Countdown to Katrina

Tuesday 30 August, 2005, T+1 day

As dawn breaks on Tuesday, the extent of the damage is becoming clear. There are multiple breaks in the levees. Some 75 percent of Greater New Orleans is now underwater. Rescue teams are massively overloaded. Africa Brumfield has had to make her own escape: "We grabbed air mattresses and pots because we needed something to paddle with and we got on the water and we started to paddle on the air mattresses with the pots. People are screaming 'help us, can you please help us.' I sent two of my really good friends back and they saved a lot of elderly people that really couldn't walk or move and a lot of little children."

The aftermath

Eventually the breaches are filled and the water begins to be pumped out. But it will take over a month before the city is dry. The chaotic official response means that there is still no food or water available to the crowds of people in the city. The rescued and displaced are told to head for shelter at the SuperDome and the Convention Center. Around 60,000 houses in New Orleans and other communities are eventually declared damaged beyond repair. In New Orleans alone, over 1,000 people have lost their lives.

Becky Lee/Pioneer Productions; Mike Theiss Flooding and devastation in the wake of Katrina

So why did the levees fail? The questions focus on the height of the storm surge. At Bay St Louis, on the dangerous eastern side of the eye, the surge hit 28 foot. New Orleans was on the less powerful western side of the hurricane. But even so, a wave of 18 to 25 feet shot up the Intercoastal Waterway and along the Industrial Canal. It overtopped the category-3 levee walls by more than five feet, scouring away their foundations and ripping up the metal pilings. It soon became clear that overtopping was the main reason why the levees had failed in eastern New Orleans.

But the breaches that flooded downtown New Orleans are more difficult to figure out. By the time the storm surge reached the 17th Street and London Avenue canals, its height was much lower.

So if they weren't overtopped, why did they fail? Engineer Joe Suhayda has found evidence to support his theory that the walls here were not overtopped, but undermined. "The floodwall failed at the base. The earth here was too weak, and the sheet-piling itself and the monolith, the concrete structure, were just pushed laterally like the blade of a bulldozer."

2005 and beyond

2005 has turned out to be the busiest hurricane season on record. Earlier in the year, hurricane Dennis had been a clear sign that things were going to be bad. Katrina was swiftly followed by Rita - causing more damage to the Gulf coast - then Stan, which smashed into Central America, and Wilma, devastating Mexico and Florida.