Sense of the Tsunami

March 27th, 2011

A new video has been released of the tsunami hitting the town of Kesennuma in Miyagi prefecture. This video has both good and bad points. The good point is that, more than any other video I have seen, it gives an excellent understanding of how high the tsunami swelled. Most people think of a tsunami as a wave, like surfers might ride–a wall of water–and so are confused when they see images of what looks to be a swift tide that seems shallow. The wave, in fact, appears very flat, a spillage more than a wave, but builds gradually but strongly. Note the building just at the (old) shore with the green roof and how it is eventually swamped. You can tell the person taking the video is on very high ground near the shore, but near the end it feels like the water might reach even them.

The bad point about the video is, as with most amateur videos of this length and scope, you become frustrated with where the person taking the video is pointing the camera, especially when you know the water is swamping a car lot and crushing a row of buildings just to the right, but the person filming stays focused on the area that has already been covered with water. So you miss a good sense of how the more central areas of the town were inundated and what the forces of the incoming water did to more than just the coast–but you do see enough to get an even greater deal of respect for exactly how powerful this wave was, and how deep it got.

  1. Troy
    March 27th, 2011 at 15:06 | #1

    Japanese needs a new word to describe this, ‘large harbor wave’ doesn’t really describe it.

    We saw the same dynamic with the 2004 Indonesian tsunami, how the water level just rose & rose.

    All these coastal coves are basically rias, which are partially-flooded river valleys (during the ice age the streams that cut these coves extended further out, and the sea floor is still eroded by that. The trainline of this area is even called Minami Rias Line三陸鉄道南リアス線

    This serves as a funnel that produces very high and powerful water surges as the water is pushed into the cove.

    Perhaps we should resurrect the old word ‘tidal wave’ to describe this, waves that come in like a tide.

    Aside from all the people and pets becoming overcome by the water, seeing everything everyone worked lifetimes for obliterated in just a few minutes is also very horrible.

    It is estimated that there is $250B worth of economic losses here. I wonder if the ~50M people not affected are willing to pitch in $5000 each to put these people’s lives back together.

    Japan can try to borrow or print the money, but in the end this loss and reinvestment has to come from somewhere.

    Good to see that Tokyo is starting to cut back electricity usage 30% as a target — JR says it is now using 1500万kwh a day.

    Good article here:

  2. Frankie
    March 27th, 2011 at 17:52 | #2

    What can Japan do to protect itself from further earthquakes and especially tsunami. It’s going to happen again maybe 10, 20 or 30 years from now or even sooner?
    Japan will have to re-evaluate where homes can be build near the coast lines. The problem is that Japan has very limited flat terrain. Any suggestions?

  3. Troy
    March 27th, 2011 at 19:39 | #3

    Actually this was a once in 900-year tsunami. Back in 1960 there was a Chile EQ that sent a 3m tsunami to this area, and also major tsunamis in 1933 and 1896.

    If we want to have people pay for their own recovery, then we could institute mandatory tsunami insurance, perhaps provided by the government since no private company can probably be able to survive paying out indemnity burdens of mass destruction events, and it’s kinda dumb to just pay billions of dollars to a company for decades when the state is much better prepared to take on this risk over the long-term.

    So in the end the best thing would just be a higher tax rate on land values and business incomes in more dangerous areas, in essence a pre-payment for the future recovery investment that will have to be made eventually.

    To be fair, it would make sense to extend this to earthquake zones, though going by how Tokyo got through this earthquake, one wonders if earthquake insurance is necessary any more.

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