by Raven Lebeau

Created on: November 16, 2008   Last Updated: January 08, 2009

Hurricanes form when warm, humid air rises off of the ocean. As the warm air cools, water vapor condenses, releasing energy in the form of heat. This energy is what drives the often deadly winds of the hurricane. In order to maintain itself, a hurricane needs a constant supply of warm, moist air from below. Hence, once over land, a hurricane will weaken and eventually dissipate. It is for this reason that coastal cities like New Orleans are in danger from hurricanes, while cities from from the coast are not.

Proximity to the coast, however, is only the first of several reasons New Orleans is especially vulnerable to hurricanes. The city's elevation, the levees along the Mississippi River, and the presence of Lake Pontchartrain are all factors in the degree to which New Orleans is affected by hurricanes. The extent of destruction New Orleans has endured when hit by hurricanes is a function of political, economic, and geographic variables.

Because New Orleans is situated between the Mississippi river and Lake Pontchartrain, it is virtually surrounded by water. This means that hurricanes can maintain their devastating force by feeding on warm, moist air rising from the river, the lake and the bayou. A hurricane which hits New Orleans will therefore remain at full strength for a longer period of time than a hurricane hitting another coastal city.

New Orleans is unique in that the city is mostly below sea level and is constantly sinking. After New Orleans endured extensive flood damage in 1927, levees were built around the Mississippi river to help keep rising waters from entering the city. Unfortunately, these levees also prevented the accumulation of natural silt deposits along the bayou. With natural erosion constantly eating away at the coastline, these silt deposits were necessary for maintaining the integrity of the land. With the silt now being washed out to sea instead of being deposited, erosion proceeded at an unnaturally rapid rate. Under the weight of the city's buildings, the land is continually sinking, deepening the bowl in which New Orleans sits and making it even more vulnerable to flooding.

Social factors also have an impact on New Orleans' vulnerability to hurricanes. Many of the city's residents are inadequately insured against flood damage, either because they cannot afford coverage or have not been properly educated about insurance. Also, the city contains many crowded neighborhoods that are located in especially flood prone areas. The population density in these areas makes evacuation procedures difficult.

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