A few days ago, I posted a blog about “The despised MR-GO.” Someone using the name “steve” posted this reply:
“Plugging the MR-GO will not solve all the issues, I get that. Ivor van Heerden is not 100% qualified to come up with a total civil engineering plan save the city, I get that too. Something needs to be done. Even if Ivor van Heerden is not qualifed is there a better voice? Is he half right? What do you think can be done? Can the city really be protected? Point us toward some qualified answers. I would like to see your ideas.”
Okay, regarding Ivor van Heerden, I gave a full explanation on an earlier post, but to recap, he simply is not qualified because he is not an engineer. Now you might want to seek medical advice from people who are not doctors, and they might even give you good advice from time to time, but I’m not willing to risk it all on a geologist when we need world-class engineering here. Who then? I have the utmost respect for Tom Jackson, past president of the American Society of Civil Engineers, currently on the Southeast Louisiana Flood Protection Authority-East Bank.
A big part of the problem here is communication. Levee safety is a complex subject. Just as I wouldn’t expect the public to understand in any detail how the Empire State Building is able to withstand wind and gravity forces, I really don’t think the average person on the street can ever understand all the ins and outs of hurricane forces and structures to protect us. At some point the public is going to need to let engineers do their jobs.
And before anyone jumps on that bandwagon and yells, “But it was misplaced trust in engineering that got us where we are now,” let me remind everyone that there were many engineers who proposed several alternatives to the hurricane protection system that we ended up with. I do not defend the oversights and shortcomings of my peers who failed us here, but I am of the opinion that we allowed ourselves to be guided by politics, short-sighted planning and false economy when we should have been listening to good engineers.
What can be done? I think we need to take a long-range, universal view of hurricane protection. We can’t expect levees to do it all. We can’t really believe that we can plant grass to stop a storm surge. We have to adopt and enact a full range of strategies to protect ourselves. This should include:
1. Significant levee protection. Not just a 100-year levee at our back door, but multiple lines of levees to an appropriate level of protection. Highly developed, densely populated areas should get 1,000-year levees at the least.
2. Rational levee alignments. Have you ever seen a map of levee alignments? It looks like a 3-year-old’s drawing of clouds. For decades, we’ve allowed politics to place the levees, and we end up with the famous “funnel” where the MRGO levee meets the GIWW levee. Every hydraulic engineer on the planet knows how stupid that is. Dutch engineers I’ve spoken to are amazed at how long and jagged our levees are. They know that levees need to laid out to be as short and smooth as possible on the map. Shorter lengths mean fewer places for potential problems, and smooth alignments mean no more funnels where storm surge concentrates.
3. Raised construction in the flood plain. Okay, so we managed to get away with slab-on-grade construction in the New Orleans area for a few decades. We were lucky. Now that we know how sudden and catastrophic a flood can be, can we please start building our homes up off the ground? Even before Katrina and the levee failures, houses in the New Orleans area would flood when there was a hard rain. I’m talking May 3, 1978, May 8, 1995, etc. We need to elevate. NOW.
4. Evacuate! When the National Weather Service says it’s going to be bad, please, get out of town. Even if we have great levees, even if we have elevated houses, nobody should be betting their lives on them. Ask anyone who stayed for Katrina: evacuation is a lot easier and safer.
Can the city really be protected? If you’re asking for foolproof, 100% protection, the answer is, “No.” Just as there is no foolproof, 100% safe automobile, medicine, or anything else, don’t even ask for a perfect hurricane protection.
I do think we can do much, much better that we have up to now. I do think that with a concerted, cooperative effort between citizens and government at the local, state and federal levels, we can do this.
18 comments:
Ivor van Heerden is too easy a target. He is too in love with himself.
I must take exception to your comparison of a map of the levee alignment with the drawings of a three-year-old. I've seen three-year-olds' drawings of clouds and I think they're way better than that.
--YH
Van Heerden is a media whore. He's looking to sell books. Just because someone has a funny accent doesn't make them more knowledgable.
Politics.... that's it. Again we have found the problem and it is us.
Engineers who think they're scientists and geologists (and ignore the innate heterogeneity of the earth) should be illegal, too.
Weren't engineers responsible for the first round of levees and flood walls in this city? Did they even look at the soil maps? No, no, what use do they have for pedologists?
Not mad at you, just the sheer non-interdisciplinary nature of applied science today that results in amazing disasters.
This is probably a function of coming from a non-degreed viewpoint (I don't count an Associate's degree...LOL), but it's always amazed me that the usual outcome when someone publicly steps outside the strictly defined discipline of his degree to make comments is not that the validity of his actual comments will be challenged, but that his right to even make comments at all in anything other than his narrowly defined field is challenged, usually with a little character attack thrown in for good measure. It's almost as though we're to accept that once you've completed the span of years it's taken to garner your degree that the die is cast--you can no longer study or learn anything outside of that strict subject, and therefore you can not ever in your life speak competantly on any subject other than the one you concentrated on for those years in your 20's. It's particularly puzzling to me when it occurs in the field of engineering, actually, since (unless things have changed) you don't even have to study engineering in college to be considered a licensed engineer by the State of Louisiana as long as you can prove your competancy by passing the state licensing exam. I say this after having worked with a gentleman who did not leave high school and go directly into an engineering curriculum at a university, but instead spent the next 20 years or so working in construction and building design while also doing a lot of independant study on engineering and the associated math. The gentleman applied for and passed the state engineering exam, and because of this Louisiana considers him a licensed engineer competent to carry out the same duties any college-educated engineer might. I, on the other hand, knowing how much study he had done on the subject, already considered him competent to speak about engineering topics before he had even taken the test.
As usual, wonderful post, Tim.
Thanks.
You sound like my engineer husband. I cannot tell you how many times I hear this rant at home. The engineers need to be allowed to do their work -- they're the experts.
Puddinhead, There used to be a provision in the law to become a PE with experience and an exam. That provision was removed from the law some years ago. Today it requires a baccalaureate degree in engineering, two 8-hour examinations administered by the National Council of Examiners for Engineering and Surveying, a separate examination on Louisiana engineering rules and ethics, four years of progressively responsible experience as an Engineer Intern under the supervision of a licensed professional, letters of recommendation from other Professional Engineers vouching for the applicant's ability and integrity, and a clean criminal record. In some circumstances, an additional four years of experience is required prior to the four years as an Engineer Intern.
Tim: It seems that the "full range of strategies" you advocate here once again do not include coastal and wetlands restoration. Has your view that "coastal restoration has very little to do with hurricane protection" undergone any changes over the past year?
I guess the 1,000 year levees could be there while we are putting the wetlands back and directing the silt from the river back onto the coast. It IS gonna take a long time, and loads o' dough, to put it all back.
Tim,
Well said. I've been a little confused from day one about Ivor investigating the engineering failure.
Oyster, what you need to understand is that wetlands are a levee of sorts. Very deep, and very low, but they are the integral lead line of defense in our levee system. As Tim mentioned, we need a series of levees, each protecting us to a greater degree. The final line should be a 1000 year or greater levee. There should be partitions within that 1000 year levee of other 1000 year levees that will segregate the protected areas from each other.
I have a dream that with some brilliant engineering over the next 30 years that the Louisiana Gulf Coast will become the fastet growing landmass on the face of the earth. The continental shelf is quite a long ways out there, and some team of engineers out there is going to come up with a system that captures silt from the river and places it right where we need it, and build an incredible first line of defense wetland that will cause our second, third and fourth line of defense levees to be upgraded year by year from 100 year levees to 200 - 400 - and on. If the landmass was fully restored in the lee of the Chandeleur islands, we'd really have something then. It's a dream, but I have to believe that there are some students at UNO and LSU that can take us there.
Oyster, my view has not changed because the facts have not changed. The best guess (please note: not science, just professional judgment based on a few observations) is that 1 mile of marsh can reduce a storm surge by 3 inches. So to knock a storm surge down by 1 foot you will need 4 miles of marsh, IF our best guess is correct.
I just don't think building miles and miles of marsh is feasible for hurricane protection. You may want to build marsh for fish and birds and all those other excellent reasons, but it just does not make sense for flood control.
Shall we look at it another way? Let's do some math:
How much fill does it take to build marsh? Assuming you're working with open water 2 feet deep and you build it up to 1 foot above sea level, that's 3 feet of fill. 3 feet of fill x 4 miles x 5280 feet per mile x 1 mile wide x 5280 feet per mile again gives us 334,540,800 cubic feet of fill. That will give us the benefit of a 1 foot reduction in storm surge.
How much fill does it take to build a levee? The quantity of fill for a levee is a little more complicated to calculate. Assuming you're working with open water 2 feet deep and you build it up to 8 feet above sea level, that's a total height of 10 feet. With a 10-foot-wide crown and 4-horizontal to 1-vertical side slopes, our levee has the shape of a trapezoid. The top is 10 feet wide and the bottom is 4 feet horizontal per ft height x 10 feet high x 2 sides, plus the 10-foot-crown, for a total base width of 90 feet. The required fill is (10 ft crown + 90 ft base)/2 x 10 ft height x 1 mile wide x 5280 feet per mile, which yields 2,640,000 cubic feet.
Obviously levees can be built with much, much less fill than it takes to build marsh. And please note: we're comparing a levee that is 8 feet above sea level to marsh that will theoretically give us 1 foot of storm surge reduction.
Now this is a very simplified example--there's a lot more to it than can fit on this page. Larger levees on poor soils will require additional fill for stability berms and other factors. But even if you triple or quadruple the levee quantity, the result will still be that levees require less fill to build.
Fill is scarce, money is scarce, the science is not firm and time’s a wastin’, so I say, let's build levees!
ClarkT, this does not negate your suggestions. As noted, wetlands can and do help, but it will take massive amounts of marsh and decades to produce them. I think that the more compelling benefits of wetlands are ecological. We need not only engineers to figure out how to do it, we also need smart policy that will promote the economic benefits of fishing and tourism in what can be the next “Wonder of the World.”
Tim,
Your conclusion is I think right, but the calculations are I think somewhat off.
I think a 1,000 year levee would be on the order of 25 feet above sea level, possibly more. You probably know that better than I do.
Coastal marsh is generally close to sea level, with at least seasonally standing water held in place by grass. Marshes must also be constantly replenished due to the subsidence of the layer of vegetable matter making up previous seasons of grass. Swamps are similar, except there are trees instead of grass.
All of that said coastal restoration cannot be accomplished by simply filling and extending existing marsh areas, it could only be temporary. What is really necessary is restoring the natural methods of replenishment, using the forces of nature to restore and extend the mash, which may not even be possible.
Mominen, Yes, the example of a 10' levee was just for comparrison to the marsh that would give 1' of protection. I would say the 1,000 year level of protection would require two lines of levees with storage for water that overtops the first levee between. A single levee would need to be on the order of 50 feet, which is simply not even feasible in the poor soils of coastal Louisiana.
First, I want to second Maitri's comment. We need teamwork, engineers, geologists, hydrologists, ecologists - and throw in a few true interdisciplinary types (engineering geologists, geohydrologists) for good measure. Everyone needs to be involved.
Second, don't forget the Mississippi River! It built south Louisiana in the first place. We need to start treating it as an ally, not an enemy.
Great work on the Picayune op-ed, sir. You make the strongest case possible in precious few words.
Keep it up!!!
Tim,
Let me submit a bit more math to add to yours. The River carries 436,000 tons of sediment per day. Assuming 125 lbs/cf, that's a bit over 2.5 billion cubic feet per year. Using your figure of 334,540,800 cf for one mile of wetland four miles deep, 100% of the annual load can make only 8 miles of wetland with a storm surge reduction value of only 1 foot. Assuming that 300 miles of wetlands are needed and a 25-foot surge reduction is the goal, if we can place it where we need it, if we can use 100% of the load - get ready for it - about 1,000 years would do the job.
I agree, let's build levees!
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