Louisiana--Hurricanes
BACKGROUND
Louisiana is a Southern state that lies on the Gulf of Mexico at the
mouth of the Mississippi River.It is also known as the Bayou State for
all of its marshes and lowlands of the southern section, made of tangled
marsh grasses and cypress trees, covered in Spanish moss.
Because of the Mississippi River, Louisiana has been an important trade
center for hundreds of years, ranking highest in the US in the annual amount
of cargo shipped through its port.
Without the 1600 miles of Louisiana levees, approximately 1/3 would be
underwater every time the Mississippi River flooded.
LEVEE SYSTEM:
Starting in the 1800s, New Orleans began a concerted project to drain New Orleans. Dry land is a valuable commodity, and as the city of New Orleans began to grow, more was required. The land along the river's bank had been claimed and developed, but more was needed. A series of canals and pumping stations were built. The pumping stations were able to drain hundreds of square miles of swampland, pumping the excess water into Lake Pontchartrain to the north of the city and into the swamps and bayous to the south, thus leaving behind a dry, yet still spongy prairie upon which the city could sprawl. As can be seen in the photo-map above, the system of canals drains the land farthest away from the River. These are the lowest areas within the city, lying below sea level and naturally covered by shallow marshes and swamps. No canals are needed to drain the land close to the river's banks since the river has built up this land to an elevation a few feet or more above sea level. As water must flow down, the canals drain into the Lake and bayous surrounding the city instead of into the River itself. The few canals that do empty into the River are connected to it in order to allow barge traffic to pass through them.
The area that has since been drained by the canal system includes most of the present metropolitan area of New Orleans, including almost all of Orleans Parish, the northern half of Jefferson Parish,, the northeastern corner of St. Charles Parish, the western portion of St. Bernard Parish, and the northern tip of Plaquermines Parish. Today, the series of canals and pumping stations continue to keep the land dry. 75% of the year, they must pump massive quantities of water out of the area into Lake Pontchartrain, due to the area's rainy season. In spite of this, the wet land of Louisiana proves, from time to time, to be too much for the pumps, and floods occur. However, not since 1927 has New Orleans flooded because of the height of the Mississippi or the lake. Added to the pumps' strength is the Bonnie Carre Spillway, built by the U.S. Army Corps of Engineers in St. Charles Parish. Through this spillway, floodwaters of the Mississippi can be diverted into Lake Pontchartrain, sparing the city of New Orleans from river floods. Most of the floods of the 20th century have been due to sustained periods of heavy rainfall and hurricanes. The levee system that has been built along the river, coupled with the canal system to keep the interior of the city dry, prevent the land from being replenished by the annual spring floods. The fresh water that is pumped into the brackish wetlands surrounding the city is creating an ecological disaster. When the Bonnie Carre Spillway is used in order to spare the city of New Orleans from floods, the consequences to the coastal estuary system is profound. As a result, in order to save itself from the waters surrounding it, the city of New Orleans has slowly been destroying its own environment. Scientists and environmentalists know that the Mississippi River is trying to change its course that will bypass the city in favor of the shorter route to the Gulf through the Atchafalaya basin. So far, the Corps of Engineers has prevented the river from doing this. During hurricane season each year, New Orleans has stood with the threat that it will lose its own lifeline.
