by Paul Lines

Created on: November 21, 2008   Last Updated: January 26, 2009

In August 2005 tens of thousands of people lost their homes and nearly two thousand p,eople lost their lives when hurricane Katrina hit the northern coast of the Gulf of Mexico and battered New Orleans almost to death. At one stage, eighty percent of the city was under water. So what makes New Orleans vulnerable to hurricanes and what caused such devastation three years ago, a catastrophe that many families and businesses are still trying to recover from?

There are a number of reasons why New Orleans is vulnerable, not least of which is the fact that the city is built right in the path of the hurricane belt. However, in addition to this is the problem of the city relative to sea level. At present the majority of New Orleans is well over ten feet below sea level. It is also surrounded by water, with the Gulf of Mexico to the south, the Mississippi river and Lake Pontantrain forming borders to its west and east. In effect therefore, New Orleans sits deep in a cup formed by these water masses.

The problem when a hurricane hits the area is not so much resulting from the storm winds, although these can be catastrophic, but rather the storm surge that precedes the hurricane itself. The high winds of a hurricane whips up great walls of water at its leading edge, with these increasing in size depending upon the category of the storm. Normally as the wave reaches the shore, because the land gradually raises both the height of the wave and the force of the water is weakened as it progresses inland.

However, with New Orleans being in a significant dip or hole, this does not happen. Furthermore, the wave is fuelled by the surrounding waterways. Thus, the consequence is that with no opposing force to combat it the storm surge will flood the area to sea level. In the case of New Orleans, as was witnessed in 2005, this leaves virtually everything submerged.

An additional problem that besets New Orleans in such cases is that of drainage. The below sea level position of the city makes the natural and manmade efforts more difficult as, effectively, one is trying to push the water uphill. This is why; following Katrina, large parts of New Orleans remained in a flooded state for weeks.

Over the years, a levee system had been built around the city to protect it from such events. However, as is well documented, these were breached in countless places. In reality, it was known that this would occur as the levees were only build to withstand a hurricane of force three scale., Katrina, when she hit the coast, was categorised at storm level five. Although hitting land reduced this strength quite rapidly, it was not sufficiently diminished by the time it reached New Orleans to save the city from disaster.

Plans are being made to increase the levee defences to protect New Orleans from the potential impact of future hurricanes of up to level five. Nevertheless, these will take some time to bring to fruition. In the meantime, the population need to hope that they can avoid another Katrina scale storm and that, when completed, the new defences will be sufficient to protect New Orleans from future hurricanes of any strength.

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