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Coppola-28201529Chapter3RiskandVulnerability.pdf
Introduction to International Disaster Management
Third Edition
Damon P. Coppola
AMSTERDAM • BOSTON • HEIDELBERG • LONDON
NEW YORK • OXFORD • PARIS • SAN DIEGO
SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO
Butterworth-Heinemann is an imprint of Elsevier
150 Introduction to International Disaster Management. http://dx.doi.org/10.1016/B978-0-12-801477-6.00003-4
Copyright © 2015 Elsevier Inc. All rights reserved.
CHAPTER
RISK AND VULNERABILITY 3 CHAPTER SUMMARIES
Citizens collectively face risks from a range of large-scale hazards. Risk is the interaction of hazard consequences
and likelihood. Using this formula, hazards are compared and ranked, allowing disaster managers to determine
the most effective and appropriate treatment options. The goal of risk analysis is a standard measurement of likeli-
hood and consequence, whether quantitative or qualitative. Consequence describes hazard effects on humans, built
structures, and the environment. Losses may be direct or indirect, and tangible or intangible. Hazard likelihood and
consequences can change considerably over time. These trends can be incremental or extreme, and can occur sud-
denly or over centuries. Risk evaluation is conducted to determine the relative seriousness of risks, and to compare
and prioritize them. Disaster managers must decide what risks to treat, what risks to prevent at all costs, and what
risks to disregard. These decisions are based on risk acceptability. The personal factors that dictate risk acceptabil-
ity are guided by risk perception. Vulnerability is a measure of the propensity of an object, area, individual, group,
community, country, or other entity to incur the consequences of a hazard, and is the result of physical, social,
economic, and environmental factors.
Key Terms: consequence; direct and indirect losses; likelihood; qualitative risk analysis; quantitative risk analysis;
risk; risk evaluation; risk matrix; risk perception; tangible and intangible losses; vulnerability.
INTRODUCTION Risk is an unavoidable part of life, affecting all people without exception, irrespective of geographic or
socioeconomic limits. Each choice we make as individuals and as a society involves specific, often
unknown, factors of risk, and full risk avoidance is generally impossible.
On the individual level, each person is primarily responsible for managing the risks he or she faces
as he or she sees fit. For some risks, management may be obligatory, as with automobile speed limits
and seatbelt usage. For other personal risks, such as those associated with many recreational sports,
individuals are free to decide the degree to which they will reduce their risk exposure, such as by wear-
ing a helmet or other protective clothing. Similarly, the risk of disease affects humans as individuals,
and as such is generally managed by individuals. By employing risk reduction techniques for each life
hazard, individuals effectively reduce their vulnerability to those hazard risks.
As a society or a nation, citizens collectively face risks from a range of large-scale hazards. Although
these hazards usually result in fewer total injuries and fatalities over the course of each year than indi-
vidually faced hazards, they are considered much more significant because they have the potential to
result in many deaths, injuries, or damages in a single event or series of events. In fact, some of these
hazards are so great that, if they occurred, they would result in such devastation that the capacity of
local response mechanisms would be overwhelmed. This, by definition, is a disaster. For these
151 TWO COMPONENTS OF RISK
large-scale hazards, many of which are identified in chapter 2, vulnerability is most effectively reduced
by disaster risk management efforts collectively, as a society. For most of these hazards, it is the govern-
ment’s responsibility to manage, or at least guide the management of, disaster risk reduction measures.
And when these hazards do result in disaster, it is likewise the responsibility of governments to respond
to them and aid in the recovery that follows.
TWO COMPONENTS OF RISK Chapter 1 defines risk as the interaction of a hazard’s consequences with its probability or likelihood.
This definition and similar derivatives are used in virtually all technical documents associated with risk
management. Clearly defining the meaning of “risk” is important, because the term often carries mark-
edly different meanings for different people (Jardine and Hrudey 1997). One of the simplest and most
common definitions of risk, preferred by many risk managers, is displayed by the equation stating that
risk is the likelihood of an event occurring multiplied by the consequence of that event, were it to occur:
Risk = Likelihood × Consequence (Ansell and Wharton 1992).
LIKELIHOOD
“Likelihood” can be given as a probability or a frequency, whichever is appropriate for the analysis
under consideration. There are multiple variants to how probability and frequency are displayed, but
these all typically refer to the same absolute value. “Frequency” communicates the number of times an
event will or is expected to occur within an established sample size over a specific period of time. Quite
literally, it tells how frequently an event occurs. For instance, the frequency of auto accident deaths in
the United States equates to approximately one death per 81 million miles driven (Dubner and Levitt
2006).
In contrast to frequency, “probability” refers to single-event scenarios. Its value is expressed as a
number between zero and one, with zero signifying a zero chance of occurrence and one signifying
certain occurrence. Using the auto accident example, in which the frequency of death is one per 81
million miles driven, we can say that the probability of a random person in the United States dying in
a car accident equals 0.000001 if he or she was to drive 81 miles.
When disaster risk managers use a standardized method of calculating risk utilizing this formula
across all identified hazards, comparison and ranking by severity is possible. If hazard risks are instead
analyzed and described using different methods and/or terms of reference for each hazard, or even for
groups of hazards, comparison and ranking becomes very difficult when prioritizing how limited
resources will be dedicated to risk reduction efforts.
This ranking of risks, or “risk evaluation,” is what allows disaster risk managers to determine which
treatment options, whether mitigation or preparedness, or both, are the most effective, most appropri-
ate, and will provide the most benefit per unit of cost. Not all hazard risks are equally serious, and risk
analysis is what enables an informed decision-making process.
Without exception, governments have limited funds available to manage the hazard risks they face.
While reducing the risk of one hazard may be less expensive or more easily implemented than reducing
the risk of another, cost and ease alone may not be valid reasons to choose a treatment option. Hazards
that have the potential to inflict great consequences (in terms of lives lost or injured, or property
CHAPTER 3 RISK AND VULNERABILITY152
damaged or destroyed) and/or occur with great frequency pose the greatest overall threat. Considering
budgetary limits, disaster risk managers should generally treat those hazard risks that pose the greatest
threat first. Fiscal realities often drive this analytic approach, resulting in situations in which certain
hazard risks in the community’s overall risk profile are mitigated, while others are not addressed to any
degree at all.
The goal of risk analysis is therefore to establish a standard, comparable measurement of the likeli-
hood and consequence factors for each hazard identified. The different mechanisms through which
values are derived for a hazard’s likelihood and consequences fall into two general categories of analy-
sis: quantitative analysis and qualitative analysis. Quantitative analysis draws upon mathematical and/
or statistical data to achieve numerical descriptions of risk. Qualitative analysis also relies upon math-
ematical and/or statistical data, but instead uses defined terms (words) to describe and categorize the
hazard risk likelihood and consequence value outcomes. And while quantitative analyses provide spe-
cific data points (e.g., dollars, probability, frequency, or number of injuries/fatalities), qualitative analy-
ses consider ranges of possible values for which each qualifier is assigned. It is often cost- and
time-prohibitive, and often not necessary, to determine the exact quantitative measures for the likeli-
hood and consequence factors of a hazard’s risk. Qualitative measures are much easier to determine and
typically require less time, money, and, most important, expertise, to conduct. For this reason, it is the
most commonly encountered method of assessment in practice. The following section provides a gen-
eral explanation of how these two types of measurements apply to the likelihood and consequence
components of risk.
Quantitative Representation of Likelihood As previously stated, likelihood can be derived as either a frequency or a probability. A quantitative
system of measurement exists for each. For frequency, this number indicates the number of times a
hazard is expected to result in an actual event over a chosen time frame. For example, a particular area
might experience flooding four times per year, one time per decade, ten times each month, and so on as
calculated. Probability considers the same base data, but expresses the outcome as a measure that lies
between 0 and 1 or as a percentage value that falls between 0 percent and 100 percent. In both cases,
this represents the chance of occurrence. For example, if an area has experienced four flood events in
the past 200 years where floodwaters reached 20 feet above the base flood elevation, then this severity
of flooding has a one-in-fifty chance of occurring in any given year, or a probability of 2 percent, or
0.02, each year. This is also considered to be a 50-year flood. An event that is expected to occur two
times in the next three years has a 0.66 probability each year, or a 66 percent chance of occurrence, and
is much more probable than the 50-year event.
Qualitative Representation of Likelihood Likelihood can also be expressed using qualitative measurement, applying words to describe the chance
of occurrence. Each word or phrase represents a pre-established range of possibilities. For instance, the
likelihood of a particular hazard resulting in an emergency or disaster event might be described as fol-
lows using a qualitative system of likelihood:
• Certain: >99 percent chance of occurring in a given year (one or more occurrences per year)
• Likely: 50–99 percent chance of occurring in a given year (one occurrence every one to two
years)
153 TWO COMPONENTS OF RISK
• Possible: 5–49 percent chance of occurring in a given year (one occurrence every two to twenty
years)
• Unlikely: 2–5 percent chance of occurring in a given year (one occurrence every twenty to fifty
years)
• Rare: 1–2 percent chance of occurring in a given year (one occurrence every fifty to one hundred
years)
• Extremely rare: <1 percent chance of occurring in a given year (one occurrence every one hun-
dred or more years)
Note that this is just one of a limitless range of qualitative terms and values that can be used to
describe the likelihood component of risk. As long as all hazards are compared using the same range of
qualitative values, the actual determination of likelihood ranges attached to each term does not neces-
sarily matter. (See exhibit 3.1.)
EXHIBIT 3.1 QUALITATIVE MEASUREMENTS: THE CONSIDERATION OF RISK PERCEPTION AND STANDARDIZATION
In brief, different people fear different hazards for many different reasons. These differences in perception can be based
on experience with previous instances of disasters, specific characteristics of the hazard, or many other combinations of
reasons. Even the word risk has different meanings to different people, ranging from “danger” to “adventure.”
Planners, or members of disaster risk management teams, are likely to draw from diverse backgrounds and may even be
from different parts of the country or the world. Each will have a unique perception of risk (regardless of whether they are able
to recognize these differences). Such differences can be subtle, but they make a major difference in the risk analysis process.
Quantitative methods of assessing risk use exact measurements and are therefore not very susceptible to the effects of
risk perception. A 50 percent likelihood of occurrence is the same to everyone, regardless of their convictions. Unfortu-
nately, there rarely exists sufficient information to make definitive calculations of a hazard’s likelihood and consequence.
The exact numeric form of measurement achieved through quantitative measurements is incomparable. The value of
qualitative assessments, however, lies in their ability to accommodate for an absence of exact figures and their ease of use.
Unfortunately, risk perception causes different people to view the terms used in qualitative systems of measurement
differently. For this reason, qualitative assessments of risk must be based on quantitative ranges of possibilities or clear
definitions. For example, imagine a qualitative system for measuring the consequences of earthquakes in a particular city
in terms of lives lost and people injured. Now imagine that the disaster management team’s options are “None,” “Minor,”
“Moderate,” “Major,” or “Catastrophic.” One person on the team could consider 10 lives lost as minor. However, another
team member considers the same number of fatalities to be catastrophic. It depends on the perception of risk that each has
developed over time.
This confusion is significantly alleviated when detailed definitions are used to determine the assignation of
consequence measurements for each hazard. Imagine the same scenario, using the following qualitative system of
measurement):
1. None. No injuries or fatalities.
2. Minor. Small number of injuries but no fatalities. First aid treatment required.
3. Moderate. Medical treatment needed but no fatalities. Some hospitalisation.
4. Major. Extensive injuries, significant hospitalisation. . . . Fatalities.
5. Catastrophic. Large number of severe injuries. Extended and large numbers requiring hospitalisation. . . . Significant
fatalities. (EMA 2000)
This system of qualitative measurement, with defined terms, makes it more likely that people of different backgrounds
or beliefs would choose the same characterization for the same magnitude of event. Were this system to include ranges
of values, such as “1–20 fatalities” for “Major,” and “more than 20 fatalities” for “Catastrophic,” the confusion could be
alleviated even more.
CHAPTER 3 RISK AND VULNERABILITY154
CONSEQUENCE
The consequence component of risk describes the effects of the risk on humans, built structures, and
the environment. There are generally three factors examined when determining the consequences of a
disaster:
1. Deaths/fatalities (human)
2. Injuries (human)
3. Damages (cost, reported in currency, generally US dollars for international comparison)
Further distinctions have been made to distinguish between damages and losses, as is the case with
the World Bank’s Damage and Loss Assessment (DALA) methodology (see chapter 6). In this case,
damages are defined as the destruction of physical assets, while losses are defined as foregone produc-
tion or income. And while damages occur immediately and can be rebuilt, losses occur over a longer
period of time and may not be recoverable.
Although attempts have been made to convert all three of these consequence factors into monetary
amounts to derive a single number to quantify the consequences of a disaster, doing so has proved
controversial (how can one place a value on life?) and complex (is a young life worth more than an old
life? by how much?). As such, it is often most appropriate and convenient to maintain a distinction
between these three factors when detailing an event’s impact.
Categories of consequence can be further divided, and often are, to better understand their influence
within social and economic contexts. Two of the most common distinctions are direct and indirect
effects (damages/losses), and tangible and intangible effects (damages/losses).
Direct effects, as described by Keith Smith in his book Environmental Hazards, are “the first
order consequences that occur immediately after an event, such as the deaths and economic loss
caused by the throwing down of buildings in an earthquake” (Smith 1992). Examples of direct
effects are
• Fatalities
• Injuries (“The prediction of injuries is often more valuable than the prediction of fatalities,
because the injured will require a commitment of medical and other resources for treatment.”
[UNDP 1994])
• Cost of repair or replacement of damaged or destroyed public and private structures (buildings,
schools, bridges, roads, etc.)
• Loss of possessions
• Relocation costs/temporary housing
• Loss of agriculture and livestock
• Loss of business inventory/facilities/equipment/information
• Loss of usable land
• Community response and cleanup costs incurred
• Loss of historical documents or records
Indirect effects, according to Smith (1992), “emerge later and may be more difficult to attribute to
the event.” Examples of indirect losses include:
• Loss of livelihoods/income potential
• Input/output losses of businesses
155 TWO COMPONENTS OF RISK
• Loss of community population
• Loss of community character
• Loss of critical services due to organization or business losses
• Reductions in business/personal spending (“ripple effects”)
• Loss of institutional/tacit knowledge
• Mental illness/psychosocial impacts
• Bereavement/emotional loss
Tangible effects “are those for which it is possible to assign monetary values” (Smith 1992). Gener-
ally, only tangible effects are included in the estimation of future events and the reporting of past
events. Examples of tangible effects include:
• Cost of building repair/replacement
• Response costs
• Loss of inventory or possessions
• Loss of wages
• Loss of tax revenue
• Loss of trained or technical staff
Intangible effects are those that “cannot be properly assessed in monetary terms” (Smith 1992). This
is the primary reason that human fatalities and human injuries are assessed as a separate category from
the cost measurement of consequence in disaster management. These effects are almost never included
in damage assessments or predictions. Examples of intangible effects include:
• Cultural impacts
• Stress
• Mental illness
• Loss of community character
• Poor morale
• Consequences of a damaged environment
• Increased health risks
• Sentimental value
• Environmental losses (aesthetic value)
Although it is extremely rare for benefits or positive effects to be included in the assessment of past
disasters or the prediction of future ones, they do arise in the aftermath of many disasters. Like losses,
gains can be categorized as direct or indirect, tangible or intangible. Examples of tangible, intangible,
direct, and indirect gains include:
• Decreases in future hazard risk by preventing rebuilding in hazard-prone areas
• New technologies used in reconstruction that result in an increase in quality of services
• Removal of old/unused/hazardous buildings
• Jobs created in reconstruction
• Greater public recognition of hazard risk
• Otherwise-unobtainable funds available for development or disaster risk reduction
• Environmental benefits (e.g., fertile soil from a volcano)
• Community cohesion
CHAPTER 3 RISK AND VULNERABILITY156
As with the likelihood component of risk, the consequences of risk can be described according to
quantitative or qualitative reporting methods. Quantitative representations of consequence vary accord-
ing to deaths/fatalities, injuries, and damages:
• Deaths/fatalities. The specific number of people who perished in a past event or who would be
expected to perish in a future event; for example, 55 people killed.
• Injuries. The specific number of people who were injured in a past event or who would be
expected to become injured in a future event. Can be expressed just as injuries, or divided into
mild and serious; for example, 530 people injured, 56 seriously.
• Damages. The assessed monetary amount of actual damages and/or losses incurred in a past event
or the amount of damages expected to occur in a future event. Occasionally, this number includes
insured losses as well; for example, $2 billion in damages, $980 million in insured losses. For past
disasters, damages may also be adjusted for inflation to enable a more meaningful comparison of
events that occurred many years apart.
Qualitative Representation of Consequence As with the qualitative representation of likelihood, words or phrases can be used to describe the effects
of a past disaster or the anticipated effects of a future one. These measurements can be assigned to
deaths, injuries, or costs (the qualitative measurements of fatalities and injuries are often combined).
The list of qualitative terms included in Exhibit 3.1 is one example.
Additional measures of consequence are possible, depending on the depth of analysis. These addi-
tional measures tend to require a great amount of resources, and are often not reported or cannot be
derived from historical information. Examples include:
• Emergency operations. Can be measured as a ratio of responders to victims, examining the
number of people who will be able to participate in disaster response (both official and unofficial
responders can be included) as a ratio of the number of people who will require assistance. This
ratio will differ significantly depending on the hazard. For example, following a single tornado
touchdown, there are usually many more responders than victims, but following a hurricane,
there are almost always many more victims than responders. This measure could include the first
responders from the community as well as the responders from the surrounding communities
with which mutual aid agreements have been made. Emergency operations also can measure the
mobilization costs and investment in preparedness capabilities. It can be difficult to measure the
stress and overwork of the first responders and their inability to carry out regular operations (fire
suppression, regular police work, regular medical work).
• Social disruption (people made homeless/displaced). This can be a difficult measure because,
unlike injuries or fatalities, people do not always report their status to municipal authorities
(injuries and deaths are reported by the hospitals), and baseline figures do not always exist. It is
also difficult to measure how many of those who are injured or displaced have alternative options
for shelter or care. Measuring damage to community morale, social contacts and cohesion, and
psychological distress can be very difficult, if not impossible.
• Disruption to economy. This can be measured in terms of either the number of working days
lost or the volume of production lost. The value of lost production is relatively easy to measure,
while the lost opportunities, lost competitiveness, and damage to reputation can be much more
157 TWO COMPONENTS OF RISK
difficult. The loss of livelihoods can be extremely difficult to measure, especially in farming
or fishing communities or communities centered around home-based production of crafts, for
example.
• Environmental impact. This can be measured in terms of the clean-up costs and the costs to repair
and rehabilitate damaged areas. It is harder to measure in terms of the loss of aesthetics and public
enjoyment, the consequences of a poorer environment, newly introduced health risks, and the risk
of future disasters.
It does not matter what system is used for qualitative analysis, but the same qualitative analysis
system must be used for all hazards analyzed in order to compare risks. It may be necessary for disaster
managers to create a qualitative system of measurement tailored to the country or community where
they are working. Not all countries or communities are the same, and what amounts to a minor impact
in one could represent a catastrophe in another. Qualitative measures of consequence should therefore
accommodate these differences. For example, a town of 500 people would be severely affected by a
disaster that caused 10 deaths, while a city of 5 million may experience that many, or even more, deaths
just from car accidents in any given week.
Another benefit of creating an individualized system of qualitative analysis is the incorporation of
the alternative measures of consequence (ratio of responders to victims, people made homeless/dis-
placed). The more tailored a system of analysis is to the needs of the study area, the more meaningful
its outcome will be to the disaster risk management process.
Intensive, Extensive, and Emerging Risk Disaster risk managers are most often focused on addressing those hazards for which the likelihood of
occurrence is highest and the consequences are greatest. The risk for such hazards is considered to be
intensive. At the opposite end of the spectrum are those hazards for which frequency is high or very
high, yet the consequences are generally much less severe—perhaps isolated to an individual or a
neighborhood. Risk for hazards falling in this category are considered to be extensive. And while inten-
sive risk is most often associated with events that impact a large area, this does not mean that extensive
risk impacts only highly localized areas (though that is often the case.)
Events resulting from extensive risk are rarely if ever noteworthy or newsworthy, and often are not
tracked by centralized disaster information systems. Likewise, the required response may be nothing
beyond what is typical for the local emergency services to perform on any given day. It is the collective
sum of extensive risk that is significant, in that it can—and often does—exceed that of the major disas-
ter events incurred in any given year with regard to consequences. (See figure 3.1.) Extensive risk is
thus important to the disaster risk manager not in terms of preparing for response, but rather because it
is often true that the same mechanisms by which intensive risk is reduced hold true for extensive risk.
(See chapter 4 for mitigation options.)
The United Nations Office for Disaster Reduction (UNISDR) reports that 97 percent of extensive
risk is weather-related. It is interesting to note that extensive and intensive risks are relative terms, such
that two events of equal consequence in two separate locations might be considered extensive—or
routine—in a large city, yet intensive in a small village. And because of these distinctions between
localities or countries, differences between extensive and intensive risk should be thought of as a matter
of capacity.
CHAPTER 3 RISK AND VULNERABILITY158
The third special category, termed emerging risk, refers to hazards with traditionally low frequen-
cies of occurrencebut which are nonetheless increasing due to new patterns of exposure, increasing
frequencies, and changes in population vulnerability. Space weather is an example of an emerging risk.
In this instance, there is not an increase in the incidence of solar flares, but the impact they have on
modern technological systems, and the reverberations that has on contemporary social and economic
systems, are significant. The expansion of tropical diseases into areas farther and farther from the equa-
tor are presenting another form of emerging risk. The chukungunya virus, which, like Dengue Fever in
the 1980s, is moving quickly through the Caribbean, threatens many countries previously unaffected
because of wetter and warmer conditions that enable breeding of the mosquitos that carry the disease.
TRENDS Whether risks have existed for centuries or are just emerging, the likelihoods and consequences associ-
ated with them are rarely static. The number of events caused by a particular hazard might increase or
decrease over time, whether due to changing global climate patterns, changes in human activities, or
FIGURE 3.1
Mortality from extensive and intensive disasters between 1989 and 2009, in 21 countries in Africa, Asia,
Latin America, and the middle East (including Argentina, Bolivia, Chile, Colombia, Costa Rica, Ecuador,
El Salvador, Guatemala, India [Orissa and Tamil Nadu], Indonesia, Iran [Islamic Republic of], Jordan, Mexico,
Mozambique, Nepal, Peru, Panama, Sri Lanka, Syrian Arab Republic, Venezuela, and Yemen)
Source: UNISDR, 2012.
159 TRENDS
both. Likewise, the damaging consequences of existing hazards might increase or decrease, even if
there are no changes observed in the total number of events that hazard causes. These trends can be
incremental or extreme and can occur suddenly or over centuries. Several short-term trends may even
be part of a larger long-term change.
CHANGES IN DISASTER FREQUENCY
A change in disaster frequency occurs when fewer or more disaster events of similar magnitude are
noted in a particular area of study. Such changes can be the result of several things, including an
increase in actual occurrences of a hazard, an increase in human activity in areas regularly exposed to
the hazard, an increase in vulnerability to the hazard among the exposed population, or a decrease in
disaster risk management capacity in the exposed area. It is important to remember that a disaster is not
determined by the occurrence of a hazard, but rather the outcome of the hazard’s consequences. A tor-
nado hitting an open field, for example, is not considered a disaster.
Changes in climate patterns, plate tectonics, or other natural systems can cause changes in the fre-
quency of particular natural hazards, regardless of whether the causes of the changes are natural (e.g.,
El Niño) or man-made (e.g., greenhouse gas emissions). Changes in frequency for technological or
intentional hazards can be the result of many factors, such as increased or decreased regulation of
industry and increases in international instability (terrorism).
Increases or decreases in human activity can also cause changes in disaster frequency. As popula-
tions move, they inevitably place themselves closer or farther from the range of effects from certain
hazards. For instance, if a community begins to develop industrial facilities within a floodplain that was
previously unoccupied, or in an upstream watershed where the resultant runoff increases flood hazards
downstream, the risk to property from flooding increases.
CHANGES IN DISASTER CONSEQUENCES
A change in disaster consequences occurs when a hazard inflicts either more or less severe impacts to
people, property, the environment, and the economy without any significant change in the number of
events caused by the hazard. Similar to changes in disaster likelihoods, changes in consequences may
be the result of one or more factors including changes in the attributes of the actual hazard (e.g.,
cyclones of greater intensity), changes in activity or development that influence the vulnerability of
people or structures, or a decrease in the willingness or ability to take pre-disaster actions to reduce the
impacts of hazard events (i.e., mitigation).
Changes in the attributes of the hazard can occur as part of short- or long-term cycles, perma-
nent changes in the natural processes if the hazard is natural, or changes in the nature of the tech-
nologies or tactics in the case of technological and intentional hazards. The consequences of
natural hazards change only rarely independent of human activities. One example is El Niño
events, with intense flooding increasing in some regions of the world and drought affecting others,
possibly for years. Technological and intentional hazards, however, change in terms of the severity
of their consequences all the time. The high numbers of deaths and the structural damage associ-
ated with the 1998 bombings of the US embassies in Kenya and Tanzania and the September 11,
2001, attacks on the World Trade Center and the Pentagon together display an increase in the
consequences of international terrorism on Americans and American interests. A mutation of a
CHAPTER 3 RISK AND VULNERABILITY160
certain viral or bacterial organism, resulting in a more deadly pathogen, can cause a drastic increase
in consequences, as occurred with the West Nile virus, tuberculosis, mad cow disease, SARS, and
MERS, to name a few.
Changes in human activities are probably the most significant cause of increases in the conse-
quences of disasters. These trends, unfortunately, are predominantly increasing. While the effects of
disasters worldwide are great, their consequences are the most devastating in developing countries.
Smith (1992) lists six reasons for these changes:
1. Population growth. As populations rise, the number of people exposed to hazard risk likewise
increases. Population growth can be regional or local if caused by movements of populations.
As urban populations grow, population density increases, exposing more people to hazards than
would have been affected previously.
2. Land pressure. Many industrial practices cause ecological degradation, which in turn can lead to
an increase in the severity of hazards. Filling in wetlands can cause more severe floods. Lack of
available land can lead people to develop areas that are susceptible to, for example, landslides,
avalanches, floods, and erosion, or that are closer to industrial facilities.
3. Economic growth. As more buildings, technology, infrastructure components, and other structures
are built, a community’s vulnerability to hazards increases. More developed communities with
valuable real estate have much more economic risk than communities in which little development
has taken place.
4. Technological innovation. Societies are becoming more dependent on technology. These systems,
however, are susceptible to the effects of natural, technological, and intentional hazards. Technol-
ogy ranges from communications (the Internet, cell phones, cable lines, satellites) to transportation
(larger planes, faster trains, larger ships, roads with greater capacity, raised highways) to utilities
(nuclear power plants, large hydroelectric dams) to any number of other facilities and systems
(high-rise buildings, life support systems).
5. Social expectations. With increases in technology and the advancement of science, people’s
expectations for public services, including availability of water, easy long-distance transportation,
constant electrical energy, and so forth, also increase. When these systems do not function, the
economic and social impacts can be immense.
6. Growing interdependence. The interdependence of individuals, communities, and even nations
is increasing rapidly. Recent outbreaks of viruses, including SARS, avian influenza, swine flu,
enterovirus 71 (EV71), and MERS highlight the ease with which pathogens can quickly impact
dozens of countries in distant regions, thanks to international travel. The economic and social
impacts of major disasters are global, as well. The September 11, 2001, terrorist attacks in the
United States caused the global tourism market to slump, while the 2011 Thailand floods caused
drastic cost increases to the global technology sector when production for more than one-third of
the global supply of hard drives was halted.
The validity of identified trends must be verified. Some trends are simply the result of better report-
ing or detection. The technology used to detect many hazards has improved, allowing for recognition
of factors where such recognition was formerly much more difficult or impossible. It is also common
for a trend to exist simply because research or records are incomplete. And finally, standardizing the
mechanisms for measurement across time is important. Costs of disasters, for instance, must be adjusted
161 COMPUTING LIKELIHOOD AND CONSEQUENCE VALUES
for inflation, or else increases in total disasters costs may be distorted. The same is true with injuries
and deaths, which should be considered in light of total populations and population densities for specific
hazard types such as epidemics.
COMPUTING LIKELIHOOD AND CONSEQUENCE VALUES Because there is rarely sufficient information to determine the exact statistical likelihood that disaster
will occur, or to determine the exact number of lives and property that would be lost, combining quan-
titative and qualitative measurements can provide highly useful yet obtainable risk measures. By com-
bining these two methods, disaster risk management practitioners can achieve a standardized
measurement of risk that accommodates less precise measurements of both risk components (likeli-
hood and consequence) in determining the comparative risk between hazards.
The process of determining the likelihood and consequence of each hazard begins with both quan-
titative and qualitative data and converts it all into a qualitative system of measurement that accommo-
dates all possibilities that hazards present (from the rarest to the most common and from the least
damaging to the most destructive).
DEPTH OF ANALYSIS
The depth of analysis disaster risk managers take is determined by three primary factors: availability of
financial and human resources, seriousness of the risk, and the complexity of the problem. Decisions
regarding the level of effort and resources dedicated to the treatment of each individual hazard are
informed by the hazard identification and assessment processes.
Each hazard may be analyzed in multiple ways as determined by the range of possible intensities
that might be exhibited. The likelihood and consequences for each possible intensity will be different,
which in turn results in different treatment (mitigation) options. (See exhibit 3.2.)
For instance, “earthquake” is a general term used to describe that hazard, though a magnitude 4.0
event is very different from a magnitude 9 event from the planning perspective. Generally, the lower a
hazard event’s intensity (and likewise the milder its consequences), the greater its likelihood of occur-
ring will be. Several thousand earthquakes of very low intensity and magnitude occur daily with few or
no consequences at all. Below a certain threshold, these low-impact events can be disregarded.
However, lower-frequency strong earthquakes must be given greater consideration because of their
potential to inflict massive casualties and damages.
EXHIBIT 3.2 F:N CURVES
Probability curves called f:N curves, which plot historical hazard intensities and likelihoods against the amount of damage
inflicted, can provide an estimation of both the likelihood of events of specific magnitude and the consequences should
those events occur. Examples of worldwide hazard f:N curves are shown in figure 3.2.
Individual communities would plot f:N curves for their locality using local historical data. This graphical representa-
tion illustrates the justification for dividing hazards according to possible intensities.
Source: UNDP, 1994.
CHAPTER 3 RISK AND VULNERABILITY192
Example C shows how new information can change the determination of what is considered accept-
able risk. In this example, we assume that alternative M determines the acceptable risk, as in example
A. However, additional information provided by experience, research, development, or analysis reveals
that the initial assessment of alternative M must be revised. Instead of confirming that M has lower cost
and lower risk than both alternatives K and L, the new information shows that M has both the high cost
of K and the high risk of L. The acceptable risk is now determined by the choice between K and L.
Example D illustrates the effect of values and preferences on the choice between alternatives. In this
example, different preferences for trading off increased cost for lower risk are represented by the two
curves. In case 1, the trade-off curve reflects the willingness to incur large costs to reduce risk by small
amounts. Alternative K is the most attractive choice with this preference. In case 2, the trade-off curve
reflects less of a willingness to increase costs in exchange for specific reductions in risk. This prefer-
ence selects alternative L as the best choice. Because acceptable risk is determined by the choice
between the two alternatives, these different preferences change what is considered acceptable.
VULNERABILITY The concept of vulnerability was defined in chapter 1 as being a measure of the propensity of an object,
area, individual, group, community, country, or other entity to incur the consequences of a hazard. As
this section illustrates, measurement of vulnerability requires examination of a combination of physi-
cal, social, economic, and environmental factors or processes. Each of these factors influences risk by
causing an increase or decrease in likelihood and/or fewer or greater negative consequences.
It is important to first clarify the difference between the concepts of vulnerability and exposure,
which are often confused. The two words are frequently used interchangeably to describe how a com-
munity, country, or region is likely to experience a certain hazard. However, this is factually incorrect
and causes confusion. We can best understand the difference between vulnerability and exposure by
considering the following statement, which appeared in the United Nations Office for Disaster Reduc-
tion document Living with Risk: “While most natural hazards may be inevitable, disasters are not”
(ISDR 2004).
While vulnerability describes a propensity to incur consequences, exposure merely suggests that the
individual, structure, community, nation, or other subject will be confronted by the forces associated
with that particular hazard. For instance, imagine that someone says, on learning that Spain regularly
experiences extended periods of lower-than-normal rainfall, “The Spanish are vulnerable to drought.”
In the absence of additional information, this statement suggests more than the speaker intended. The
use of the word “vulnerable” implies that the population is likely to incur negative consequences,
whether because of poor coping capacity or other factors, rather than simply stating that droughts hap-
pen there. The reality, as figures 3.10 and 3.11 illustrate, is that while Spain is regularly exposed to
drought, the nation is not vulnerable to its consequences.
Remember that risk is composed of two components: likelihood and consequence. Exposure, or the
measure of whether a person, building, population, or nation is likely to experience a hazard, looks only
at a hazard’s likelihood. Vulnerability, however, is a factor of how small or great the consequences will
be should the hazard manifest. Figures 3.10 and 3.11 illustrate how the many different nations that are
exposed to drought each exhibit differing levels of vulnerability to this hazard. In light of this, it would
be more accurate to state that the Spanish face a drought risk because their exposure likelihood is
193 VULNERABILITY
FIGURE 3.10
National vulnerabilities to drought risk as a factor of population exposure
Source: EM-DAT – International Disaster Database.
FIGURE 3.11
National vulnerabilities to drought risk as a factor of population exposure
Source: EM-DAT – International Disaster Database.
CHAPTER 3 RISK AND VULNERABILITY194
greater than zero, but because of the measures that nation has taken to minimize drought consequences,
it is no longer vulnerable to the hazard.
Vulnerability, like likelihood and consequence, is something that can be studied and measured.
Likewise, it can be decreased or increased depending on actions that are taken or events that transpire.
By taking action to prepare for a hazard or mitigate that hazard’s risk, the propensity to incur harm is
thus reduced. (Mitigation and preparedness are detailed in chapters 4 and 7, respectively.) As vulnera-
bility is decreased, resilience is increased. Resilience, which can be defined as the ability to prevent or
avoid the negative consequences of hazards, is the opposite of vulnerability.
As the definition of vulnerability in chapter 1 explains, two identical manifestations of a hazard may
result in a minor issue in one country and a major catastrophe in another. The impacted countries’ vul-
nerabilities are what account for the difference in presentation. There are generally four different types
of vulnerabilities: physical, social, economic, and environmental. Each is determined by a set profile of
factors that are identifiable and measurable.
Physical vulnerability looks at the interaction between living things, structures, material objects,
systems, and the physical forces of hazards. The choices societies make about placing structures, trans-
portation routes, and populations either in or out of harm’s way effectively determine physical vulner-
ability. Most of the risk reduction (mitigation) measures taken to reduce disaster risk seek to enable
people, structures, objects, and systems to resist these physical forces, thus reducing societies’ physical
vulnerability to them. For instance, when a building constructed in a flood hazard zone is elevated
above the limits of anticipated flood heights, its physical vulnerability is reduced. People are also physi-
cally vulnerable to hazards any time they have little protection from the physical forces of the hazards
they encounter (or the forces of objects affected by the disaster and conditions created by the hazard).
As populations move into areas of high risk of disaster, their exposure increases, and the knowledge
they have and actions they take determine whether or not their vulnerability also increases.
Social vulnerability is a measure of the behavioral, social, political, and cultural factors that increase
or decrease a population’s propensity to incur harm or damage as a result of their exposure to a specific
hazard. Certain collective and/or individual behaviors can contribute to or reduce each person’s and
each population’s ability to protect themselves from harm. Within more general populations there are
typically subgroups that exhibit different vulnerability factors than the population as a whole, as is
often the case with the elderly, the poor, those with functional needs, and the very young, to name a few.
Economic vulnerability measures the financial means of individuals, towns, cities, communities, or
whole countries to protect themselves from the effects of disasters. Within societies, there may be many
economic delineations that further divide groups into economically vulnerable subgroups. As previ-
ously discussed, the poor are much more likely to suffer the consequences of disasters as they often do
not have the financial means to avoid extreme hazards.
Environmental vulnerability refers to how health and welfare of the natural environment within the
area of study factors into the propensity of the affected population to incur disaster consequences. Poor
environmental practices, such as deforestation, a lack of land-use planning, and management of hazard-
ous materials, can turn what would have been minor events into major disasters.
Each of these vulnerability elements is interconnected. Economic vulnerability in the form of pov-
erty can lead to limited housing options (social vulnerability), which in turn causes populations to build
on dangerous hillsides (physical vulnerability) thus reducing the ability of those slopes to remain intact
during rainstorms (environmental vulnerability). This is but one of limitless examples of how each fac-
tor is equally important when considering impact of the vulnerability on risk.
195 VULNERABILITY
Disaster risk managers can achieve a more comprehensive understanding of vulnerability by devel-
oping physical, social, economic, and environmental profiles for the area or population being studied.
These four factors provide the context for a vulnerability assessment, which in turn better enables a
planning team to estimate likely consequences and understand which mitigation and preparedness mea-
sures would be most appropriate to treat the causative hazards. Descriptions and samples of these pro-
files are provided in the following section.
THE PHYSICAL PROFILE
The physical profile of a country, which dictates its physical vulnerability, is generally a collective
examination of three principal components: geography, infrastructure, and populations. The more that
is known about each component, the better understood physical vulnerability will be. Each of these
components contributes to the nature of risk, including how likely a risk is to occur and how its conse-
quences will manifest themselves.
The geographic component of the physical profile focuses on the natural makeup of the area of
study. For instance, it is estimated that almost three billion people, or about half of the world’s popula-
tion, currently reside in what is classified as coastal land. This includes all but two of the world’s 15
largest cities (ISDR 2004). The economic and industrial benefits associated with a seaside location
were the drivers behind the original siting of coastal settlements, but in moving there, the residents
increased their exposure to many different hazards, including severe windstorms, flooding, and tsuna-
mis. Whether or not this physical location represents vulnerability depends on the actions that individu-
als and communities take to reduce their risk.
The following list provides several examples of what geographic factors are important to consider
in forming a geographic profile:
• Land cover (vegetation)
• Soil type
• Topography
• Slope
• Aspect (the direction something such as a mountain slope faces)
• Water resources (lakes, rivers, streams, reservoirs, etc.)
• Wetlands and watersheds
• Seismic faults
• Climate (wind, rainfall, temperature)
The infrastructure component of the physical profile focuses primarily on the interaction between
people and the land. This profile is diverse, and may be generalized for regions or segments. (See exhibit
3.10.) Examples of infrastructure factors commonly studied when forming a physical profile include:
• Land use
• Location and construction material of homes
• Location and construction material of businesses
• Zoning and building code delineations
• Critical infrastructure components
• Hospitals and clinics
CHAPTER 3 RISK AND VULNERABILITY196
EXHIBIT 3.10 SECTORING
Sectoring helps to further understand the ways in which a disaster would affect segments of a country or community. Not
all areas of a community will be affected by an unforeseen event. Sectoring divides an area into manageable segments or
portions based on local geography in relation to a specific hazard. It allows disaster managers to categorize parts of their
study area in terms of response and impacts. It is used to identify local service areas in relationship to a hazard and physi-
cal features, and allows for the identification of especially vulnerable areas, evaluation of how an area could be or has been
affected, and what can be done to respond to specific events.
Knowing the hazard and the potential of its impact in each sector allows for a more accurate identification of appro-
priate mitigation actions as well as warning and emergency response needs. Sectoring can also be used to organize and
conduct emergency response needs within a sector or across adjacent sectors.
Sectors should be defined by easily identifiable boundaries that can be seen on the ground, such as bluffs, rivers, and
major highways. These features often dictate who responds and how a response is managed. Things to think about in
identifying sectors include:
• People
• How many people in each sector
• How many subdivisions in a sector
• Where people work
• Where people recreate
• Where people live
• Where people gather for civic events
• Where the special needs populations are located
• Animals and livestock
• Where animals are located
• What types of animals are in a specific sector
• Housing and living quarters
• How many housing units in the sector
• What types of housing units are present
• Whether all units are insured
• Critical facilities and response
• Fire station locations
• Ambulance locations
• Hospital locations
• Emergency first-response locations
• Emergency coordination locations
• What the responding zones are
• Special facilities and community resources
• School locations
• Nursing home locations
• Health care service locations
• Prison and jail locations
• Important historical or cultural locations
• Infrastructure and lifelines
• Utilities, including pipelines and power lines
• Roads and bridges
• ailroads and yards
• Airports
• Navigable waterways
• Dikes, dams, and flood protection
• HAZMAT facilities/public health concerns
• Leaking underground storage tank (LUST) sites
197 VULNERABILITY
• Schools
• Senior citizen centers
• Daycare/child care centers
• Government and other public facilities
• Prisons and jail facilities
• Power generation facilities and transmission
• Water purification facilities and pipes
• Wastewater treatment and sewer lines
• Gas lines
• Oil and gas transport pipelines
• Oil and gas storage facilities
• Transportation systems
• Roads and highways
• Railroads
• Airports
• Public transportation systems
• Waterways and port facilities
• Bridges
• Communication facilities
• Landfills
• Dikes and flood protection structures and facilities
• Nuclear power generation plants
• Dams
• Military installations
• Industrial sites that manufacture and/or store hazardous materials
• Emergency management systems
• Ambulance services
• Fire services
• Law enforcement services
• Emergency first response services
• Early warning systems
• Municipal emergency services (MES) sites
• Chemical storage sites
• Hazardous materials locations
• Funeral homes
• Sites containing radioactive materials
• Commercial and industrial facilities
• Commercial business areas defined
• Industrial business areas defined
• Agricultural business areas defined
• Port facilities identified
EXHIBIT 3.10 SECTORING—cont’d
CHAPTER 3 RISK AND VULNERABILITY198
• Emergency operations centers
• Emergency equipment (fire trucks, ambulances, response vehicles, etc.)
• Hazardous materials (HAZMAT) equipment
• Weapons of mass destruction (WMD) detection teams
• Evacuation routes and shelters
• Historical and cultural buildings and areas
The population component of the physical profile is a study of where people are and how they move
throughout the day and the year. Disasters that occur at different times of the day or the year can have
different consequences, and knowing where people are likely to be at certain times helps to determine
vulnerability. Some cities can double or triple in size during the day on weekdays, when workers arrive
from outlying areas. New York City’s Manhattan Island, for instance, grows from a population of 1.5
million at night to over 3 million during the day when commuters arrive. Time of day also factors into
what types of structures people will be inhabiting, which can influence how they are impacted by a
disaster. At night, most people are likely to be in their homes, while during the day on weekdays they
will be at their jobs. The 2008 Sichuan Earthquake struck at 2:28 pm local time, which meant that chil-
dren were in schools and workers were in factories. Because so many schools and factories had not
been constructed to resist seismic forces, this timing of the event translated to thousands of children and
workers being crushed. For this reason, physical vulnerabilities vary depending on the time as popula-
tion movements occur. Examples of measures that help form the physical profile include:
• Population by jurisdiction (i.e., county, city)
• Population distribution within a county or city
• Population concentrations
• Animal populations
• Locations of schools, major employers, and financial centers
• Areas of high-density residential and commercial development
• Recreational areas and facilities
THE SOCIAL PROFILE
The social makeup of the population found within a planning area has a strong influence on disaster vul-
nerability. Aspects of the social profile are diverse and comprise education, culture, government, social
interaction, values, laws, and beliefs, among others. Within most countries, and even within individual
communities, the vulnerability of different groups varies because of a range of sociocultural peculiarities
that help or prevent people from being able to protect themselves from disasters. The prevalence of epi-
demics, in particular, is heavily influenced by social norms and behaviors. (See figure 3.12.)
Certain religious, cultural, and traditional practices and beliefs can help or hinder disaster manage-
ment practices. Although it may not be evident to the people practicing such behavior, their practices
be a product of adjustment to a hazard. In India, for instance, there is a group of people called the Banni
who adapted to the use of a traditional style of single-story, round houses called bhungas after a particu-
larly devastating earthquake in 1819. In 2001, when an earthquake struck in Gujarat, India, killing more
than 20,000 people (primarily as result of residential structure failure), not a single bhunga collapsed.
Disaster managers must be able to recognize when social interactions are either helping or hindering
people in reducing their vulnerability to hazards, and must recognize what aspect of that social process is
199 VULNERABILITY
causing the alteration. People tend to be very attached to places and practices. For instance, despite an ongo-
ing epidemic of the Middle East Respiratory System (MERS) virus in Saudi Arabia in 2014, two million
pilgrims from around the world felt their religious duty to visit Mecca superseded the risk of infection and
possible death (Batrawy 2014). An outsider recommending change without considering the original reasons
for the social practices is unlikely to be taken seriously in that community. Additionally, changing certain
social practices without regard for their historical bases can actually increase vulnerability because of the
common but unintended consequences resulting from a social reaction in response to the change.
Culture can also influence the manner in which response and recovery are conducted, especially
when external resources are involved. Responders need to understand and respect the culture—even if
they don’t understand its basis or it conflicts with their own—if they are to avoid compromising the aid
operation. For instance, in the island country Tonga, maintaining the Sunday Sabbath is a constitutional
requirement. The docking of ships and the landing of planes is prohibited. In past disasters, foreign
responders have had to postpone deliveries of aid until Monday when the government of Tonga refused
their entry on Sunday. To the outsider this may seem extreme, but many if not most of the victims
impacted by the cyclone that caused the disaster agreed with the decision.
Examples of factors to consider in scoping a social profile include:
• Religions
• Age breakdown
FIGURE 3.12
Number of epidemics by country from 1974 to 2003
Source: EM-DAT – International Disaster Database.
CHAPTER 3 RISK AND VULNERABILITY200
• Gender-related issues
• Literacy
• Language
• Health
• Politics
• Security
• Human rights
• Government and governance (including social services)
• Social equality and equity
• Traditional values
• Customs
• Culture
THE ENVIRONMENTAL (NATURAL) PROFILE
The natural environment of a country or community plays a critical role in defining its hazard vulner-
ability (see figure 3.13), and helps to define what risk reduction practices and actions are possible and
most effective. For instance, a mountainous country whose government does not or is not able to
restrict clear-cutting of timber on unstable slopes is likely to have an increased probability of mass-
movement disasters, whereas a country that does not manage the draining or filling in of wetlands may
FIGURE 3.13
Regional differences in hazard portfolios from 1990 to 2011
Source: EM-DAT – International Disaster Database.
201 VULNERABILITY
show an increase in flood propensity. And the natural environment itself can be impacted by a disaster,
which has associated social and economic impacts and can further impact the likelihood that future
hazards result in disasters.
The health and vitality of the natural environment are critical when measuring vulnerability to each
identified hazard. A healthy and productive natural environment can provide excellent protection from
a variety of hazards, while a damaged and unhealthy natural environment can reduce protection from
specific hazards and, in some cases, increase a hazard’s impact. Healthy and productive wetlands pro-
vide invaluable flood protection by soaking up excess rainwater. Healthy forests are less vulnerable to
catastrophic wildfires and reduce landslide dangers on slopes. Dunes on coastlines provide buffers from
storm surges caused by hurricanes and severe storms. Figure 3.14, developed by the UN as part of the
International Strategy for Disaster Reduction (ISDR), illustrates this process of risk augmentation
through environmental degradation.
Understanding the direct link between a healthy and productive natural environment and a country’s
vulnerability to specific hazards is critical to developing an effective risk management strategy. Con-
ducting an inventory of the features of the country’s natural environment is an important step.
FIGURE 3.14
The link between environmental degradation, natural disasters, and vulnerability
Source: ISDR, 2004.
CHAPTER 3 RISK AND VULNERABILITY202
Measuring the health of the country’s natural environment is vital in understanding the role that it can
play in protecting a community and reducing the impacts from hazard events. (See figure 3.15.) Features
of a community’s natural environment include, but are not limited to,
• Health of waterways (rivers, streams, creeks, etc.)
• Status of wetlands
• Management of lakes
• Management of forests
• Health of coastal dunes
• Health of coral reefs
Human practices that affect the environmental profile of a country (see exhibit 3.11) include:
• Diking or damming rivers and creeks
• Filling in wetlands for development
• Channeling coastal areas such that marsh and wetlands areas are destroyed
• Clear-cutting forests
• Mismanaging forests such that deadwood builds up (serving as fuel for a forest fire)
• Destroying coastal dunes
FIGURE 3.15
Number of severe windstorm events by country between 1974 and 2003
Source: EM-DAT – International Disaster Database.
203 VULNERABILITY
Natural processes also affect the natural environment, such as:
• Rainfall averages
• Wind
• Snowfall and snowmelt averages
• Seasonal trends in severe storms and cyclonic storms
• Seasonal drought
• Lightning
THE ECONOMIC PROFILE
The financial status of a government, the nonprofit sector, businesses, and populations deeply affects
how a country or community is able to protect itself from the consequences of disaster. Financial
EXHIBIT 3.11 ILLEGAL DESTRUCTION OF CORAL REEFS WORSENED IMPACT OF TSUNAMI
The illegal mining of corals off the southwest coast of Sri Lanka permitted far more onshore destruction from the 26
December 2004 tsunami than occurred in nearby areas whose coral reefs were intact. This is the principal finding of a team
of researchers from the United States and Sri Lanka who studied the area earlier this year. Their report is published in the
August 16 issue of Eos, the newspaper of the American Geophysical Union.
Some of the differences were startling. Lead author Harindra Fernando of Arizona State University reports that in the
town of Peraliya, a wave of 10-meter (30 foot) height swept 1.5 kilometers (one mile) inland, carrying a passenger train
about 50 meters (200 feet) off its tracks, with a death toll of 1,700. Yet, a mere three kilometers (two miles) south, in Hik-
kaduwa, the tsunami measured just 2–3 meters (7–10 feet) in height, traveled only 50 meters (200 feet) inland, and caused
no deaths.
The researchers found that this pattern of patchy inundation to be characteristic of the study area and was not related to
such coastline features as headlands, bays, and river channels. Rather, the key factor was the presence or absence of coral
and rock reefs offshore. At Hikkaduwa, the hotel strip is fronted by a rock reef and further protected by coral reefs that the
local hoteliers protect and nurture, the researchers report. Relatively little damage and few deaths were recorded from there
to Dodanduwa, around 6 kilometers to the south.
From Hikkaduwa north to Akuralla, however, damage and loss of life were extensive. Local residents, interviewed
by the authors, say that illegal mining had decimated coral reefs in that area, especially by use of explosives that result in
harvests of both coral and fish.
Some eyewitnesses to the tsunami described a visible reduction in the height of the water wall and its deflection paral-
lel with the shore as it approached the coral reef. The researchers conclude that waves that had been blocked by the reef
caused even more inundation and damage where they found low resistance gaps due to removal of coral by humans.
The scientists note that the brunt of the tsunami had hit Sri Lanka’s eastern shore, but that the southwestern, or
leeward, side had also been hit hard. Their analysis of the available data concludes that two or three waves hit the area
within an hour, having been channeled and bent around the southern tip of the island, and that another wave struck around
two hour later, having bounced back after hitting India or the Maldives. They say that existing computer models cannot
adequately explain or predict the wave amplitudes in southwest Sri Lanka, likely due to small-scale ocean processes,
including topographic variations due to coral removal, that are not yet well understood.
The authors note that the low-lying Maldives islands directly in the path of the tsunami escaped destruction. They sug-
gest that this may have been due to the presence of healthy coral reefs surrounding the islands. Apparently, in Sri Lanka,
very little healthy coral was damaged by the tsunami.
Source: American Geophysical Union, 2005.
CHAPTER 3 RISK AND VULNERABILITY204
well-being, however, does not indicate that these entities and individuals will take protective action;
rather, it is merely a measure of the capacity to do so. Other insight may be gained from the economic
profile. Trends and tendencies associated with wealth, or the lack thereof, can be deduced. For instance,
the poor are often marginalized and forced to live on more dangerous land. Their housing is more likely
to be constructed of materials unable to withstand environmental pressures. They are more likely to
have little to no tolerance for delays in basic commodities and services that often follow disasters.
Economic measures that inform vulnerability assessments include:
• Gross domestic product
• Debt
• Access to credit
• Insurance coverage
• Sources of national income
• Availability of disaster reserve funds
• Social distribution of wealth
• Prevalence of business continuity planning
• Economic diversity (the range of products and resources that drive the economy)
• Philanthropic giving
It is recognized that poor countries experience more disasters than wealthy ones, as figure 3.16
illustrates. This is not surprising, however, when considering the definition of a disaster and the concept
of vulnerability. An event only becomes a disaster when the local capacity to respond to the event is
exceeded, requiring external assistance to manage the consequences. The economic strength of wealthy
nations better enables them to develop preparedness, mitigation, response, and recovery mechanisms
before events occur, and thus these nations are better able to manage disasters effectively when they
happen. Identical events that occur in a high-income country and a low-income country may manifest
as a routine event in the high-income country but result in a full-scale disaster in the poor country.
Income is not the only factor that would play into the variance in vulnerability between the two coun-
tries, but it is a dominant one.
Another economic factor that influences how significantly an event affects a country is the gross
domestic product (GDP). GDP is a measure of the value of all goods and services produced within a
nation in a given year. When considered in the absence of a nation’s GDP, the financial consequences
of a disaster do not provide a relative sense of how badly the country was impacted. However, present-
ing damages and losses as a percentage of GDP provides a much better perspective of how deeply the
nation’s economy was impacted. For example, a disaster that causes $2 billion in damages may repre-
sent upward of 38 percent of total GDP for a country like Honduras, while it would be equal to less than
one-tenth of a percent of Japan’s GDP. Large-scale disasters that affect poor countries can literally wipe
out all of their economic gains for a year or more. Wealthy nations with strong economies are better
able to absorb the effects of disasters, and many even have reserve funds set aside for expected events,
which would further lessen the impact. Poor countries, on the other hand, often must borrow significant
amounts of financial capital while concurrently cutting vital social and economic programs in order to
cover the expenses of disaster relief and recovery. Long-term development can stall in the face of such
measures and may lag for many years after the disaster has struck—especially when debt responsibili-
ties weigh heavily on future budgets. Figures 3.17 and 3.18 illustrate how differently disaster events
affect economies of varying sizes.
205 VULNERABILITY
RISK FACTORS THAT INFLUENCE VULNERABILITY
In the United Nations Development Programme report Reducing Disaster Risk: A Challenge for Devel-
opment, two main factors influencing the risk levels of nations and their populations are identified:
urbanization and rural livelihoods (UNDP 2004). Each of these factors influences and is influenced by
the four main hazard vulnerability factors previously discussed.
FIGURE 3.16
Total number of disasters by year from 1994 to 2003 (by income; reference map provided)
Source: EM-DAT – International Disaster Database.
CHAPTER 3 RISK AND VULNERABILITY206
FIGURE 3.17
Disaster damages as a percent of GDP between 1991 and 2005
Source: EM-DAT – International Disaster Database.
207 VULNERABILITY
Urbanization Populations are concentrating in urban centers throughout the world. Between 2008 and 2010, the
world shifted from a majority rural to a majority urban population as urbanization rates topped 50 per-
cent. This number will exceed 70 percent by 2050 if the current rates are maintained. This movement
is fueling the development of large “megacities,” defined as urban centers containing more than 10
million inhabitants. As of 2014, there are 30 megacities. An increase in the number of cities that exceeds
one million people is also occurring. In 1950, there were 75 cities that met this threshold, while in 2014
that number has risen to more than 450, and it is expected to continue to rise to more than 545 by 2025.
(Minto 2011). Of these, 69 cities currently have more than 5 million inhabitants (World Atlas 2014).
Urbanization, especially rapid urbanization, presents significant challenges for disaster risk manag-
ers and urban planners. In the most basic terms, the concentration of people concentrates risk. The
absolute numbers of people who are exposed to individual hazards increases as those people settle in
closer and closer proximity. As populations become denser, land pressures require the poor to settle in
undesirable, often dangerous, parts of urban centers, such as unstable slopes, in floodplains, and on
seismically unstable soil. Without current census data and risk assessment, governments may not be
aware for months, or even years, that these groups are at such high risk.
In addition to concentrating populations, urbanization concentrates national wealth and resources
into small, often vulnerable pockets. Exposure is likewise concentrated, and when disasters occur, there
is a great increase in the likelihood that a significant portion of the nation’s infrastructure, industrial
output, and governance will be affected. As urbanization increases, housing, distribution of food, trans-
portation, communications, public health, and many other resources and services are also impacted to
a much greater degree.
The ability of government to ensure the safety of urban populations decreases significantly when
surges in population occur in a haphazard, informal manner. It can be very difficult, if not impossible,
for officials to prevent people emigrating from rural areas from building and operating in a way that
increases their risk, most significantly in the short term. Disaster management and emergency services
0.00
1962 1965 1968 1971 1974 1977 1980
Fiscal Year
Federal Disaster Relief as a Percentage of GDP
FEMA relief + 15%
SBA loan activity
1983 1986 1989 1992 1995 1998
0.01
0.02
0.03 %
0.04
0.05
0.06
0.07
FIGURE 3.18
Disaster relief costs as a percentage of GDP in the United States
Source: Congressional Natural Hazards Caucus and Princeton University, 2001.
CHAPTER 3 RISK AND VULNERABILITY208
capacity must grow in line with population expansion to ensure adequate protection. Even wealthy
countries often experience capacity gaps as recognition and funding catch up. In poor countries, these
lags are compounded by political pressures and the competition of financial interests that rob disaster
management programs of much-needed funding.
Several reasons why urbanization contributes to risk and vulnerability have been identified by the
UNDP, including:
• Risk by origin. Some cities are inherently risky because of their location. Mexico City, for exam-
ple, is located very near active seismic faults and was built upon soft soil that amplifies seismic
waves to dangerous levels in certain parts of the city. In this case, the vulnerability of the popula-
tion is increasing through urbanization because the urban center itself is inherently risky.
• Increasing physical exposure. As mentioned earlier, when rapid urbanization occurs, marginal-
ized groups are very often pushed to the more dangerous, riskier parts of the city, even to places
where construction may previously have been prohibited. In this case, overall population exposure
increases because people are moving into higher risk pockets that exist within the overall bound-
aries of the urban environment.
• Social exclusion. Rural areas often have community-based coping and support systems that allow
for decreased overall vulnerability to the consequences of hazards. However, these bonds are
much less common in urban areas. Migrants often have trouble adjusting to the new demands of
city life, requiring them to disregard many of the protection measures they may have otherwise
taken. Their social safety nets are reduced or eliminated when they move away from families and
friends, and it may be years before they are able to fill the resulting void. These groups tend to
face the greatest risk from disaster consequences.
• Modification and generation of hazard patterns. Rapid urbanization not only changes the charac-
ter and size of a city but also affects its natural and built environments, as well. Growing popu-
lations alter the way many services and resources, such as water, sewerage, garbage disposal,
and hazardous materials generation, are managed. These increased pressures can easily create
or modify existing hazards, or can result in completely new hazards. For instance, land pressure
often results in the filling of wetlands to allow for new construction. The decreased hydrological
holding capacity of the land may result in increased flooding where flooding was previously not
a problem. This filled land may be less stable in the event of an earthquake because of the lack of
bedrock below foundations.
• Increasing physical vulnerability. In addition to causing people to move into high-risk areas
(increasing their physical exposure), urbanization tends to cause groups to live and function in a
manner that increases the likelihood that they will become victim to a disaster. Moving into risky
areas does not automatically imply that vulnerability has been increased. With the proper mitiga-
tion measures, the likelihood and consequence factors of risk can be reduced. However, because
it is the poor who are most likely to move to these areas, expecting that the great (and expensive)
measures required to compensate for the increased hazard risk in the area will be taken is unrealis-
tic. As such, population vulnerability increases. It should be noted, however, that even in previ-
ously populated areas, increased density can result in conditions that increase vulnerability.
• Urbanization of new regions. It is not uncommon, in the modern age of transportation, commerce,
and communications, for previously undeveloped areas to transform into large urban centers in a
relatively short time. New markets, newly discovered resources, and increased population mobility
209 VULNERABILITY
can result in rapid settlement of people in an area at particular risk for one or more hazards about
which few or no people are aware. The UN points out that the disasters resulting from earthquakes
in Peru in 1990 and 1991, in Costa Rica in 1991, and in Colombia in 1992 were consequences of
new region urbanization.
• Access to loss mitigation mechanisms. Rapid urbanization places increased pressure on the gov-
ernment to provide mitigation and other disaster reduction and response services. However, even
if these services are increased or developed, there is always a lag in time between recognition of
the increased vulnerability and the development of services to reduce that vulnerability. Apart
from major disasters, marginalized groups, especially those in informal squatter communities,
face the risk of devastating consequences from minor storms, fires, landslides, and other hazards
that normally would cause little or no damage.
Rural Livelihoods More than half the world’s population and, according to the World Bank (2014), more than 70 percent
of the impoverished live in rural areas. Like their urban counterparts, rural populations experience vul-
nerability from disasters because of a unique set of factors resulting directly from the classification of
their living conditions as rural. The following lists several of these factors.
• Rural poverty. In the absence of large, organized government entities, rural communities may
be left to fend for themselves for disaster mitigation and response resources. This is pronounced
in the developing world. With little or no money to spend on prevention, the rural poor have
few options to mitigate for disaster risk. When what little they are able to do ultimately fails as
result of a disaster, the catastrophic loss of crops, equipment, livestock, housing, and posses-
sions is devastating, and relief resources may be nonexistent. Although they may have developed
long-established social systems to counteract the effects of disasters, those systems may fail for
many reasons, including changes in the demographic makeup of the community, climate change,
changes in markets, and environmental degradation.
• Environmental degradation. Many of the world’s rural poor engage in environmentally destruc-
tive practices. Most often, these practices are directly related to agricultural or other income-
generating practices. Deforestation, overgrazing of land, poor farming practices, and alteration
of waterways all can lead to an increase in the likelihood or consequence factors of risk. In these
cases, it is typical for common events such as normal annual rains to begin resulting in disasters
such as mudslides and flash floods, which had not previously affected the region.
• Nondiversified economies. Many rural areas rely on just a few sources or even a single source of
income. This increases the possibility that a hazard could significantly impact or fully destroy the
area’s capacity for income generation. A plant epidemic is one example of a hazard capable of
causing a disaster but which could have been easily mitigated with greater diversification. Shifts
in global market prices for a specific commodity can also cause significant reductions in local
income if there exists a high degree of dependence on that one resource. If market demands shift
during the crisis as a result of customers looking elsewhere for the same product or moving to
adapt an alternate product, the negative impacts on the nondiversified economy could become
permanent.
• Isolation and remoteness. Rural populations that are far outside the reaches of national and
regional government services often have little outside intervention to reduce their vulnerability
CHAPTER 3 RISK AND VULNERABILITY210
from disasters. Poor transportation and communications infrastructure severely hinders pre- and
post-disaster assistance. When a disaster does occur, days or weeks may pass before news of it
reaches the outside world and assistance is provided. War-torn areas are especially susceptible, as
was evident after the 2004 tsunami events in Banda Aceh province in Indonesia.
RISK PERCEPTION
A key requirement of effective disaster risk management is recognition that a hazard exists. However,
recognizing the hazard is only the beginning, as one must also be able to judge the relative seriousness
of that hazard in comparison to other hazards. The process of risk analysis helps disaster managers to
do just that. For lay people, however, and in the absence of such technical and involved analysis, the
mechanisms by which they perceive the hazards that threaten them can be very different, and very
complex.
The study of why people fear the things they do (and also why they do not fear other things) is called
risk perception. Traditionally, people do not tend to fear the things that are statistically most likely to
kill them, and an abundance of research has been dedicated specifically to finding out why. Understand-
ing these trends in public risk perception can help disaster managers understand why people are dispro-
portionately afraid of spectacular hazards they are statistically less vulnerable to than, for instance,
automobile accidents, food poisoning, heart disease, or cancer.
In their article “Rating the Risks,” acclaimed risk perception experts Paul Slovic, Baruch Fischhoff,
and Sarah Lichtenstein begin, “People respond to the hazards they perceive” (Slovic et al. 1979). This
statement is important for two reasons. First, its opposite is true. People generally do not respond to the
hazards they do not perceive. Second, it has been found that these stated perceptions are primarily
based on inaccurate sources of information, such as mass media outlets, social networks, and other
external sources, as opposed to personal experience and expert knowledge.
Slovic et al. (1979) identified four “risk perception fallibility” conclusions to explain the ways in
which people tend to inaccurately view the hazards in their world. These conclusions, which help to
explain how populations decide which disasters to prepare for and why, are:
1. Cognitive limitations, coupled with the anxieties generated by facing life as a gamble, cause
uncertainty to be denied, risks to be distorted, and statements of fact to be believed with unwar-
ranted confidence (Slovic et al. 1979). People tend to fear a specific risk less as they become
better informed and have more details of the risk. However, what a person can discover about
a risk will almost never be complete, as the actual likelihood or consequence most risks pose
cannot be quantified in a way that addresses the specific threat faced by individuals, even well-
known risks such as cancer or heart disease (Ropeik 2001).The more uncertainty a risk poses or,
as Slovic et al. (1979) state, “the more of a gamble something is,” the more people fear it. In the
face of uncertainty, people consciously or subconsciously make personal judgments based on
very imperfect information to establish some individual concept of the risk they face. Judgments
based on uncertainties and imperfect information often cause people to wrongly perceive their
own risk in a way that overstates reality. In Mexico City, for instance, where a public insecurity
crisis is a priority political topic and a constant subject in the press, but where no reliable crime
statistics have been available for more than seven years, people have overestimated their personal
risk from violent crime by up to 86 percent. According to a 2002 comprehensive countrywide poll
211 VULNERABILITY
measuring the incidence of crime, approximately 14 of every 100 citizens of Mexico City would
fall victim to some form of crime in the 12 months following the survey (ICESI 2002). However,
when asked in a poll what they believed their chance was of falling victim to crime in that same
time period, many people thought they had an 80 to 100 percent chance.
2. Perceived risk is influenced (and sometimes biased) by the imaginability and memorability of the
hazard. People, therefore, may not have valid perceptions about even familiar risks (Slovic et al.
1979). People are more afraid of those things that they can imagine or remember. The likelihood
of occurrence of these easily available risks, as they are called, tends to be overestimated. For
instance, we rarely hear about a person dying from a “common” cause such as a heart attack,
unless somebody close to us dies of that specific cause. However, the media will report heavily
on a death that is the result of an “uncommon” cause, like the West Nile virus. The result tends to
be that people underestimate common risks and overestimate rare risks. Social scientists Slovic,
Fischhoff, and Lichtenstein performed a study to measure this phenomenon and found that people
greatly overestimated their risk from rare events such as botulism, tornadoes, pregnancy compli-
cations, and floods while underestimating their risk of stroke, diabetes, cancer, and heart disease
(Slovic et al. 1979). Generally, people tend to fear what they hear about repetitively or often. This
phenomenon is referred to as the “availability heuristic,” which states that people perceive an
event to be likely or frequent if instances of the event are easy to imagine or recall. This percep-
tion bias can be correct when considering events that really are frequently observed, such as
people who believe that automobile accidents are common because almost everyone they know
has been involved in one. However, when a risk that is spectacular but not necessarily common
receives constant media attention, people often wrongly assume that similar events are very likely
to occur.
3. [Disaster management experts’] risk perceptions correspond closely to statistical frequencies of
death. Lay people’s risk perceptions [are] based in part upon frequencies of death, but there were
some striking discrepancies (Slovic et al. 1979). It appears that the concept of risk for lay people
includes qualitative aspects such as dread and the likelihood of a mishap being fatal. Their risk
perceptions are also affected by catastrophic potential. It can be difficult for people to fully under-
stand statistics they are given, and even more difficult to conceptualize how those statistics apply
to them personally. Furthermore, statistics tend to do little to affect how people perceive the calcu-
lated risks. This is not to say that the average person lacks sufficient intelligence to process num-
bers; rather, the numbers are not the sole source of influence on public risk perception. Extensive
research has discovered that people rank their risks by using other, more heavily weighted qualita-
tive factors, as well as the quantitative likelihood of a hazard resulting in personal consequence
(Slovic et al. 1979). People are generally more concerned with the consequence component of
risk than they are about the likelihood component (recall that Risk = Likelihood × Consequence).
It is important to examine the quality and usefulness of statistics provided to the public by the
media regarding risks. Without complete information, media-provided statistics are meaningless
and likely misleading. In the absence of complete information, people tend to overestimate rather
than underestimate their vulnerability. Economists have classified this tendency to overestimate
unknown or unclear risks as “risk-ambiguity aversion” (Economist 2002).However, even if statis-
tics provided by the media or other sources are straightforward, people have difficulty understand-
ing how those numbers affect them as individuals, even if they are risk “experts.” Few people can
conceptualize the difference between a “one-in-a-million” and a “one-in-one-hundred-thousand”
CHAPTER 3 RISK AND VULNERABILITY212
chance of occurrence (Jardine and Hrudey 1997). People tend to need other clues to help them
put these numbers into perspective. Many tend to view their chances of being affected by rare but
spectacular hazards in a comparable fashion to how people believe they can beat long odds to win
a state lottery. James Walsh writes in his book True Odds:
The odds are greater you’ll be struck by lightning than win even the easiest lottery. They’re better
that you’ll be dealt a royal flush on the opening hand of a poker game (1 in 649,739). They’re better
that you’ll be killed by terrorists while traveling abroad (1 in 650,000). Bill Eadington, director of the
Institute for the Study of Gambling and Commercial Gaming at the University of Nevada at Reno,
looks at it this way: If you bought 100 tickets a week your entire adult life, from age 18 to 75, you’d
have a 1 percent chance of winning a lottery. “[Lotteries] really play on the inability of the general
public to appreciate how small long odds are.” (Walsh 1996)
In Walsh’s calculations, the odds of winning the lottery are 1 in 57 × 52 × 100 × 100 =
29,640,000. It is the qualitative factors that people consider most heavily when weighing their per-
sonal risk. Slovic, Fischhoff, and Lichtenstein (1980) propose that there are 17 risk characteristics
that influence public risk perception. These characteristics fall under two subgroups called factors:
Factor 1 is related to dread, and Factor 2 is related to how much is known about the risk. A third
factor, encompassing a single, eighteenth characteristic that measures the number of people
exposed to the hazard, is not covered in this section.
Using these 17 characteristics, Slovic et al. (1980) examined public perceptions of 90 risks and
plotted their findings on a two-dimensional graph depicting Factor 1 on the x axis and Factor 2 on
the y axis. Characteristics of Factors 1 and 2 are described in the following lists:
Factor 1: Factors Related to Dread
a. Dreaded versus not dreaded. People fear risks that cause painful, violent deaths more than
risks that do not. David Ropeik, director of risk communication at the Harvard Center for Risk
Analysis, wrote, “What are you more afraid of: being eaten by a shark or dying of a heart
attack in your sleep? Both leave you equally as dead, but one—being eaten alive—is a more
dreadful way to go” (Ropeik 2001). Of course, millions of people around the world die from
heart attacks while sleeping every year, but fewer than 15 fall victim to sharks in the same time
period (Wiggins 2002).
b. Uncontrollable versus controllable. People tend to be less fearful of risks that they feel
they can control. For instance, most people feel safer as a driver in a car than as a passenger
because they are controlling the movement of the vehicle, and they know their own skills in
accident avoidance. When people lack control of a situation, a risk seems more pronounced.
Examples of uncontrollable risks are airplane travel, street crime, pesticides in food, and
terrorism.
c. Globally catastrophic versus not globally catastrophic. Risks that have the potential to affect
the entire world tend to be deemed greater than those that would only affect local or national
populations. For instance, the effects of nuclear war, whose aftermath could include wide-
spread nuclear fallout and long-term physiological effects beyond the borders of any one state,
is far scarier than are the effects of a conventional war taking place in a country other than
one’s own.
d. Fatal consequences versus not fatal consequences. A risk that results in death is more feared
than other, nonlethal risks. For example, even though auto accidents are much more likely than
213 VULNERABILITY
airplane accidents, the chance of fatality is much greater for airplane accidents, and airplane
accidents are thus more feared.
e. Not equitable versus equitable. Risks that affect one group with a greater statistical likelihood
and/or consequence than the general population tend to be considered greater risks than those
that affect all people equally, especially to those within the groups more severely affected. This
is especially true if the risk disproportionately affects children.
f. Catastrophic versus individual. Risks that affect a great number of people in one location or at
one time are more feared than those that affect individuals one at a time over a wide location.
Terrorism and earthquakes are examples of catastrophic hazards, while heart disease, auto
accidents, and drowning are considered individual hazards.
g. High risk to future generations versus low risk to future generations. A risk that extends
across generations, especially one that will affect future generations, is considered scarier than
ones that will be mitigated or prevented in our own lifetimes. The most apparent example of
this is nuclear radiation, which can remain dangerous for thousands of years. Because of this
extended danger, there are still no agreements on where spent nuclear fuel will be stored in the
United States after it is no longer useful for power generation.
h. Not easily reduced versus easily reduced. People are more afraid of risks that cannot be eas-
ily mitigated. The effort required to reduce crime or drug use is much greater than the effort
required to prevent drowning or bicycle injuries. Simply wearing a helmet on a bike, or a life
preserver on a pleasure boat, greatly reduces the likelihood of injury or death. However, it
takes months or years to combat a crime wave or drug problem plaguing a town or city.
i. Risk increasing versus risk decreasing. A risk that appears to be growing in likelihood or
consequence becomes more feared. However, if a risk appears to be more easily mitigated or is
decreasing in likelihood or consequence, people begin to fear it less.
j. Involuntary versus voluntary. Why are people more afraid of drunk drivers than of eating
high-cholesterol food that will raise their risk of heart disease? How can some people smoke
cigarettes, wholly unconcerned about their cancer risk, while those around them complain
incessantly? The most obvious answer for both questions is that people are more concerned
with risks that are involuntary than with those they bring upon themselves. Keith Smith, in
Environmental Hazards: Assessing Risk and Reducing Disaster, discusses voluntary and
involuntary risk and states, “there is a major difference between voluntary and involuntary risk
perception with the public being willing to accept voluntary risks approximately 1,000 times
greater than involuntary risks” (emphasis added; Smith 1992).
k. Affects me versus does not affect me. Terrorism has been reported almost daily in the media for
years, but until September 11, 2001, Americans who did not travel abroad did not worry about
it. After that date, preventing terrorism became a national concern and a government prior-
ity. The statistical risk to the average person in the United States was raised only a minuscule
amount, but the mere fact that people suddenly knew for certain that foreign terrorism could
occur at home made them much more afraid.
l. Not preventable versus preventable. A risk that cannot be mitigated or prepared for is more
feared than one that can be. For instance, in the early 1980s HIV and AIDS were seen as
always fatal and were terribly feared. With modern medicine, people who are HIV-positive can
live for years without contracting AIDS. While the disease is still feared, it is not perceived to
be as dangerous as it was 20 years ago.
CHAPTER 3 RISK AND VULNERABILITY214
Factor 2: Factors Related to How Much Is Known about the Risk
m. Not observable versus observable. Risks that can be seen are less feared than those that cannot
be seen or visualized. The dangers associated with radon or genetic manipulation are consid-
ered not observable, while secondhand smoke is observable.
n. Unknown to those exposed versus known to those exposed. If people have no way of knowing
whether they are exposed to a risk, they will fear that risk more. Food irradiation and biologi-
cal terrorism are examples of risks where people may not be able to know if they have been
exposed.
o. Effect delayed versus effect immediate. Risks that cause immediate harm or damage tend to be
less feared than those that cause negative effects at some future time following exposure. This
is the primary reason people tend to fear the effects of biological terrorism more than conven-
tional or even chemical warfare.
p. New risk versus old risk. Risks we are facing for the first time are much scarier than risks we
have had plenty of time to become “accustomed” to. Few people fear cars for their accident
risk or fear the risk posed by vaccines, as we have lived with these technologies for decades.
When anthrax was mailed to news agencies and politicians in New York, Washington, DC, and
Florida, people became extremely frightened when opening their mail, while today it is highly
unlikely that anyone continues to wear a mask and rubber gloves while opening letters.
q. Risks unknown to science versus risks known to science. When risks can be explained using
scientific evidence, people fear them less because of increased understanding. Many diseases
raise questions when they are first discovered, but once their methods of transmission, preven-
tion, and cure are revealed, they become less of a concern.
4. Disagreements about risk should not be expected to evaporate in the presence of “evidence.”
Definitive evidence, particularly about rare hazards, is difficult to obtain. Weaker information is
likely to be interpreted in a way that reinforces existing beliefs (Slovic et al. 1979). Slovic et al.
(1979) discovered that “people’s beliefs change slowly and are extraordinarily persistent in the
face of contrary evidence. . . . New evidence appears reliable and informative if it is consistent
with one’s initial belief; contrary evidence is dismissed as unreliable, erroneous, or unrepre-
sentative.” They added, “Convincing people that the catastrophe they fear is extremely unlikely
is difficult under the best conditions. Any mishap could be seen as proof of high risk, whereas
demonstrating safety would require a massive amount of evidence” (Slovic et al. 1979), evidence
that is sometimes impossible to obtain in an accurate or timely manner This stubbornness is com-
pounded by the fact that once people make their initial judgments, they believe with overwhelm-
ing confidence that they are correct. This phenomenon, called the “overconfidence heuristic,”
states that people often are unaware of how little they know about a risk, and of how much more
information they need to make an informed decision. More often than not, people believe that they
know much more about risks than they actually do. Slovic and his colleagues (1979) conducted
a study to determine whether people knew if homicides were more frequent than suicides. Of
participants who answered incorrectly, 12.5 percent gave odds of 100 to1 that their answer was
correct, and 30 percent gave odds of 50 to 1 that their answer was correct. In fact, suicides hap-
pen much more frequently than homicides, with an incidence of 1.7 suicides per homicide (CDC
2002).The overconfidence heuristic has been linked to media coverage of other spectacular events,
specifically regarding how people’s rating of risks is dependent on the amount of media coverage
a risk receives. For example, one study showed that a greater percentage of crimes covered by the
215 VULNERABILITY
media involve perpetrators and victims of different races than occurs in reality. In other words, a
news story is more likely to describe a white victim of a black attacker than a black victim of a
black attacker, even though the latter is more common. This inconsistency in coverage is seen as
the main reason Caucasians overestimate their likelihood of being a victim of interracial crime by
a factor of three (Twomey 2001). Paul Slovic writes that “strong beliefs are hard to modify” and
“naïve views are easily manipulated by presentation format” (Slovic 1986). Often, only time will
change people’s opinions about the risks they personally face. One reason that people are more
scared of a new risk than an old risk is that they have not been able to gather enough information
to alter their initial fearful impression. After time has passed and they realize that their expecta-
tions for victimization have not been realized for themselves or anybody they know, they can
begin to question the validity of their views.
Elspeth Young of the Australian National University describes social constructs of risk. These are
human attributes that define how different people assess risk and determine personal vulnerability.
Young (1998) writes:
1. Socioeconomic characteristics (e.g., age, gender, ethnicity, income, education, employment,
and health). Older people and children may be much more vulnerable than active adults. Poorer
people, with fewer capital resources, are likely to suffer far more from the effects of hazards such
as flood invasion of their homes. Some specific ethnic groups . . . may be much less able to take
advantage of the assistance offered because of communication problems and cultural differences.
2. People’s knowledge of the environment and the hazards that the environment poses to them e.g.,
traditional ecological knowledge (TEK). TEK may be effectively used to cope with a situation
that outsiders perceive to be threatening, and generally provides much more detailed understand-
ing of local environments. It can be valuable in predicting the threats posed by hazards (e.g., when
significant floods are actually likely).
3. Their ignorance. . . . For example, people who have newly moved into a vulnerable area often
lack knowledge of the actual threats posed by hazards such as severe [wild]fires, and fail to take
suggested precautions seriously.
4. Their ability to cope with those hazards. [People are able to cope] through technology, financial
attributes, education, political power, and having a voice. Knowledge, high levels of education and
high incomes generally give people more confidence in articulating their feelings and needs and
hence they may be able to cope better with adversity.
5. Their ability to access help from outside. Having confidence . . . makes asking for assistance much
easier.
The ways in which hazard risk is presented or reported greatly influence how people perceive the
hazard. For instance, Slovic and Weber (2002) describe several ways that a risk manager could explain
the risk from a nearby factory to an exposed population. All of the measurements will describe the same
risk factor, but each one is likely to produce a different number. The ways in which people perceive that
number will be different, as well. Such measurements include (Slovic and Weber 2002):
1. Deaths per million people in the population
2. Deaths per million people within x miles of the source of exposure
3. Deaths per unit of concentration
4. Deaths per facility
CHAPTER 3 RISK AND VULNERABILITY216
5. Deaths per ton of air toxin released
6. Deaths per ton of air toxin absorbed by people
7. Deaths per ton of chemical produced
8. Deaths per million dollars of product produced
9. Loss of life expectancy associated with exposure to the hazard
Richard Wilson (1979) describes ways in which risks can be compared by calculating risks that
increase a person’s chance of death by one in one million (0.000001). It must be noted that these risks
are population risks as opposed to individual risks. See exhibit 3.12.
Risk comparisons can also cause incorrect perception of risk if they are not presented in an appro-
priate manner. Kenneth Warner (1989) describes how the media often use vivid comparisons to better
explain risks to their audience. He gives the following three examples of comparisons provided by the
media to describe the risks associated with cigarette smoking:
1. On average, cigarettes kill as many people as would die if three passenger-laden jumbo jets
crashed every day, month after month, year after year.
2. In one year, cigarettes kill more Americans than died in World War I, the Korean War, and the
Vietnam War combined.
3. The annual death toll associated with cigarette smoking is equal to that of a hydrogen bomb
dropped in the heart of a city such as Miami, Kansas City, Cleveland, or wherever. (Warner 1989)
EXHIBIT 3.12 RISKS WHICH INCREASE CHANCE OF DEATH BY 0.000001 (1 IN 1 MILLION; FOLLOWED BY CAUSE OF DEATH)
• Smoking 1.4 cigarettes (cancer, heart disease)
• Drinking one-half liter of wine (cirrhosis of the liver)
• Spending 1 hour in a coal mine (black lung disease)
• Spending 3 hours in a coal mine (accident)
• Living 2 days in New York or Boston (air pollution)
• Traveling 6 minutes by canoe (accident)
• Traveling 10 miles by bicycle (accident)
• Traveling 300 miles by car (accident)
• Flying 1000 miles by jet (accident)
• Flying 6000 miles by jet (cancer caused by cosmic radiation)
• Living 2 months in Denver on vacation from N.Y.(cancer caused by cosmic radiation)
• Living 2 months in average brick or stone building (cancer caused by natural radioactivity)
• One chest X-ray taken in a good hospital (cancer caused by radiation)
• Living 2 months with a cigarette smoker (cancer, heart disease)
• Eating 40 tablespoons of peanut butter (liver cancer caused by aflatoxin B)
• Drinking Miami drinking water for 1 year (cancer caused by chloroform)
• Drinking 30 12 oz. cans of diet soda (cancer caused by saccharin)
• Living 5 years at site boundary of a typical nuclear power plant in the open (cancer caused by radiation)
• Living 20 years near PVC plant (cancer caused by vinyl chloride [1976 standard])
• Living 150 years within 20 miles of a nuclear power plant (cancer caused by radiation)
• Eating 100 charcoal-broiled steaks (cancer from benzopyrene)
Source: Wilson, 1979.
217 VULNERABILITY
Warner describes how the conceptual differences between the slow death associated with smoking-
induced cancer or emphysema and the immediate deaths associated with being shot in a war, inciner-
ated in a hydrogen blast, or killed in a plane crash render such comparisons ineffective. These
comparisons attempt to elicit the fear associated with the risk characteristics identified by Slovic et al.
(1979). Studies have shown, however, that these types of comparisons lack the desired effect.
People’s perceptions of risk can also be influenced by the emotions elicited by a particular report on
a hazard. According to a report in the Washington Post, Jennifer Lerner of Carnegie Mellon University
discovered that people who watched media reports framed in a way to cause fear, like one on bioterror-
ism, would likely overestimate their personal exposure to risk. However, people who watched reports
that elicited anger, such as ones showing Palestinians and other people celebrating the 9/11 attacks,
were likely to perceive their exposure to terrorism as relatively less than the fearful group’s perception.
Lerner attributes to the effects of these fear-inducing reports the fact that “in surveys conducted after
9/11, Americans felt they faced a 20 percent chance of being a direct victim of future attacks, and felt
that the ‘average American’ faced a 48 percent chance” (Vedantam 2003) of being a victim.
Lerner found that women tended to respond more with fear to terrorism risk-related articles, while
men tended to respond more with anger. She contends, “the government and the media can unwittingly
alter risk perception by making people either fearful or angry,” and further states, “Used responsibly,
that connection could also be used to better communicate the real degree of risk” (Vedantam 2003).
Risk Perception Is Necessary for Disaster Management and Communications Most people do not rely on statistical likelihoods to determine what risks they fear but consider other
qualitative aspects, which can be due to attributes of the hazard itself or each individual’s personal
experience and information exposure. The outcome of these risk perception effects is that there is no
single, universal, agreed-upon ranking of hazard risks.
Disaster managers need to consider risk when performing their assessments, but also are influenced
by the effects of risk perception, regardless of their knowledge or expertise in risk management. C. J.
Pitzer writes in the Australian Journal of Emergency Management:
We make a fundamental mistake when we, as safety managers, deal with risk as a “fixed attribute,”
something physical that can be precisely measured and managed.
The misconception of risk as a fixed attribute is ingrained into our industry and is a product of the
so-called science of risk management. Risk management has created the illusion that risk can be
quantified on the basis of probability, exposure to risk, and from the likely consequences of acci-
dents occurring. Risk management science can even produce highly technical and mathematically
advanced models of the probabilistic nature of a risk.
The problem with this is that risk is not a physical quantum. It is, instead, a social construction.
Everyone has a unique set of assumptions and experiences that shape their interpretations of objects
or events. People tend to ignore, “misperceive” or deny events that do not fit their worldview. People
find what they expect to find. (Pitzer 1999)
Elspeth Young (1998) writes:
Risk should not be defined solely by pre-determined, supposedly objective criteria that enable its
various levels to be gauged through quantification. It is also a social construct, interpreted differently
CHAPTER 3 RISK AND VULNERABILITY218
by all of us. Some find certain events or situations unacceptably risky and will do their utmost to
avoid being involved, while to others the same events may offer exhilaration and thrills that stimulate
their whole purpose of living. There may even be others to whom the particular event is a non-issue,
something to be totally ignored. These differences in perception and response, coupled with differ-
ences in people’s socio-economic characteristics and circumstances, result in a wide range of vul-
nerability in any community. Social aspects of risk interpretation must be recognized if risk is to be
effectively managed, and community participation in the practical management of the problem faced
is a vital component of this approach.
When disaster risk managers perform the hazards risk management process, they take many steps
during the process that require the use of both qualitative assessments and personal experience and
opinions. Because of differences in risk perception, the hazards risk management process can be flawed
if risk managers do not accommodate inconsistencies between their own and their constituents’ percep-
tions and reality.
During hazard identification, a hazard first must be perceived as a risk before it is identified as one.
Perception is not the same as awareness. An obvious example is a hazards risk management team that
is unaware that chlorine is used to purify water in the community. Without this knowledge, they may
not know that the hazardous chemical (capable of causing mass casualty disasters) is not only trans-
ported by truck through populated areas several times a year, but also stored in a location where a leak
or explosion could result in many fatalities. This is not an issue of risk perception. Now, imagine that
the same team is aware of the above information but they have never heard of a disaster actually hap-
pening, or the one accident they have heard of did not result in any deaths, and they decide that the
chlorine is something they do not need to worry about in their assessment. This is a result of the effects
of risk perception (the availability and overconfidence heuristics, in this case).
Risk perception may have the opposite, compounding effect for disaster managers. For instance, it
is possible that a risk that is essentially harmless or has extremely low likelihood or consequence is
perceived to be much greater than reality by a manager or by the public. Such faulty perceptions on the
part of the disaster management team could result in time or funding wasted in mitigation and prepara-
tion for a risk that may never happen, at the expense of neglecting a more severe risk that threatens the
population to a greater degree. However, if the disaster managers have an accurate impression of a risk
and determine that it is low enough to not worry about, while the public perceives it to be significant,
they run the risk of appearing negligent. Only effective public education and risk communication can
counter the effects of public (mis)perception of risk.
Risk perception can also influence the way the mitigation of a hazard is considered by decision
makers or by constituents within a community. If a hazard is not perceived to be a significant risk by
those who decide to fund mitigation projects, funding is unlikely to be provided without significant
efforts to correct those perceptions. Likewise, if the public does not perceive a hazard to affect them
personally, they are unlikely to take any personal measures to prepare or mitigate for that hazard. Once
again, the presence of differing risk perceptions highlights the need for effective risk communication as
a component of mitigation and preparedness.
Risk perception can lead to difficulties in making important decisions on the management of hazard
risks. Slovic and Weber (2002) write:
Public perception of risk plays an important role in risk analysis, adding issues of values, process,
power, and trust to the quantification issues typically considered by risk assessment professionals
219 VULNERABILITY
(Slovic 1999). Differences in risk perception lie at the heart of many disagreements about the best
course of action. Such differences have been demonstrated between technical experts and members
of the general public (Slovic, 1987), men vs. women (Finucane et al. 2000; Flynn et al. 1994; Weber
et al. 2002), and people from different cultures (Weber and Hsee 1998, 1999). Both individual and
group differences in preference for risky decision alternatives and situational differences in risk pref-
erence have been shown to be associated with differences in perceptions of the relative risk of choice
options, rather than with differences in attitude towards (perceived) risk, i.e., a tendency to approach
or to avoid options perceived as riskier (Weber and Milliman, 1997; Weber, 2001).
Managing risk perceptions is an important component of the hazards risk management process.
With an understanding of the perceptions and misperceptions of risk made by their constituents, haz-
ards risk managers can work to correct those misperceptions and address the public’s fears and con-
cerns. Failure to do so could easily lead to any of the mistakes discussed here.
Barry Glassner provides one example of the secondary effects of misperception of risk on a com-
munity. In the 1990s, the media widely reported on a “crime wave” against tourists in Florida that
resulted in 10 murders. Glassner writes,
[It was called] a crime wave because the media chose to label it as such. Objectively speaking, ten mur-
ders out of 41 million visitors did not even constitute a ripple, much less a wave, especially considering
that at least 97 percent of all victims of crime in Florida are Floridians. Although the Miami area had
the highest crime rate in the nation during this period, it was not tourists who had most cause for worry.
One study showed that British, German, and Canadian tourists who flock to Florida each year to avoid
winter weather were more than 70 times more likely to be victimized at home (Glassner 1999).
This widespread misperception of risk was not adequately managed and made many tourists think
twice before traveling to Florida; the tourism industry suffered as a result.
It is important for risk managers to evaluate personal perceptions because they will undoubtedly
influence the process of risk identification, subsequent analysis, and treatment. Because much of the
risk identification and analysis processes are based on qualitative information, great discrepancies can
exist, even between experts.
Risk managers must be as certain as possible that their assumptions and perceptions concerning risk
mirror reality as closely as possible. Risk managers who incorrectly overstate a hazard will devote a
disproportionate and inappropriate amount of available resources and time to that hazard.
For hazards risk management to be effective, an overall philosophy of cost-effectiveness must be
employed, and without accurate information and risk perceptions, such cost-effectiveness is unlikely.
Disaster risk managers must not assume anything. They must utilize as many historical records and
officially recognized hazard profiles as possible. Many public, private, and nonprofit agencies special-
ize in specific hazards and are likely to have the most accurate information concerning risk likelihood
and consequence data.
The public is likely to overestimate some risks and underestimate others, depending on the general
risk perception characteristics listed above. If the public collectively overestimates the likelihood or
consequence of a particular hazard, such as the presence of a nearby nuclear power plant, then they may
demand from public officials a significant effort to decrease what they see as a great risk. While initiat-
ing an increased level of preparedness and mitigation may not be a particularly effective and efficient
use of resources, simply ignoring the public’s concerns can have significant political implications.
CHAPTER 3 RISK AND VULNERABILITY220
With an understanding of the public’s perceptions, disaster risk managers can initiate a program of
risk communication and public education to increase understanding and steer public concern toward
risks of greater consequence and likelihood, such as house fires and floods.
Conversely, disaster risk managers should be aware of a collective public risk perception that under-
estimates the incidence or consequences of a certain hazard, such as underground power lines. A sig-
nificant number of people have been killed who made contact with underground power lines while
performing construction or landscaping work. Public education campaigns have regularly stressed to
citizens the significance of the hazard. Similar campaigns are employed for risks such as drug abuse,
forest fires, smoking, poisons, and so on. These risks tend to be ones that kill many more people than
all natural hazards combined, but are not considered appropriately “risky” by the public.
The Term Safe Those involved in disaster risk management are often faced with defining what level of safety from hazard
exposure is considered sufficient. There is not necessarily a correct answer to the question “How safe is
safe enough?” (Derby and Keeney 1981). Most people assume that referring to something as “safe”
implies that all risk has been eliminated. However, because such an absolute level of safety is virtually
unattainable in the real world, risk managers must establish thresholds of risk that define a frequency of
occurrence below which society need not worry about the hazard. Derby and Keeney (1981) contend that
a risk becomes “safe” or “acceptable” if it is “associated with the best of the available alternatives, not
with the best of the alternatives which we would hope to have available” (emphasis added).
This definition can cause great disagreement between the public and disaster risk management offi-
cials. The public may expect a level of safety determined to be zero risk for some hazards, such as
terrorism in the United States. Officials may need to continually recalibrate the public’s perception of
these hazards to let the public know that, while the risks are in fact still possible, they have been miti-
gated to the best of the country’s or community’s social, economic (available resources), and techno-
logical abilities. While the chances of a terrorist attack will always exist, governments strive to attain
levels of security dictating that the risks are so low that people need not worry.
To determine what level of safety is most acceptable, Derby and Keeney (1981) contend that “the
best combination of advantages and disadvantages” must be chosen from among several alternatives.
For instance, although the risk of car accidents is one of the greatest we face on a daily basis, eliminat-
ing the risk by prohibiting the use of cars is impractical. However, we can make cars more resistant to
impact, add seat belts and air bags, and enact laws and regulations that limit the ways in which cars are
operated. The result is a level of safety upon which society agrees is acceptable in relation to the ben-
efits (mobility) retained.
Paul Barnes of the Australia Department of Primary Industries explains the importance of establish-
ing an agreement on what constitutes safety in the community. He writes:
Is our goal Community Safety or Safer Communities? As a societal outcome, Community Safety
can be sought via efficient and effective regulation at an institutional level. Associated with this
regulation must be similarly high standards of risk management applied at the community level. The
establishment of safer communities, however, is a different matter. Before this can be sought as a
goal, determinations must be made about what safety means to the communities themselves. To do
this, institutional regulators must ensure that use of their expertise does not promote inflexibility in
understanding the world-views of the public. (Barnes 2002)
221 REFERENCES
CONCLUSION Reduction of risk and vulnerability is paramount to reducing the injuries, deaths, and damages associ-
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