New Orleans Geography
The city of New Orleans is located in Louisiana, in the Mississippi River Delta. It is on the banks of the Mississippi River, south of Lake Pontchartrain, and 105 miles upriver from the Gulf of Mexico. The city’s area is 350 square miles, 169 of those square miles being land and 181 square miles being water. The Orleans Parish is the smallest parish in Louisiana when considering the land area. The land along the Mississippi River is characterized by hollows and ridges.
New Orleans, Louisiana was originally settled on the Mississippi River’s natural levees or high ground, but the Flood Control Act of 1965 allowed the US Army Corps of Engineers to build floodwalls and man-made levees around a larger geographic footprint that included previous swamps and marshlands. The pumping of water over time allowed for the development of the city into lower elevation areas. Today, half of New Orleans is either at or below local mean sea level, while the other half of the city is just slightly above sea level. There is evidence that suggests that portions of New Orleans may be dropping in elevation due to subsidence, which is the sinking or gradual downward settling of the ground’s surface with very little horizontal motion.
A study by Tulane and Xavier University done in 2007 suggested that just over half of the contiguous urbanized portions of New Orleans and surrounding parishes lie at or above sea level and that more densely populated areas tend to be on higher ground.
The American Society of Civil Engineers reports that large portions of New Orleans and surrounding areas are currently below sea level and are still sinking. The city of New Orleans is built upon soft sand, clay, and silt. Subsidence occurs due to the consolidation and oxidation of organic soils as well as local groundwater pumping. Because flood control structures have been built upstream on the Mississippi River and around New Orleans, new layers of sediment are not restoring the ground lost through subsidence.
The climate for New Orleans is humid subtropical. The winters are generally mild and short, and the summers are humid and hot. The summer months tend to be the wettest, while October is typically the driest month of the year for New Orleans. The average precipitation is 62.5 inches per year, and the precipitation in the winder usually come with a cold front. The average daily temperature ranges from 53.4 °F in January to 83.3 °F in July. It’s rare for the temperature to reach 20 or 100 °F. The last occurrences of these temperatures were in February of 1996 and June of 2016, respectively.
New Orleans, Louisiana does face the threat of tropical cyclones. The city is at risk due to its low elevation and the fact that it is surrounded by water from three directions New Orleans is the most vulnerable city to hurricanes, according to the Federal Emergency Management Agency. The risks from hurricanes are much greater today due to the coastal erosion caused by human interference.