Drainage in New Orleans

Drainage in New Orleans, Louisiana, has been a major concern since the founding of the city in the early 18th century, remaining an important factor in the history of New Orleans today. The central portion of metropolitan New Orleans (New Orleans/Metairie/Kenner) is fairly unusual in that it is almost completely surrounded by water: Lake Pontchartrain to the north, Lake Borgne to the east, wetlands to the east and west, and the Mississippi River to the south. Much of the land area between these bodies of water is at or below sea level, and no longer has a natural outlet for flowing surface water. As such, virtually all rainfall occurring within this area must be removed through either evapotranspiration or pumping. Thus, flood threats to metropolitan New Orleans include the Mississippi River, Lake Pontchartrain, and natural rainfall. Artificial levees have been built to keep out rising river and lake waters but have had the negative effect of keeping rainfall in.

New Orleans was originally built on natural levees along the Mississippi River that were a result of soil deposits left from the river's annual floods. The site chosen for New Orleans had many advantages. Because it sits where distance between the river and Lake Pontchartrain is shortest, Louisiana Indians had long used the area as a depot and market for goods carried between the two waterways. The narrow strip of land also aided rapid troop movements, and the river's crescent shape slowed ships approaching from downriver and exposed them to gunfire, however flooding was always a hazard.

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