Blogs from the Coastal Structures Team - Tohoku, Japan Earthquake and Tsunami of 2011 - page 87

Day7—Tuesday,May17
Figure A.16 COPRI team member Catherine Petroff observes how a
“yashkirin” vegetable barrier may have offered some protection to this
home from the ravages of the tsunami. (Source: Bryan N. Jones)
In our meeting with Professors Imamura and Sugarawa at Tohoku University
yesterday afternoon, they suggested that we view two particular sites for our last day
in the field. The first site was an example of a vegetative barrier south of Arahama
beach that may have mitigated flow damage to a block of homes. There are only a
few such barriers, called “yashkirin” (or “green house-belt”) in the Sendai Plain due
to the cost and effort to maintain, as well as the local custom to show off their houses
rather than hide them behind walls or vegetation.
While on site we had the opportunity to interview a Mr. Shibasaki, who was busy
cleaning out the interior of his house - one of the few left standing. He showed us an
aerial photograph of his house and yashkirin surrounded by fields before the event,
and explained that the barrier was originally constructed as a wind break for his
home. He also showed us that although the tsunami inundated his house to a depth of
approximately two meters, there was no major structural damage from the flow.
Our final stop on the survey was a coastal revetment at the beach adjacent to Sendai
Airport, where the tsunami run-up was surveyed by our Japanese colleagues at more
than ninr meters above the mean sea level. The revetment was five meters high and
was constructed of concrete units shaped like hourglasses that were two meters by
two meters by 0.6 meter thick. We measured the beach in front of the revetment at
100 meters wide. There was also a vegetated buffer of regularly-spaced pine trees on
the landward side of the revetment. The tsunami damage observed included a 5.3
meter deep by 4 meter wide continuous scour swale on the landward side of the
structure, which in turn caused several long sections of the revetment to fail.