An analysis of human damage caused by recent heavy rainfall disasters in Japan

Motoyuki USHIYAMA¹¹ Iwate Prefectural University, Iwate, Japan

Abstract: The development and analysis of a database that will aid in the mitigation of human damage (that is, deaths or
missing persons) caused by natural disasters are very important, and a method to do these tasks has been established in Japan.
First, we developed a victim database for the typhoon No. 0423 disaster, the typhoon No. 0514 disaster and the heavy rainfall
disaster of July 2006, and the victims were classified based on whether they were dead or missing. In the present study, we
estimate whether any loss was mitigated by the use of disaster information. In the case of the typhoon No.0514 disaster, theestimated mitigation percentage of victims is 75%. However, in the case of the typhoon No.0423 disaster, the mitigation is
only 36%. Disaster information is a useful disaster mitigation measure, but there is a limit to its effect.
Key words: heavy rainfall disaster, deaths or missing persons, disaster information, disaster mitigation.

1

INTRODUCTION

Analyzing the causes of death in a natural disaster isimportant for disaster prevention efforts. In Japan, there
have been studies on the causes of death during earthquakes(Japan's National Land Agency, 2000, Kobayashi, 1981),
and there have been several studies on the human damage
caused by heavy rainfall disasters, such as the case studies ofthe "Nagasaki heavy rainfall" (Matsui et al., 1984, andothers). However, since the mid-1980s, little attention has
been paid to the causes of death by heavy rainfall disasters,
probably because no such events have occurred since theNagasaki event in which many people were killed. What is
important in the mitigation of human damage by heavy
rainfall disasters is advances in non-structural measures,
especially in the gathering and dissemination of disaster
information, such as warnings, hazard maps, communication
systems and the like. In Japan, disaster information haschanged considerably in recent years, so persons involved indisaster prevention must analyze human damage underpresent-day conditions.
The purposes of this study were:
1) Construction of a death or missing person database basedon the data of recent heavy rainfall disasters; and2) Estimation of the number of victims whose death or
missing status could have been mitigated by the use ofdisaster information.
In this paper we are concerned with three recent heavy
rainfall disasters: The first is the typhoon No. 0423 disaster(hereinafter called "T0423"); the second is the typhoon No.
0514 disaster (hereinafter called "T0514"); the third is theheavy rainfall disaster of July 2006 (hereinafter called"HR2006"). These events were the most severe rainfall
disasters for 2004, 2005 and 2006, respectively.

2

METHODOLOGY

Basic data come from the outline of disaster statistics
provided by the Fire and Disaster Management Agency(FDMA). Detailed information of victims was collectedfrom the national newspapers, local newspapers and web
pages of the prefectural offices, municipality offices andelsewhere.
In addition, field surveys and interview surveys were
performed in areas that had been seriously damaged. In thecase of T0423, Toyooka city in Hyogo prefecture, Maizuru
city, Miyazu city and Ooe town in Kyoto prefecture wereresearched in October 2004. Sumoto city, Tsuna town and
Ichinomiya town in Hyogo prefecture and Sanuki city and
Higashi-Kagawa city in Kagawa prefecture were researchedin November 2004. In the case of T0514, Miyazaki city,
Takachiho town and Hinokage town in Miyazaki prefecture
were researched in October 2005. In the case of HR2006,
Okaya city, Tatsuno town and Suwa city in Nagano
prefecture were researched in July 2006. Hishikari town,
Ookuchi city and Satsuma town in Kagoshima prefecture
were researched in August 2006.

3

OUTLINE OF EVENTS

3.1 T0423
A heavy rainfall caused by typhoon No. 0423 (Tokage,
GLIDE: TC-2004-000109-JPN) and a stationary front
occurred in western Japan from October 20 to 21, 2004.
The highest 1-hour amount of precipitation in the last 25
years was recorded at one observatory, and the highest 24hour amounts of precipitation in the last 25 years wererecorded at 30 observatories based on the data of the Japan
Meteorological Agency (JMA, Fig. 1).

In this heavy rainfall, 96 persons were killed, 1,155 houses
were destroyed (ruined and half-ruined) and about 62,528
houses were inundated. People died in 16 prefectures,
including 7 in Gifu prefecture, 15 in Kyoto, 26 in Hyogo, 11
in Kagawa and 8 in Kochi. The deaths of 31 persons were
due to drowning, and 28 people died in sediment disasters.

Fig. 1 24-hour precipitation distribution map at 24:00,
October 20, 2004

the Japan Meteorological Agency since 1979. Based ondata from the JMA, the highest 24-hour precipitation records
in the last 25 years were revised at 56 observatories, and thehighest 48-hour precipitation records were revised at 64
observatories as a result of this rainfall. However, there
was no observatory where the highest 1-hour precipitation
was revised. In this heavy rainfall, 2,834 houses weredestroyed and 21,834 houses were inundated; most of theproperty destruction was caused by inundation. In total, 29
persons were killed or listed as missing in 8 prefectures: 13
in Miyazaki prefecture, 5 in Kagoshima, 4 in Ohita, 3 inYamaguchi and 4 in others. Of these deaths, 22 were
attributable to sediment disasters.
3.3 HR2006
A heavy rainfall caused by a stationary front (Bai-u front)
occurred in Japan from July 15 to 24, 2006. A 1107-mm,
72-hour precipitation was recorded at Shibisan in
Kagoshima prefecture (Fig. 3). Based on data from the
JMA, the highest 1-hour precipitation records since 1979
were revised at 5 observatories, the highest 24-hour
precipitation records were revised at 22 observatories andthe highest 48-hour precipitation records were revised at 62
observatories as a result of this rainfall.
Due to this heavy rainfall, 342 houses were destroyed and10,968 houses were inundated (GLIDE: FL-2006-000102JPN, MS-2006-000102-JPN). In total, 28 persons were
killed or listed as missing in 9 prefectures: 12 in Nagano
prefecture, 5 in Kagoshima, 4 in Shimane and 7 in others.
諏訪
370mm

200

600

40
0

300

800

200

紫尾山
1107mm

御嶽山
554mm

大口
981mm
えびの
1071mm100

Fig. 3 72-hour precipitation distribution map of HR2006

4

Fig. 2 72-hour precipitation distribution map at 24:00,
September 6, 2005
3.2 T0514
A heavy rainfall caused by typhoon No. 0514 (Nabi,
GLIDE: TC-2005-000154-JPN) and a stationary front
occurred in Japan from September 4 to 8, 2005. A 1238mm, 48-hour precipitation was recorded at Mikado in
Miyazaki prefecture (Fig. 2).
This was the highest
recorded precipitation of all observatories administered by

ANALYZATION OF HUMAN DAMAGE

4.1 Identification of the location of the deadRough addresses of the places where the dead were foundwere identified based on the data posted on the web and innewspapers. This address data was converted into latitude
and longitude data by use of the "Free Address Geocoding
Service for CSV Formatted Files on WWW" (Center for
Spatial Information Science, University of Tokyo, 2001).
In addition, some locations were modified based on fieldsurvey and interview survey results.
Fig. 4 shows the distribution of deaths caused by T0423
based on the latitude and longitude data. The total numberof deaths was 96 persons, as stated previously, and the deadwere found in 78 places in 60 municipalities. The largest

number of deaths was in the area of Uno, in Tamano city,
Okayama prefecture, where 5 persons were killed by asediment disaster. At Murotosaki-cho, Muroto city, Kochi
prefecture, 3 persons were killed by high waves. In each of
the other localities, one or two persons were killed. Thus,
this disaster cannot rightly be called a "local type heavy
rainfall disaster" but rather a "wide area type heavy rainfall
disaster". Some events known as serious heavy rainfall
disasters, such as the Sainin heavy rainfall in 1983 (117dead) and the Nagasaki heavy rainfall in 1982 (299 dead)were considered local type heavy rainfall disasters. It is
likely that a serious wide area type heavy rainfall disasterhas not occurred since the heavy rainfall disaster caused bytyphoon No. 17 in 1976 (169 dead).
Fig. 5 shows the distribution of deaths caused by HR2006.
The total number of deaths was 29 persons. The largest
number of deaths was in the area of Minato, in Okaya city,
Nagano prefecture, where 7 persons were killed by asediment disaster. At Sata-cho, Izumo city, Shimane
prefecture, 3 persons were killed by flooding. In each of
the other localities, one person was killed.

Fig. 4 Distribution map of deaths (T0423)▲: Floods, ★: Sediment disaster, ●: High waves,▼: Strong winds, ■: Active accident

Okaya
TatsunoOokuchiHisikari

Fig. 5 Distribution map of deaths (HR2006)
4.2 Classification of causes of death
A method for classifying the deaths caused by heavy rainfall
disasters has not been established in Japan. In the Japan

Statistical Yearbook, printed by the Ministry of Internal
Affairs and Communications, the causes of deaths by natural
disaster are classified into "typhoon", "storm", "strong
winds", "high tide", "earthquakes", "volcanoes" and"tsunamis". However, there are several problems with thisclassification system. One is that it is not clear what thedifference is between a "typhoon" and a "storm".
Classification by hazards, such as a flood or sedimentdisaster, is needed. In addition, among the deaths that
occurred in the most recent heavy rainfall disaster in Japan,
some people were killed due to careless behavior. A
classification that takes this into account is also needed.
Therefore, in this study, we developed the followingclassifications:
1) "High waves": death by sea waves along the coast, e.g.,death that occurred when the person was inside a house
destroyed by high waves, or death caused by being
struck by a wave during work or when visiting an area.
2) "Strong winds": death related to strong winds, e.g., deaththat occurred when a person died because of being
blown off a roof by strong winds, or being crushed by atree felled by strong winds.
3) "Active accident": death by persons who approached adangerous area instead of evacuating it, or by persons
who died after falling into an irrigation canal while
patrolling a paddy field or irrigation canal.
4) "Flood": death by flood flow or inundation, e.g., deaththat occurred by a person drowning in their house, or
being carried away by floods while driving a car orwalking.
5) "Sediment disaster": death by debris flow, slope failure
and landslide.
"Active accident" is the classification that is original to thisstudy.
This classification was defined in order todistinguish it from "floods" and "sediment disaster".
Passive victims may be considered to be those persons who,
for example, stayed indoors, not realizing that their houses
would be flooded and that they would drown. Moreover,many of the people who drowned while driving their car orwalking were attempting to escape the danger, and they canalso be considered "passive" victims. On the other hand,
generally persons who died after falling into an irrigation
canal while patrolling a paddy field or other area can beclassified as "flood victims". As we have seen, there aremany such victims recently. They must have known that aswollen irrigation canal could be dangerous, but they still
went to the dangerous area and died. They are thus, so to
speak, "active victims." Of course, there are various
reasons for their behavior, but the behavior of "passive
victims" and "active victims" can be considered to differ.
Therefore, methods for preventing disaster deaths must also
differ. For these reasons, we developed the classification"active accident".
Fig. 6 shows the classification of causes of death from
T0423, T0514 and HR2006. In the case of T0423, thirtytwo persons died by "flood", and 20 died by "active
accident". Deaths by "active accident" were included in thedeaths caused by flood in ordinal disaster statistics. Thus,in ordinal disaster statistics, the death toll by flood would beconsidered 52. The numbers of deaths by flood were far
sediment disaster. In Hyogo prefecture, which suffered thefewer in the latest disaster in Japan. However, in T0423,
worst damage, 15 of 26 deaths were by flood. Even in
the number of deaths by flood was higher than that by
Kyoto prefecture, 10 of 15 deaths were caused by flood.
Table 1 Heavy rainfalls causing the deaths of 50 or more persons since the 1980s
Date

Cause of heavy rainfall

1982. 7.10 - 26
1982. 8. 1 - 3
1983. 7.20 -27
1991. 9.24 - 10.1
1993. 7.31 - 8.7
2005. 7.13

Nagasaki heavy rainfall
Typhoon No. 10 and front
Sanin heavy rainfall
Typhoon No. 19
Kagoshima heavy rainfall
Niigata and Fukushima heavy rainfall

High wave
10

Strong wind
5

Activeaccident
20

Flood
32

T0423(N=96)

T0514(N=29)

3 1 2

HR2006(N=29)

Flood
5

0%

Sediment
disaster
28

Sediment
disaster
22

Activeaccident
6

20%

1

1

Sediment
disaster
17

40%

Death
(persons)
299
95
107
62
49
16

60%

1

80%

Niigata and Fukushima heavy rainfall
on 2004

14

2

Activeaccident

6

14

17

Flood

11

0%
25%
50%
Less than 65 years old
65 years old or more

39

33

by flood in the Nagasaki heavy rainfall disaster of 1982
(about 30 persons) was the most serious of these events.
The death toll by T0423 is the largest since 1982. Many
persons were killed by flood in the Niigata and Fukushimaheavy rainfall disasters, but the death toll by flood in T0423
exceeded those numbers. Serious harm to humans causedby floods has not occurred for about the past 20 years.
However, this was evidently a matter of luck, as the harmcaused by T0423 shows that there is always a possibility that
serious damage will occur.
In the case of T0514 and HR2006, the majority of victims
were killed by sediment disasters. These events show
similar characteristics to those of the other heavy rainfall
disasters shown in Table 1.

Sediment
disaster

61

191

Kagoshima heavy rainfall on 1993

Sediment disaster: 263
Sediment disaster: 56, flood: 15, unknown: 24
Sediment disaster: 91, flood: 11
Most deaths caused by strong wind.
Most deaths caused by sediment disasters.
Flood: 12, active accident: 2, sediment disaster: 2100%

Fig. 6 The number of deaths by cause
Numbers in the bars show the deaths from each cause. "N"is the total number of dead.

Nagasaki heavy rainfall on 1982

Breakdown (persons)

14

17
75%

100%

Fig. 8 The death toll by age and cause of death (T0423).
T0423

34

61

T0514

8

21

HR2006
Less than 60 years old
60 years old or more

12
0%

20%

17
40%

60%

80%

100%

Fig. 7 The death toll of elderly and non-elderly people in the
recent serious heavy rainfall disasters.
Numbers in the bars show the deaths from each cause.
Table 1 lists the events since the 1980s in which the numberof deaths was 50 persons or more based on three reports(Yoshikawa, 2003; Hiroi and Nakamura, 1992; Takamine,1994). As the table shows, since the 1980s, most of thedeaths were caused by sediment disasters. The death toll

4.3 Relationship between cause of death and age
To examine the relationship between cause of death and age,
I first totaled the victims according to age. In the case of
T0423, 41 victims were under age 65 and 54 over age 65,
the typical age labeled the “elderly.” When the thresholdfor the elderly label was set at 60 years old, there were 34
persons under age 60 and 61 persons over age 60. Thus,
elderly people accounted for about 60 percent of the total
victims. Fig. 7 shows the death toll of the elderly in recent
serious heavy rainfall disaster events. In this figure only,"elderly people" are defined as persons over 60 years old bydata constraint. This figure shows that the majority ofvictims were elderly people in recent heavy rainfall disasterevents. We can say with a fair amount of certainty that the"victims by heavy rainfall disaster were unevenly distributed
among elderly people". However, it is necessary toexamine this issue from another point of view as well.
Fig. 8 shows the relationship between cause of death and age
in T0423. The death rates of elderly people (over 65 years
old) were slightly more than half the totals in the active
accident and sediment disaster classifications. However,the death rate by flood among non-elderly people (under 65
years old) is less than half the totals. Almost all of thesevictims were washed away by floods while driving or
walking.

have been difficult to save the victims in location type (3),24 persons, using this information. Seventeen of themwere not elderly people. That is, people become vulnerable
to disasters regardless of age when they are taking a trip. It
is necessary to develop an information transmission method
or system for people who are traveling, not only using IT but
T0423
All death toll
96 persons

Strong wind,High wave: 16
out of analysis

4.4 Possibility of human damage mitigation by using disaster prevention information
I attempted to estimate how much human damage can be
mitigated when disaster prevention information, such as
rainfall forecasts, real-time precipitation data, hazard maps
and other tools, is used. The objects of estimation are thevictims of flood, sediment disaster and active accident.
First, the victims by flood were classified based on thelocation where they were killed. The locations wereclassified as follows:(1) In their home(2) Outdoors near their home(3) Outdoors far from their residence area.
It is possible that the victims who died in locations (1) and(2) could have been saved if the following necessary
conditions had been satisfied:(a) By viewing a hazard map, they understood that it was
dangerous near their house.
(b) The real-time precipitation or river water level
information was gathered and disseminated through theInternet, radio and other means.
(c) The present precipitation or water level was understoodto have reached dangerous levels for the region.
The information contained in (b) is disseminated now inJapan, and hazard maps of floods have been released innational administrated rivers to the public via printed matteror web pages. Of course, it is not easy for the three
conditions listed above to be satisfied, but it is not
impossible.
On the other hand, it could be very difficult to save (3) typevictims. They are killed at far from their residence area.
Most of these victims are making trips by car or walking forcommuting purposes or on business. Therefore, it is likelythat hazard information would not be useful to them, even if
they could see the hazard map for their residence area. It is
not impossible to pass information gathered about real-time
rainfall and river water levels by mobile phone and othermethods, but it is not easy for non-experts to use thisinformation, because most people don't know how gather
information on real-time rainfall and river water levels or
how to use this information to help them remain safe. In
addition, the present information on flood forecasts does notshow the inundation depths inland (away from rivers).
In the case of T0423, 32 persons were killed by flooding.
Judging from the above criteria, the number of victims who
could have been saved by additional information was
estimated at 8 persons. This was the sum of victims inlocation type (1) (6 persons) and victims in location type (2)(2 persons). All were elderly, over 65 years old. It would

Flood: 32

Indoor

6

Place

Near

Others: 80
OutdoorResidence
area
Distant

Passive

2

24

Indoor25

Passive
Approach todangerous area

Sediment
disaster: 28

Place

Near
2

ActiveOutdoorResidence
area

Active accident: 20

1
Distant

T0514
Near
All death toll
29 persons

Strong wind,High wave: 4

Indoorout of analysis

Distant
Flood: 1

Near

Outdoor

Near

IndoorPassive

Sediment
disaster: 22

0

Residence
area
Distant

Approach todangerous area

0

Place

Others: 25

Passive

0

Residence
area

1

22

Residence
area
Distant

0

Place

ActiveNear

OutdoorActiveAccident: 20

Residence
area
Distant

0HR2006Near
All death toll
29 persons

Strong wind,High wave: 1

Indoorout of analysis

Distant
Flood: 5

Near

Outdoor

Near

Passive

IndoorSediment
disaster: 17

1

Residence
area
Distant

Approach todangerous area

0

Place

Others: 28

Passive

0

Residence
area

4

13

Residence
area
Distant

0

Place

ActiveNear

OutdoorActiveAccident: 6

1

Residence
area
Distant

Fig. 9 Flow chart analysis of causes of death in a disaster3

all available technology.
In the case of T0423, most of the 25 persons killed by
sediment disasters were killed inside their homes.
Although three persons were killed outdoors, two of themwere killed beside their homes. That is, 27 victims were inlocation type (1) or (2). Therefore, it is possible that thevictims could have been saved if the necessary conditions(a), (b) and (c) listed above had been satisfied. Judging
from the above, in the case of victims by sediment disaster,
27 persons could have been saved by obtaining information.
As we have seen, the victims who died by an "active
accident" were defined as "persons who died because they
approached the dangerous area by themselves instead ofevacuating". Since these people approached the dangerous
area of their own free will, it is probable that their decision
would not have been changed only by receiving disaster
information. Therefore, it is unlikely that these victims
could have been saved, even if all necessary conditions had
been in place.
Refuge guidance at the time of a disaster is often considered
support for elderly people. However, in the case of T0423,
14 of the 20 victims who died from an "active accident"
were elderly people. It is possible that this number could
not have been reduced, even if an evacuation guiding systemfor elderly people had been in place. Nonetheless, it isimportant to provide the elderly with information andsupport so that they do not become victims of an "active
accident".
Fig. 9 is a diagram of the results of the above estimation.
The thick line is a connector related to disaster prevention
information. In the case of T0423, the number classified
into the lower side of the connectors is 35 persons. It is
possible that if the proposed disaster prevention information
had been used, 35 persons (39% of all) maximum would
have been saved. In the case of T0514 and HR2006, 22
persons (76%) and 15 persons (52%) might have been saved,
respectively.

5

CONCLUSIONSIn the case of T0423, 96 persons were killed, the highest
death toll by heavy rainfall in Japan since the “Heavy
rainfall in July 1983” (117 persons dead). Several heavy
rainfall disasters occurred in 2004 in Japan, including the"Niigata and Fukushima heavy rainfall in 2004", in which 16
persons died, the the "Fukui heavy rainfall disaster in 2004"(5 persons), Typhoon No. 0416 (17 persons), Typhoon No.
0418 (45 persons) and Typhoon No. 0421 (27 persons).
These disasters had a strong impact on the Japanese
government, and several committees for heavy rainfall
disaster prevention policy were formed. The Ministry ofLand, Infrastructure and Transport (MLIT, 2005) made thefollowing points about the recent heavy rainfall disasters:(1) The damage was unevenly distributed among "people
vulnerable to disasters", such as the elderly and handicapped
persons.
(2) Mutual help of resident communities at the time ofdisaster became inactive.

(3) The awareness among residents of the dangers of natural
disasters is decreasing.
(4) The danger of underground spaces flooding is increasing.
The above points need to be discussed further. As we haveseen, one of the most important points to note about thedisaster studied here is that 32 of the 96 victims were killed
outdoors by floods. This was a very rare circumstancewhen other recent heavy rainfall disaster events are
considered. The victims were not only elderly people, andit would have been difficult to save them by mutual help,
point (2), or improvement in the awareness about disasters,
point (3).
It must be noted that there is a limit to the effect of disaster
information. Based on the analysis of this study, it isestimated that if the available disaster prevention
information had been used, 22 persons (76% of all victims)
maximum would have been saved in the case of HR2006.
However, in the case of T0423, the estimation is only 39%(36 persons). Further research and analysis into the causesof death by heavy rainfall disaster would clarify the issues
that need to be addressed.
NOTE
This paper is a revision of an earlier study by Ushiyama(2006).
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