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Performance Evaluation of the New Orleans and Southeast Louisiana Hurricane Protection System (Final Report) Volume IV – The Storm “Hurricane Katrina produced unparalleled wave and storm surge conditions for the New Orleans vicinity. Hurricane Katrina was a very large Category 3 storm when it passed the New Orleans area on the morning of 29 August 2005. Twenty-four hours earlier this storm had been the largest Category 5 and most intense (in terms of central pressure) storm on record within the northern Gulf of Mexico. Due east of the Mississippi River delta, a deepwater National Oceanic and Atmospheric Administration (NOAA) buoy recorded the highest significant wave height (55 ft) ever measured in the Gulf of Mexico. The large size of Katrina throughout its history, combined with the extreme waves generated during its most intense phase, enabled this storm to produce the largest storm surges (reliable observations up to 28 ft) that have ever been observed within the Gulf of Mexico, as determined from analyses of historical records. As another example of Katrina’s strength in terms of storm surge, the previous highest high-water mark (HWM) from Hurricane Camille was 24.6 ft; Camille is the only Category 5 storm to make landfall in the Gulf of Mexico over the interval that records have been kept (approximately 150 years). In the vicinity of Biloxi, MS, the surge produced by Camille was 15.8 ft, the highest surge that had ever been recorded at that location prior to Katrina. Katrina generated surges of 24 to 26 ft at Biloxi. In other words, Katrina (a Category 3 storm at landfall) generated substantially higher surges than Camille (a Category 5 storm at landfall) in the area where they both made a direct hit.” (p. IV-1) “Peak significant wave height along the south shore of Lake Pontchartrain reached at least 8.7 ft, exceeding design values by about 1.0 ft. Wave periods were about equal to design values. Along the levees adjacent to Lake Borgne, computed significant wave heights were consistent with or less than design values, but wave periods (15 to 16 sec) exceeded the design wave periods by a factor of 3. In south Plaquemines Parish maximum significant wave heights reached as high as 10 ft, and wave periods were 15 to 16 sec; design wave height conditions were exceeded by up to 4 ft, and design wave periods were exceeded by a factor of 2 to 3. Since both wave height and wave period influence the potential for wave runup and overtopping, the design wave height and period values should be reexamined for these east-facing levee systems, as well as the west-facing levees in Plaquemines Parish.” (p. IV-2) |
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