Hazards 2002, October 3-6, Antalya / TURKEY

STUDY ON RISK IMAGE OF FLOOD
AND ITS EFFECT ON EVACUATION BEHAVIOR
Makoto Kodama
Graduate Student, Department of Civil Engineering, Gunma University
1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515 JAPAN
Phone: +81-277-30-1654 Fax:+81-277-30-1601
kodama@ce.gunma-u.ac.jp
Toshitaka Katada
Associate Professor, Department of Civil Engineering, Gunma University

When the water level of a river rises and evacuation is deemed necessary, the authority issues
an evacuation order. However, the evacuation rate of residents is said to be fairly low.
Probably, residents think that a flood is not dangerous, so they don’t evacuate in spite of thedangerous situation.
In this study, we carried out a questionnaire survey among residents of Kiryu City, which had
suffered heavy damage from the flood disaster caused by Kathleen Typhoon in 1947, and weanalyzed the actual situation of the risk image of a flood and its effect on an evacuation
behavior.
We defined the risk image of a disaster as the following two recognitions:-The recognition of the probability of a disaster occurrence, “occurrence
probability image”.
The recognition of the danger level when one is exposed to the disaster, “dangerlevel image”.

Then, we examined the risk image about 5 disasters (flood, earthquake, volcanic eruption, fire
and accident of a nuclear power plant). As residents replied questions about the risk image,they compared the risk image of each disaster with the risk image of an airplane clash and anautomobile accident, and they put a mark on the scale of the risk image like Fig.1.
The results of this study are shown below.

Occurrence probability image z
yInfrequent
Frequent

Safe

11234

Airplane clash

5678

9Automobile accident

y anger level image z
D2345

Automobile accident

Fig.1. The scale of the risk image

175

67

Dangerous
8

Airplane clash

9

Hazards 2002, October 3-6, Antalya / TURKEY

1) The actual situation of the risk image

Fig.2 provides a plot of the average of occurrence probability image and danger level imageof each disaster. The risk image of a flood is lower than the risk image of fire and earthquake though
Kiryu city have suffered heavy damage from the flood.

Automobile accident

Airplane clash
Automobile accident

87Fire653
21
1EarthquakeFlood4

Volcanic eruption

23

Safe

4

Airplane clash

Occurrence probability image
Frequent
Infrequent

9Accident of anuclear power plant

56

Danger level image

789

Dangerous

Fig.2. The actual situation of the risk image of disaster2) Formation factors of the risk image

We analyzed the relation between the risk image of a flood and experience of the flood
disaster caused by Kathleen Typhoon, resident’s age, and so on. Residents who haveexperienced the flood recognize that it is either frequent and danger or infrequent and safe. Inaddition, it is the same as the advanced age group.
3) The risk image of a flood effects on an evacuation behavior

Relation between the risk image of a flood and the timing of decision-making of anevacuation behavior when residents supposed a flood disaster is shown in Fig.3. Residents
who think that a flood occurs frequently indicate early evacuation timing, while residents whothink it is not dangerous replied that they evacuate when their house is inundated.

176

Occurrence probability image zyHazards 2002, October 3-6, Antalya / TURKEY

The group of residents who think that a flood is less dangerous than an automobile accident
The group of residents who think that a flood is more dangerous than an automobile accident
but less dangerous than an airplane accident
The group of residents who think that a flood is more dangerous than an airplane accident
P3

The group of residents who think that a flood occurrence ismore frequent than an automobile accident

P2

The group of residents who think that a flood occurrence ismore frequent than an airplane accident but less frequent than an automobile accident

P1

The group of residents who think that a flood occurrence isless frequent than an airplane accident
D1
D2
D3
y anger level image zD

90.0%
20.0%

8.8%
10.1%

15.0%

7.2%

10.0%

3.5%
gee
nc imarre tycu bili
Oc oba
pr

P3

3.3%

P2

2.8%
4.1%

P1

3.1%

2.9%

D2D1Daeng

D3

lver le5.0%
0.0%

ge
im a

80.0%
66.
6%
66.
6% 75.0%
66.5%
74.3% 70.0%
72.1%
71.9%
60.0%
53.9% 66.0%
50.0%
62.0%
40.0%

O
P3
pr ccuob r r e
ab nc P2
ilit e
P1
yimag
e

DD2

D3 ge

imelleverganD1a(a) The rate of residents who evacuate (b) The rate of residents who evacuate
when it rains heavily
when an authority issues evacuation
order.

50.0%
40.0%
24.6%
26.3%
30.0%
25.1% 21.5%
30.7%
22.6%
20.0%
34.0% 25.2%

36.0%

10.0%
Opr ccuP3ob rre P2
ab nc
ilit eP1yimage

0.0%

D2
D1erng
DaD3 eagimellev(c) The rate of residents who evacuate
when their house is inundated

Fig.3. Relation between the risk image of a flood and an evacuation behavior

177