Shimizu Proposes Green Mounds for Tsunami Defense

Anti-tsunami mounds would be placed in vulnerable coastal communities.

Shimizu Corporation last week announced a proposal to build low-tech, low-cost “green mounds” in areas with an elevated risk of being struck by a tsunami. The hills, which would rise between 10 and 15 meters, would be constructed from last year’s tsunami debris and would serve primarily as an evacuation site that would delay the entry of tsunamis. The structure of the mounds, the company states, would absorb the force of the tsunami, rather than push against it the way conventional seawalls are designed to do.

The mounds would come in 3 sizes – small, medium, and large. A small mound will accommodate 50 evacuees, would cost 100 million yen (about $1.3 million) and could be built in about 6 months. On the higher end, a large mound will accommodate 1,300 evacuees, would cost 500 million yen (about $6.3 million) and would take 18 months to build.


Below are some of the specs that the company lists:

Small Mound Medium Mound Large Mound
Height 10m 15m 15m
Evacuee Capacity 50 470 1300
Cost 100 million yen 250 million yen 500 million yen
Construction period 6 months 12 months 18 months

It’s hard to take this company serious given their history of large-scale imaginative yet wholly impractical proposals. However, this idea seems a bit more realistic than their 6,800 mile long “Luna Ring” of solar panels that wrap around the moon. Or their floating islands with cities in the sky.


  1. Actually I would point out floating cities are feasible, though totally impractical right now. Japanese architects in the 1960’s and onward have become the experts in floating reclamation technologies. You don’t have to look farther than Kenzo Tange’s proposal for Tokyo Bay in the 60’s which was fully documented and calculated to be a feasible solution for the overcrowding Tokyo.

  2. Shimizu is one of the largest architectural/engineering/contracting corporations in Japan, and even the world. I think they do enough real world work to indulge once in a while in more imaginative proposals – especially proposals that would be awesome if realized.

    Part of progress is building, another part is inspiring. Shimizu does both, and their proposals are indeed inspiring.

    Thanks for these links btw, yet another hidden gem uncovered on Spoon-Tamago.

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