Question 1

1- How does the physical environment of New Orleans affect the city, and how does the city affect the physical environment?

In this blog entry I will attempt to examine how the physical environment of New Orleans, mainly the topography, affects the city, and vice-versa.

First of all, I think it is important to understand that New Orleans is basically a bowl. The average elevation of New Orleans is 1 to 2 feet below sea level, with some points touching as low as 10 feet below sea level. The reason water does not constantly flood New Orleans is because of levees- long walls that protect the city against storm surges of 18-20 feet. Some of the levees are natural- New Orleans was actually originally settled along a natural levee on the bank of the Mississippi River. This levee formed from years of sediment from the Mississippi building up on the banks. In fact, New Orleans became the capital of French Louisiana, replacing Mobile, Alabama, because of its' location making it less vulnerable to hurricanes. However, once more people came to New Orleans, more land had to be developed to make room for everyone.

In 1965, the U.S. Army Corps of Engineers built extensive flood walls and levees around a larger portion of New Orleans to accommodate the rising population of New Orleans, which involved making normally swampy territory habitable. What is up to debate is whether this interference from humans on natural land is causing subsidence, or the lowering of land. New Orleans lies upon layers of clay and silt, very soft substances. Normally, naturally occuring subsidence would happen, but occasional flooding from the Mississippi River would bring in new sediment from the river to take the place of the land that had lowered, minimizing the impact of subsidence. Now, however, the levees prevent most flooding, which prevents sediment from reaching the ground surface. The result is most of New Orleans slowly sinking below sea level, making Hurricanes a bigger threat. Before the levees were constructed, flooding in the spring time were considered common place, and residents of New Orleans would canoe to work, or the richer members of the community would simply take a vacation during the flood season.

The levees designed by the Army Corps of Engineers were designed to be very strong. However, the validity of that statement was proved false when Hurricane Katrina hit the Gulf Coast area, causing catastrophic failure of the levees, flooding 80% of the city. The levee system was breached in about 50 areas, 5 of which caused massive flooding. About 1,464 people died in the New Orleans area alone. It is estimated that if the levees and flood walls hadn't failed, and the pumps had worked, about 2/3 of the deaths could have been avoided. As of now, New Orleans is set to have a 100-year-flood protection, which means that the new protection will be able to hold against the worst possible storm in a 100 year period.

The way in which New Orleans affects its' physical environment, and vice-versa is a very interesting and classic example of that relationship today.