3.11, reconstruction & seawalls

Today is the 6th anniversary of the Great East Japan Earthquake. As such, I want to talk about an issue that is always in the back of my head, and comes to mind every time I am near a coast in Japan. And that is the seawalls.

More than 50% of Japan’s coasts have been modified in some form through the construction of seawalls and erosion control structures according to the Ministry of Environment. Now, these walls failed in an epic fashion in 3.11. testimony of the scale of the tsunami that ensued the magnitude 9 seism. Now, i’m not saying that engineers and planners should have seen it coming. The impact of this kind of high impact low frequency events is very hard to assess, and we all know that predictions are very hard, especially when about the future (You can attribute this claim to whoever you want, I’m gonna stick with Yogi Berra), what I am asking is whether rebuilding taller, longer, stronger is the right solution in the first place. Rebuilding taller, longer, stronger is perhaps ignoring the very lesson the tsunami taught us. Is like saying “we got it wrong last time, but we ain’t gonna fail next time!”. And the key issue here is exactly how effective these walls really are, and is this the best way to address this problem?

First of all, we have now way of telling whether or not these new seawalls will be effective when “the one” happens. Nonetheless because we don’t know which one will be “the one”. that is, we have now way of tsunami-proofing a town against all possible scenarios. There can always be one that overcomes our walls. And a first step to a more successful planning is to acknowledge this. Then we have other issues that are completely disregarded in current plans: ecosystem disruption, scenery and effective evacuation.

The construction of a seawall strongly disrupts beach ecosystems, but under Japanese law, seawall construction does not require an environmental impact assessment. And if ecosystems is not your thing, well, seawalls are just plain ugly, and they can really destroy the natural beauty of a coast almost instantly. And by this point you are probably thinking, “well if it means saving lives!”which brings me to the third point, does it really? In the aftermath of 3.11, one theory suggested that the very existence of the seawalls might have actually delayed evacuations as a result of a false sense of security. Granted, this theory is to the best of my knowledge yet to be validated, but we are working on that right now.

At any rate, it really begs the question, if seawalls negatively affect beach ecosystems, are unsightly, and we are not even sure they save lives, why are we building them to begin with? In earthquake prone Japan I certainly see the need for some sort of protection against less destructive yet more frequent tsunamis, but does it have to come at the cost of ecosystem & scenery disruption? When locals started complaining about the fact the with the new seawalls they would be unable to see the sea, the government responded with the idea of adding some acrylic “windows” to the walls, which sounds to me like a really, really bad joke. And do note that amidst the hollowing of local industry, and an increasing influx of foreign tourists to Japan, tourism might become a way to revitalize the Tohoku region, and for that you need to have resource that you can sell, and that ain’t concrete. Finally, there is the issue of safe evacuation. Prompt evacuation is the best way to save lives in the case of tsunami, and while a seawall of certain height might buy priceless time, relying on the assumption that the wall will hold is dangerous, as it might be the fact that if you cannot see the sea, it is even harder to assess the level of risk you are exposed to.

So is there a better way to deal with this problem. I certainly think there is. First, set the walls back enough so they disrupt the ecosystems as little as possible,and allow for tidal flats to recover. I’m pretty sure there are a lot of marine biologists ready to give their assessments and recommendations on this issue. Second, the wall should be high enough that they protect the city from more frequent type of tsunami, Now, what type of tsunami this is, I’ll leave it up to the experts, but it is not a once in a millennia type of tsunami. Furthermore, the wall should not be that high the it leads us to believe we are fully protected and that there is no need to evacuate, or that it makes you feel you are trapped inside a citadel. Again, prompt evacuation is the best way to save lives. This is important because, while anyone who lived through 3.11 might remember the devastation, future generations will not (as we did not remember documented damage by previous disasters). I’m thinking of a seawall that is probably lower than the existing ones in 2011, and way lower than the ones that are being built right now. Third, design the walls so that the blend with the context as much as possible. It sounds to me like a great subject for an urban landscape international design competition, specially given that some plans suggest converting low lands into parks and relocating people to higher ground.

I am not in any way suggesting that the reconstruction process is an easy one, certainly it is not. But it seems to me we could use some more creativity to address these problems in a more comprehensive manner, and come up with solutions that are more satisfactory to all parties involved.


2 thoughts on “3.11, reconstruction & seawalls

  1. Hi Gian, because we all love comments, here are my 2 cents.

    I fully agree with the first parts of what you wrote here, but don’t share your concluding two suggestions, which are: set the walls back, and built higher walls.

    The historical perspective: In the “old” pre-engineering days the forefathers were pretty aware of the destructive effects from tsunamis and the like based on stories handed down from generation to generation; it was accepted as something that couldn’t be avoided and which they had to live with. As such they mostly built on higher ground; except of course for infrastructure that requires access to the sea like ports etc. But is it really that simple? When industrialisation and better health care led to a rapid increase in population and economic success led to increase in land prices, towns expanded in all directions, up the hills, into the countryside populating fertile agricultural land with buildings and of course towards the shore as well, and by reclaiming land and by constructing artificial islands the shore lines were pushed even further into the sea. Have a look at older maps of Tokyo Bay or the Kobe region or the Sendai area and discovering streets named “Kyuu Kaigan Dori” meaning “former shore line street” is revealing how far the shorelines have been pushed out into the bay or sea. Try to find a beach in the Kobe area nowadays and compare it with photographs taken 50 years ago, urbanisation takes a toll. Now that all these additional square meters are sold to corporations and individuals, the administration feels forced to protect it.

    As such, setting the walls back will still expose the areas outside the wall to the devastating effects and the administration will be left with the question of how to protect those parts of the town. The common procedure of compiling hazard area maps has not limited the erection of buildings in hazard prone areas. Second, building higher walls will not alleviate the argument that it blocks the view. Rather the opposite will happen, that even the upper floors of buildings behind the wall will be below the top of the seawall.

    As such I’d like to suggest a positive take on research, science and engineering and collaboration between disciplines:
    (1) I’m not saying that building seawalls a dozen metre high is the best answer, but if they are to be built, than use or develop transparent concrete, or a material that is cheap enough and transparent with sufficient compressive and tensile strength. Aquariums feature transparent walls, the tallest being more than 10 metres high already.
    (2) Human settlements have an impact on ecosystems, no doubt. But this impact is not necessarily negative only. Studies on Satoyama and Satoumi show, that on the borderline of “natural/wild”and “artificial/human” ecosystems a rather diverse ecosystem, more diverse than the sum of its neighbours can develop and prosper. As such the “borderline” should be “engineered” taking into account all the available best insights from a wide range of scientific fields, wherever they are located.


    Liked by 1 person

    1. Hi Robert, long time no see! hope things are good. Perhaps the writing was not very clear. What I was trying to say is to set back the walls in a way that outside the walls tidal flats can recover, hence the listening to marine biologists suggestion. As for the height, I’m not advocating for higher walls, if anything the opposite. By setting walls back, first you gain some natural height from the slope of the terrain, the remaining altitude should be able to protect the town from more frequent, say 1 in 50 years perhaps, that wall should not be that high and it could be integrated somehow in the landscape with good design. I just edited the text to make that point clear.


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