This report indicates that the storm surge that hit New Orleans was larger than its classification (by wind speed) as a Category 4 storm would indicate:
Katrina weakened slightly to a Category 4 hurricane with maximum sustained winds estimated at 145 mph as it made landfall early Monday, but it maintained a storm surge that is only generally found in category 5 storms.
It’s the storm surge, not the wind, that is most relevant to the levee breaks. So the levees, which were meant to withstand a Category 3 storm, really got a Category-5-type beating.
Some numbers begin to appear:
The lake, which normally is 1 foot above sea level, peaked at 8.6 feet above sea level, said English.
How tall are the levees?
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