MONITORING OF GRAVEL NOURISHMENT ON MAKUHARI BEACH IN TOKYO BAY
Akio Kobayashi1, Takaaki Uda2 and Yasuhito Noshi1
On Makuhari Beach located in Tokyo Bay, an artificial beach was built in front of the reclaimed land in 1979, and
this beach was widely used for recreation. However, the beach had gradually been eroded. In 2009, a jetty was
extended in the middle of the beach, and 12,000 m 3 of gravel with the grain size of 4.2 mm was nourished on the
beach between the south and the central jetties. Although an artificial beach was produced in parallel with the seawall
line, the nourishment gravel was transported northward and was deposited to form a high berm in the northern part.
This movement of the nourishment gravel was investigated by field observation.
Keywords: gravel nourishment; Makuhari Beach; Tokyo Bay; field observation; longshore sand transport
INTRODUCTION
In recent years, gravel nourishment has been widely carried out in Japan because of the high
stability of the gravel beach against storm waves and its effectiveness as a measure against scouring as a
result of the deposition of the gravel at the toe of the seawall. Kumada et al. (2010) investigated the
effect of the beach nourishment using 87,000 m3 of gravel with the grain size ranging between 2.5 and
13 mm at the Jinkoji coast originally composed of fine sand. They found by an excavation test that
alternate layers of sand and gravel were formed instead of the uniform deposition of nourishment gravel,
and they assumed that the deposition of fine sand over the gravel layer was caused by shoreward sand
transport under calm wave conditions. Ishikawa et al. (2011) investigated beach changes after an
extensive nourishment using 3.5×105 m3 of a mixture of sand and gravel at the Hamamatsu-shinohara
coast facing the Pacific Ocean, and they showed their effectiveness. Ishikawa et al. (2012) further
proposed the moving gravel body method using the contour-line change model, in which the change in
grain size is evaluated as the change in the equilibrium slope. They showed that when coarse material is
nourished on sandy beaches with a predominant longshore sand transport, the downcoast of the
nourishment area is eroded, because the movability of gravel is much smaller than that of sand, and
gravel is preferentially deposited on the foreshore. However, the deposition of the gravel while
maintaining the mixture conditions is still unknown and has not yet been sufficiently investigated. On
Makuhari Beach located in Tokyo Bay, an artificial beach was built in front of reclaimed land in 1979,
and this beach was widely used for recreation. However, the beach had gradually been eroded. In 2009,
a jetty was extended in the middle of the beach and 12,000 m3 of gravel of 4.2 mm grain size was added
between the jetties. Although the artificial beach was widened particularly in the south part of the study
area for the shoreline to be parallel to the seawall, the nourishment gravel was transported northward
and was deposited to form a high berm in the north part of the study area. In this study, this movement
of nourishment gravel was investigated by field observation.
METHOD OF FIELD OBSERVATION
The study area is Makuhari Beach located in Tokyo Bay, as shown in Figs. 1 and 2, where jetties
were constructed at the south and north ends at 1,820 m intervals in front of the reclaimed land, and
beach nourishment of 2.38×106 m3 using fine sand of d = 0.184 mm, which was dredged from the
offshore bottom in Tokyo Bay, was carried out between the jetties by 1979. Because the beach was
gradually eroded after the construction of the original beach because of the predominant northward
longshore sand transport generated by waves obliquely incident to the direction normal to the shoreline,
another jetty of a 82 m length and with a crown height of +1.87 m above the mean sea level (MSL) was
extended between the jetties by October 2009 as a measure against erosion, and gravel nourishment was
carried out between the south and the central jetties.
First, the long-term changes in the shoreline position of Makuhari Beach between 1980 and 2012
were investigated using aerial photographs, and then the shoreline changes since the gravel nourishment
were investigated in detail. Beach surveys were carried out along transects A, B, and C between the
south and the central jetties, as shown in Fig. 2, and the foreshore material was sampled at 200 grams at
each point on the beach surface along transects A, B, and C, on May 19, August 1, and October 31,
1
2
Nihon University, 7-24-1 Narashinodai, Funabashi, Chiba 274-8501, Japan
Head, Shore Protection Research, Public Works Research Center, 1-6-4 Taito, Taito, Tokyo 110-0016, Japan
1
2
COASTAL ENGINEERING 2016
N
Harumi
study area
Tokyo Bay
Kisarazu port
Futtsu Point
0
5
10
15
20 km
south jetty
gravel nourishment
A
0
B
central jetty
C
north jetty
Figure 1. Location of Makuhari Beach in Tokyo Bay.
200m
Figure 2. Aerial photograph of Makuhari Beach in 2010.
2012, and the distribution of the composition of grain size of the foreshore material was investigated.
Holes were excavated near the shoreline along each transect on May 19 and October 31, 2012, and the
depth change in the composition of the grain size was measured along with the measurement of the
deposition zone of gravel on the beach surface using a GPS on June 17, August 5, and October 25,
2012. The wave rose during the observation period between April 1, 2010 and September 1, 2012 was
obtained from the observation data at Chiba Port. As for the tide level of the study area, the high, mean,
and low water level (HWL, MWL, and LWL) are +0.97, ‒0.13, and ‒1.13 m above MSL, respectively.
LONG-TERM SHORELINE CHANGES AFTER INITIAL NOURISHMENT
Figure 3 shows aerial photographs of Makuhari Beach taken in 1980, 1990, 2000, and 2012 to
investigate the long-term shoreline changes. In 1980, an almost straight shoreline extended between the
jetties with alongshore variations in shoreline position to some extent. Thereafter, additional
nourishment using fine sand of 8.6×104 m3 was carried out between 1983 and 1986, so that no large
changes were observed in 1990. However, sand volume gradually decreased and additional nourishment
was further required in 1994 and 1999. Despite such additional nourishment, the shoreline retreated
north of the south jetty by 2000, while forming a concave shoreline, and sand was transported
northward and the low-tide shoreline advanced south of the north jetty.
By 2012, the central jetty was extended 500 m north of the south jetty and gravel nourishment was
carried out between the south and the central jetties. After the gravel nourishment, gravel was
transported northward and was deposited on the south side of the central jetty. At the same time, on the
north side of the central jetty, a concave shoreline was formed together with the advance of the low-tide
shoreline south of the north jetty.
Figure 4 shows the shorelines in 1980 and 2012 and long-term shoreline changes between them with
reference to that in 1980. The shoreline of this beach retreated in the entire area, implying loss of sand
owing to the offshore sand transport, which was caused because the initial slope was as steep as 1/20
compared with the equilibrium slope of fine sand, which is milder than approximately 1/30. After the
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COASTAL ENGINEERING 2016
north jetty
south jetty
(a) February 2, 1980
north jetty
south jetty
(b) January 5, 1990
north jetty
south jetty
(c) January 4, 2000
central jetty
north jetty
south jetty
(d) March 29, 2012
Figure 3. Aerial photographs of Makuhari Beach taken in 1980, 1990, 2000, and 2012.
construction of the central jetty, the shoreline locally advanced on the south side, whereas it retreated
on the north side. The fact that no large shoreline advance occurred near the north jetty, even though a
large amount of sand was transported northward and it is blocked by the north jetty (impermeable),
clearly shows that the sand transported northward discharged offshore along the north jetty. The
shoreline change, as shown in Fig. 4(b), also shows that the shoreline recession is large in the entire
beach with the loss of sand, and before the extension of the central jetty, the shoreline rotated
counterclockwise with a pivot at the intersection between the shoreline and the north jetty. After the
construction of the central jetty, the shoreline between the south and the central jetties and between the
central and the north jetties individually rotated counterclockwise.
The shoreline changes between 2009 and 2012 in the same area are shown in Fig. 5. In 2009, the
shoreline extended almost straight between the south and the north jetties except the vicinity of the
south jetty, where the shoreline was locally of concave shape, whereas the shoreline extended straight to
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COASTAL ENGINEERING 2016
(a) Shoreline configuration
岸沖方向距離Y（ｍ）
distance Y(m)
Cross-shore
岸沖方向距離（ｍ）
south jetty
north jetty
160
140
140
120
120
100
100
80
80
60
60
40
40
20
20
1980
2012
central jetty
00
3928
0
4128
200
4328
400
4528
600
4728
800
4928
1000
1200
沿岸方向距離（ｍ）
Longshore
distance X(m)
沿岸方向距離X（ｍ）
(b) Shoreline change
岸沖方向距離（ｍ）
汀線変化量　⊿Y（ｍ）
change ΔY(m)
Shoreline
south jetty
north jetty
20
160
Reference year: 1980
0
140
central jetty
120
-20
100
80
-40
60
1990
2000
1990
2012
40
-60
20
2012
-800
0
3920
200
4120
400
600
800
4320
4520
4720
沿岸方向距離（ｍ）
Longshore
distance X(m)
1000
4920
1200
5120
沿岸方向距離　X（ｍ）
Figure 4. Shoreline in 1980 and 2012, and long-term shoreline changes relative to the shoreline in 1980.
north jetty
south jetty
(a) January 2009
parking lot
0
500m
central jetty
north jetty
south jetty
(b) April 2010
parking lot
0
500m
Figure 5. Shoreline changes on Makuhari Beach between 2009 and 2012.
the north jetty with increasing beach width near the north jetty, implying the predominance of
northward longshore sand transport under the obliquely incident waves counterclockwise relative to the
direction normal to the shoreline. Furthermore, although a parking lot was constructed behind the south
jetty in parallel with the shoreline, as shown in the aerial photograph taken in 2009, the distance
between the north end of the parking lot and the shoreline was as narrow as 40 m, showing a high
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COASTAL ENGINEERING 2016
north jetty
south jetty
(c) January 2011
central jetty
parking lot
0
500m
Ｃ
Ｂ
north jetty
south jetty
(d) March 2012
Ａ central jetty
parking lot
0
500m
Figure 5. Shoreline changes on Makuhari Beach between 2009 and 2012 (continued).
possibility of wave overtopping to the parking lot. As a measure against the wave overtopping, a central
jetty was constructed 500 m north of the south jetty, and gravel nourishment was carried out between
the south and the central jetties by 2010. Because of the black color of the gravel, a band showing the
deposition area of the gravel along the shoreline can be observed in the aerial photograph taken in April
26, 2010. Then, nourishment gravel in front of the parking lot was transported northward by January 27,
2011, and most gravel was deposited south of the central jetty and part of the gravel was deposited on
the crown of the central jetty.
RESULTS OF FIELD OBSERVATIONS
Wave Rose during the Observation Period
Figure 6 shows the significant wave height and wave period at every hour between April 2010 and
July 2012 measured off Chiba Port. The wave height is relatively low compared with that on beaches
exposed to the open sea, because Makuhari Beach is located deep in Tokyo Bay. When selecting the
significant wave height H1/3 of 2.0 m as the lower limit of the extreme wave height in the observation
period, a wave height larger than this critical wave height was observed only four times in 2010, but
thereafter, the number of occasions increased by 16 and 27 times in 2011 and 2012, respectively. The
2.5
2.5
H1/3=2m
1.5
1.5
1/3
HH
1/3 (m)
(m)
2.0
2.0
1.0
1.0
0.5
0.5
0.0
0.0
10
10
T1/3 (s)
T1/3(s)
88
66
44
22
00
2010/4/1
Apr.
July
Oct.
Apr.
July
Oct.
Apr.
July
2010/6/30 2010/9/28 2010/12/27 2011/3/27 2011/6/25 2011/9/23 2011/12/22 2012/3/21 2012/6/19
2010
2011
2012
Figure 6. Wave rose between April 2010 and July 2012 measured off Chiba Port.
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COASTAL ENGINEERING 2016
maximum value of H1/3 in the observation period was 2.37 m, and the mean H1/3 of waves with the
significant wave height larger than 2 m was 2.18 m. The wave period varied between 2 and 4 s, with a
rare case of a long period of 8 s corresponding to the occurrence of storm waves.
Deposition of Gravel and Profile Changes
Figure 7 shows the changes in beach condition in the area south of the central jetty between May 30
and October 8 in 2012, together with the shoreline on May 30 by the dotted line. It is seen that the
shoreline markedly advanced immediately south of the central jetty, and a large amount of gravel (black
(a) May 30, 2012
central jetty
(b) October 8, 2012
central jetty
Figure 7. Changes in beach condition in area south of central jetty between May 30 and October 8 in 2012.
change ΔY(m)
Shoreline
汀線変化量⊿Y(m)
south jetty
central jetty
15
10
5
0
Referrence: March 29, 2012
-5
0
100
200
300
400
500
沿岸方向距離X(m)
Longshore distance X(m)
Figure 8. Change in shoreline position between March 29 and October 31, 2012.
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COASTAL ENGINEERING 2016
2012年6月17日
南 2012年8月5日
突
堤 2012年10月25日
A B
南
突
堤
A
C中
B
2012年6月17日
June 17, 2012
2012年6月17日
2012年8月5日
August 5, 2012
2012年8月5日
October 25, 2012
2012年10月25日
2012年10月25日
B C
A
央
突
堤
0
200m
central jetty
南
突
堤
south jetty
color) was deposited on the beach surface near the jetty with berm formation. Figure 8 shows the
change in shoreline position between March 29, 2012 and October 31, 2012. Although the shoreline
had an irregular variation with a wave length of approximately 100 m, similarly to a large cusp, a large
shoreline advance was observed on average in the north part between the south and the central jetties,
implying the predominance of northward longshore sand transport.
Figure 9 shows the distribution of the deposition area of gravel on the beach surface measured using
a GPS. The deposition area of gravel was narrow in the south part, and the cross-shore width of the
deposition zone of gravel increased with the proximity of the central jetty, and gravel was deposited up
to the crown of the groin from the south side. Furthermore, the south end of the slender deposition zone
of gravel expanded southward between June 17 and August 5, but then it retreated northward on
October 25 with a variation, resulting in the narrowness of the deposition zone of gravel in the south
part. In contrast, the deposition zone of gravel monotonically expanded over time in the vicinity of the
central jetty.
Figure 10 shows the superimposed profiles along transects A, B, and C in each observation. Along
transect A near the south jetty, although a scarp with a steep slope was formed near an elevation of 2 m
above MSL on May 19, 2012, sand was deposited to form a uniform slope by August 1, and the same
2012年6月17日
中
央 2012年8月5日
南 突
突 堤 2012年10月25日
堤
A B
C
中
央
突
堤
C中
央
突
Figure 9. Distribution of deposition area of gravel on beach surface.堤
Z(m)
Elevation
標高 Z(T.P.m)
(a) May 19, 2012
6
Transect B
Transect C
2
0
-2
0
20
(b) August 1, 2012
6
Z(m)
Elevation
標高 Z(T.P.m)
Transect A
2.52m
4
40
60
80
沖向き距離 Y（m)
Transect A
2.53m
4
Transect B
Transect C
2
0
-2
0
20
40
60
80
沖向き距離 Y（m)
Z(m)
Elevation
標高 Z(T.P.m)
(c) October 31, 2012
6
2.50m
4
Transect A
Transect B
Transect C
2
0
-2
0
20
40
60
Longshore
distance
沖向き距離
Y（m) Y(m)
80
Figure 10. Temporal changes in longitudinal profiles along transects A, B, and C between May 19, 2012
and October 31, 2012.
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COASTAL ENGINEERING 2016
0
標高 Z(T.P.m)
-2
6 0
4
2
0
標高 Z(T.P.m)
-2
6 0
4
2
0
-2
Elevation
Z(m)
標高 Z(T.P.m)
2
6
5月19日
May 19,5月19日
2012
4
Oct. 31, 10月31日
2012
10月31日
2
0
-2
0
20
20
6
40
60
80
沖向き距離 Y（m)
(b) Transect B
Elevation
Z(m)
標高 Z(T.P.m)
4
(a) Transect A
40
60
沖向き距離 Y（m)
80
5月19日
May 19,5月19日
2012
4
10月31日
Oct. 31, 10月31日
2012
2
0
-2
0
20
20
6
40
60
80
沖向き距離 Y（m)
(c) Transect C
Elevation
Z(m)
標高 Z(T.P.m)
標高 Z(T.P.m)
6
40
60
沖向き距離 Y（m)
80
5月19日
May 19,5月19日
2012
4
10月31日
Oct. 31,10月31日
2012
2
0
-2
0
20
40
60
80
沖向き距離
Y（m)
Longshore
distance
Y(m)
Figure 11. Temporal
in longitudinal
0 changes20
40profiles along
60 transects A,80B, and C (May 19 vs October 31,
2012).
沖向き距離 Y（m)
uniform slope was maintained until October 31. Along transect B, a uniform slope was formed in every
occasion. The foreshore slope measured between Y = 20 and 40 m was constant: 1/10 (May 19), 1/10
(August 1), and 1/10 (October 31). Along transect C immediately south of the central jetty a wide berm
was formed with an upward convex profile. The berm height was constant: +2.52 m on May 19, 2.53 m
on August 1, and 2.50 m on October 31. The berm top moved seaward over time owing to the
successive deposition of gravel, as shown by arrows in Fig. 10, at Y = 16.8 m on May 19, 21.3 m on
August 1, and 22.5 m on October 31. The measured berm height was approximately 2.5 m, which was
close to the mean value of H1/3 (2.18 m) averaged over the observation period regarding the waves with
H1/3 larger than 2 m, as shown in Fig. 6.
Figure 11 shows the temporal change in longitudinal profiles along transects A, B, and C between
May 19 and October 31, 2012. Along transect A, the beach was eroded owing to the storm waves that
occurred in April and a scarp was formed at an elevation of +2 m, but sand was deposited, while
forming a foreshore of a uniform slope of 1/12 by October 31. Along transect B, located at the central
part, no profile changes occurred, while maintaining the same profile over time. Along transect C near
the central jetty, the longitudinal profile moved in parallel with each other, while maintaining a constant
berm height of 2.3 m, and beach material was deposited only in the area seaward of the berm top.
Change in Composition of Beach Material on Surface
As the results of the sieve analysis of the beach material sampled along transects A, B, and C, as
shown in Fig. 9, Fig. 12 shows the cross-shore distribution of the composition of the grain size of the
foreshore material sampled along transect A with the location of the sampling point of the beach
material. Along transect A, there existed a small-scale berm near Y = 37 m on May 19, 2012, and the
gravel content was relatively high at 35% near the berm top. However, the berm was eroded and a
uniform foreshore slope of approximately 1/12 was formed until August 1, resulting in a marked
decrease in the content of the gravel. Along transect A, the beach material is mainly composed of
medium-size sand, as shown in Fig. 12, and therefore shoreward sand transport is considered to occur
during storm waves in April 2012, and a concave profile was formed, as shown in Fig. 12. In contrast,
such profile changes did not occur along transects B and C because the beach face was covered with
gravel and offshore sand transport was difficult to occur, while maintaining upward convex profiles
owing to the deposition of gravel. The same condition continued on October 31, and the shoreline
advanced compared with that on May 19 owing to the deposition of medium-size sand with decreasing
volume of gravel. This means that gravel was transported away from the vicinity of transect A by
100
80
60
40
200
northward longshore sand transport.
シルト(～0.075mm)
細砂(0.075～0.25mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
dredge
point
中砂
細砂(0.075～0.25mm)
sand (0.075
– 0.25
mm) medium
size sand
(0.25
Sampling
point fine
中砂(0.
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
1-59cm1-59cm
60cm-60cmシルト(～0.075mm)
60cm表層
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
シルト(～0.075mm)
; fine
sand
(0.075
–0.25
0.25mm)
mm) medium
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
dredge point
6
粗砂
fine
sand
(0.075
–中砂(0.25～0.85mm)
size sand 粗砂(0.85～2mm)
(0.25 – 0.85 mm)粗砂(0.
coa
細砂(0.075～0.25mm)
シルト(～0.075mm)
1-59cm
60cm中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
表層
表層 1-59cm 60cmシルト(～0.075mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
; me dium
sand
(0.25
– 0.85
mm)
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
粗砂(0.85～2mm)
fine
sand (0.075 – 0.25 mm) medium
sizesize
sand
(0.25
– 0.85
mm)
coarse sand (0.85
– 2.0 mm) 礫(2mm
gravel
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
粗砂(0.85～2mm)
中砂(0.25～0.85mm)
礫(
シルト(～0.075mm) 4dredge point
粗砂(0.85～2mm)
礫(2mm～)
1-59cm 60cm80 808080
含有率（％）
含有率（％）
80
60
40
含有率（％）
含有率（％）
含有率（％）
75
50
25
60 606060
40 404040
20 202020
20
0 00 0
0
Y=19.2m
Y=19.2m
Y=27m
Y=19.2mY=32.6m
Y=32.6m
Y=19.2m
Y=27mY=35.9m
Y=32.6m
Y=35.9m
Y=32.6mY=40m
Y=27mY=27m
Y=35.9m
Y=40m
Y=32.6m
Y=27m
Y=35.9mY=44.1m
Y=44.1m
Y=35.9m
Y=44.1m
Y=40m Y=44.1m
Y=40mY=40m
Y=44.1m
Z=1.2m
Z=0.9m
Z=1.2m Z=0.6m
Z=0.6m
Z=0.9m Z=0.3m
Z=1.2mZ=1.2m
Z=0.3m
Z=0.9mZ=0.9m
Z=0.6mZ=-0.2m
Z=-0.2m
Z=0.9m
Z=0.6mZ=0.6m
Z=-0.2m
Z=-0.6m
Z=0.3mZ=-0.6m
Z=0.3mZ=0.3m
Z=-0.6m
Z=-0.2m Z=-0.6m
Z=-0.2m
Z=-0.6m
Y=19.2m
Z=1.2m
2
細砂(0.075～0.25mm)
fine
sand
(0.075 – 0.25 mm)
細砂(0.075～0.25mm)
; c oarse
sand(0.85
(0.85
2.0mm)
mm) 礫(2mm～)
粗砂(0.85～2mm)
礫(2mm～)
coarse
sand
––2.0
礫(2mm～)
gravel
(2.0 mm -)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
礫(2mm～)
中砂(0.25～0.85mm)
medium
size
sand (0.25 – 0.85 mm)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
0
; gravel
(2.0mm
mm-) -)
礫(2mm～)
gravel
(2.0
礫(2mm～)
礫(2mm～)
粗砂(0.85～2mm)
0.25mm)
75
– 0.25 mm)中砂(0.25～0.85mm)
medium
size sand (0.25 – 0.85
mm) 粗砂(0.85～2mm)
coarse
sand (0.85 – 2.0 mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
85mm)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
mm)
礫(2mm～)
礫(2mm～)
-2
0
礫(2mm～)
礫(2mm～)
礫(2mm～)
20
40
60
80
沖向き距離 Y（m)
(c) October 31, 2012
40
40 40
20 20
20
6
60 60
0 0
0
Y=21.9m
Z=1.7m
Y=35.3m
Z=0.5m
75
50
25
60
40
20
Y=21.Y=46.
Y=35.
3Y=35.
m9m 533mm
Y=35.
Z=1.5mZ=0.
7Z=0m
m 55mm
Z=0.
Z=0.
Y=35.Y=55.
Y=42.
0Y=42.
m3m 060mm
Y=42.
Z=0.1Z=-0.
5Z=0.
m 141mm
Z=0.
mZ=0.
Y=42.Y=46.
Y=46.
5Y=46.
m0m 5m5m
Z=0.1Z=0m
mZ=0m
Z=0m
Y=46.Y=55.
5m 6m6m
Y=55.
6mY=55.
Z=-0.
Z=-0.Z=0m
4mZ=-0.4m4m
Y=55.6m
Z=-0.4m
4
2
0
-2
100
100
8080
8080
60
60
40
40
20
20
0
0
6060
4040
6060
4040
2020
2020
00
00
Y=20.6m
Y=25.8m
Y=20.6m Y=32.3m
Y=32.3m
Y=25.8m Y=36.6m
Y=36.6m
Y=32.3m Y=46.3m
Y=36.6m Y=50.3m
Y=46.3m
Y=20.6m
Y=20.6m
Y=25.8m
Y=25.8m
Y=32.3m
Y=20.6mY=20.6m Y=25.8m
Y=25.8m Y=32.3m
Y=36.6m
Y=46.3m
Y=32.3m
Y=50.3mY=46.3m
Y=36.6m
Y=46.3m
Y=36.6m
Y=50.3m
Y=46.3m
Y=50.3m
Z=2.1m
Z=1.4m
Z=2.1m Z=0.9m
Z=0.9m
Z=1.4m Z=0.6m
Z=0.6m
Z=0.9m Z=-0.1m
Z=0.6m Z=-0.1m
Z=0.1m
Z=2.1mZ=1.4m Z=0.9m
Z=2.1m
Z=1.4mZ=0.9m
Z=1.4m
Z=0.9mZ=0.6m
Z=2.1mZ=2.1m Z=1.4m
Z=0.6mZ=0.1m
Z=0.1m
Z=-0.1mZ=0.1m
Z=0.1m
Z=0.6m
Z=-0.1m
Z=0.1m
Y=50.3m
Y=50.3m
Z=-0.1m
Z=-0.1m
4
2
0
-2
0
20
40
60
80
100
0
20
沖向き距離 Y（m)
40
60
80
沖向き距離 Y（m)
Longshore distance Y(m)
Longshore distance Y(m)
Figure 12. Cross-shore distribution of composition of grain size of foreshore material sampled along
100
80
60
40
transect A.
100
200100
80
100
60
80
40
60
80
200
表層
100100
100 100100100
100
80
60
40
200
10642
100
80
60
40
200 8
表層 1-5
シル
1-59cm
60cmシルト(～0.075mm)
表層
シルト(
60cm1-59cm
表層 1-59cm
1-59cm60cm60cm表層
表層
シルト(～0.075mm)
細砂
1-59cm 60cm60cmシルト(～0.075mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
細砂(0
表層 シルト(～0.075mm)
1-59cm
60cm表層
1-59cm
1-59cm
60cm表層
200
100
80
60
40
100
20
80
60
40
100
20
80
60
40
20
000
Transect B
(a) May 19,
2012
100
80
60
40
200 100
40
80
200
60
100
40
200 60
40
200
シルト(～0.075mm)
細砂(0.075～0.25mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
dredge
point
中砂
細砂(0.075～0.25mm)
sand (0.075
– 0.25
mm) medium
size sand
(0.25
Sampling
point fine
中砂(0.
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
1-59cm1-59cm
60cm-60cmシルト(～0.075mm)
表層
60cm細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
シルト(～0.075mm)
6
; fine
sand
(0.075
–0.25
0.25mm)
mm) medium
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
dredge point
粗砂
fine
sand
(0.075
–中砂(0.25～0.85mm)
size sand 粗砂(0.85～2mm)
(0.25 – 0.85 mm)粗砂(0.
coa
細砂(0.075～0.25mm)
シルト(～0.075mm)
1-59cm
60cm中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
表層
表層 1-59cm 60cm4
シルト(～0.075mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
; me dium
sand
(0.25
– 0.85
mm)
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
粗砂(0.85～2mm)
fine
sand (0.075 – 0.25 mm) medium
sizesize
sand
(0.25
– 0.85
mm)
coarse sand (0.85
– 2.0 mm) 礫(2mm
gravel
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
粗砂(0.85～2mm)
中砂(0.25～0.85mm)
礫(
シルト(～0.075mm) dredge point
粗砂(0.85～2mm)
礫(2mm～)
1-59cm 60cm75
50
25
80 80 80 808080
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
80
含有率（％）
60 60 60 606060
60
40 40 40 404040
40
20 20 20 202020
20
0 0 0 00 0
0
2
細砂(0.075～0.25mm)
fine
sand
(0.075 – 0.25 mm)
細砂(0.075～0.25mm)
Y=19.3m
Y=19.3m
Y=25.6m
Y=25.6m
Y=33.0m
Y=19.3m
Y=33.0m
Y=36.0m
Y=25.6m
Y=19.3m
Y=36.0m
Y=39.6m
Y=33.0m
Y=25.6m
Y=39.6m
Y=42.4m
Y=36.0m
Y=33.0m
Y=42.4m
Y=45.1m
Y=39.6m
Y=42.4m
Y=36.0m
Y=45.1m
Y=45.1m
Y=39.6m
Y=42.4m
Y=45.1m
Y=19.3m
Y=25.6m
Y=33.0m
Y=25.6m
Y=19.3m Y=19.3m
Y=36.0m
Y=33.0m
Y=39.6m
Y=25.6m
Y=36.0m
Y=42.4m
Y=33.0m
Y=39.6m
Y=45.1m
Y=36.0m
Y=42.4m
Y=39.6m
Y=45.1m
Y=42.4m
Y=45.1m
Z=1.8m
Z=1.8m
Z=1.6m
Z=1.6m
Z=1.0m
Z=1.8m
Z=1.0m
Z=0.5m
Z=1.6m
Z=1.8m
Z=0.5m
Z=1.0m
Z=0 Z=0Z=0
Z=1.6m
Z=0.5m
Z=-0.5m
Z=-0.8m
Z=1.0m
Z=-0.5m
Z=-0.8m
Z=0.5m
Z=-0.8m
Z=0Z=-0.5m
Z=-0.5m
Z=-0.8m
Z=1.8m
Z=1.6m
Z=1.0m
Z=1.6m
Z=1.8m Z=1.8m
Z=0.5m
Z=1.0m
Z=1.6m
Z=0
Z=-0.5m
Z=0.5m
Z=1.0m
Z=-0.8m
Z=0.5m
Z=0
Z=-0.5m
Z=0
Z=-0.8m
Z=-0.5m
Z=-0.8m
; c oarse
sand(0.85
(0.85
2.0mm)
mm) 礫(2mm～)
粗砂(0.85～2mm)
礫(2mm～)
coarse
sand
––2.0
礫(2mm～)
gravel
(2.0 mm -)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
礫(2mm～)
中砂(0.25～0.85mm)
medium
size
sand (0.25 – 0.85 mm)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
0
; gravel
(2.0mm
mm-) -)
礫(2mm～)
gravel
(2.0
礫(2mm～)
礫(2mm～)
粗砂(0.85～2mm)
0.25mm)
75
– 0.25 mm)中砂(0.25～0.85mm)
medium
size sand (0.25 – 0.85
mm) 粗砂(0.85～2mm)
coarse
sand (0.85 – 2.0 mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
0
礫(2mm～)
礫(2mm～)
礫(2mm～)
20
40
60
80
沖向き距離 Y（m)
(b) August 1, 2012
40
4040
(c) October 31, 2012
75
50
25
60
40
20
20
20
2020
20
0
0
0
00
0
Y=15.1m
Y=22.4m
Y=15.1mY=31.6m
Y=31.6m
Y=22.4m
Y=38.0m
Y=31.6m
Y=15.1mY=15.1m
Y=42.9m
Y=38.0m
Y=22.4mY=22.4m
Y=15.1mY=15.1m Y=22.4m Y=22.4m
Y=42.9m
Y=31.6mY=31.6m
Y=53.3m
Y=38.0mY=38.0m
Y=38.0m
Y=42.9mY=42.9m
Y=31.6m
Y=42.9m
Y=53.3mY=53.3m
Y=38.0m
Y=53.3m
Y=42.9m
Y=53.3m
Z=2.3mZ=0.9m
Z=1.7m
Z=2.3m Z=0.9m
Z=0.9mZ=-0.7m
Z=1.7m
Z=0.9m
Z=2.3m Z=2.3m
Z=0mZ=-0.7mZ=-0.7m
Z=-0.6m
Z=1.7m Z=1.7m
Z=0m
Z=-0.6m
Z=2.3m Z=2.3m Z=1.7m Z=1.7m
Z=-0.7m
Z=0m Z=0m
Z=-0.6mZ=-0.6m
Z=0m Z=0.9m
Z=0.9m
Z=-0.6m
Z=0m
Z=-0.6m
Z=-0.7m
標高 Z(T.P.m)
4
2
0
-2
100
100
100 100
80
80
80
80 80
60
40
20
6
Y=53.3m
Z=-0.7m
100
0
60
40
20
60
40
20
0
0
Y=14m
Z=2.7m
Y=14mY=20.8m
Z=2.7Z=1.
m 9m
含有率（％）
80
6060
含有率（％）
100
8080
60
含有率（％）
40
100 100100
含有率（％）
40
60
含有率（％）
含有率（％）
6
60
80
80
80
含有率（％）
含有率（％）
100 100
75
50
25
含有率（％）
礫(2mm～)
礫(2mm～)
含有率（％）
粗砂(0.85～2mm)
粗砂(0.85～2mm)
Z(m)
Elevation
標高 Z(T.P.m)
85mm)
-2
含有率（％）
100
80
60
40
200100
80
60
40
200
Z(m)
elevation
標高 Z(T.P.m)
dge
point
5mm)
mm)
100
100
80
80
6
0
Y=21.Y=42.
9Y=21.
m 09mm
Z=1.7Z=0.
mZ=1.17mm
100 100
含有率（％）
含有率（％）
60
含有率（％）
含有率（％）
80
含有率（％）
100
80 80
含有率（％）
100 100
80
含有率（％）
含有率（％）
100
標高 Z(T.P.m)
Z(m)
Elevation
標高 Z(T.P.m)
75
50
25
含有率（％）
(b) August 1, 2012
含有率（％）
100
80
60
40
200100
80
60
40
200
dge
point
5mm)
層
10642
100
80
60
40
200 8
表層 1-5
シル
1-59cm
60cmシルト(～0.075mm)
表層
シルト(
60cm1-59cm
表層 1-59cm
1-59cm60cm60cm表層
表層
シルト(～0.075mm)
細砂
1-59cm 60cm60cmシルト(～0.075mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
細砂(0
表層 シルト(～0.075mm)
1-59cm
60cm表層
1-59cm
1-59cm
60cm表層
200
表層
100100
100 100
100
100
80
60
40
20
100
80
60
80
40
60
20
40
00100
200
100
80
60
40
200
100
80
60
40
100
20
80
60
40
100
20
80
60
40
20
000
Transect A
(a) May 19,
2012
100
80
60
40
200 100
60
40
80
200
Z(m)
Elevation
標高 Z(T.P.m)
層
9
COASTAL ENGINEERING 2016
60 60
40 40
20 20
0
0
Y=14m
Y=20.8m
Y=20.
Y=28.8m
8Y=28.8m
m Y=14mY=14m
Y=35.7m
Y=28.
8Y=35.7m
m Y=20.8mY=20.8m
Y=38.4m Y=38.4mY=38.4m
Y=35.
7Y=38.4m
m Y=28.8mY=28.8m
Y=38.
4m Y=35.7mY=35.7m
7Z=1.
m2mZ=0.
9Z=1.
m5mZ=0.
m1m5m Z=0.5mZ=0.5Z=0.
m 1m Z=0.1m Z=0.1m
Z=2.9mZ=1.
7m 2mZ=2.7mZ=2.Z=1.
9m 5mZ=1.9mZ=1.Z=0.
Z=1.
2m 1mZ=1.2mZ=1.Z=0.2Z=0.
4
2
0
-2
0
20
40
60
沖向き距離 Y（m)
80
Longshore distance Y(m)
100
0
20
40
60
80
沖向き距離 Y（m)
Longshore distance Y(m)
Figure 13. Cross-shore distribution of composition of grain size of foreshore material sampled along
transect B.
COASTAL ENGINEERING 2016
100
80
60
40
100
20
80
60
40
100
20
80
60
40
20
000
Transect C
(a) May 19,
2012
100
80
60
40
200 100
40
80
200
60
200
表層
100
100
100
100
100
100100 100
100
100
100
100
100
10642
100
80
60
40
200 8
表層 1-5
シル
1-59cm
60cmシルト(～0.075mm)
表層
シルト(
60cm1-59cm
表層 1-59cm
1-59cm60cm60cm表層
表層
シルト(～0.075mm)
細砂
1-59cm 60cm60cmシルト(～0.075mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
細砂(0
表層 シルト(～0.075mm)
1-59cm
60cm表層
1-59cm
1-59cm
60cm表層
100
80
60
40
200
80
80
8080
80 80 8080
8080
80
80
80
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
含有率（％）
60
60
6060
60 60 6060
6060
60
60
60
40
40
4040
40 40 4040
4040
40
40
40
20
20
2020
20 20 2020
2020
20
20
20
0 00000 0
0 0000 0
Y=16.0m
Y=19.3m
Y=16.0m
Y=22.4m
Y=19.3m
Y=16.0m
Y=26.4m
Y=22.4m
Y=19.3m
Y=31.9m
Y=26.4m
Y=22.4m
Y=39.1m
Y=16.0m
Y=31.9m
Y=26.4m
Y=16.0m
Y=43.4m
Y=19.3m
Y=39.1m
Y=31.9m
Y=19.3m
Y=46.4m
Y=22.4m
Y=43.4m
Y=39.1m
Y=50.8m
Y=26.4m
Y=16.0m
Y=46.4m
Y=43.4m
Y=26.4m
Y=16.0m
Y=22.4m
Y=31.9m
Y=55.7m
Y=19.3m
Y=50.8m
Y=46.4m
Y=16.0m
Y=19.3m
Y=31.9m
Y=22.4m
Y=39.1m
Y=58.7m
Y=55.7m
Y=50.8m
Y=16.0m
Y=19.3m
Y=22.4m
Y=39.1m
Y=26.4m
Y=43.4m
Y=61.5m
Y=58.7m
Y=55.7m
Y=19.3m
Y=16.0m
Y=22.4m
Y=26.4m
Y=43.4m
Y=31.9m
Y=46.4m
Y=62.9m
Y=61.5m
Y=58.7m
Y=16.0m
Y=22.4m
Y=19.3m
Y=26.4m
Y=31.9m
Y=50.8m
Y=62.9m
Y=61.5m
Y=65m
Y=16.0m
Y=19.3m
Y=22.4m
Y=26.4m
Y=31.9m
Y=39.1m
Y=46.4m
Y=55.7m
Y=62.9m
Y=67.9m
Y=65m
Y=19.3m
Y=22.4m
Y=26.4m
Y=31.9m
Y=39.1m
Y=43.4m
Y=50.8m
Y=58.7m
Y=67.9m
Y=65m
Y=22.4m
Y=31.9m
Y=26.4m
Y=39.1m
Y=43.4m
Y=46.4m
Y=55.7m
Y=61.5m
Y=67.9m
Y=26.4m
Y=39.1m
Y=31.9m
Y=46.4m
Y=43.4m
Y=50.8m
Y=58.7m
Y=62.9m
Y=43.4m
Y=31.9m
Y=39.1m
Y=50.8m
Y=46.4m
Y=55.7m
Y=61.5m
Y=65m
Y=46.4m
Y=39.1m
Y=43.4m
Y=55.7m
Y=61.5m
Y=50.8m
Y=58.7m
Y=62.9m
Y=67.9m
Y=50.8m
Y=65m
Y=43.4m
Y=46.4m
Y=62.9m
Y=58.7m
Y=55.7m
Y=61.5m
Y=65m
Y=55.7m
Y=67.9m
Y=46.4m
Y=50.8m
Y=61.5m
Y=65m
Y=58.7m
Y=67.9m
Y=62.9m
Y=58.7m
Y=50.8m
Y=55.7m
Y=67.9m
Y=62.9m
Y=61.5m
Y=65m
Y=61.5m
Y=55.7m
Y=58.7m
Y=65m
Y=67.9m
Y=62.9m
Y=62.9m
Y=58.7m
Y=61.5m
Y=67.9m
Y=65m
Y=61.5m
Y=62.9m
Y=67.9m
Y=62.9m
Y=65m
Y=65m
Y=67.9m
Y=67.9m
Y=16.0m
Y=16.0m
Y=19.3m
Y=22.4m
Y=22.4m
Y=26.4m
Y=26.4m
Y=31.9m
Y=31.9m
Y=39.1m
Y=39.1m
Y=43.4m
Y=43.4m
Y=46.4m
Y=46.4m
Y=50.8m
Y=50.8m
Y=55.7m
Y=55.7m
Y=58.7m
Y=58.7m
Y=61.5m
Y=62.9m
Z=3.4m
Z=3.0m
Z=3.4m
Z=2.3m
Z=3.0m
Z=3.4m
Z=2.2m
Z=2.3m
Z=3.0m
Z=2.5m
Z=2.2m
Z=2.3m
Z=2.4m
Z=3.4m
Z=2.5m
Z=2.2m
Z=3.4m
Z=2.2m
Z=3.0m
Z=2.4m
Z=2.5m
Z=3.0m
Z=2.1m
Z=2.3m
Z=2.2m
Z=2.4m
Z=1.7m
Z=2.2m
Z=3.4m
Z=2.1m
Z=2.2m
Z=2.2m
Z=3.4m
Z=2.3m
Z=2.5m
Z=1.2m
Z=3.0m
Z=1.7m
Z=2.1m
Z=3.4m
Z=3.0m
Z=2.5m
Z=2.3m
Z=2.4m
Z=0.9m
Z=1.2m
Z=1.7m
Z=3.4m
Z=3.0m
Z=2.3m
Z=2.4m
Z=2.2m
Z=2.2m
Z=0.4m
Z=0.9m
Z=1.2m
Z=3.0m
Z=3.4m
Z=2.3m
Z=2.2m
Z=2.2m
Z=2.5m
Z=2.1m
Z=0.2m
Z=0.4m
Z=0.9m
Z=2.3m
Z=3.0m
Z=2.2m
Z=2.5m
Z=1.7m
Z=0.2m
Z=0.4m
Z=0m
Z=3.4m
Z=3.0m
Z=2.3m
Z=2.2m
Z=2.5m
Z=2.4m
Z=2.1m
Z=1.2m
Z=-0.3m
Z=0.2m
Z=0m
Z=3.0m
Z=2.3m
Z=2.2m
Z=2.5m
Z=2.4m
Z=2.2m
Z=1.7m
Z=0.9m
Z=-0.3m
Z=0m
Z=2.3m
Z=2.5m
Z=2.2m
Z=2.4m
Z=2.2m
Z=2.1m
Z=1.2m
Z=0.4m
Z=-0.3m
Z=2.2m
Z=2.4m
Z=2.5m
Z=2.1m
Z=2.2m
Z=1.7m
Z=0.9m
Z=0.2m
Z=2.2m
Z=2.5m
Z=2.4m
Z=1.7m
Z=2.1m
Z=1.2m
Z=0.4m
Z=0m
Z=2.1m
Z=2.4m
Z=2.2m
Z=1.2m
Z=0.4m
Z=1.7m
Z=0.9m
Z=0.2m
Z=-0.3m
Z=1.7m
Z=2.2m
Z=2.1m
Z=0.2m
Z=0.9m
Z=1.2m
Z=0.4m
Z=0m
Z=1.2m
Z=-0.3m
Z=2.1m
Z=1.7m
Z=0.4m
Z=0m
Z=-0.3m
Z=0.9m
Z=0.2m
Z=0.9m
Z=1.7m
Z=-0.3m
Z=1.2m
Z=0.2m
Z=0.4m
Z=0m
Z=0.4m
Z=1.2m
Z=0.9m
Z=0m
Z=-0.3m
Z=0.2m
Z=0.2m
Z=0.9m
Z=0.4m
Z=-0.3m
Z=0m
Z=0.4m
Z=0.2m
Z=-0.3m
Z=0.2m
Z=0m
Z=0m
Z=-0.3m
Z=-0.3m
Z=3.4m
Z=3.4m
Z=3.0m
Z=2.3m
Z=2.3m
Z=2.2m
Z=2.2m
Z=2.5m
Z=2.5m
Z=2.4m
Z=2.4m
Z=2.2m
Z=2.2m
Z=2.1m
Z=2.1m
Z=1.7m
Z=1.7m
Z=1.2m
Z=1.2m
Z=0.9m
Z=0.9m
Z=0.4m
Z=0.2m
2
細砂(0.075～0.25mm)
fine
sand
(0.075 – 0.25 mm)
細砂(0.075～0.25mm)
; c oarse
sand(0.85
(0.85
2.0mm)
mm) 礫(2mm～)
粗砂(0.85～2mm)
礫(2mm～)
coarse
sand
––2.0
礫(2mm～)
gravel
(2.0 mm -)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
礫(2mm～)
中砂(0.25～0.85mm)
medium
size
sand (0.25 – 0.85 mm)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
0
; gravel
(2.0mm
mm-) -)
礫(2mm～)
gravel
(2.0
礫(2mm～)
礫(2mm～)
粗砂(0.85～2mm)
0.25mm)
75
– 0.25 mm)中砂(0.25～0.85mm)
medium
size sand (0.25 – 0.85
mm) 粗砂(0.85～2mm)
coarse
sand (0.85 – 2.0 mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
0
礫(2mm～)
礫(2mm～)
礫(2mm～)
20
40
60
80
沖向き距離 Y（m)
6
100100 100100
100
80
8080 80 8080
60
40
20
0
0
Y=26.7m
Z=2.0m
75
50
25
4040 40 4040
40
20
(c) October 31, 2012
6060 60 6060
60
2020 20 2020
00 0
Y=26.7m
Y=35.3m
Z=2.0m
Z=2.5m
Y=35.3m
Y=60.7m
Z=2.5m
Z=1.1m
Y=60.7m
Y=64.8m
Z=1.1m
Z=0.7m
Y=26.7m
Y=35.3m
Y=60.7m
Y=26.7mY=26.7m
Y=35.3m
Y=64.8m
Y=35.3mY=35.3m
Y=60.7m
Y=26.7m
Y=60.7mY=60.7m
Y=67.2m
Y=64.8m
Y=35.3m
Y=64.8mY=64.8m
Y=69.9m
Y=67.2m
Y=60.7m
Y=67.2mY=67.2m
Y=69.9m
Y=74.7m
Y=64.8m
Y=69.9mY=69.9m
Y=74.7m
Y=64.8m
Y=67.2m
Y=74.7mY=74.7m
Y=67.2m
Y=69.9m
Y=67.2m Y=26.7m
Y=69.9m
Y=74.7m
Y=69.9m
Y=74.7m
Y=74.7m
Z=2.0m
Z=2.5m
Z=1.1m
Z=2.0m
Z=2.5m
Z=0.7m
Z=2.5m
Z=1.1m
Z=2.0m
Z=1.1mZ=1.1m
Z=0.3m
Z=0.7m
Z=2.5m
Z=0.7mZ=0.7m
Z=0.3m
Z=0mZ=0m Z=0m
Z=1.1m
Z=0.3mZ=0.3m
Z=-0.6m
Z=0m
Z=0.7m
Z=-0.6m
Z=0.7m
Z=-0.6mZ=-0.6m
Z=0.3m
Z=0.3m
Z=0m
Z=0.3m Z=2.0m
Z=0m Z=2.5m
Z=-0.6m
Z=0m Z=2.0m
Z=-0.6m
Z=-0.6m
標高 Z(T.P.m)
4
2
0
-2
100
100
100
100 100
80
80
80
8080 80
60
40
60
40
20
20
6
00
100
0
0
Y=28.2m
Z=2.2m
Y=28.2m Y=52.2m
Y=36.3m
Y=36.3m
Z=2.4mZ=2.2m Z=1.9mZ=2.4m
Y=52.2m
Y=62.9m
Z=0.7mZ=1.9m
60
40
含有率（％）
含有率（％）
100
80
含有率（％）
含有率（％）
含有率（％）
100
含有率（％）
含有率（％）
含有率（％）
75
50
25
含有率（％）
(b) August 1, 2012
含有率（％）
礫(2mm～)
礫(2mm～)
含有率（％）
粗砂(0.85～2mm)
粗砂(0.85～2mm)
Z(m)
Elevation
標高 Z(T.P.m)
85mm)
-2
含有率（％）
100
80
60
40
200100
80
60
40
200
含有率（％）
dge
point
5mm)
mm)
100
80
60
40
20
100
80
60
80
40
60
20
40
00100
200
100
80
60
40
200
シルト(～0.075mm)
細砂(0.075～0.25mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
dredge
point
中砂
細砂(0.075～0.25mm)
sand (0.075
– 0.25
mm) medium
size sand
(0.25
Sampling
point fine
中砂(0.
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
1-59cm1-59cm
60cm-60cmシルト(～0.075mm)
表層
60cm細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
シルト(～0.075mm)
6
; fine
sand
(0.075
–0.25
0.25mm)
mm) medium
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
dredge point
粗砂
fine
sand
(0.075
–中砂(0.25～0.85mm)
size sand 粗砂(0.85～2mm)
(0.25 – 0.85 mm)粗砂(0.
coa
細砂(0.075～0.25mm)
シルト(～0.075mm)
1-59cm
60cm中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
表層
表層 1-59cm 60cm4
シルト(～0.075mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
; me dium
sand
(0.25
– 0.85
mm)
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
粗砂(0.85～2mm)
fine
sand (0.075 – 0.25 mm) medium
sizesize
sand
(0.25
– 0.85
mm)
coarse sand (0.85
– 2.0 mm) 礫(2mm
gravel
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
粗砂(0.85～2mm)
中砂(0.25～0.85mm)
礫(
シルト(～0.075mm) dredge point
粗砂(0.85～2mm)
礫(2mm～)
1-59cm 60cm75
50
25
Z(m)
elevation
標高 Z(T.P.m)
層
10
6060 60
4040 40
20
2020 20
0
00 0
Y=28.2m
Y=28.2m
Y=28.2m Y=36.3m
Y=36.3m
Y=36.3m Y=52.2m
Y=52.2m
Y=52.2m
Y=62.9m
Y=52.2m
Y=62.9m
Y=65.7m
Y=62.9m
Y=65.7m Y=68.9m
Y=68.9m
Y=62.9mY=28.2m
Y=65.7m Y=62.9m
Y=68.9m
Y=65.7mY=36.3m Y=68.9m
Y=68.9m Y=65.7m
Y=65.7m
Y=68.9m
Z=2.2m
Z=2.2m
Z=2.2m Z=2.4m
Z=2.4m
Z=2.4m Z=1.9m
Z=1.9m
Z=1.9m
Z=0.7m
Z=1.9m
Z=0.7m Z=0.3m
Z=0.3m
Z=0.7m
Z=0.3m Z=-0.1m
Z=-0.1m
Z=0.3m Z=0.7m
Z=-0.1m
Z=-0.1m
Z=0.3mZ=0.7m Z=2.2mZ=-0.1mZ=0.3m Z=2.4m Z=-0.1m
4
2
0
-2
0
20
40
60
沖向き距離 Y（m)
80
Longshore distance Y(m)
100
0
20
40
60
80
沖向き距離 Y（m)
Longshore distance Y(m)
Figure 14. Cross-shore distribution of composition of grain size of foreshore material sampled along
transect C.
Along transect B, as shown in Fig. 13, the foreshore slope was as steep as 1/8 in a zone with the
elevation lower than 1 m above MSL on May 19, whereas a gentle slope of 1/10 was formed in the area
higher than 1 m above MSL. The composition of grain size corresponded well to the change in beach
slope, and the gravel content is high on the foreshore of the steep slope. Furthermore, gravel was
deposited only in the area with the elevation lower than 2 m above MSL along this transect.
Similarly, the longitudinal profile along transect C, where a large amount of gravel was deposited,
and the cross-shore distribution of the composition of foreshore material are shown in Fig. 14. Although
an upward convex profile had already formed with a berm of 2.52 m height by May 19 in the zone
seaward of Y = 24 m, the gravel content was less than 20% landward of this berm, whereas the gravel
content markedly increased over 60% seaward of this berm, suggesting that this berm was formed
mainly by the deposition of gravel, which was transported from the south part of the study area. The
same characteristics can be seen in the results on August 1 and October 31, showing that the gravel that
was transported by northward sand transport was successively deposited by the blockage by the central
jetty.
11
COASTAL ENGINEERING 2016
Results of Excavation Study
To investigate the deposition of gravel, vertical holes were excavated on May 19 and October 31,
2012 near the shoreline, as shown by arrows in Figs. 12‒14, and beach material was sampled vertically.
Figure 15 shows the depth distribution of composition of the beach material obtained by the excavation
test along transects A, B, and C on May 19, 2012. The grain size composition of the materials sampled
on the surface and at depths below the surface is shown. It is seen that the contents of gravel and coarse
sand on the surface increase from 65, 76, and 84% in the order of transects A, B, and C, respectively,
implying that coarse material was selectively transported northward and deposited near the shoreline.
The content of coarse material below the surface is small at transect A, whereas the content at transect
C is as large as 60%, while decreasing with depth. The decrease in the content of the coarse material
means that medium-size sand, which has a larger movability than gravel, was transported at the first
stage, and then the gravel content increased over time. Similarly, Fig. 16 shows the results of the
excavation study along transects A, B, and C on October 31, 2012. Because gravel was transported
away from transect A, the gravel content markedly decreased along this transect, whereas the content of
the coarse material is high owing to the successive deposition of the coarse material along transect C.
100
80
60
80
40
60
20
0 100
40
20
0
100
80
60
40
200
表層
100
80
60
40
20
0
100
80
60
40
100
20
80
0
60
40
20
100
80
60
40
20
00
1-59
表層 1-59cm
表層
シルト(～0.075mm)
1-59cm
60cm1-59cm 60cm表層
1-59cm 60cm- シルト(～0.075mm)
表層
60cm表層 1-59cm
シルト(～0.075mm)
シルト(～0.075mm)
1-59cm 60cm60cm表層 1-59cm
表層
シルト(～0.075mm)
1-59cm
60cmシルト(～0.075mm)
表層
1-59cm 60cm表層
シルト(～0.075mm)
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
シルト(～0.075mm)
1-59cm
60cm-60cm表層 表層
1-59cm
シルト(～0.075mm)
細砂(0.075～0.25mm)
100
80
60
40
20
0
100
80
60
40
80
20
60
0 100
40
20
0
100
80
60
20
0
100
80
60
40
20040
(%)
content
含有率（％）
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
1-59cm 60cm60cm細砂(0.075～0.25mm)
表層 1-59cm
中砂(0.25～0.85mm)
シルト(～0.075mm)
シルト(～0.075mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
細砂(0.075～0.25mm)
表層
;細砂(0.075～0.25mm)
finesand
sand(0.075
(0.075––0.25
0.25 mm)
mm)
fine
medium
size sand (0.25 – 0.85 mm) 粗砂(0.85～2mm)
coarse sand (0.85 – 2.0 mm
中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
60cm層 1-59cm シルト(～0.075mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
細砂(0.075～0.25mm)
;
medium
size
sand
(0.25
–
0.85
mm)
細砂(0.075～0.25mm)
fine sand (0.075 – 0.25 mm) medium
size sand (0.25 0.85 mm) 粗砂(0.85～2mm)
coarse sand (0.85 – 2.0 mm) 礫(2mm～)
gravel (2.0 mm -)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
礫(2mm～)
粗砂(0.85～2mm)
mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
細砂(0.075～0.25mm)
; coarsesand
sand(0.85
(0.85 –
細砂(0.075～0.25mm)
fine
sand (0.075 – 0.25 mm) medium
size sand (0.25 – 0.85 mm) 粗砂(0.85～2mm)
coarse
– 2.0
2.0mm)
mm) 礫(2mm～)
gravel礫(2mm～)
(2.0 mm -)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
礫(2mm～)
;gravel
gravel(2.0
(2.0 mm
.25mm)
5 – 0.25 mm) 中砂(0.25～0.85mm)
medium
size sand (0.25 – 0.85 mm) 粗砂(0.85～2mm)
coarse sand (0.85 – 2.0 mm) 礫(2mm～)
礫(2mm～)
mm -)-)
中砂(0.25～0.85mm)
Transect A
粗砂(0.85～2mm)
粗砂(0.85～2mm)
礫(2mm～)
礫(2mm～)
5mm)
礫(2mm～)
粗砂(0.85～2mm)
100
粗砂(0.85～2mm)
礫(2mm～)
礫(2mm～)
80
m)
礫(2mm～)
礫(2mm～)
60
40
20
0
surface
表層
2-24cm
surface
表層
3-45cm
Transect B
(%)
content
含有率（％）
100
80
60
40
20
0
Transect C
100
content (%)
含有率（％）
100
80
60
40
20
100
80
60
40
20
00
80
60
40
20
0
surface
表層
20-26cm 29-40cm
Figure 15. Depth distribution of composition of beach material along transects A, B, and C on May 19,
2012.
5mm)
m)
(%)
content
含有率（％）
.25mm)
5 – 0.25 mm)
12
1-59
表層 1-59cm
表層
シルト(～0.075mm)
1-59cm
60cm1-59cm 60cm表層
1-59cm 60cm- シルト(～0.075mm)
表層
60cmシルト(～0.075mm)
シルト(～0.075mm)
60cm60cmシルト(～0.075mm)
60cm-
40
20
0
surface
表層
15-22cm
Transect B
100
含有率（％）
(%)
content
1-59cm
100
80
60
20
0
100
80
60
40
20040
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
1-59cm 60cm60cm細砂(0.075～0.25mm)
表層 1-59cm
中砂(0.25～0.85mm)
シルト(～0.075mm)
シルト(～0.075mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
細砂(0.075～0.25mm)
表層
;細砂(0.075～0.25mm)
finesand
sand(0.075
(0.075––0.25
0.25 mm)
mm)
fine
medium
size sand (0.25 – 0.85 mm) 粗砂(0.85～2mm)
coarse sand (0.85 – 2.0 mm
中砂(0.25～0.85mm)
細砂(0.075～0.25mm)
中砂(0.25～0.85mm)
シルト(～0.075mm)
60cmシルト(～0.075mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
細砂(0.075～0.25mm)
; mediumsize
sizesand
sand(0.25
(0.25 – 0.85
細砂(0.075～0.25mm)
fine
sand (0.075 – 0.25 mm) medium
0.85mm)
mm) 粗砂(0.85～2mm)
coarse sand (0.85 – 2.0 mm) 礫(2mm～)
gravel (2.0 mm -)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
礫(2mm～)
粗砂(0.85～2mm)
中砂(0.25～0.85mm)
粗砂(0.85～2mm)
細砂(0.075～0.25mm)
; coarsesand
sand(0.85
(0.85 –
細砂(0.075～0.25mm)
fine
sand (0.075 – 0.25 mm) medium
size sand (0.25 – 0.85 mm) 粗砂(0.85～2mm)
coarse
– 2.0
2.0mm)
mm) 礫(2mm～)
gravel
(2.0
mm
-)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
礫(2mm～)
粗砂(0.85～2mm)
粗砂(0.85～2mm)
礫(2mm～)
;gravel
gravel(2.0
(2.0 mm
medium
size sand (0.25 – 0.85 mm) 粗砂(0.85～2mm)
coarse sand (0.85 – 2.0 mm) 礫(2mm～)
礫(2mm～)
mm -)-)
中砂(0.25～0.85mm)
中砂(0.25～0.85mm)
Transect A
粗砂(0.85～2mm)
粗砂(0.85～2mm)
礫(2mm～)
礫(2mm～)
礫(2mm～)
粗砂(0.85～2mm)
100
粗砂(0.85～2mm)
礫(2mm～)
礫(2mm～)
80
礫(2mm～)
礫(2mm～)
60
100
80
60
40
20
100
80
60
40
20
00
mm)
表層 1-59cm
1-59cm
表層 1-59cm
表層
1-59cm
シルト(～0.075mm)
表層
COASTAL
ENGINEERING
2016
1-59cm
60cm表層
シルト(～0.075mm)
シルト(～0.075mm)
1-59cm
60cm-60cm表層 表層
1-59cm
シルト(～0.075mm)
シルト(～0.075mm)
細砂(0.075～0.25mm)
100
80
60
40
20
0
100
80
60
40
80
20
60
0 100
40
20
0
80
60
40
20
0
surface
表層
4-10cm
surface
表層
15-20cm 22-28cm
10-21cm
Transect C
100
含有率（％）
content (%)
層
100
80
60
40
20
0
100
80
60
40
100
20
80
0
60
40
20
100
80
60
40
20
00
100
80
60
80
40
60
20
0 100
40
20
0
100
80
60
40
200
表層
80
60
40
20
0
Figure 16. Depth distribution of composition of beach material along transects A, B, and C on October
31, 2012.
CONCLUSIONS
A monitoring survey after a gravel nourishment at Makuhari Beach showed that nourishment gravel
moved along the shoreline and was deposited on the foreshore, while forming a thick gravel layer south
of the central jetty and a berm of 2.5 m height above MSL. Ishikawa et al. (2011) investigated the effect
of beach nourishment using gravel by tracking the movement of gravel on the Hamamatsu-shinohara
coast, which is composed of fine and medium-size sand and that westward longshore sand transport
prevails. Because this coast had an open boundary on the west side of the study area, the coarse
material was transported westward with the gradual mixing with fine and medium-size sand, and the
thickness of the mixing layer decreased with the westward distance. Makuhari Beach is separated by the
south and central jetties, and has a closed system of sand movement, although originally northward
longshore sand transport prevails. After the gravel nourishment, nourishment gravel was transported
northward, and gravel was successively deposited on the beach surface south of the central jetty,
forming a thick gravel layer. The gravel nourishment on this coast was carried out as a measure against
erosion in front of the parking lot where the foreshore width was narrowed by the successive erosion
immediately north of the south jetty, while anticipating the stability of gravel. However, even though
the diameter of the nourishment material is large, such material could be transported by longshore sand
transport particularly under the storm wave conditions, and it was ineffective in widening the narrow
foreshore, although the beach nourishment itself was useful for increasing the entire volume of the
beach.
REFERENCES
Ishikawa, T., T. Uda, and T. San-nami. 2011. Effect of beach nourishment using gravel and tracking
movement of gravel, Asian and Pacific Coasts 2011, Proc. 6th International Conf., 191-198.
COASTAL ENGINEERING 2016
13
Ishikawa, T., T. Uda, and S. Miyahara. 2012. Moving gravel body method to control downcoast erosion,
Proceedings of 33rd International Conference on Coastal Engineering, ASCE, management.40, 114.
Kumada, T., T. Uda, T. Matsu-ura, and M. Sumiya. 2010. Field experiment on beach nourishment using
gravel at Jinkoji coast, Proceedings of 32nd International Conference on Coastal Engineering,
ASCE, sediment.100, 1-13.