Warning and Evacuation
in Disaster Situations
David Alexander
University College London

WARNING SYSTEMS

KANSAS
5 dead, 150 injuredOKLAHOMA
38 dead, 669 injured
TEXAS
1 dead, 12 injured
Monday 3 May 1999
76 tornadoes in 7 hours
damage exceeded $500 million
4319 buildings destroyed
WARNING TIME: 20-120 minutes
ONLY 44 DEATHS
Largest tornado max.
F5 (420-510 km/hr)
path 130 km x 1.5 km

What does this picture
tell us about warning
and preparedness?

Definition:-
A warning is a recommendation
or order for action to take place
based on a prediction or forecast.

Predictions and forecasts
should be made by scientists
(or other appropriate
and qualified experts)
Warnings should be issued
by civil authorities (such as
as an emergency management agency)
on the basis of valid predictions.

Scientists
Hazard
Evaluation
Administrators
Risk
communication
Decision
to warn
General
Public
Warning
Protective
action
The warning process
Organisational SocialTechnical
Precise Diffuse

Factors that influence the
effectiveness of a warning
• how predictable the hazard is
• how long the precursors (if any) last
• how quickly the disaster
strikes (speed of onset)
• how far the impact can be controlled
• frequency, duration and size of impact.

A warning system consists
of a combination of:-
• physical and social components
• technology and organisation
• planning and communication.
• monitoring and evaluation

Stages in the warning process
• decision-makers recognize
existence of hazard and decide
to create a warning system
• they decide who to warn, about
what, and how to warn them
• a system is designed to monitor changes
in the hazard and issue warnings
• the system is installed and tested.

• what is likely to happen -
the nature of the impact
• when it is likely to happen -
the time window of the prediction
• where it is likely to happen -
the geographical area affected.
What a warning message should say:-

What a warning message should say:-
• what actions are required
• who to contact for further information.
• what the consequences of the
impact are expected to be
• whether the response is
obligatory or merely recommended

Stages in the warning process
• the public must be educated to
respond appropriately to a warning
• the system must be tuned
to make it work better
• changes in the hazard are
detected and monitored
• incoming information is
collated and evaluated.

The phases of warning:-
• warning message sent
• content evaluated
• risk perceived
• choice of behaviour
• action taken
(choice realised).
• message received

Transmission
of warning
messages:-
• a hazard watch
- "conditions have occurred that
normally precede a disaster"
• a hazard warning
- "impact is certain,
or at least very likely".

Post-warning actions
• issue of all-clear, stand-down
and end-of-emergency messages
• debriefing and hindsight review
• revising and testing the warning system.

Factors that influence the
effectiveness of a warning:-
• what the probable consequences
of the impact are
• how much assistance is available
• quality of personnel
and command structure
• legal responsibilities.

Warning messages that succeed are:-
• from official (and credible) sources
• clear, consistent, precise
• repeated and confirmed
• the content of messages
• how messages are interpreted.
But social factors influence...
• the channels of communication

People interpret warning messages
differently according to...
• circumstances
• personality factors
• revised and repeated warning messages
will almost certainly be needed.
• social contexts
Public reaction to warnings needs
to be monitored and the results
fed back to the issuers of warnings

The initial response to warnings
tends to be disbelief, followed
by confirmation behaviour
Public awareness and participation
are crucial to the success
of warning systems.

Warning verification processes
• normalcy bias: lack of confirming
evidence (usually visual)
• latent confirmation: does the
information square with beliefs
and personal knowledge?
• socialisation of response:
seeking confirmation from
family, friends and colleagues
• contact with officialdom.

• unconflicted inertia: the
tendency to undervalue warnings
• cognitive dissonance: unease
when two conflicting beliefs
are held simultaneously
• some deviant behaviour is possible.
• panic is an unlikely
response to warnings

People who react best to warnings
• are under 40 but over 25
• are female
• are not members of an ethnic minority
• have not lived long in the area
but are well integrated with the
community and its institutions.

• have middle-to-high social status
• are parents with children living at home
• live near relatives and
utilise kinship networks
• are well able to understand the risk.
People who react best to warnings

How much time does it take to warn
a community of modest dimensions
(a small town, for instance)?
• 3-4 hours for 90% of inhabitants
• using various means of communication:
- official emergency personnel
- informal contacts
- the mass media
• longer warnings lead to more
confirmation behaviour
• confirmation is most important
when impacts are common.

Examples of imprecise predictions
that led to inefficient warnings
• an 86% chance of a
magnitude 7 earthquake in
Southern California in 25 years
• a 5% chance that a magnitude
5.1 earthquake would occur
in the San Francisco Bay region
during specified 5-day periods
• a 20% chance of a magnitude 5.1
or greater in a restricted area of
S. California over a 30-day period.

Nevado del Ruiz, Colombia, Nov. 1985:
the worst failure of warning processes
in modern times.

Nevado del Ruiz, 13 November 1985
• a nocturnal phreatic eruption
with attenuated precursors
• 23,000 dead in lahars (mudflows),
most in the town of Armero
• a hazard map had been made
• the volcano was heavily instrumented
• there was a failure of communication
between scientists, civil authorities
and the general public.

Parkfield, California,
1992-3: a 90% chance
of a mag. 6 earthquake
300 scientific instruments
deployed, 80 of them
recording continuously

The earthquake didn't happen!

EVACUATION

Evacuation is the most widespread
and effective short-term measure
to protect the public
against sudden-impact disasters
BUT: it is not always appropriate,
feasible or advisable.

Types of evacuation
Sort-term Long-term
Pre-impact
Emergency
protection
Preventative
Post-impact Rescue
For
reconstruction

The 'evaluation-dissemination subsystem'
• identify and measure risk
• collect and interpret data
• decide to evacuate
• determine content of message to public
• apportion these tasks
to appropriate agencies.
• transmit message
• direct evacuation and monitor result

The phases of evacuation
• decision time
• notification time
• evaluation time
• preparation time
• verification time.
• journey time

Some precepts of evacuation
• evacuation should only be attempted if
there is enough time to accomplish it
• evacuation should move people into
progressively safer areas, not
through areas of danger
• bottlenecks must be managed
• destinations need to be planned.

The evacuee's choice
• be unaware and do nothing
• understand the risk but do nothing
• do something to protect oneself,
but not evacuate
• prepare to evacuate but not go
• evacuate.

Immediate
adaptive
actions
ADAPTIVE
Eventual
adaptive
actions
Efforts to
confirm
information
Failure to act
on received
information
Total
denial of
threat
MALADAPTIVE
A CONTINUUM OF PUBLIC REACTIONS
TO HAZARD IMPACT WARNINGS
Supply
interpretable
information
ADAPTIVE
Supply
"raw"
information
Supply
theoretical
information
Fail to
deliver
information
Have no
applied
contacts
MALADAPTIVE?
A CONTINUUM OF SCIENTISTS' REACTIONS
TO THE NEED FOR USABLE INFORMATION

Sociological processes
in family evacuation
Evacuation by....
• default
• invitation
• compromise
• decision.

Things that facilitate evacuation
• a personal action plan
• is what the mass media say consistent?
• can one calm fears of looting?
• are there public information centres?
• do potential evacuees have faith in
the authorities and institutions that
issue the evacuation order? .

Factors that influence the
choice of destination
• will relatives offer shelter?
• how long is the warning time?
• how long is the evacuee expected
to be away from home?
• how well-prepared is the evacuee?
• from what social class is the evacuee?
• what is the risk?

Efficiency of evacuations as
reported in the research literature
(Sorenson & Mileti 1988 and other sources)
• minimum 32% in low-risk areas
• maximum 98% in high-risk areas
• almost 90% left within 1 hour
• nearly 60% left within 10 minutes
• 60-88% went to friends and relatives.
• 6-36% went to public shelters
[X]

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