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Fig. 15.2
Orthorectifi ed aerial photographs of coastal areas in September 2006, March 2011, June
2011, March 2012, June 2012, November 2012, and June 2013. -see Fig.
15.1
(Source: Tohoku
Regional Bureau and GeoEye satellite image (
©
Digital Globe))
longshore direction behind the seawall and at the same time, sediment deposition
was notable just behind the water channels (Figs.
15.1c
,
15.2c
, and
15.3a
). In Area
D, the longshore water channels expanded even further compared to Area C and the
entire beach disappeared seaward of the seawall crevasse (Figs.
15.1d
,
15.2d
, and
15.3b
). Erosion was severer in the southern coast, especially in Area D where beach
erosion was also signifi cant in the past. Further, the old river channel was eroded in
Area A (Tanaka et al.
2012
; Tappin et al.
2012
). In Area B, the sandbanks were
eroded (Figs.
15.1b
and
15.2b
).
Nearshore morphology changes due to the tsunami in the period from September
2010 to April 2011 were greater than other periods and the erosion reached contour
lines deeper than 10-15 m in the whole study area (Figs.
15.1
and
15.4
). It should
be noted that the closure depth due to storm waves is reported to be 8 m or 15 m
(Widyaningtias et al.
2013
) and the depth due to the tsunami was deeper than that
due to storm waves. Deposition with a width of more than 0.5 km expanded in the
longshore direction in Area C and D where the water depth was between 5 and
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