Environmental Engineering Reference
In-Depth Information
Fig. 13.7
Tsunami survey at
the Nakoso Coast, Fukushima
Prefecture; Yellow zone
represents inundation. The
coastal area is divided into
fi ve districts, Iwama, Power
Plant, Ooshima, Suga and
Sekita Districts. The symbol
'A', 'B' and 'C' refers to
Fig.
13.9
the most predominant river in this area fl ows into the northern part of the Nakoso
Coast. About 1.5 km south of the Samegawa River, a small river, the Bindagawa
River, is located. A coal thermal power plant is located to the north of the Samegawa
River mouth. The yellow area in Fig.
13.7
represents the area inundated by the tsu-
nami, which covers a wide area in Iwama and Ooshima Districts located to the north
of the Samegawa River, Suga District between the Samegawa River and the
Bindagawa River and the Sekita District located to the south of the Bindagawa River.
13.2.2.1
Seawalls Performance
Field surveys were conducted twice on March 24-25 and April 1-2, 2011, 2-3
weeks after the tsunami attack (Sato et al.
2012
). On March 24-25, the survey was
focused on the general information of the tsunami damage, e.g
.
, tsunami inundation
height and run-up height, which were identifi ed from the mud-line watermark on
the wall or window of surviving buildings and the diffused debris on the slope
ground, respectively. On April 1-2, attention was focused on the performance of
seawalls and the relationship between the inundation area and the inland topogra-
phy. According to the inundated stopped clock found in the Iwama District, the
tsunami inundation time is 15:38 JST, approximately 1 h after the earthquake. A
video clip was taken from the top of a building of the power plant located to the
north of the Samegawa River. The clip recorded the arrival of the fi rst tsunami at
15:33 which overfl owed the seawall at 15:35 JST. The inundation level appeared to
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