Katrina, Andrew

For my sister, I've written a brief summary of the difference between Hurricane Andrew in 1992 and Hurricane Katrina in 2005.

As shown in Figure 1, Hurricane Andrew made landfall in south central Louisana while Hurricane Andrew made landfall just east of New Orleans, shown in Figure 2.


Figure 1: Path of Hurricane Andrew, 1992


Figure 2: Path of Hurricane Katrina, 2005

A close up of New Orleans, shows a better picture of what the differences are, shown in Figures 3.

Figure 3: New Orleans

The most notable difference between the two is the location where landfall was made. Hurricane Andrew storm passed to the west of New Orleans and would have reduced in strength prior to hitting New Orleans. To simplify the analysis of the 2 storms, I'll neglect this and assume that Andrew passed New Orleans at the same strength it made landfall at.

To further simplify the analysis, I will just refer to wind direction and setup. There are of course other factors that amplified the differences between the two storms, such as pressure, size of the hurricanes, the rivers/channels that flow through New Orleans, and then there's wave dyanmics, and other coastal processes, but wind provides the simpliest explanation.

Hurricanes rotate in a counter clockwise direction. For a storm that passes to the west of New Orleans, the wind direction would have been to the north and east. This is important because the wind would have pushed water away from New Orleans rather than directly at it. In addition to waves, the wind would create a buildup along the northern shore of Lake Pontchartrain, called setup. This is what happened during Hurricane Andrew.

Hurricanes that pass to the east of New Orleans would have had a wind direction to the west and south. This would have pushed water directly onto the levees protecting New Orleans, like Katrina did. The water build up would have run along the levee, down channels, sort of probbing for weak spots.

Now, from my sources through work, the levees were built to withstand a category 3 hurricane, and Katrina was on the upper tolerance of the levees design. Tack on that sections of the levee had sunken by four feet (much of LA is sinking and losing more than an acre of wetland every 30 minutes that protect LA from storms and the gulf, but that's a whole different story.

If you're interested I recommend reading Bayou Farewell by Mike Tidwell. I also have some other Coastal studies at work) and were not repaired due to budget cuts and other constraints, its easy to see how such a disaster occured.