Cover Image
close this bookCommunity Emergency Preparedness: A Manual for Managers and Policy-Makers (WHO, 1999, 141 p.)
close this folderChapter 3 Vulnerability assessment
View the documentIntroduction
View the documentThe process of vulnerability assessment
View the documentThe planning group
View the documentHazard identification
View the documentHazard description
View the documentDescribing the community
View the documentDescription of effects and vulnerability
View the documentHazard prioritization
View the documentRecommending action
View the documentSummary
View the documentReferences


The value of vulnerability assessment

Vulnerability assessment (also known as “hazard analysis”, “threat assessment”, and “risk assessment”) is a procedure for identifying hazards and determining their possible effects on a community, activity, or organization. It provides information essential for:

- sustainable development (because development will be undermined without programmes and strategies to reduce vulnerability);

- emergency prevention, mitigation, and preparedness (without knowledge of what is likely to go wrong, and what the effects will be, it is impossible to be effectively prepared and difficult to prevent problems);

- emergency response (many emergencies seriously disrupt transportation and communications, and information may become either unreliable or non-existent; vulnerability assessment will suggest where most of the damage might occur);

- emergency recovery (vulnerability assessment can provide a baseline that describes the prior condition of the community, against which the effectiveness of recovery work can be compared).

There are numerous ways of assessing vulnerability. The process described in this manual consists of a series of steps, each containing a number of techniques. Some of these steps are hazard identification, community and environmental analysis, and hazard description. In turn, there are techniques for identifying hazards, for describing the people, property, and environment they may affect, and for describing hazards.

The meaning of “vulnerability”

Vulnerability is the result of a number of factors that increase the chance that a community will be unable to deal with an emergency. Not all sections of a community are vulnerable to hazards, but most are vulnerable to some degree. Vulnerability comprises two aspects - susceptibility and resilience.

Susceptibility concerns the factors operating in a community that allow a hazard to cause an emergency; examples of such factors range from a community’s level of development to its location in an earthquake-prone area.

Resilience is the community’s ability to withstand the damage caused by emergencies and disasters; it is a function of the various factors that allow a community to respond to and recover from emergencies.

Communities and the individuals of which they are composed have a number of general needs during and after emergencies, of which personal safety is the most obvious. Thus, caring for the injured and protecting people from further harm are of paramount importance, together with providing food, drink, and shelter.

The meaning of “hazard”

In emergency management, “hazard” has various definitions. This manual defines “hazard” as any phenomenon that has the potential to cause disruption or damage to people and their environment.

Other definitions within the context of emergency management include:

- a threat to people and what they value;

- a threat to life, well-being, material goods, and environment from the extremes of natural processes and technology;

- potential for an agent or process to do harm.

Common to all these definitions is the potential for harm. A hazard is not an event - it is the potential for an event. Thus “flood”, in a general sense or even as applied to a particular place, is a hazard. An actual flood is an “incident”, “emergency”, or “disaster”, depending on the damage it causes or how well it is managed. A vulnerability assessment relating to a flood in a particular community examines the potential for flood events and the possible effects of such events. Analysing a flood that has occurred is not a vulnerability assessment because each event is unique, and emergency management based on a specific event will contain too many unjustified assumptions. What is true of one flood will not necessarily be true of another.

Communities, environments, and hazards

In terms of emergency management, a community has an intimate relationship with its environment and its hazards. The following example illustrates how a community interacts with its environment and hazards. People move into a hilly, forested area, with a medium to high annual rainfall, and clear land for agriculture. Before the forest was cleared, rainfall was absorbed and trapped by vegetation and accumulated humus before it could run off into creeks and rivers. Forests and many other natural ecosystems, such as swamps, act as sponges during heavy rain by storing water, some of which then evaporates or is released slowly. While there is still the potential for flood, only the heaviest rain will cause serious flooding. Once a forested area is cleared, drainage characteristics change. There is less vegetation and humus to collect and store water, so the water runoff is greater. There is also more erosion, and the profile of the river bed is altered by the accumulation of silt. When heavy rainfall occurs, therefore, there is a greater likelihood of serious flooding, which may lead, in turn, to further changes in the drainage system.

If part of this community lives on or near flood plains, and the settlement took account only of the flood characteristics that existed before forest clearing, problems might occur, including:

- severe floods leading to loss of life and destruction of buildings, bridges, roads, dams, and livestock;

- removal of valuable topsoil from agricultural areas and, hence, decreasing productivity;

- river siltation, leading to changes in the navigability of the river.

Thus, changes in the environment caused by the community alter the hazards in the area, and the changed hazards may then have effects on the environment, the community, and the community’s vulnerability. It is essential, therefore, to examine how the community, the environment, and the hazards interact when performing a vulnerability assessment.

Even normal population growth can increase vulnerability, by forcing communities into marginal and hazardous areas.