Should We Rebuild New Orleans?

By Geologist David Jungblut

Oakcrest High School Teacher

Before deciding about the future development of New Orleans, the geology and the rich history of the Mississippi River and Delta should be reviewed.

New Orleans was built in a river delta environment that was formed from the wash of melting glaciers over millions of years.

The Mississippi River reaches over forty percent of the land area of the United States; it became a major transportation route for boats, starting with the Native Americans about five thousand years ago.

Today sediment is carried downstream from the Mississippi River to the delta area of the Gulf of Mexico.

The Mississippi River drains thirty-three states, and two Canadian provinces, that lie between the Appalachians Mountains to the east and the Rocky Mountains to the west. See map.

De La Salle claimed the entire river basin for France in 1682.

From 1684 to 1687, De La Salle explored the mouth of the Mississippi River but failed to find a connection to the Mississippi River itself.

He failed to find a connection to the Mississippi River because: The flatness of the area exists with

no fall line present. Extensive deposits of sediment and

organic matter along the large delta were present.

Multiple river mouths, called the “bird’s-foot delta,” confused the explorer.

On March 20, 1687, La Salle was assassinated in Texas by three of his own men.

The French felt that a city at the mouth the Mississippi River would be strategically situated to control trade between the vast interior of North America and the rest of the world.

French explorers discovered a major development problem. From the mouth of the

Mississippi to a point about 200 miles upstream (Baton Rouge), there was no ground high enough to provide a natural site for a city.

The French wanted to build a city where: Deep-water vessels and river

boats could dock. Goods could be unloaded and

stored without risk of frequent flooding.

New Orleans area was location but far from being ideal choice:The area sinks at an

average rate of three inches per century.

The ground consists of silt, clay, sand, and a large bulk of soupy organic matter produced by rotting swamp and marsh vegetation.

The land between Lake Pontchartrain and the Mississippi River resembles a “shallow saucer filled with layers of jello.”

New Orleans’ bedrock: Lies seventy to one hundred

feet beneath New Orleans. Skyscrapers’ pilings need to be

driven down to at least seventy feet.

The bedrock itself is not really "rock;" it is a varied mix of semi-compacted clay, silt and silty sand.

The Mississippi River built the delta in two ways:By depositing sediment

where the river meets the sea.

Periodic flooding provides the sediment.

Natural Levees

Natural levees were formed by the deposit of sediment on the banks of the river by the periodic flooding.

Jean Baptiste La Moyne,

in 1718, established New Orleans as the capital of Louisiana and a fortress to control the wealth of the North American interior.

New Orleans’ City Plan:

Central square Church Walls Towers

During the forty-five years of French rule, most buildings, including the church, were simple, wooden structures.

The streets were muddy ruts. Few people lived in New Orleans

until 1800.

France was defeated in the Seven Years’ War (1756-63):

Britain took over Canada and all the territory between the Appalachians and the Mississippi, including West Florida and parts of Louisiana.

Spain took the rest of Louisiana, including New Orleans.

New Orleans did grow under Spanish rule, primarily because of English colonials and, later, American settlement of the Ohio Valley.

Anglo settlers in the Ohio Valley sought trade outlets through the city and within New Orleans itself.

The direction of growth was upriver.

Napoleon

Napoleon re-established the French Empire in Louisiana, taking away control of New Orleans from Spain in 1802.

Louisiana Purchase:

On December 1, 1803, official word of French ownership reached New Orleans.

The Louisiana Purchase followed soon afterwards.

A scant three weeks later brought news that Louisiana and New Orleans were American property.

Thomas Jefferson, who negotiated the "Louisiana Purchase," had pulled off one of the great real estate buys in history.

The older and main parts of New Orleans rest on the natural levees of the Mississippi (about fifteen feet above sea level), with the ‘firmest, most solid soil’ being silt.

http://www.nola.com/katrina/graphics/continuous.swf

http://www.nytimes.com/interactive/2007/08/28/us/2007_NOLA_GRAPHIC.html#section1

New Image BMP

Conclusion by Geologist David Jungblut

Should We Rebuild New Orleans?

1. The levee system needs to

be a second line of defense for New Orleans.

2. The first line of defense should involve water diversion to “overflow areas,” which would include parks, recharge basins and other low-lying areas, away from neighborhoods and historical districts.

3. When the water level rises to ¾ of the height of the levees, pumps should activate removal of water to pipes that carry water into unused (or newly closed) canals.

4. “Water, water everywhere…” It is hard to keep it out, when things are sinking lower and lower. Therefore, allowing more escape routes through which the water can be channeled, after a levee is breached, is essential.

The “bedrock,” at 70 to 100 feet, must be reached in order to keep New Orleans’ buildings stable.

When supports for buildings are installed, geothermal energy can also be installed within each block.

Bridges’ support design may work as a model for housing reconstruction.

To stop subsidence, water needs to flow more freely though the city, recharging the soil beneath the city.

Building techniques learned from bridge and skyscraper construction need to be used so that New Orleans’ neighborhoods and historical areas can be rebuilt.

Credits

NORDHEIMER, JON, “Nothing's Easy for New Orleans Flood Control.” ABBOTT, CARL, 2005, “Do We Need New Orleans? The Oregonian.”BROWN, L. R., 2004, “Outgrowing the Earth” BUNCH, WILLILAM, 2005, “Rebuilding ‘The Big Easy,' Possible?”EHRLICH, PAUL, and EHRLICH, ANNE, 2004, “One With Nineveh.” YOUONGQUEST, WALTER, “Should New Orleans Be Rebuilt?” NELSON, STEOHEN A., Dept. Earth & Environmental Sciences, Tulane

University, New Orleans, LA 70118-5698, snelson@tulane.edu., “The Geology of the Katrina Disaster in New Orleans.”

McNABB, DONNALD and MADERE, LOUIS E., “A History of New Orleans”

Websites: http://encarta.net/map_701514720/Mississippi_(river).htmlhttp://response.restoration.noaa.gov/book_shelf/783_Gnome_LMiss_UG.pdf http://library.thinkquest.org/4034/lasalle.htmlhttp://cgee.hamline.edu/rivers/Resources/river_profiles/mississippi.htmlhttp://www.infoplease.com/ce6/people/A0828919.html

Should We Rebuild New Orleans? By:  David Jungblut, Geologist

Teacher at Oakcrest High School1824 Dr. Foreman DriveMayslanding, NJ 08330E-mail: DJungblut@geh.nj.k12us.com

All rights reserved, May, 2008