Any geniuses understand the physics of New Orleans?

Aloha, some things about New Orleans are driving me crazy.

To wit:

1. Does anybody know the elevation of the Mississippi River as it flows through New Orleans?

2. If New Orleans is below sea level, how does the river flow through it to the sea?

If you say, "Levees," then how did it work before the levees were built?

3. I can dig that what is now New Orleans was spared the river by the action of a meander creating a natural levee, but why wouldn't there have been backflow or the occasional river flood that would make the area a permanent, unsettle-able water-filled depression?

It seems an area below sea level would not have ever stayed dry enough to settle.

4. If the river is 200 feet deep as it flows through New Orleans (fact), then how does the bottom 190 or so feet of the river flow to the sea if it's already below sea level?

You'd think the river would only flow for the part that is above sea level and the part below would hold still.

5. If the bottom 190 feet of the river does flow, how come there isn't a "hump" in sea level where the river pushes against the sea?

If ya watch a stream hit a pond, there are big ripples where they meet and the water level is in ridges and there is an area that has a higher water level than the rest of the pond.

6. If the river was 500 feet deep at the end of the ice age, where'd the bottom 300 feet go?

I've looked all over for answers and haven't seen any satisfactory explanations.

[ Edited by: Geeky Tiki on 2004-09-23 22:14 ]

...and my favorite bit of info about "The Big Easy" is the infamous French Explorer LaSalle, who got lost looking for what's now New Orleans, ended up between Galvaston and Corpus Christi, when mutieers, killed him and fed his body to wild animals.

Alot of explorers met grizzly ends...but this is amoung the least dignified.

Hey, if I was trying to get to New Orleans and some guy took me to someplace halfway between Galveston and Corpus Christi, I'd kill him and feed him to the beasts, too!

On 2004-09-23 22:12, Geeky Tiki wrote:
Aloha, some things about New Orleans are driving me crazy.

To wit:

1. Does anybody know the elevation of the Mississippi River as it flows through New Orleans?

2. If New Orleans is below sea level, how does the river flow through it to the sea?
   [/quote}
   That's why most of our nation's finest voodoo witchdoctors live there. Their powerful gris-gris keeps the river genie in his bottle.

Evidently only PARTS of the city are below sea level. The Mississippi River definitely isn't one of those parts. And the lowest parts are only 9 feet below sea level. The press likes to make broad generalizations (generally), to beef up the fear-factor.

Found this bit of info by Donald Bruehl, Consultant,Geologic Resources

New Orleans is a city that is very vulnerable to flooding because much of
the city is below sea level. The below sea level parts of the city must
be keep dry by constantly pumping water into the Mississippi or to the
sea, or those areas would flood from groundwater alone. Even the
portions of New Orleans that are not below sea level are a part of the
vast Mississippi flood plain. Flood plains are places where rivers flood
during normal conditions. Dam-like ridges form along the banks of rivers
on flood plains and under normal conditions keep the river in its
channel. During floods rivers flow over the tops of levees and flood the
flood plains that lie adjacent to the river channel. Man has constructed
channel walls to "beef up" the natural levees to protect the flood
plains. However, all of New Orleans and the flood plain beyond the city
is constantly threatened by flooding of the Mississippi River.

Sabu

Geeky Tiki:
If New Orleans' sea level bugs you, don't go near Rotterdam in the Netherlands at the Ijssel river: 22 feet below sea level. Most of the country is built on land reclaimed from the sea by pumping the water out, thus all the windmills originally, and today, amazing feats of water engineering works.

In 1780 John Adams was the American envoy to the Dutch parliament. I wonder if he brought any of the Dutch "drain the flood plains" ideas to New Orleans? Or maybe he took the idea "Drink in the streets!" to Amstersdam?

I attended a geology seminar a couple years back, and the instructor mentioned that, without measures taken by the Corps of Engineers during the 1993 floods, the Mississippi river would have broken through to the Gulf of Mexico at a point where it bends near the Gulf, before it hits New Orleans, permanently making a new route and leaving New Orleans the port city, no more.
He also said that the city fathers of New Orleans have long known this was a possibility and have attempted to build the city's tourism economy even more to compensate for a possible loss in revenue if the powers that be choose to protect interests other than New Orleans the next time.