Half of New Orleans is below sea level, humans sank it: report

http://www.nola.com/environment/index.ssf/2018/02/report_half_of_new_orleans_is.html#incart_m-rpt-2

By Sara Sneath NOLA.com | The Times-Picayune

French settlers built New Orleans on a natural high point along the Mississippi River about 300 years ago. The land beyond that natural levee was swamp and marsh. It would take more than a hundred years for settlers to figure out how to drain the swamp. In the process, they'd sink New Orleans.

In a story on The Atlantic, Tulane University geographer Richard Campanella details how New Orleans was transformed from marsh to a city dependent on levees, canals and steam-driven pumps. One French settler described the city 300 years ago as "nothing more than two narrow strips of land, about a musket shot in width," surrounded by "canebrake (and) impenetrable marsh."

Over the last 300 years, Campanella writes, more than 30,000 acres were converted from swamp to dry land. The effort resulted in the gradual settling or sinking of land, called subsidence.

The transformation from swamp to suburbs has at times had dire consequences. In the 1970s, several houses in Metairie exploded when subsidence cracked gas lines, leaking flammable vapors into the homes. While more flexible pipes has lessened the risk of houses exploding in the future, subsidence has placed most of New Orleans below sea level, and at increased risk from the next storm.

Read the full story on The Atlantic at: https://www.theatlantic.com/technology/archive/2018/02/how-humans-sank-new-orleans/552323/