JAPAN P& I CLUBVol.43 July 2018

P&I Loss Prevention Bulletin
The Japan Ship Owners Mutual Protection & Indemnity Association Loss Prevention and Ship Inspection Department

Dragging Anchor- Case Studies and Preventive Measures -Dragging Anchor- Case Studies and Preventive Measures ＩＮＤＥＸ§1 Introduction ................................................................................................................................................1§2 Typhoons
２−１ Definition of a typhoon (from the Japan Meteorological Agency website [available only in Japanese]) .....2
２−２ Number of typhoon landings (from the Japan Meteorological Agency website) ................................4
２−３ The paths and the wind speeds of the typhoons that landed in 2004 ....................................................5
２−４ Typhoon marine accidents in 2004 ..............................................................................................................7§3 Dragging Anchor Cases(From the Maritime Casualty Analysis Report [Vol.6]):
Typhoons and marine accidents issued by the Marine Accident Inquiry Agency [MAIA] in 2006)

３−１ The Aomori - Hakodate ferry “Touya Maru” accident .............................................................................12
３― ２ Cargo Vessel B Dragging anchor and grounding accident ..................................................................21
３― ３ Cargo Vessel C Dragging anchor and grounding accident ..................................................................26
３−４ Questionnaire conducted by the Marine Accident Inquiry Agency (MAIA)
for Masters of the coastal vessels that experienced sheltering from the typhoon................................36§4 Mechanism of dragging anchor
４−１ Accidents involving ships at anchorr ........................................................................................................... 38
４−２ The reasons as to why an anchor drags .....................................................................................................39
４−３ Detection of dragging anchorr .................................................................................................................... 42
４−４ Wind pressure force.......................................................................................................................................45
４−５ Holding power created by anchor and anchor cable ............................................................................47
４−６ Countermeasures to prevent an anchor from dragging in stormy weatherr ......................................... 51
４−７ Difficulty in maintaining manoeuvrability after dragging anchor has started .......................................58
４−８ Safe distance from other ships, shallows and other facilities ...................................................................59§5 Conclusion ..................................................................................................................................................62§1

Introduction

In the event of anchoring, it is common tocarry out single anchor mooring, using one of
the anchors outfitted on either side of the ship.
However, due to strong winds from typhoons orviolent storms, as a dragging anchor preventative
measure, one must be ready to drop the snubber
anchor on the opposite side (to the sea bottom),or carry out two-anchor mooring or ride at two
anchors.
In order to learn from the Aomori - Hakodate“Touya Maru” ferry accident that occurred on
26th September, 1954, the anchor dragging
mechanism, which will be introduced in §3 wasstudied and it was ascertained that once the JIS
type anchor started dragging, the holding powerof the anchor system was lost.
In addition, the Master decided on an anchoring
method and length of anchor chain needed toveer, taking the following into account: space
for anchorage, depth of the water, nature of thesea bottom, other ships’ anchoring situations,
expected maximum wind speed and tidal currents
etc. However, this has not led to a significant
decline in dragging anchor cases.
In 2012, we provided a lecture mainly focusing
on the technical aspects of preventing an anchor
from dragging and also issued the Loss Prevention
Bulletin No. 25.
This time, we are going to introduce typhoon anddragging anchor cases, referring to “Typhoons
and marine accidents” in the Maritime Casualty
Analysis Report (Vol. 6), that was issued by the
Marine Accident Inquiry Agency (MAIA) at thattime in 2006.

Snubber anchor

Riding at two anchorsTwo-anchor mooring

Fig. 1 Anchoring method

Photograph 2
AC14 type anchor−1−

Photograph 3
JIS type anchor§2Typhoons

Accidents due to a dragging anchor are not only caused by Typhoons, but also occur during gales. However, according
to statistics they predominantly occur when a typhoon has just passed. First, it is necessary to understand how
typhoons move.

２−１ Deﬁnition of a typhoon (from the Japan Meteorological
Agency website [available only in Japanese])
Typhoons are deﬁned as follows.

Deﬁnition:“Atmospheric depression that comes forth in the tropical ocean is called ‘tropicaldepression’. Among them, those which are found in the north-western part of the
Pacific Ocean (sea area to the north of the equator and west from 180 degrees
east longitude) or in the South China Sea, moreover, with a maximum wind speed
within the region of atmospheric depression (10 minutes average) of more thanapproximately 17m/s (34 knots and wind force 8) are called ‘typhoons’”.

A typhoon also has characteristics whereby it is moved by
the wind in the sky and heads north due to the rotation of theearth. Therefore, the typhoon gradually moves northward
while being blown to the west at a low latitude, where
regular easterly winds blow. Then, once it reaches middle
and high latitudes, where strong westerly winds (heights of 8
- 13km and speeds of approximately 100km/h) are in the air,
the typhoon proceeds north east at a high speed.
Also, regarding the force and the size of the typhoon which
we frequently hear of in weather forecasts and so on, theJapan Meteorological Agency expresses the “size” and“strength” of a typhoon based on the wind speed (at an
average within ten minutes). This can be seen in Tables 5 and6. In addition, the range where there is a wind speed of morethan 25m/s blowing or when it has the possibility of beingthat speed, it is referred to as the storm area. For example, it
is expressed as a “very large and violent typhoon” when it isa typhoon with a maximum wind speed of more than 54m/s
with more than an 800km radius of strong wind at 15m/s.
−2−

Fig.4 Surface weather chart at 9:00 on July 13th, 2007
（The centre of typhoon No.4, which is large andseverely strong, found in the sea around Okinawa's
main island)

Typhoon categorised by strength
Category

Maximum wind speed

N/A

Less than 33m/s (64 knots)

StrongMore than 33m/s (64 knots) but less than 44m/s (85 knots)

Severely strong

More than 44m/s (85 knots) but less than 54m/s (105 knots)

Violent

More than 54m/s (105 knots)
Table ５Typhoon categorised by size
Category

Radius of more than 15m/s wind speed

N/A

Less than 500 km

Large

More than 500 km, but less than 800 km

Super large

More than 800 km
Table 6

Fig.7 shows a comparison of a typhoon’s size with thatof the Japanese islands. In the event of such a supertyphoon appearing, a strong wind area with a windspeed of 15m/s will cover most of Honshu. Because adragging anchor is often caused in the event of the windspeed exceeding 15m/s (approximately 30 knots), it isnecessary to pay attention to the size of the typhoon.
In addition, the wind of a typhoon has the following
characteristics.
Although there is a region called the “eye of thetyphoon” where the wind is relatively mild close to
the centre, the region surrounding the eyewall has
the strongest wind. A typhoon is a swirling mass ofair, which blows anticlockwise to the centre of thetyphoon close to the ground. Moreover, it is common toobserve the typhoon’s right side blowing stronger whencompared to the left side. This is because the typhoon’s
wind itself and the flow direction which moves thetyphoon are identical in terms of the right side of thetyphoon. To the contrary, it will be less strong on the left
side of the typhoon, because it is reversed.
Furthermore, at the front right side of the typhoon, it isreferred to as a “dangerous semicircle” due to the factthat vessels drift into the centre. On the other hand, it is
known as a “navigable semicircle” on the left side of theRadius of more than 15m/s wind speed

Large（500〜800 km）

Super large（800 km more or more than 800km）

Fig. 7path
wind
direction
Typhoondangerous
semicircle

navigable
semicircle

typhoon because it is blown away from the centre.
Fig. 8−3−

２−２ Number of typhoon landings (from the Japan Meteorological Agency website)
According to the Japan Meteorological Agency, “in the event that the centre of a typhoon approaches the coastline of
Hokkaido, Honshu, Shikoku and Kyushu, it is deﬁned as being ‘a typhoon that visited Japan”. However, if it goes backto the sea again only crossing small islands and peninsulas, it is said to be a “pass”. Tables 9 and 10 show the typhoons
that have landed between 2001 and 2017. There are 10 typhoons that landed in 2004, which makes it a remarkable
year. The average number of typhoons that landed within this speciﬁc 16 year period, except 2004, is 2.7 per year.
Also, the typhoons that landed between July and October came to 92% of the total. Within those, the typhoons thatlanded among the months of August and September came to 60% of the total. On the contrary, there were no typhoons
that landed between the months of November and April in sixteen years.

Jan. Feb. Mar. Apr. May June

2017

July

Aug.

Sept.

Oct.

1

1

1

1

4

2

6

1

4

2016
2015

2

1

2014

1

1

Nov.

Dec. Yearly total
4

2

2013

4

2

2012

1

2011

1

2010

1

2

1

2

2

3

1

2

2009

1

1

2008

0

2007

1

1

1

3

1

1

2

1

1

1

1

3

2

2006
2005
2004

2

2003

1

2

2

1

2001
Sum total

0

0

0

0

1

10

1

2002

%

3
2

1

1

3
2

3

10

16

16

7

0

0

53

0% 0% 0% 0% 2% 6%

19%

30%

30%

13%

0%

0%

100%


92%

Number of typhoon landings in Japan (2001-2017）
Year

Annual average number oftyphoon landings over 16
years excluding 2004:

2.7

Table 9

(Number of Typhoon Landings)
10

10

Number of typhoon landings (2001-2017）

Prominent only in 20148

6

Annual average
number of typhoon landings over
16 years excluding 2004:

4

2.7

3

3
2

2

2

3
2

6
4

4

14

15

4

3
2

2

2

12

13

1
0

0
01

02

03

04

05

06

07

08

09
Table 10

−4−

10

11

16

17
(Year）

２−３ The paths and the wind speeds of the typhoons that landed in 2004
The paths and wind speeds of ten typhoons that landed in 2004 are shown in Fig. 11 and Table 12. It was observedthat the maximum instantaneous wind speed was more than 60m/s for typhoons No. 10, 18 and 22. Also, it wasobserved that the maximum instantaneous wind speed was more than 50m/s for eight typhoons except No. 11 and 15.
The solid line indicates the typhoon path and the dotted line is the path in the event of a tropical dipression.

No. 18Hiroshima 60.2m/s

No. 22Iro Zaki 67.6m/s
No.10
Muroto-Misaki 60.9m/s

Typhoon No.15
Typhoon No.18

Typhoon No.11

Typhoon No.10

Typhoon No.21
Typhoon No.4

Typhoon No.22

Typhoon No.23
Typhoon No.6

Typhoon No.16

Fig. 11

TyphoonMaximum wind Maximum instantaneous
speed
wind speed (m/s)

Period■ No. 4

June 11th■ No. 6stJune 21 to 22■ No. 10

July 31st to Aug. 2nd■ No. 11

th

29.2
nd

th

Aug. 4 to 5

Meteorological Office

51.5

Miyako Island

43.7

57.1

Muroto-Misaki

47.7

60.9

Muroto-Misaki

20.3

29.8

Shiono-Misaki■ No. 15th

Aug. 20

27.1

48.7

Izuhara■ No. 16

Aug. 30th to 31th

46.8

58.3

Muroto-Misaki■ No. 18

th

33.3

60.2

Hiroshimath

Sept. 7 to 8thth

■ No. 21

Sept. 29 to 30

31.5

52.7

Kagoshima■ No. 22

Oct. 9th to 10th

39.4

67.8

Iro Zaki■ No. 23

Oct. 20th to 21st

44.9

59.0

Muroto-Misaki

Table 12−5−

Coastal vessels that experienced anchoring problems, following the passing of ten typhoons, are shown in Fig. 13
and Table 14. Approximately half of the number of ships anchored at Seto Inland Sea. In addition, 30% of the ships
anchored at main sea areas such as: Tokyo Bay, Ise Bay, Mikawa Bay, Osaka Bay etc.

Sum total

700
Off Hokkaido 9

Hakodate Bay 9

Mutsu Bay and Aomori Bay 16

Coast of Japan sea(Oga Peninsula-Oki)
16
Hiroshima Bay
and Port of Kure 55

East coast of Honshu(off Shiriyazaki-off Choshi) 25

Osaka Bay 63

Tokyo Bay 82

Tokuyamakudamatsu area 48
South coast of Honshu (Iro Zaki -Cape Shiono -misaki) 6
Northwest coast of Kyushu 33

Ise Bay and Mikawa Bay 68

Yatsushiro Sea 24

Eastern Seto Inland Sea(Kii Suido〔Strait〕, Awaji-shima Island and westward-Bingonada) 163

South coast of Kyushu 4

Western Seto Inland Sea(Akinada and Bungo Suido〔Channel〕) 76
Okinawa and Amami Oshima 3

Fig. 13

Others 145

Osaka Bay 63

Ise Bay and Mikawa Bay 68

21%

9%

Area ofanchorage
by ratio

10%
11%

Tokyo Bay 82

Table 14

−6−

Seto Inland Sea

49%(except Osaka Bay)

342

Prefecture (Authority
name name)

0

10

20

30

40

50
（m/s）

× 3.2

Aichi (Owase)
Aichi (Irago)

× 1.9

Aichi （Nagoya）

× 2.1
× 1.7

Shizuoka (Iro Zaki)

× 2.0

Shizuoka (Omaezaki)
× 2.5

Shizuoka (Shizuoka)

× 2.1

Kanagawa (Yokohama)
Chiba (Chiba)

× 1.7

Chiba (Tateyama)

× 2.3

Chiba (Choshi)

× 1.5

Maximum wind speed
Maximum instantaneous wind speed

× 1.8

Tokyo (Oshima)
× 2.4

Tokyo (Tokyo）

× 1.7

Ishikawa (Wajima)

× 1.8

Ishikawa (Kanazawa)× 2.1

Toyama (Fushiki)

× 1.8

Toyama (Toyama)
× 2.8

Niigata （Niigata）
0

10

20

30

40

（m/s）
50

Table 15

Following a comparison of the maximum wind speed (the maximum value of the 10 minute average wind speed) andthe maximum instantaneous wind speed (the maximum value of the instantaneous wind speed) which were detected
at each meteorological oﬃce, at the time when typhoon No.23 landed on October 20th and 21st, is shown in Table 15.
Maximum instantaneous wind speed becomes 1.5 - 3.2 times greater the average wind speed.
At sea, where there are few structures that stand against the wind, it is particularly necessary to estimate the maximum
instantaneous wind speed to be at least 1.5 - 2 times that of the average wind speed.

２−４ Typhoon marine accidents in 2004
Typhoons have caused large-scale disasters, not only for ships, but also on shore. Figs. 16, 17, 18, 19, 20, 21, 22 and23 indicate damage statuses.

−7−

No.4 and 6

6

4

No.10 and 11

June 10th to 22nd
No. of deceased and missing: 5
No. of totally or partially destroyed houses: 6

July 29th to Aug. 6th
No. of deceased and missing: 3
No. of totally or partially destroyed houses: 32

It brought damage to the Chubu,
Kinki and Shikoku regions. Alongwith major disruptions caused toeach form of transportation, part of
the national highway in Tokushima
prefecture was closed.

It brought heavy rain mainly in the
Shikoku regions, and continuously,
it caused landslides and mudslides
in Tokushima and Kochi prefectures.

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200404/0/512x512/GOE904061106.200404.jpg
http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200406/0/512x512/GOE904062003.200406.jpg

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200410/0/512x512/GOE904080103.200410.jpg
http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200411/0/512x512/GOE904080403.200411.jpg

15

No.15

No.16

Aug. 17th to 20th
No. of deceased and missing: 10
No. of totally or partially destroyed houses: 105

Aug. 27th to 31st
No. of deceased and missing: 17
No. of totally or partially destroyed houses: 256

It brought extremely heav y rain,
not only to the Kyushu and Shikoku
regions, but a storm that swept eacharea on the Sea of Japan side from
Kyushu to Hokkado.

It brought heavy rain and flooding,due to high tide, to the Pacific coastof western Japan. A wide area of
the Seto Inland Sea coast, suchas Kagawa Prefecture, Okayama
Prefecture and Hiroshima Prefecture
were affected.

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200415/0/512x512/GOE904081903.200415.jpg

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200416/0/512x512/GOE904083003.200416.jpg

18

No.18

No.21

Sept. 4th to 8th
No. of deceased and missing: 46
No. of totally or partially destroyed houses: 1,650

Sept. 25th to 30th
No. of deceased and missing: 27
No. of totally or partially destroyed houses: 893

In the regions of Okinawa, Kyushu,
Chugoku and Hokkaido, there wereareas that recorded the highest
instantaneous wind speeds.
Buildings were damaged and trees
were fallen in each area while a large
number of people were injured.

S h e c r o s s e d t h e Ky u s h u a n d
Shikoku regions, kept proceeding to
the Kinki and Hokuriku regions andfinished up in the Tohoku region.

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200418/0/512x512/GOE904090704.200418.jpg

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200421/0/512x512/GOE904092803.200421.jpg

22

No.22

No.23

Oct. 7th to 9th
No. of deceased and missing: 9
No. of totally or partially destroyed houses: 435

Oct. 18th to 21st
No. of deceased and missing: 98
No. of totally or partially destroyed houses: 8,836

The typhoon was not so big, however,the vicinity of the centre wasaccompanied by raging rain and wind.
It caused sediment damage suchas landslides, flooding and damage
caused by gusts, from the Tokai
region to the southern part of Kanto.

Because she crossed Honshu with alarge force, she brought overflow torivers, flooding and sediment damage
to a wide area. There were a large
number of the deceased and missing
on a wide scale, mainly in Hyogo,
Kyoto and Kagawa prefectures.

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200422/0/512x512/GOE904100803.200422.jpg

Fig. 16 〜 23
Source: “Digital Typhoon Project” courtesy of the National Institute of Informatics−8−

http://agora.ex.nii.ac.jp/digital-typhoon/wnp/by-name/200423/0/512x512/GOE904101803.200423.jpg

Table 24 indicates each typhoon marine accident situation that occurred in 2004 (as published in the Marine Accident
Inquiry Agency [MAIA]).. The total number of marine accidents was 233, however, the number of marine accidents (72
accidents) and the number of vessels (88 vessels) aﬀected by Typhoon No. 18 are remarkably prominent.

2004

Typhoon marine accident situation

100
90

No. of accidents caused by
Typhoon No.18

88

No. of accidents

80

No. of ships

70

No. of deceased and missing

72 cases/88 ships

72

60
52

50

48

45
39

40

31

30

27

20

14 14

12 13

10

6

No. 4

14

6
2

0

No. 6

No. 1026

2

2

No. 11

No. 15

4

No. 16171

No. 18

No. 21

1

No. 22

No. 23

Table 24

Typhoon marine accidents in 2004 (regions that had more than 5 accidents)
Port of Mizushima 5Port of Tokuyamakudamatsu 6

Port of Hiroshima 37

Aioi‐Ieshima 7

Amagasaki Nishinomiya
Ashiya port 5

Seto Inland Sea

Mishima-Kawanoe port 5

Nansei Shoto

Kanmon port 6

Akashima Island
15

Tokyo Bay 8
Kagoshima Bay 7
Port of Kochi 6

Fig. 25−9−

＝ Summary of Typhoon No. 18 (From the Japan Meteorological Agency website) ＝
On the 28th of August 2004, approximately 09:00 Japan Standard Time (here in after referred to as JST),
Typhoon No.18 which was formed in the sea around the Marshall Islands moved northwestward over thesouthern Sea of Japan and passed through the northern part of the main Okinawan island with great size andforce on the 5th of September. Afterwards, she proceeded north, to the East China Sea and changed path to thenortheast. At approximately 9:30 on the 7th of September, she landed in the vicinity of Nagasaki-city and passed
through the northern part of Kyushu. In the afternoon of the 7th she reached the Sanin offing. Then, while
accelerating northeastward up the Japan Sea, on the morning of the 8th she headed north on the western offingof Hokkaido with a storm area accompanying after. Then, after changing into an extratropical cyclone at 09:00
on the 8th, she reached the Soya Strait, while still growing.
Gale force winds with a recorded maximum instantaneous wind speed of 50m/s were observed in regions of
Okinawa, Kyushu, Chugoku and Hokkaido, for example, 60.2 m/s in Hiroshima and 50.2 m/s in Sapporo. In
addition, there was an area of the Kyushu region where heavy rain which exceeded 900mm was observed.
Moreover, damage caused by high water levels on the coast of the Seto Inland Sea and on the coast of theJapan Sea from western Japan to northern Japan was also observed.
This typhoon caused damage to buildings and trees to fall in each area it passed. A large number of people were
injured because of falling debris. Also, grounding accident of ships occurred one after another in western Japan.

Fig. 26
The route of Typhoon No.18 in 2004

Photograph 27

Fig. 28 shows the routes of Typhoons No. 18 and 23. Moreover, the severe dragging anchor accident of the
cargo ship "MV TRI ARDHIANT" (6,315 tons) and grounding accident of the training ship “Kaiwo Maru” (2,556
tons) may be familiar.

− 10 −