New Orleans is one of North America’s most distinctive and culturally diverse cities, located on the Mississippi River in southeastern Louisiana, in the United States of America, about 180 km (about 110 mi) from the Gulf of Mexico.

The city was founded in 1718 on the east bank of the Mississippi and south of Lake Pontchartrain.

New Orleans, named for Philippe II, Duc d’Orléans, regent of France under Louis XV, has been a leading commercial center since its founding and has one of the most active ports in the United States.

Since World War II (1939-1945), the city’s rich cultural heritage has contributed to its emergence as a major international tourist center.

New Orleans’s location near the Gulf Coast makes it vulnerable to tropical storms. The city is especially susceptible to flooding from hurricane storm surges due to its position in a bowl-shaped area mostly below sea level between the Mississippi River and Lake Pontchartrain, which connects with the Gulf of Mexico.

The city was devastated in August 2005 by Hurricane Katrina, the costliest natural disaster in U.S. history which called for the mass evacuation of the city.

The original French settlement of New Orleans was built on the east bank of the Mississippi, where sediment from the river had created areas of elevated land. As the population grew, the city spread out into the low-lying area bordering Lake Pontchartrain.

Originally, this area was a huge cypress swamp, but in the early 20th century engineers began building a network of pumps to drain it dry. Over the years, engineers also built about 560 km (about 350 mi) of earthen levees, concrete floodwalls, and canals to keep water out of the city.

At the same time, this system of protection meant that water had no natural way of flowing out. Even rainwater had to be pumped over the lip of the bowl formed by the levees.

Today, more than 80 percent of New Orleans is below sea level and the lowest parts of the city are about 3 m (10 ft) below sea level. The city has been sinking at a rate of about 1 m (3 ft) every 100 years.

The city was constructed on soft silt, sand, and clay—sediments deposited by the Mississippi River over centuries of flooding. However, after a massive flood in 1927, levees along the river were raised and lined with concrete to prevent further flooding. As a result, the river’s sediments have been channeled into the Gulf of Mexico.

Over time, New Orleans’s underlying sediments have compacted, and without the river’s replenishing sediments the land has sunk. Rising sea levels due to global warming threaten to speed up the sinking process.

Although levees and other barriers have long prevented flooding from the Mississippi River, they have been less effective against storms from the Gulf of Mexico.