As Hurricane Katrina hit New Orleans on Monday, experts said it could turn one of the United States' most charming cities into a vast cesspool tainted with toxic chemicals, human waste and even coffins released by floodwaters from the city's legendary cemeteries.
Experts have warned for years that the levees and pumps that usually keep New Orleans dry have no chance against a direct hit by a Category 5 storm.
That is exactly what Katrina was as it churned towards the city. With top winds of 160 kilometres per hour and the power to lift sea level by as much as 9 metres above normal, the storm threatened an environmental disaster of biblical proportions, one that could leave more than 1 million people homeless.
"All indications are that this is absolutely worst-case scenario," Ivor van Heerden, deputy director of the Louisiana State University Hurricane Centre, said Sunday afternoon.
The centre's latest computer simulations indicate that by Tuesday, vast swaths of New Orleans could be under water up to 10 metre deep. In the French Quarter, the water could reach 7 metres, easily submerging the district's iconic cast-iron balconies and bars.
Estimates predict that 60 per cent to 80 per cent of the city's houses will be destroyed by wind. With the flood damage, most of the people who live in and around New Orleans could be homeless.
"We are talking about in essence having in the continental United States having a refugee camp of a million people," van Heerden said.
Aside from Hurricane Andrew, which struck Miami in 1992, forecasters have no experience with Category 5 hurricanes hitting densely populated areas.
"Hurricanes rarely sustain such extreme winds for much time. However we see no obvious large-scale effects to cause a substantial weakening the system and it is expected that the hurricane will be of Category 4 or 5 intensity when it reaches the coast," National Hurricane Centre meteorologist Richard Pasch said.
As they raced to put meteorological instruments in Katrina's path on Sunday, wind engineers had little idea what their equipment would record.
"We haven't seen something this big since we started the programme," said Kurt Gurley, a University of Florida engineering professor. He works for the Florida Coastal Monitoring Programme, which is in its seventh year of making detailed measurements of hurricane wind conditions.
Warning for years
Experts have warned about New Orleans' vulnerability for years, chiefly because Louisiana has lost more than a million hectares of coastal wetlands in the past seven decades. The vast patchwork of swamps and bayous south of the city serves as a buffer, partially absorbing the