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. Half 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, canals throughout the city, 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, and have failed on numerous occasions.

As of 2017, the New Orleans pumping system - operated by the Sewerage and Water Board - can pump water out of the city at a rate of more than 45,000 cubic feet (1,300 m³) per second.^[1][2] The capacity is also frequently described as 1 inch (2.5 cm) in the first hour of rainfall followed by 0.5 inches (1.3 cm) per hour afterward.^[2] The scope and scale of the Mississippi River levees, built along either side of the river to keep it on its course, has often been compared to the Great Wall of China.^[3]