Geography

The City of New Orleans is located exactly at 90 degrees west longitude, and 30 degrees north latitude. Actually, the exact coordinate lies in the marshes of New Orleans East, just southwest of NASA's Michoud Assembly Facility. The Vieux Carre', the original city built by Bienville (also known as the French Quarter), presides over a huge 90 degree curve in the Mississippi River some 110 miles north of its confluence with the Gulf of Mexico. The city limits of New Orleans are co-terminous with the boundaries of Orleans Parish. However, the metropolitan area of the city has grown well beyond these boundaries. In just under three hundred years, New Orleans has grown from the one-square mile settlement founded by Bienville to cover parts of four parishes in southeastern Louisiana.

The Mississippi River deposits more silt closer to its banks during the spring floods. For that reason, the land is higher closer to the river. As one moves away from the river's edge, the land sinks to about 5 to 10 feet below sea level, maybe higher in some places. Because the river deposits more silt closer to its banks, the riverbed itself has been built up so much that the river's surface is actually higher than the surrounding land. Only the natural levee along its banks is higher than the river's surface, and the river is naturally prone to overflow this levee and inundate the low land around it. Because of this, the U.S. Army Corps of Engineers has extended the height of this natural levee in an attempt to keep the river within its natural course. Tourists in Jackson Square delight in sitting on a bench and looking up at the river's traffic. The river's surface is several feet above sea level. Ships traveling down the Mississippi appear to hover over the city below.

The Mississippi's present riverbed at New Orleans is only about 1000 years old. Before that, the river flowed a few miles to the north through what is today Metairie, Mid City, and Gentilly. When the river retreated to its present course, it left behind a series of small bayous. These were called Metairie Bayou, Bayou St. John, and Gentilly Bayou by the early French explorers. Though Metairie and Gentilly Bayous have long since silted up and disappeared, the natural levee along the old river's bed remained, creating a causeway through the murky swamp. Indians, and later Europeans, used this causeway as a portage through the swamp. The Indians built their villages upon it, and farmed its rich soil. The route of the causeway can still be seen on a map of the modern city, and is labeled "Metairie Road" and "Gentilly Boulevard". The name Le Metairie, which is given to New Orleans' western suburb, is French, meaning "The Little Farms".

Lake Pontchartrain and Lake Maurepas were created about 5000 years ago, at the end of the last Ice Age. As the polar ice cap retreated, the melted ice raised the sea level. The area that is now inundated by these two lakes was very low, perhaps as much as ten to twenty feet below the surrounding land. Like the rest of the land, swampy forests inhabited by alligators, water moccasins and swarms of mosquitoes covered the area. As the sea level rose, the Gulf of Mexico overflowed into this bowl of swampy land. Today, Lake Maurepas empties into Lake Pontchartrain through Pass Manchac, which in turn empties into the Gulf through a narrow and shallow channel called the Rigolets (Rig-a-lees).

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 (except the most eastern portions of that parish), the northern half of Jefferson Parish to an area just south of the cities of Westwego and Gretna, 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. Throughout the rainy season (which is nearly 3/4 of the year), they pump massive quantities of water out of the area into Lake Pontchartrain. In spite of this, the wetness 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.