A Potential Portable Storm Surge Barrier Design

Imagine a tube, 20 feet in diameter (the size of a house) filled with seawater, floating in the sea. Now imagine another tube inside that tube, maybe 5-10 feet in diameter, filled with air. So the air-filled tube floats above the water, like a beach ball. But the air-filled tube can’t go anywhere, because it’s inside the water-filled tube.

Imagine that these tubes extend tens of miles, parallel to the shore, but several miles out to sea. When the hurricane comes from way out at sea towards the shore, the water stacks up behind the air-filled tubes. Some flows over it, but not much. The air-filled tubes get pushed towards shore, but because they’re inside the water-filled tubes, the tubes move very slowly (say 1 mile per hour). In contrast, the hurricane is moving towards shore more rapidly, say 10 miles per hour. So eventually, the eye of the hurricane passes over the tubes. As long as this happens before the tubes get pushes completely to shore, the water behind the tubes just flows back out to sea, and the storm surge is minimal.

The air-filled tube would be filled with a giant compressor/fan. The water-filled tube would get filled by dragging the tube behind a ship, like a fishing net. The most important aspect of the design is that it's portable, and can be deployed essentially anywhere with a couple days' notice.

Comments

[john hare]

I've had a little time to think on this and look at a couple of things.

In policy, this is far too early to become a national goal. A phase one SBIR, possibly if you could put together a good enough presentation. A friend of mine suggests that acceptance runs in the 10% range depending on the agency and how well it meshes with what they are trying to research. The Manhattan project and similar shots in the dark, weren't shots in the dark as they had considerable theory by high powered theoreticians behind it before becoming a national program.

Credibility is coin of the realm in getting government backing. I have blogged about rocket and jet engine concepts that I believe would be superior to anything operating. I have blogged about at least three methods of diverting asteroids, one of them beating NASA to publication. I have never bothered trying for backing due to lack of credibility. If I were on the other side of the desk, I would turn me down. No credentials and no experience in the field. I know people that live off of those grants and others that have gone broke trying. Nobody being a jerk or unfair, just making decisions based on agency guidelines and the information available. It is a serious effort just getting started in this sort of thing.

I'm more comfortable technically. Historically, how much damage have barrier islands prevented that you can point to when the questions are raised? Something along the lines of "In 19xx, hurricane Bahner came ashore as a catagory 3 at Rich Beachaven East Carolina. A 2.5 foot high barrier island masked the southern 17 miles of Fat Cat resort while the northern 15 miles was exposed to the full fury of the storm surge. It was found that storm surge was reduced by 6.45 feet behind the barrier on the southern half of the resort, with the averages being 7.25 feet of surge behind the barrier island vs 13.7 feet of surge in the Norther unprotected section." Or something of that nature to prove that it has already worked in a serendipitous manner, and the proposal is to learn to do it deliberately. If there is no data anywhere that this works even on a limited scale, the chances of funding are virtually zero.

For your well out at sea surge only being 1-3 feet, you may be missing the momentum of the miles of 1-3 feet higher seas behind your initial barrier. That is that the initial 1 foot is stopped, but then the next climbs over the barrier or floats it higher such that it must stop 2 feet then 3 and so on. This is going to be a temporary sea wall and it is going to be highly stressed and take a beating in hurricane force winds and the surge you are holding back. Structurally, I think you might mitigate 1-3 feet of surge with what I see as your concept. Stopping the surge cold would require further research as to how surge reacts to abrupt barriers such as he cliffs more prevalent in the Pacific areas. There should be considerable data on how well sea walls and cliffs slowed, diminished, or even stopped a surge coming in from the open ocean with little to no shallowing before impact.

Assuming the concept works, it may not be necessary or desirable for the skirt to reach the ocean floor. Environmentalists, or at least people that claim to be, are likely to claim that you are destroying some habitat or another. Environmental impact statements are project killers even if you can clearly prove that you will be saving far more than you damage. Scraping the ocean floor is liable to trigger at least one group that can screw up your project. Nuclear power is an example of fear mongering damaging an industry. It would also be difficult to match contours with a moving barrier on a variable sea floor. It may be possible to design your system in such a way that the skirting only goes far enough down to work as a sea anchor. The sea achor in this case would use the momentum of the surge wave to accelerate lower layers of water shore ward. It may be possible to achieve a geometry that will induce an undertow that is working against the surge direction. Or it may be that there is a natural undertow in some locations that can be used to depower the surge to some extent.

Assuming it works, I think it likely that it will need to be deployed as a series of baffles rather than a single barrier. It may be possible that a half dozen barriers could mitigate a couple of feet each for a total of a dozen feet of surge height reduction. I think eliminating surge completely is unlikely to be cost effective.

[Mark Bahner]

Hi John,

Thanks for your comments. I'll address them sort of in reverse order.

1) I have an extremely thick skin (as long as people are respectful, such as you certainly are). I don't mind at all when people tell me things I think will work won't work. I probably won't agree, at least initially, especially if they're *my* things. But I certainly don't mind. And if you are eventually able to persuade me, I'll even let you know.

2) I completely disagree with your statement that things should get elevated to policy once it's shown they'll work. A classic example of that is the Manhattan Project. There were so many things that could have resulted in failure of the Project. They didn't know they could enrich uranium. They didn't know they could compress enough to achieve supercriticality. They didn't know they could make the detonation happen at just the right time. But they went ahead with the Project. Why? Because if it *did* work, it could end the War.

In this case, the cost of storm surge damage in the U.S. is approximately $40 BILLION per decade. And the cost globally is approximately $100 billion per decade. The only system that can appreciably change that is a portable system.

So I completely disagree. Policy should immediately move to discussions of how a portable system could be designed. OR (and this is a big "OR")...systems should be developed that "de-power" hurricanes. That would probably be better than portable storm surge systems, because portable storm surge systems only reduce storm surge. (Not winds or inland flooding.) But if we're not going to work on de-powering hurricanes, we should be working on portable storm surge protection systems.

3) I'll post a drawing of my conceptual design later (I'm very busy with some personal things through the end of March). But picture a tube with air and seawater in it, and a "skirt" from that tube that extends to the sea bed. The end of the skirt has something very dense in it. Picture iron balls or something like that. So the end of the skirt stays in contact with the sea floor...but it is not fixed to the sea floor. The tubes are deployed far offshore. What happens with storm surge is that storm surge is never a very large value far offshore. In the open sea, storm surge might only be 3-5 feet high. But it becomes high in large runs of shallow water, because there's nowhere for the water to go back out to sea. So in my conceptual design there is never more than 1-4 feet of height difference between high water on the upwind side of the tubes and the low water on the downwind side of the tubes.

The tubes don't get pushed quickly to shore because F=ma. The force pushing the tube towards shore is the is the water pressure difference across the tubes. The mass equals...whatever it needs to be. Fill it with whatever amount of water will make certain the tubes don't get pushed to shore until the hurricane passes overhead. (Note that the water height across the tubes goes back to zero as the wind dies down.)

Think of the whole thing as a *temporary* barrier island...where the barrier island is not actually fixed in place. And where the barrier island never becomes completely submerged. (With the air in the tubes, the air is always going to be a little bit above water.)

Best wishes,
Mark

[john hare]

With the information provided to this point, it seems that your floating barrier would just get washed ashore to become more debris. There was a comment in your 2008 post that questioned the anchoring and wasn't addressed. Unanchored, it would move with the storm surge at the same velocity. If not continuous to the sea floor, water would flow under it as it does a ship such that it would provide no barrier.

It seems that you are thinking in terms of holding back large storm surges on the order of 20-30 feet. An anchored barrier with a 24 foot sea height differential from seaward to shoreward would have a force of 9 tons per linear foot driving it shoreward. That's a lot of anchoring which would be extremely difficult to achieve with a portable system. Unanchored, it will do damage as it is washed ashore. Can't have it both ways.

Our discussion on econlog is properly about policy. Policy should be grounded in reality. With information available, this system will not work in the technical sense, in which case policy should be to ignore it. Only if you can provide a solid technical case should it be elevated to policy. I would suggest a small scale field experiment in a pond or lake with the intent of holding back inches of water to get some data.

I am an inventor with a construction company and an engineering background. A very high percentage of new ideas, including mine, do not work technically. You simply do not know until you crunch numbers and do experiments. The ones that do work technically often still do not work financially. Even the ones that work financially often are overtaken by other concepts that are better, or better promoted.

You really need a thick skin to present new ideas as most of them will get hammered. The real skill is not to have new ideas, but to have the ability to sort the good ones from the bad.