Hurricane Katrina: Leaning I-Walls, the Loop Current and FEMA's Pull System

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On August 28, 2005, the National Weather Service office in Slidell, Louisiana, issued a bulletin warning that high-rise buildings would sway dangerously and windows would blow out. Katrina had formed near the Bahamas on August 23 and crossed Florida as a Category 1, but over the Gulf of Mexico's Loop Current, a deep pool of warm water, it went from Category 3 to Category 5 in nine hours, peaking at 175 mph winds and 902 millibars. An eyewall replacement cycle cut it to a high-end Category 3 at landfall but spread hurricane-force winds 120 miles from the center. Contraflow on Interstate 10 helped about a million people leave, yet roughly 97,000 stayed in New Orleans, many without cars or money, relying on shelters such as the Superdome.

Surge reached 25 to 28 feet in parts of Mississippi, but in New Orleans 80 percent of the city flooded because floodwalls breached before they were overtopped. I-walls driven into soft, peaty soil leaned, water scoured beneath them and sections slid or toppled, where engineers said T-walls would have held. The Army Corps of Engineers was shielded from liability by the Flood Control Act of 1928. Flooded 911 centers and cell sites left over 20 million calls failing in a day. Bipartisan reviews blamed a federal pull system that waited for requests from local governments that had lost the means to make them.

• Text messages sometimes went through when voice calls failed, because small data packets can be stored and forwarded.
• Ham radio operators and WWL AM radio became lifelines when the digital grid went down.
• The Coast Guard staged crews outside the storm and rescued more than 33,500 people.
• FEMA was slow to grasp the levee breaches because the worst-hit areas had no way to transmit news.
• Katrina killed 1,392 people, caused an estimated $125 billion in damage, and its name was retired.