New Orleans flooding question

[Bill V]

With every news story about the flooding in New Orleans, you hear a report that most of the city "is built below sea level". But they never bother to answer the obvious follow-up questions--How, and why? If it's below sea level, and that close to the ocean, wouldn't that mean that at one time it was regularly under water? If so, how did they initially dry it out, to the point where they could build on it? And why did they do that, rather than building in some other area that is above sea level? Wasn't it obvious at that time that someday in the not too distant future, something like this was going to happen--a strong enough possibility to rule out developing a city there, regardless of what levees they might construct?



I'm not looking to point a finger or place blame here--just trying to get a better understanding of how this situation ever came to be. Thanks.

 

[Jeff C]

Actually it's sinking. And French people built it...that should answer most of your questions right there.



As for how and why? Same way and reasons the Dutch did. Most of Holland is below sea level too but the soil is so fertile that it is worth the risk and effort.





At least this is what I've gathered from my past history classes and stories from my grandparents who immigrated from the Netherlands after WWII.



edit: forgot to say how. They converted windmills into water pumps and just pumped the water out (in holland anyways)

 

[Thomas Rogers]

How is with levys and pumps that hold back the water.



Why, because people like shore towns.



It's an old city...in a "mostly naturally dry" basin. The problem with "once in a century or so" storms is that they hit, once every century or so.



A lot of development can happen in 100 to 200 years. I hope it doesn't get renamed "New Venice".



TJR

 

[TomT]

It was a time bomb waiting to happen. They have always had a problem with the water table there. That's why people are buried above ground. It was convenient several hundred years ago as a port town. Now as a modern city, they are either going to have to take drastic measures or consider abandoning the city. Can't believe many business will want to rebuild after that disaster. It's a shame. NO is a cool city. I used to live there as a kid.

 

[user 62394]

Actually, I just heard someone on the radio adressing this. When New Orleans was originally founded, it was above sea level. It was built on the silt-bed from the Mississippi. Over the years (for several reasons that I can't can't fully recall from the report), the land is sinking. Apparently when New Orleans was founded, it was also on the shore line, and today it is significantly inland.

 

[Bill V]

There are reports that they're going to have to pump all the water out. Is that even possible/practical on that large of a scale??

 

[TomT]

Not until the levy is repaired. And that may not be possible for a long while.

 

[Fer Echegaray]

In 1718, French colonist Jean Baptiste Le Moyne de Bienville ignored his engineers' warnings about the hazzards of flooding and mapped a settlement in a pinch of swampland between the mouth of the Mississippi River, the Gulf of Mexico and a massive lake to the north

 

[Frank Z]

I've heard stats that they sink an average of 1/3" per year. This rate has increased do to flood abatement measures which have slowed the amount of silt that is deposited in the area. Also sea levels have risen and eroded some of the natural barriers to the sea. All of this worked toward a disaster in the making.

 

[Jim Johnson]

I've seen a program a couple times on the History Channel, which talked about the potential for a great flood of historic proportions that would devastate the city. Maybe many of you have seen the same program. It hit me today, while watching video of New Orleans in the aftermath of Katrina, that this may, in fact, be that very event. The similarities are eerie, including the depth of the water and the failure of one or more levees which would allow at least some of Lake Ponchatrain to spill into the city.



It just seems weird to have seen the program, thinking that it was something that surely would never happen in my lifetime, and then witness (via TV) the actual event just a couple years later!

 

[Deleted deleted]

I was in New Orleans a few weeks ago when that last hurricane hit Panama City, FL. The locals were saying "oh, it'll never happen to us". Well, looks like the unthinkable happened.



It was wierd walking UP a hill to the Mississippi River near downtown. You could look across the horizon and tell that the river level was at least a dozen feet above the city on the other side of the levee. And those levees aren't all that tall.... it was only about a 20 ft climb up a short hill to the top of the levee.

 

[Richard L]

Most of southern Louisiana is built on a swamp and every thing sinks. Most of their freeways and interstates are built up on 8 foot high burms of gravel to keep them from buckling and sinking.



...Rich

 

[Shawn Hennessy]

NO was built on a river delta...which is nothing more than sedimentary deposit (i.e. soft soil). It is unstable and unsuitable for building. The river is ever changing the landscape by further depositing more sediment. Since the city is levee'd and they are trying to control the river, the river wins out. The city is sinking as the sediment compresses or erodes away deep beneath the walls of the levees.

 

[Snooze]

Everyboy's got some great input. It was very interesting to read. I want to see what everybody has to say.

 

[Dreman]

I understand the engineers that built the dikes in the Netherlands are astounded that New Orleans is having this problem. After all, they perfected the technology necessary to protect their cities decades ago. What it looks like is everyone in New Orleans thought the same thing about the program on the History Channel that Jim Johnson did, that it'll happen someday, but not in my lifetime. But someone in a position to do something should have taken note and done something about it long ago. After all, isn't that the mayor's job, to do whatever is necessary to maintain the city? But the "it'll never happen here" mentality is easy to adopt.

 

[Deleted deleted]

dreman: The big difference is the Netherlands doesn't have to face a Cat 5 hurricane. Never have. Would their dikes hold up under that onslaught?

 

[Dreman]

They don't have to deal with hurricanes, but I understand the North Sea is difficult enough all by itself!

 

[Paul Maurer 2]

Actually, the water treatment plants in New Orleans discharge 50% into the river and 50% into the lake. Millions of tourists peeing out their Hurricanes from Pat O' Briens have caused the levels of both to rise over the decades. Legislation was proposed to stop this, but Lester "Bugsy" Boudreaux, the president of the legislature, had a lucrative crawfish and alligator tour business which depended on high water and the groups supporting it couldn't raise the $500,000 bribe it took for Gov. Edwin Edwards to pass the bill.

Actually, I did my residency at Tulane in New Orleans, have some business ties there and am deeply saddened by the mess its in. I always was amazed that you had to get out of your car on River Road and climb a levee to see the river, and that the freighters heading upriver seemed to tower over us when viewed from my apartment.

 

[WXMotorSports DecalsPartsAccs]

Somewhat related...



One of my customers, who lives in So Cal, was asking why in earth I would want to live in Seattle? I said...well no earth quakes, no hurricanes, no flooding and the mountains don't come rushing down the hill sides.

 

[TomT]

The worst thing about Louisiana is the amount of corruption the state has had in years past. A lot of projects have been put under the table while the fat cats have profited. It's a shame because it is a very poor state and they need all the help they can get.