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Who is an engineer?

Katrina Engineers NOLA Importance Economy

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#1 eloisel

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Posted 08 September 2005 - 07:44 PM

There is an excellent essay posted in one or more of the Katrina threads about the importance of New Orleans to American economy.

Considering that billions have been spent on the levees and drainage systems in that area since 1965 and billions more are going to be spent to recover the physical area, I have some questions.

I've got in mind how Abu Simbel was moved when the dam caused the original location to be flooded.

I'm wondering if the entire city of New Orleans could be raised above sea level.  As seen from the remainder of 90,000 miles of devastated coastline, being above sea level wouldn't have been much protection in the Katrina case.  However, specific to New Orleans, being below sea level was more detrimental than the hurricane.

So, my initial questions are:

Would the City be better off it were raised up above sea level?

If so, could it be done?

Are there other methods to protect it from the wind damage of a cat 5 hurricane?

And, is a cat 5 hurricane the worst there is?

#2 Corwin

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Posted 08 September 2005 - 08:26 PM

Part of the problem is that the levees did not breach to due Katrina or the resulting storm surge.  The largest levee break (over 200 gap) was caused by the impact of a barge that had broken loose from its mooring and slammed into the levee on Monday morning....  This accident is what caused the major flooding of the city.  The hurricane only contributed to the conditions.


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#3 eloisel

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Posted 08 September 2005 - 08:35 PM

Ohhhhh, I hadn't heard about a barge crashing into the levee.

Still, the levees were designed for a cat 3 hurricane.  And, they are still going to have to be rebuilt and/or some other solutions found for flooding problems.

Edited by eloisel, 08 September 2005 - 08:36 PM.


#4 Corwin

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Posted 08 September 2005 - 08:42 PM

I agree.   The city, state and Feds, including the Army Corps of Engineers, knew that some flooding would happen in the city to do storm surges from a Cat 3 hurricane, with more flooding from stronger storms....  The levees as designed did their job.  Only parts of the city were flooded and most of that part was less than 5 feet.  

Also keep in mind that these engineering marvels are designed to withstand stresses up to several hundred percent what they are rated for in some cases.

That still doesn't mean that a better system could not be designed and put into place.  It would also help if the State didn't refuse federal funds or divert them for other projects.  That is not a good way to keep those funds coming in.

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#5 Shalamar

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Posted 08 September 2005 - 08:47 PM

I would guess that most of the wooden frame house are going to be an absolute write offf- infact almost all of the houses that have been under ten pluss feet of water are just so much mold, mildew and worse waiting to happen- so they probably all need to be razed. I'd raze them and any other buildings that are going to take too much to fix, then do what they did to Galvestion-

Jack the buildings up and bring in enough strong fill to get the city at least to sea level, bring in the Dutch experts and have them design a system of levees, dikes, polders, breakwaters and flood drainage areas to keep NO and it s port safe in a Cat 5.

and yeah, theoretically there is worse than a Cat 5. But erm, oh please that would be something nothing could withstand, and is probably a 'once in a thousand years' storm.
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#6 eloisel

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Posted 08 September 2005 - 08:55 PM

That's interesting - a city has been raised up to sea level.  What is a polder?

#7 Shalamar

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Posted 08 September 2005 - 08:59 PM

A polder is how one creates land from the water, as I understand it you dike in an 'u' area of shore line & water , and the water gets pumped out, and as the water goes they beging filling it with dirt, baffles, and other substructors.

The break waters keep the polders from bearing the brunt of storm surges and general wave errosion action.
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#8 Shalamar

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Posted 08 September 2005 - 09:04 PM

And if it can be done in 1900, raising a city in some places a full 11 feet or more...

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In the first week after the storm, according to McComb's book, telegraph and water service were restored. Lines for a new telephone system were being laid by the second.

"In the third week, Houston relief groups went home, the saloons reopened, the electric trolleys began operating and freight began moving through the harbor," McComb wrote.

Residents of Galveston quickly decided that they would rebuild, that the city would survive, and almost as soon, leaders began deciding how it would do so.

The two civil engineering projects leaders decided to pursue - building a seawall and raising the island's elevation - stand today and are almost as great in their scope and effect as the storm itself.

Raising the grade...

It's impossible to stand anywhere in the historical parts of Galveston and get exactly the same perspective a viewer would have gotten 100 years ago.

Everything is higher than it was back then, and some spots are much higher.

The feat of raising an entire city began with three engineers hired by the city in 1901 to design a means of keeping the gulf in its place.

Along with building a seawall, Alfred Noble, Henry M. Robert and H.C. Ripley recommended the city be raised 17 feet at the seawall and sloped downward at a pitch of one foot for every 1,500 feet to the bay.

The first task required to translate their vision into a working system was a means of getting more than 16 million cubic yards of sand - enough to fill more than a million dump trucks - to the island, according to McComb.

The solution was to dredge the sand from Galveston's ship channel and pump it as liquid slurry through pipes into quarter-square-mile sections of the city that were walled off with dikes.

Their theory was that as the water drained away the sand would remain.

Before the pumping could begin, all the structures in the area had to be raised with jackscrews. Meanwhile, all the sewer, water and gas lines had to be raised.

McComb wrote that some people even raised gravestones and some tried to save trees, but most of the trees died. In the old city cemeteries along Broadway, some of the graves are three deep because of the grade raising.

The city paid to move the utilities and for the actual grade raising, but each homeowner had to pay to have the house raised.

By 1911, McComb wrote, 500 city blocks had been raised, some by just a few inches and others by as much as 11 feet.

The 1900 Storm Rebuilding

Edited by Shalamar, 08 September 2005 - 09:05 PM.

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#9 Anarch

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Posted 08 September 2005 - 09:08 PM

It'd probably make more sense to ask this in EtU...

#10 eloisel

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Posted 08 September 2005 - 09:11 PM

Thats a lot of stuff to take into consideration.  One of the few things I know a little about New Orleans is the graveyards.  Don't know about how the trees survived this storm and then the toxic soup afterwards, but old trees are such necessary things.  I wonder if we are any better at saving trees now than we were back in the early 1900s.

#11 eloisel

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Posted 08 September 2005 - 09:13 PM

Anarch, on Sep 9 2005, 02:08 AM, said:

It'd probably make more sense to ask this in EtU...

<{POST_SNAPBACK}>

Why?

What is EtU?

#12 DWF

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Posted 08 September 2005 - 09:29 PM

eloisel, on Sep 8 2005, 10:13 PM, said:

What is EtU?

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Exploring The Universe it's the forum right on top of this one.  ;)
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#13 Jid

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Posted 08 September 2005 - 10:20 PM

In order...

eloisel, on Sep 8 2005, 06:44 PM, said:

Would the City be better off it were raised up above sea level?
Probably.  At the very least, the water would have somewhere to flow to, out of the city.  However, with the constant sinking of the soil (due to lack of flooding) it would be a temporary (in the long term) fix.

Quote

If so, could it be done?
Technically, yes.  The skyscrapers would be the hardest to lift, but hey, considering that's how they build some super-tall sky scrapers these days (Build, lift up, build a floor underneath, repeat).

The hard part would be finding enough soil to hardpack well enough to fill the basin.  You'd almost be better off building up all the major buildings on extra concrete foundations, and filling around....

It would, however, be cheaper in the long (and probably short) term to continuously maintain and upgrade water maintenance devices, as well as better flood-resistance for buildings.

Quote

Are there other methods to protect it from the wind damage of a cat 5 hurricane?
Raising the city above sea level would do little to mitigate damage due to wind, first off.  All it would do is prevent flooding.

The best defenses against wind damage are: steel frames, strong glass, and luck.  (Unless they invent completely transparent aluminum soon)

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And, is a cat 5 hurricane the worst there is?

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Yes.
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#14 eloisel

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Posted 10 September 2005 - 01:21 AM

Oh, okay, seems like every time I've looked at EtU it is mostly about science fiction, space, and such.  Maybe that is what caught my eye.  I'll give it another serious look because I do love discussing worm holes, warping space/gravity for time travel and the like.

Jid, are you serious about building skyscrapers that way - jacking them up to install a new floor, repeat?  If so, I'd love to see that.  Would be a most interesting endeavor.

In raising New Orleans, I was thinking about saving any valuable historic structures.  Have to agree some structures aren't going to be salvageable because of the amount of damage and the exposure to the toxic soup that flooded them.  Maybe build up the part of the city closest to the areas water would come in from to act as a buffer to the lowest places of the city with concentrated drainage in the lowest areas.  

It is times like these I wished I was an educated engineer and could see some solutions to the problems left in the wake of storms and hurricanes all along the coast.

#15 Anarch

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Posted 10 September 2005 - 05:29 PM

Jid, on Sep 9 2005, 03:20 AM, said:

Quote

And, is a cat 5 hurricane the worst there is?

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Yes.

<{POST_SNAPBACK}>


By definition, yes.  There was some talk during Katrina's ramp-up of extended the definition to include Category 6 hurricanes (something ridiculous like 180mph+), since, well, we're probably gonna need it.



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