Lessons Learned from Katrina: How Can Engineers Apply Them for the Future?

[Astronuc]

Ivan and I discussed the evolution of information from NHC/NOAA regarding Kartina and the storm surge here

https://www.physicsforums.com/showpost.php?p=731868 in post 9.

It was Saturday evening, 7 PM and 10 PM, when NHC announced that Katrina was Cat 3 (with sustained with winds of 115 mph), but by 1 AM Sunday Morning Aug 28, Katrina had strengthened to a Cat 4 with sustained winds of 145 mph. That was 27 hrs before landfall (not 36 hrs).

Landfall was Monday (Aug 29) morning just after 4 am. I posted some satellite images
http://www.everything-science.com/index.php?option=com_smf&Itemid=82&topic=6337.msg56430#msg56430

Earlier on Saturday Katrina was just a Category 3.

 

[LURCH]

The problem is the hydraulic force, with water having a density of 1000 kg/m³ or 1 metric ton/m³. That's a lot of force! They have tried to drop 3 ton sand bags, but with little effect.

Yes, that's exactly the problem that this solution addresses. The sandbags are ineffectual because they rely on their weight and lack of buoyancy to sit in the rapidly flowing water and not be swept away. What is needed is an obstruction that is larger than the opening the water is leaking out of. Granted, the hydraulic force may be too great for the re-rod to withstand, and it may break. If that is true, then steal I-beams such as those used in the skeletons of tall buildings might be a more appropriate material. The important thing is the different approach. Don't try to use heavy things and hope that they will sink and sit in place. Instead, use structurally strong materials and span the gap.

Another problem is that breaches continue to widen by virtue of erosion.

I was thinking of a span that is significantly wider than the breach (say, by about ¹/₃). This should be sufficient to keep the two ends of the barrier anchored until the plug can be completed. Once the flow is decreased, erosion should stop.

 

[Astronuc]

Well think about how much steel bar - one inch diameter - say 20 feet high, 300 feet, with a 6 inch pitch, and perhaps a cage design so it has some structure. And the supports. How many tons are involved?

Then figure the coefficient of drag - at say 20-30 mph (29-44 ft/sec).

One might need some Skycranes to hand a structure.

Barge cranes may not be able to get close to a breach - or we need something like jack-up rigs.

 

[hitssquad]

The problem is the hydraulic force, with water having a density of 1000 kg/m³ or 1 metric ton/m³.

And that is just the density of clean water. Salty/dirty water is even denser.

 

[Kenneth Mann]

Much of the recriminations about response times are (at least, partially) unfair. The response was about as fast as could be expected - - after the fact. If all our leaders had decided resolutely and immediately, upon knowing that a "big one" was coming, to do all possible, it would have made little difference. It takes considerable planning and time to set-up an effective response (letting alone the preventive measures), for a disaster such as this one. This planning simply cannot be done in hours, or days, or even weeks to get us ready. It takes months, and more probably, years. If we want to pass blame for not responding faster, then we need to put it on all of us; going back at least fifty years, and that includes Eisenhower, Johnson, Bush I, Clinton, Bush II, All the Congresses, all the associated bureaucrats, all the Governors, all the mayors, all the state legislators, and all the rest of us. We simply kept rolling the dice, and New Orleans kept coming up lucky; until this time.

KM

 

[jaap de vries]

First of all, do not build dwelling and commercial structures in an area that is below the prevail water level. On the other hand, if one does, learn from the Dutch in the Netherlands - they seem to do it very well - but then they do not get Category 3 or 4 hurricanes.

I am from the Netherlands but for the past 2 years I have been living in Florida. This puts me in the unique position since we (in Florida) have been hit 6 times within close to a year, including katrina.

In Holland we had a disaster in 1953 killing close to 2000 people, about 0.02% of the population at that time. Eversince we (the Dutch) have comitted ourselves to build the greatest waterworks ever created, the Delta works, proving that water can be fought even while respecting nature. People can live below sealevel as long as we (engineers) comit ourselves to doing our jobs.

 

[Skyhunter]

According to the mayor of NO, and I don't know exactly how this is measured, but he stated that the storm surge drops one foot for every acre of intervening wetlands.

Also, don't forget, NO is just one town involved in all of this. Even if we ignore the general interpretation of Global Climate Change, meteorologists are predicting decades of increased storm activity as compared to our current definitions of "normal" activity. Of course, to me it seems reasonable to begin incorporating GCC into our thinking.

The Mayor doesn't know what he is talking about Ivan, but the wetlands are crucial because land reduces the strength of a hurricane, thereby reducing the surge

Sidney Coffee, executive assistant to the governor for coastal activities, said about 1,900 square miles of wetlands have disappeared from the area since the 1930s, and the receding continues at a rate of about 24 square miles per year. The erosion has a direct impact on New Orleans' ability to absorb the blow of a storm like Katrina, she said. For every 2.7 miles of wetlands, storm surges are reduced by about one 1 foot, she said.

http://www.msnbc.msn.com/id/9118570/

This is a good article. about wetlands and hurricanes.

 

[Skyhunter]

Indeed. Juxtapose this. In one part of New Orleans, a long line of school buses now submerged. In another part of New Orleans, tens of thousands of people in the Superdome because they lacked transportation to leave the city.

The city was using the metro buses for evacuation.

 

[Moonbear]

I heard on the news last night that engineers are now "speculating" (I put that in quotes because I'm not sure how strong the data is yet) that the levee failure was not due to the storm surge flowing over it weakening it or because the hurricane was just stronger than it was designed for, but that there were design flaws or defects of some sort in the levee that lead to it breaching. Did anyone else hear similar reports who could comment on it from a greater level of expertise?

I also heard they were bringing in large steel plates to cover the gap, apparently something that has not been tried before, according to the news again. I was wondering why this was not tried before. In a conversation with a friend of mine who used to be a civil engineer (he left the field a few years ago for greener pastures, so might not be fully up-to-date on stuff anymore), that was my first thought when I heard they were trying to stopper up the flow of water with sandbags, which sounded ridiculously infeasible to me given the size of the hole. I was thinking that if you just slid a long steel plate in place (with necessary braces to reinforce it of course), you could quickly stop the flow of water and then use it like a form to pour your concrete on the other side. But then he told me they would never do that, so I figured there was some reason that was a bad idea. (And, yeah, I rubbed it in a bit when I heard on the news that they were now doing just that. )

Another lesson that I think needs to be considered is that when climate conditions change or modern building practices have more stringent codes, it might not be acceptable to just keep grandfathering in older structures or to keep preserving old buildings out of an emotional attachment to the past. Sometimes you just need to tear down old buildings and replace them with newer construction, especially if you're in a vulnerable location, otherwise nature will come along and do the demolition for you.

 

[willib]

What the hell!
the Levee broke again , ok ,
What is the army corp of engineers doing ?? NOTHING !...
Ooo its too windy and too wet... waaaahhhh waaaaahhhhhh
so they are going to wait till the ninth ward fills up again,, idiots...
there was a camera guy filming the water comming in , standing on a good part of the Levee..with no corps of engineers in sight...
they booked outa there . and its not even going to meke a direct hit on New Orleans
Any thoughts on their responsibilities in this situation.??

 

[Moonbear]

they booked outa there . and its not even going to meke a direct hit on New Orleans
Any thoughts on their responsibilities in this situation.??

Yep, protect their lives before property. What could they do while the storm was hitting? You can't fly in helicopters with anything to patch the levee in high winds. You have to just let it fail and patch it when the weather conditions have eased up. This is why everyone was telling the mayor of N.O. that he was an idiot to even think the residents could start returning to the city until more of the infrastructure has been repaired. Those levees weren't repaired yet, they were patched. I think they need to sit down and evaluate the design of the levees in light of the strength of the recent hurricanes and the likelihood that they'll continue to get hit by strong hurricanes in years to come and consider rebuilding with a new design capable of withstanding higher storm surges than the current design.

One thought I have is that they need more than one levee wall. The government should use the eminent domain laws to buy up property within a reasonable distance inside the levees and leave it deserted, then build a second levee within the perimeter so if the outer levee breeches, there's a second levee as back-up. If they want to clean up the land between the levees, they can put in a park or something that won't have anything built on it so won't be a big deal if it floods in the future. Sure, it'll be expensive to build, but considering the expense of rebuilding an entire city, it seems worth considering now while everything in that region is pretty well flattened anyway.

 

[russ_watters]

This is why everyone was telling the mayor of N.O. that he was an idiot to even think the residents could start returning to the city until more of the infrastructure has been repaired. Those levees weren't repaired yet, they were patched.

Realistically, I think that it will be a good month or two until even temporary repairs can be completed. I don't think it would be wise to repopulate those parts of the city in danger until the hurricane season ends in six weeks.

I think they need to sit down and evaluate the design of the levees in light of the strength of the recent hurricanes and the likelihood that they'll continue to get hit by strong hurricanes in years to come and consider rebuilding with a new design capable of withstanding higher storm surges than the current design.

It is something they've been kicking around, but unfortunately, governments don't tend to close the gate until the horses have already run off. I think there is a good chance the government will make that choice now, considering the ~$10 billion or so it will cost to upgrade the system is peanuts compared to the ~$300 billion or so that will be spent due to this 1-2 punch.

One thought I have is that they need more than one levee wall. The government should use the eminent domain laws to buy up property within a reasonable distance inside the levees and leave it deserted, then build a second levee within the perimeter so if the outer levee breeches, there's a second levee as back-up. If they want to clean up the land between the levees, they can put in a park or something that won't have anything built on it so won't be a big deal if it floods in the future. Sure, it'll be expensive to build, but considering the expense of rebuilding an entire city, it seems worth considering now while everything in that region is pretty well flattened anyway.

I tend to think that would be overkill. If the levees are built to the same specs, if one fails, the other will likely fail as well. I think the solution needs to be to simply build the levees to withstand the strongest storm imaginable: we're talking 50 feet of storm surge. Such a levee would be so massive, though (they are several times wider than high) that the govt would probably need to exercise eminent domain anyway.

 

[russ_watters]

I heard on the news last night that engineers are now "speculating" (I put that in quotes because I'm not sure how strong the data is yet) that the levee failure was not due to the storm surge flowing over it weakening it or because the hurricane was just stronger than it was designed for, but that there were design flaws or defects of some sort in the levee that lead to it breaching. Did anyone else hear similar reports who could comment on it from a greater level of expertise?

I hadn't heard about that.

I also heard they were bringing in large steel plates to cover the gap, apparently something that has not been tried before, according to the news again. I was wondering why this was not tried before. In a conversation with a friend of mine who used to be a civil engineer (he left the field a few years ago for greener pastures, so might not be fully up-to-date on stuff anymore), that was my first thought when I heard they were trying to stopper up the flow of water with sandbags, which sounded ridiculously infeasible to me given the size of the hole. I was thinking that if you just slid a long steel plate in place (with necessary braces to reinforce it of course), you could quickly stop the flow of water and then use it like a form to pour your concrete on the other side. But then he told me they would never do that, so I figured there was some reason that was a bad idea. (And, yeah, I rubbed it in a bit when I heard on the news that they were now doing just that. )

It seems like a good idea to me, but where do you get a steel plate that size and how do you put it there? They were kicking around a similar idea: putting a large barge in front of the breach.

Another lesson that I think needs to be considered is that when climate conditions change or modern building practices have more stringent codes, it might not be acceptable to just keep grandfathering in older structures or to keep preserving old buildings out of an emotional attachment to the past. Sometimes you just need to tear down old buildings and replace them with newer construction, especially if you're in a vulnerable location, otherwise nature will come along and do the demolition for you.

I'm generally not a big fan of historical preservation: it costs an enormous amount of money and just because a building is old does not automatically imply that it has historical value. But the political pull of historical preservation is strong enough that rather than demolish buildings that don't meet new codes, they'd just spend more money reinforcing them.

In Philly, people spend hundreds of thousands of dollars bracing the facades of old brick row-homes (they tend to bow outward as the house settles). Every now and then, they have a blowout, where the facade literally explodes onto the street. Such building should just be demolished.

 

[Astronuc]

In order to comment on the design of the levees, one would need some detailed diagrams, particularly of the cross-section.

I have heard recently from comments by Corp of Engineers staff that there was scouring of the levees, which had not been previously detected. This certainly could have undermined the levee.

Perhaps the levees are a combination of concrete and compacted fill. Unless the fill is properly engineered, water may seep into the structure and weaken it, e.g. water reduces the internal cohesion of the fill, and basically the levee creeps/flows and then fails. Water infiltration may occur because the hydraulic pressure, which increases with water depth, forces the water into the levee structure. Here is where one needs the details of the design.

I am wondering if the structure was simply reinforced concrete slab/form set over a compacted Earth fill. This is the type of structure used in channels or concrete bayous or along freeways. Water getting under or behind the concrete can undermine the earthen fill.

The other problem is corrosion of the reinforement bar in the concrete. If the concrete is not of the correct composition, is not mixed right or cured properly, it can be relatively porous, and over decades, Cl (chlorine ions) can infiltrate and cause corrosion of the steel rebar. Perhaps that is one factor in New Orleans levees.

Anyway, there will certainly be an investigation, which hopefully will shed light on the failures.

 

[Moonbear]

I have heard recently from comments by Corp of Engineers staff that there was scouring of the levees, which had not been previously detected. This certainly could have undermined the levee.

Maybe that's the "defect" I heard them mention on the news yesterday.

 

[Moonbear]

It seems like a good idea to me, but where do you get a steel plate that size and how do you put it there? They were kicking around a similar idea: putting a large barge in front of the breach.

That's what they pay the engineers to figure out? Okay, it seems they were using 60 ft plates (I think I heard that on CNN). I'm not sure how they were doing it, but since the breach was 200 ft wide, I guess it wouldn't be quite as easy as I was thinking (and they might not have been able to do this sooner if they needed to get that plate custom manufactured for the job). I kind of like that barge idea. Maybe they need a Navy Corps of Engineers instead of an Army Corps for this job; just park a big ship planned to be decommissioned in the hole. (Shhh...Don't tell my friend that I wasn't quite right about that steel plate idea, he'll never let me live it down after I rubbed it in.)

 

[russ_watters]

I kind of like that barge idea. Maybe they need a Navy Corps of Engineers instead of an Army Corps for this job; just park a big ship planned to be decommissioned in the hole.

I don't know where else they have boneyards, but Philly operates one where they have dozens of WWII ships parked, including supply ships (huge, but maybe not strong enough) and battlecrusiers (a foot of armor makes them pretty strong).

 

[Astronuc]

It seems like a good idea to me, but where do you get a steel plate that size and how do you put it there? They were kicking around a similar idea: putting a large barge in front of the breach.

The idea of getting a ship or barge in the breach is complicated because of the geometry of the barge or whatever vessel - it has to fit just right or the water will simply flow around it and wear out a larger hole.

When the breach was small (100-200 ft), it would have been difficult to maneuver a barge 'just so' while the water was flowing through the breach, and then the barge, which would be floating, would have to be rapidly ballasted so sink it. In fact, I believe I saw one image in which a barge had floated through one of the breaches into the neighborhood behind.

Elsewhere, when construction is taking place along waterways, barriers are built with interlocking corrugated steel channels. Perhaps that would have taken time to arrange though.

Anyway, I found an interesting article on the levees of the West Jefferson Levee District (WJLD). It highlights some of the problems with the levee system. I am not sure if this levee (the eastern side of the canal) was one that failed.

Levees are supposed to line both banks of the canal to protect homes and businesses from high water. The west side levee is a solid continuous structure built in 1991 with federal funds by the Army Corps of Engineers. Containment structures on the east side, however, are a hodgepodge of wooden bulkheads, cement sea walls, consolidated earthworks and even an abandoned barge.

Maintenance of these structures is officially the responsibility of property owners there. Most of these back levee owners are industrial businesses involved in construction, fishing and offshore petroleum operations.

“The east side is not really a levee system, and there’s a difference in elevation between the two sides,” says Giuseppe Miserendino, deputy director of the West Jefferson Levee District (WJLD). “Water would spill over the east side of the canal if there were a tidal surge.”

Tidal surges pose serious dangers in that section of Louisiana where many residential and commercial areas reside below sea level. In fact, the entire system of canals, levees and river locks built in the area has been constructed to protect New Orleans and outlying suburbs from those tidal surges on the Mississippi and the Gulf of Mexico following a major storm.

from - http://www.pobonline.com/CDA/ArticleInformation/Article/1,9169,74573,00.html

 

[amuron]

Someone posted earlier in the thread.

"It is both a matter of public policy, as well as engineering, and engineers need to be heard in the public forum."

As a rule, we tend to ignore politics and go about our business... or at least I do. I spent 2 years at a state govt appointed position while holding down my engineering job, and had my fill of it. When the position ended, that was it for me.

A friend who retired from NBS (yes, before they became NIST) told me the DC beltway had one of the highest concentrations of multidisciplinary scientists and engineers compared to anywhere else in the country. But at the same time, he also told me that virtually none of them were active in politicis due to all the BS. I think too many of us come to the same stance. We let politicians do their bungling, shake our heads and walk away in disgust.

Otoh, if engineering had a decent voice, imho, their might have been some proactive cost effective solutions that would have made a difference.

Ron

 

[zhen]

I just wonder why they don't think about those underwater city project?
because no matter what the government do, another hurricane will still come, the place will be flood again... the best thing to do is to build underground or under water city...

 

[Moonbear]

I just wonder why they don't think about those underwater city project?
because no matter what the government do, another hurricane will still come, the place will be flood again... the best thing to do is to build underground or under water city...

Can you expand on what you mean by this?

At the least, it seems some of those houses, if rebuilt in the same locations, should be put up on stilts as houses are in other coastal/flood-prone areas. (For an example, see the pictures on this site: http://www.amazingplans.com/beach_pilings_style_house_plans.html )

 

[Andre]

Sorry that I did not scrutinize this thead about what has been said but I think I have some fresh information comparing the Dutch way of fighting the sea with the sad fate of N.O.

Dutch water engineers are on side now and their first impression was: a disaster waiting to happen. The Levees were designed to withstand a cat 3 storm, with a mean life of 30 years worth of weather extremities . The Dutch dams are designed to hold up for ...10.000 years. Yes of course there are no cat 5 hurricanes here in the Netherlands but the 1953 flood combining a westery orkan of 12 beaufort with highest tide caused a major disaster. So it took some 30 years to complete the most powerful defence against the sea. Have a look

A New Orleans Levee:

http://gpc.edu/~pgore/myphotos/neworlen/levee1.gif

http://gpc.edu/~pgore/geology/geo101/hydro2.htm

compared to the Dutch "Deltawerken":

http://www.coachdriver.com/countryinfo/netherlands/image/grevelingen.jpg

resisting the pressure of water is not about the height of the levee but it width. You need at least 100 yards or something not the mere ten yards in N.O. That will simply be washed away.

In America everything is bigger and better, is the standard saying in Holland. However this is not about the pumps. The Dutch engineers were shocked about the size and capacity of the pumps designed to balance the water levels. Dwarfs compared to what is installed here. No wonder that it proves to be quite difficult if not impossible to get the area dry again.

So what caused the Katrina disaster? The buildings in N.O seem to have withstand the wind forces quite well, but their feed are wet. Why were the levees quite chanceless against a cat 4-5 storm? Poor politics? I fear the the worst but if the same greenies that shout "climate change" now also had prevented the levees from being upgraded in the past, to preserve nature, then we are sure that mankind is digging it's own grave.

Furthermore I'm convinced that our "deltawerken" would have resisted Katrina with flying colors.

 

[Astronuc]

Shortcuts alleged in building levees
USATODAY.com

WASHINGTON - Several of the levees that flooded New Orleans may have been built with shoddy materials or by contractors who took shortcuts to save money, an investigator told Congress Wednesday. About a dozen people, including engineers and contractors, made the allegations of poor workmanship in recent weeks to investigators probing the levee failures, said Raymond Seed, the head of a National Science Foundation team examining the levees.

Preliminary report - http://hsgac.senate.gov/_files/Katrina/Preliminary_Report.pdf

from - http://news.yahoo.com/fc/US/Hurricane_Katrina/ (Nov 3, 2005)

About a dozen people, including engineers and contractors, made the allegations of poor workmanship in recent weeks to investigators probing the levee failures, said Raymond Seed, the head of a National Science Foundation team examining the levees.

Seed would not identify the tipsters and he cautioned that the allegations may ultimately have nothing to do with the levee disaster that led to hundreds of deaths. But he said that investigators are taking the tips seriously and intend to turn them over to federal officials.

"What makes us nervous is we're hearing multiple accounts," Seed said after testifying before the Senate Homeland Security Committee. The National Science Foundation, which gave Seed a grant to investigate the levees, is an independent federal agency charged with promoting science and the nation's welfare.

The complaints focus on two canals where levees topped with flood walls were built in stages over the past 15 years. One of the claims is that contractors used steel sheets - which were driven into the levees to prevent water seepage - that were shorter than what was called for in designs. If true, that could have made the levees weak and prone to failure.
Other tipsters complained that inferior materials, such as porous soil, were used to construct the levees.

Robert Bea, another University of California, Berkeley professor working with Seed, said in an interview that he talked on the phone with two women who said they had specific information from their late husbands on construction shortcuts taken on the levees. Seed said other investigators received similar complaints.

He wants the Army Corps of Engineers, which oversaw design and construction of the levees, to dig up portions of them to make sure they were built properly.

A preliminary report issued Wednesday by Seed's group and an American Society of Civil Engineers team said key levee failures on the canals near Lake Pontchartrain in New Orleans occurred because water oozed beneath the steel sheets and pushed aside the soft delta soil.

The levees were supposed to be able to withstand water heights seen in Hurricane Katrina, which hit Aug. 29. Investigators have not pinpointed whether designs were inadequate or the levees were built improperly.
Seed was joined by the heads of three other groups investigating the levee failures. The investigators raised questions about poor federal and local oversight of the levees, steadily decreasing budgets for the Army Corps of Engineers and decades of safety compromises.

http://en.wikipedia.org/wiki/Levee_..._in_New_Orleans_(following_hurricane_Katrina)

 

[Astronuc]

I fear the the worst but if the same greenies that shout "climate change" now also had prevented the levees from being upgraded in the past, to preserve nature, then we are sure that mankind is digging it's own grave.

Greenies had nothing to do with poor quality of the levees - they were most built before the environmental movement took off. Rather, corruption and greed on the part of some in government and some in the construction industry, and also the insufficient funding from the government (again due to politics)

Furthermore I'm convinced that our "deltawerken" would have resisted Katrina with flying colors.

I would agree with that.