Environmental Engineering Reference
In-Depth Information
Elevated
prefectural road (6m)
Affected
Ratio
Tsunami flow depth
(meter)
0.0-0.2
0.0-1.0
5.1-6.0
6.1-7.0
7.1-8.0
8.1-9.0
9.1->10.0
0.2-0.4
0.4-0.6
0.6-0.8
0.8-1.0
Tohoku
express
way
1.1-2.0
2.1-3.0
3.1-4.0
4.1-5.0
0
2.5
5
10 Kilometers
0
2.5
5
10
Kilometers
Fig. 10.9
The affected ratio (
left
) and the maximum simulated tsunami fl ow depth (
right
) of the
Sendai plain by considering the new land use
there is almost no settlement remaining in the tsunami-affected area. The new land
use will apply multi-layer tsunami protection, which consists of 7.2 m high coastal
dikes and 6 m high elevated roads for areas located 1 km from the shore and the
existing Tohoku expressway (Fig.
10.9
). The confi guration and design height of
these structural protections are determined based on the simulation of the 2011
Japan tsunami, using the earthquake scenario from Imamura et al. (
2012
). The
numerical simulations for both the existing and future topographic conditions con-
ducted by Koshimura et al. (
2013
) show that the multiple barriers reduce the tsu-
nami energy signifi cantly. Thus, the remaining waves are expected to be less than
2 m high if the tsunami overtops the elevated prefectural road (Sendai Reconstruction
Bureau
2011
).
By taking into account the existence of the multiple barriers in the topographic
input for numerical model, we obtained a pattern consistent with the research men-
tioned previously. With the assumption that the barriers withstand the tsunami, the
simulated tsunami inundations from scenarios of M 8 and M 9 class earthquakes,
excluding the 2011 event, were localized to the area between the coastline and the
elevated prefectural road. However, in contrast with the previous research
(Koshimura et al.
2013
), our simulated tsunami inundations (other than the 2011
event) indicated that tsunamis from M 9 class earthquakes could still penetrate up
to the maximum inundation distance of the 2011 East Japan event, even if the mul-
tiple barriers functioned properly (Fig.
10.9
). In this case, it should be noted that
there are always uncertainties in simulated tsunami heights and fl ow depths. The
recent study of MacInnes et al. (
2013
) argued that variable results could be obtained
if modelers use different slip distributions to model a tsunami. Additionally, the
probability of the barriers being damaged by the tsunami is not included in the
numerical model, as indicated in Koshimura et al. (
2013
). In this sense, estimating
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