This document summarizes a study on risk communication and evacuation decision-making for debris flows in Taiwan. The study examined residents living in vulnerable areas in Kaohsiung City and found that while residents highly trust warnings from public authorities, many had little understanding of evacuation plans and alerts. Environmental cues like rainfall levels and neighbors evacuating were the strongest influences on evacuation decisions. Past disaster experience also increased residents' preparedness. The study concludes risk communication must go beyond one-way messages and consider social and environmental factors to improve evacuation responses.

1. Jie-Ying Wu, Ph.D.
Dept. of Urban Planning and Disaster
Ming-Chuan University, Taiwan August 27,2012

2. Overview
1 Background
2 Literature Review
3 Research methods
4 Results and discussion
5 Conclusion
2

3. Background: Discover Taiwan
Taiwan
【 Capital 】 【 Population density 】
Taipei City 632 per km2
【 Area 】 (Switzerland 190 per km2)
36,000 km2 【 Jurisdictions 】
【 Population 】 22 counties/cities & 319 townships
23 million 【 GDP/capita 】
$20,101 (Switzerland $ 41,950)

4. 4

5. Background
 World bank (2005) : 73 ％ of the population
live in areas that can be affected by more
than 3 types of natural disasters
5

6. Background
 Heavy rainfall, usually caused by typhoons,
and frangible geology make debris flow
happen frequently.
 Currently 1,578 potential debris flows in
Taiwan, and roughly 20,000 people live in the
impacted areas.
 Even the public authority set up various
preparedness works, still lots of deaths .
 This study tries to understand the risk
communication operation and the evacuation
decision making among stakeholders. 6

7. Literature Review
 Risk communication and disaster
decision making
US National Research Council suggested
interactive approach of risk communication,
from dissemination to dialogue
 Lindell and Perry (2000) provided Protective
Action Decision Model (PADM) , and suggest
effective risk communication should cover
households characteristics, social context,
environmental condition
7

8. Literature Review
 Warning and evacuation
The warning sources (authority, media, peers--- )
will influence evacuate decision making
People judge the source credible by expertise and
trustworthiness.
Environmental cue such as weather condition and
behavioral response of others tend to prompt to
evacuate.
8

9. Literature Review
 Current debris flow preparedness in Taiwan
Soil and Water Conservation Bureau (SWCB) decides
the sector area (vulnerable area) of each debris flow
Survey the households in the vulnerable areas
9

10. 10

11. 11

12. Literature Review
 Current debris flow preparedness in Taiwan
SWCB examines the precaution rainfall of each
debris flow
 SWCB holds training courses and teach residents
regarding yellow and red alerts
Warning Explanation Evacuation
Type order
Yellow Predict rainfall will over Suggest to
Alert precaution rainfall evacuate
Red Alert Current rainfall already Mandatory
over precaution rainfall evacuation
12

13. Literature Review
Warning System Warning-Responding Situations
Source Hearing Environmental cues
(Government, Friend etc.) Risk identification Agent
Credible(Expertise, Handle Behavioral
Trustworthiness) Understanding
Feedback Believing
Accessible Level of Threats
Personalization? Socio-Economic
Attribute
Chanel Risk assessment
Culture and Ethnic
Dissemination Confirming Kinship/ Friendship
Penetration networks
Distortion Responding Household
Feedback Evacuation Attributes
In-place sheltering
Message type and Alternatives action
Protective action
content assessment Psychological
Immediacy Evaluation: Time Attribute
Seriousness needed, Mobile time , Hazard awareness
Precision Cost, Mind Past Experience
Repetition Controllability
Incentives Awareness on
Timing and Language Public aids Alterative action
used NGOs help Self action ability
13

14. Study Design
 Choose Liugui District in
Kaohsiung city as study
area.
 2009 Typhoon Morakot
caused 43 deaths and
164 houses collapsed
 Heavy rainfall caused
debris flows and floods
1,190 mm in 1 day
1,946 mm in 3 days
14

15. 15

16. 16

17. Study Design
Baolai
Village
Laonong Village
Xinfa
Village
Liugui Village
Yibao Xinglon Village
Village
Zhongxing Village
Dajin
Village
Xingliao
Village 17

18. Study Design
Households in
# #
Neighborhood Vulnerable
Sampling Response
area
Xinglong Village 48 29 25
Dajin Village 108 65 61
Liugui Village 38 23 10
Yibao Village 97 58 23
Baolai Village 93 56 39
Xinfa Village 73 44 33
Zhongxing
Village
117 70 70
Laonong Village 60 36 19
Xingliao Village 7 4 4
Total 642 385 284 (74% ) 18

19. Results and Discussions
 Residents have little knowledge on
evacuation preparedness
62.7% knowing stay in the debris flow
vulnerable area
Only 34.9% clearly understand/ understand the
meaning of red/yellow alert
Only 35.3% clearly understand/ understand the
contents of risk map
51.9% clearly understand/ understand the
evacuation plan
19

20. Results and Discussions
 Warning Source from public authority
has high degree of trustworthy
5.00
5
4.00
4 4.13 3.93 3.91
3.63 3.43 3.49
3.00
3 Public 3.12
TV 2.41 2.70
Authority Friends/
2.00
2 Newspaper neighbors Internet
1.00
1
20
0.00
0
 78.5% will reconfirm the warning
messages
20

21. Results and Discussions
 Environmental Cue is the most important
factor influencing evacuation decision-
making
People consider the signals of debris flow
 52.7 % water flux in the steam
55.6% the changes of surrounding condition
People will decide to evacuate if
 83.5% rainfall become higher
85.9% seeing the evacuation actions of neighbors
21

22. Results and Discussions
 Past disaster experience is the key factor
for resident’s preparedness
 By using t-test, households having past
disaster experience will
 willing to attend training courses or exercises
 higher briefing the debris flow will occur
consider village leader play an important role
during evacuation period
22

23. Conclusions
 From the Taiwan case, residents living in
debris flow vulnerable area obviously do
not prepare enough to face the disasters
 Risk communication should no longer
one-way message dissemination from
public authority through training course
 The public authority should consider
environmental cues and past disaster
experience as important factors while
conducting evacuation order
23

24. Jie-Ying Wu
paulwu@mail.mcu.edu.tw