New Orleans:City at Risk

http://www.flickr.com/photos/tidewatermuse/38963405/

How could one of the largest and

most important

port cities in the U.S. get destroyed by a hurricane?

http://www.flickr.com/photos/911review/222610404/

The pink areas are built below sea level. And why is that?

http://www.fas.org/irp/imint/docs/rst/Sect14/NewOrleansDikes.jpg

The French built New Orleans on the high banks of the Mississippi River. (1726)

The first area settled

was called the “French Quarter.” It was built on high ground

by the Mississippi

River.

Jackson Square

1798

Swamps and marshlands were left empty in early New Orleans.

In 1803, New Orleans became part of the U.S. through the Louisiana

Purchase.

http://www.enchantedlearning.com/history/us/1800/louisianapurchase/

Even 150 years after the city started,the marshes and swamps were mostly

empty. (1878)

Topographical Map(Contour Map)

1895

In the late 1890s, canals were dug to partially drain the swamps.

Through a system of drainage

canals and levees, the

swamps were turned

into dry land and the city grew.

But the only thing keeping the city from drowning was the levee system.

National Geographic

And the levees could not stand up to the storm surge of Katrina.

satellite images of

New Orleans

After Katrina looked like

this

Before had looked like

this. http://earthobservatory.nasa.gov/images/imagerecords/15000/15421/Louisiana_AMO_2005243.jpg

So, 100+ years of building on former swamplands – and not being able to adequately protect them – led to much of the deadly flooding.

GEOGRAPHIC LESSON #1:

WHERE we build cities MATTERS!

But many cities are already built in dangerous places. So we

have to figure out how to protect them from future disasters.

GEOGRAPHIC LESSON #2:

STOP DESTROYING the natural “buffer zone” between the ocean

and the occupied land.

Louisiana originally had miles and miles of coastal marshes. These came from the Mississippi River’s delta as the river

deposited

rich silt at the mouth of the river.

Hurricanes gain energy from the heat of warm water in the Gulf of Mexico. So

when a hurricane travels over the marshlands, it loses some energy BEFORE it hits populated areas.

Scientists sometimes refer to coastal mashes as “nature’s speed bumps” for

hurricanes.

Scientists also tell us that for every 3 miles of marshland, a hurricane’s

storm surge is knocked down by 1 foot -- before it hits populated areas.

But humans have been draining the marshes over the past many years. That turns marshes into solid land,

and people move in.

And canals they built further erode the marshlands. Old marshes are

turning into open ocean.

Concrete levee systems also prevent silt from naturally rebuilding the delta.

Louisiana is losing 25 square miles a year of marshlands.

Rock jetties are now used in some places to slow marshland erosion.

And the U.S. Corps of Engineers has actually built pumping sites to pump silt-filled Mississippi water

over the levees & into the marshes.

So the marshland erosion problem is getting a little better. But New

Orleans is still vulnerable to flooding.

What about other cities built in “impractical” locations”? For

example:

Los Angeles, California, is sitting on the San Andreas earthquake fault line.

Miami, Florida, will be underwater if global warming melts the polar ice

caps.

Seattle and Tacoma, Washington, sit near three volcanoes which could

explode in the next few years. Massive mudslides would be the main danger.

What is being done to prepare for these possible natural disasters in these

highly populated areas?

Sources

• Caernarvon Freshwater Diversion Project, March 11, 1998.” Available online at http://www.lacoast.gov/programs/Caernarvon. Accessed 27 July 2007.

• Fischitti, Mark. “Drowning New Orleans,” Scientific American, 1 October 2001. Available online at www.sciam.com. Accessed 27 July 2007.

• Independent Levee Investigation Team. “Investigation of the Performance of the New Orleans Flood Protection Systems in Hurricane Katrina on August 29, 2005,” 31 July 2006. Available at http://www.ce.berkeley.edu/~new_orleans. Accessed 27 July 2007.

• Jenkins, Robert. “From New Orleans' founding, riches outweighed risks,” St. Petersburg Times, 4 September 2005.

• Lockwood, C.C. Available at www.cclockwood.com. Accessed 27 July 2007. • Madson, Chris. “Louisiana’s Coastal Marshes are Melting Away,” Wildfowl

Magazine. Available online at www.wildfowlmag.com. Accessed 27 July 2007.• “New Orleans Flood map.” GISUser.com. Accessed 27 July 2007. • Photonics Knowledge. Photonicsknowlege.com. Accessed 27 July 2007.