Geoscience Reference
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in the community, and with vulnerabilities ever-present, an EWS cannot exist
intermittently or rarely to be visible only when a hazard manifests. Bangladesh's
cyclone warning and shelter system provides an example. Haque and Blair ( 1992 )
describe how Bangladeshis were often reluctant to evacuate to fl ood shelters, not
because they disbelieved the warnings, but because they feared that their property
left behind would be looted, while also being concerned that they would need to
pay rent in order to use the shelters. Now, Bangladesh's cyclone warning and shel-
ter system incorporates day-to-day aspects of life (Akhand 2003 ): Disaster aware-
ness education is included as part of the EWS, plus some of the shelters are in
schools, colleges, offi ces, and community centres, so that people are familiar with
these locations and do not see the shelters as being strange or frightening.
Timeliness : For a warning to be useful, information must provide enough usable
lead time for those at risk to decide whether and how to react. This characteristic
varies from hazard to hazard and from vulnerability to vulnerability. For tornadoes,
minutes are needed to reach a shelter—longer if the whereabouts of shelters are not
known, if no formal shelters are nearby, or if people have limited mobility. Many
tornado shelters—particularly informal shelters such as ditches—are not particu-
larly hospitable (so people might not want to stay in them for very long) nor are they
easy to reach for people with limited mobility. For hurricanes on a trajectory towards
major cities, evacuation can take a few days, which is usually how much lead time
can be provided with a fair degree of certainty. That does not preclude last-minute
trajectory changes which frequently occur. On the vulnerability side, it is often
harder for less affl uent people to evacuate because they do not have access to private
transportation.
For the El Niño Southern Oscillation (ENSO) phenomenon, forecasts with rea-
sonable confi dence can sometimes be made months ahead of time, giving people a
chance to change the location or type of crops that they plant, the water that they
store, and the ploughing techniques that they use. Recent migrants, forced or volun-
tarily, might be less able to use such information because they have not lived in the
location long enough to know how to adjust their activities in response to the warn-
ing. Climate change has given humanity decades of lead time and there are clear
directions which could be taken, and which some groups are taking, with respect to
reacting to that warning.
Not all hazards give a lead time commensurate with the action time. Flash fl oods
in mountainous regions might have 2-20 min of lead time following a localised
cloudburst, giving little time to climb to higher ground—even less opportunity if
you have diffi culty climbing. On 17 July 1998, several minutes after an offshore
earthquake, a large tsunami inundated parts of coastal Papua New Guinea which
lacked tall buildings or higher ground. Even if a tsunami warning had been issued
instantaneously following the earthquake, there would not have been suffi cient lead
time for people to reach higher ground. Over 1,500 people died.
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