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New Orleans and Hurricane Katrina

A city below sea level  

This is a map of New Orleans from 1888 edition of the German dictionary "Meyers Konversations-Lexikon".  The highest ground was settled first, including the French Quarter (see the notation "French Market" above the sharp bend in the river).


As the city grew, the areas below sea level were increasingly populated.  80% of New Orleans (50% of the urban area) is below sea level.  In this diagram, all of the yellow and red areas are at or below sea level.  During a hurricane, the wind-driven "storm surge" further raises the level of the waters surrounding the city.

Levees to protect the city

An elaborate system of levees (embankments) is used to protect New Orleans from routine flooding.  The city essentially sits in a bowl.  After it rains, pumping stations pump the water up and out of the bowl, into Lake Pontchartrain or the Mississippi River.  The system is only as good as its weakest point.

Hurricane Katrina floods New Orleans

When Hurricane Katrina hit New Orleans in August 2005, the Mississippi River levees held, but the city levees were overtopped or breached in multiple locations.  Lake Pontchartrain spilled into the city, the pumping stations failed, and the flooding didn't stop until the water level inside New Orleans reached the level of the lake.  The French Quarter stayed dry, but most of the city was underwater (see picture).  Previous hurricanes had spared New Orleans, and there had been no serious attempt to evacuate the city or to designate evacuation areas.  The New Orleans police abandoned their posts and fled.  The flooded residents climbed onto their rooftops, highway overpasses, and the high ground around the Superdome to await rescue.  The nation watched transfixed for days while the city, state, and federal governments did nothing to help the people of New Orleans.  News teams simply drove to the Superdome; relief personnel and supplies did not.


Here is another diagram of the New Orleans levee breaches caused by Hurricane Katrina.  Click the picture for a larger image.  The pink areas were flooded.  The blue stars mark levee breaches.  The red dots mark pumping stations that failed.  Note the long canals that point like daggers into the center of the city.  In the event of a storm, the entrances to these canals cannot be closed, and it was levee failures along these canals that permitted Lake Pontchartrain to flood the city.

Slow recovery

Many of the people who left New Orleans after Hurricane Katrina have not returned.  This picture shows the New Orleans phone book before and after Katrina.  The 2004 directory has 1086 pages (300 listings per pages) of residential listings (above the blue line); the 2007 directory has only 765 pages (and only 250 listings per page) of residential listings.


An uncertain future

Longer term, New Orleans will continue to be threatened by the ocean, because the city itself is sinking, and because the oceans are rising.

New Orleans is sinking.  As noted by Curt Stager in his book "Deep Future: The Next 100,000 Years Of Life On Earth":

New Orleans ... has long been sinking into the Mississippi Delta as sediments compress and de-water under their own weight and that of overlying buildings, as levees prevent the deposition of regenerating river muds, and as bedrock responds to lingering ice age distortions of the continental crust.  In fact, most of the Gulf coast is also subsiding as a result of petroleum and groundwater extraction; some sites have dropped 10 feet (3 meters) during the last century.  Much of New Orleans itself is sinking by a quarter of an inch (6 millimeters) per year, with some sections dropping four times faster than that.

The oceans are rising.  By the year 2100, global warming is expected to cause the Earth's oceans to rise by 1 meter (39 inches).  This will put much of southern Louisiana (including New Orleans) underwater.  With ocean rise caused by global warning, this is how southern Louisiana will look in the year 2100.


With ocean rise caused by global warning, this is how southern Florida will look in the year 2100.


With ocean rise caused by global warming, this is how North Carolina will look in the year 2100.