talking from home as he prepared to flee the city himself. The Corps' local staff was being relocated Tuesday evening 166 miles north to Vicksburg, Miss., and Hall was worried about what he'd find left of his home when he eventually came back.

"I'm sitting here at minus 6 (feet below sea level) and I'm scared to death," he said.

If Ivan hits east of the city, New Orleans would be on the low side of the storm surge and would not likely have catastrophic flooding, van Heerden said.

Forecasters said the track appeared to be to the east along the Mississippi coast as of Tuesday afternoon.

But even if New Orleans escapes this time, it will remain vulnerable until Louisiana gets billions of dollars from the federal and state government to help restore coastal wetlands that act as a buffer to storms coming in from sea. Louisiana has lost about a half million acres of coast to erosion since 1930. The lost wetlands were built by the Mississippi River, which is now corralled by levees and can only dump sediment at its mouth. That allows waves from the Gulf to chop away at the rest of the coastline with no new sediment replacing it.

"My fear is, if this storm passes (without a major disaster), everybody forgets about it until next year, when it could be even worse because we'll have even less wetlands," van Heerden said.

(Copyright 2004 by The Associated Press. All Rights Reserved.)