Atmosphere And Weather

Why the new Orleans Levees Failed during Hurricane Katrina



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The first levees in New Orleans were constructed in the early 1720s. Portions of the city was sitting several feet below sea level and in 1728, a law was passed that required every land owner to build their own levee to prevent flooding, if their property faced the water.  By the time the Civil War started in 1861, most of the levee systems were finished and working to keep the land dry.

Since that time, there have been dozens of additions, replacements, improvements and repairs made, whenever necessary. Even with the extensive levee systems and the water being pumped out, there has always been problems keeping the Gulf of Mexico out of the low-lying areas.

Due to the rains associated with hurricane season and other weather conditions, there are now several methods in different areas of the State to combat possible flooding. Because of the addition of modern levees that worked with mechanized pumps - that work by constantly driving the water out - the land level in New Orleans is steadily, albeit gradually, sinking.

There is more land below sea level in New Orleans today than there was in 1720, at the beginning of the levee system and this is directly related to water being pumped out of so many different areas. This gradual sinking has almost guaranteed a breach in the levee systems and numerous breaches are the main cause of the devastating floods, in 2005.

Over time, some of the natural wet-lands were dried out due to the water being pumped out. Land that was raised up because of moisture sank several inches below sea level, when it was dry. Storm surges during hurricane Katrina made the outdated levees almost insignificant, in part because of the settling of the land. The levees were no match for the walls of water that pounded the coast of New Orleans and caused unheard of destruction and killed more than 1,800 people.

One situation that make the New Orleans levee system difficult to perfect is the damp, marshy land that make up most of the Southern part of the State. When water is pumped out, the result causes the land to settle lower and lower. A city that is partially below sea level has a greater chance of being inundated from the rains during tornadoes, hurricanes and regular thunder storms and many parts of New Orleans is situated well below sea level.

During hurricane Katrina in 2005, more than 50 different incidences of flooding were reported and to many experts, these breaches came as no surprise. The existing flood walls and levees were no match for the high winds, the amount of rain and resulting storm surges of Katrina. For decades predictions have been made of the probability of wide-spread flooding - when and if the levees were breached and overrun by water.

The levees and flood walls were designed and constructed by the United States Army Corps of Engineers. After several investigations, their experts have come to no real conclusion as to why the levees were not able to keep the storm surges and floods out of the areas.  A look at the flood and dyke systems in Amsterdam could be a possible guide to the new and improved levee system that will be built to replace the present system.

After a flood in 1953 that resulted in the death of many residents, the government in Amsterdam, a low-lying area, designed and built the Deltaworks system that is seemingly flawless. A system designed to work as well as Deltaworks may be the best way to hold back the flood waters in New Orleans.


References;

1] Levees.Org

2] WashingtonPost.com

3] NPR.org/templates/story/story.php?storyId=4830065

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