Disaster and Earth Science

Basic concepts of Vulnerability

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I. Basic concepts of Vulnerability

A set of conditions and processes resulting from physical, social, economic, and environmental factors, which increase the susceptibility of a community to the impact of hazards. Positive factors that increase the ability of people and the society they live in to cope effectively with hazards and can reduce their susceptibility are often designated as capacities.

The relationships between hazard, vulnerability and disaster have been commonly represented as:

Disaster = Hazard + Vulnerability or Disaster= Hazard x Vulnerability

Disasters occur when hazard strikes a vulnerable community whose capacity is limited. Disasters may decrease in frequency and severity as capacities are increased. Disaster = (Hazard x Vulnerability)/ Capacity

Vulnerability and capacity assessment is a basic process used to identify the strengths and weaknesses of households, communities, institutions like National Societies and nations. Vulnerability can be defined as The characteristics of a person or group in terms of their capacity to anticipate, cope with, resist and recover from the impact of natural or man-made hazards.

The definition of vulnerability suggests that it cannot be described without reference to a specific hazard or shock. So, the question that must always be asked is, “Vulnerability to

what?” People living along coastal areas or rivers may be vulnerable to seasonal storms and flooding, while the inhabitants of countries with social, political and economic problems may face difficulties in achieving a satisfactory and sustainable quality of life. Or a National Society may have specific organizational limitations that impede progress in developing its capacity to carry out more effective disaster preparedness and response programes.

The following chart describes the progression of vulnerability from underlying causes and the results of a hazard event that becomes a disaster.

II. The progression of vulnerability


Source: Blaikie, Piers et al. At Risk. London: Routledge, 1994.

III. Difference between vulnerability and risk:

VULNERABILITY (V): Vulnerability is a component of risk

• V is context-dependant and subject-dependant : one is vulnerable to something

• Presence of stakes: someone or something threatened

• Presence of a hazard: threatening phenomena=> Existence of a risk: probability for the stakes to undergo damages

• Hazard alone cannot convert a Risk (R) into a Disaster: V is necessary

• V = presence of stakes (exposure) and some of their internal properties which render the damages possible: fragility and incapacity to face impact. So that V is part of R.

R = H x V

•Tendency to undergo damages: state of fragility that raises the susceptibility of the stake to suffer the impact of a damaging phenomenon

• Incapacity to anticipate, copes with, resist to, adapt to, and recover from hazards

So that Vulnerability defines a state of non-resistence : incapacity to withstand the shock (without adapting) and non-resilience: incapacity to absorb the shock and adapt to come back to an acceptable state.

Global Level: ↑ number and severity of disasters faster than ↑ hazards due to manifestations of climate change => ↑ vulnerability of human societies, favourizing the transformation of hazards into disasters.

RISK: The probability of harmful consequences, or expected losses (deaths, injuries, property, livelihoods, economic activity disrupted or environment damaged) resulting from interactions between natural or human-induced hazards and vulnerable conditions.

Risk: (noun) in terms of a hazard, chance, bad consequences, loss, etc.. 

Verb in terms of: to expose to chance of injury or loss, venture on, accept the chance of.


Source: The UN International Strategy for Disaster Reduction (UNISDR, 2006)

or Risk (or Disaster) = Vulnerability + Hazard

IV. Vulnerability Analysis:

A. Analysing vulnerability through slicing

– socio-ecological: human-induced ecosystemic perturbations aggravating the natural hazard (deforestation, land degradation, street pavement, some engineering practices, climate change, etc.)

Decomposition of vulnerability types/components

1. Exposure: physical exposure: presence and density of the people, habitat, networks, goods and services in risk zones, defining potential losses or damages, both human and non-human (stakes).

2. Insufficient capacities to prevent, prepare for, face and cope with hazards and disasters

-Physical vulnerability: insufficient capacity of an individual or an asset to resist or recover from a hazard’s impact.

-Juridical-legal v.: inadequate state of the legislative and judiciary regulations to prevent, mitigate, prepare for, face and recover from disasters.

– Institutional v.: inadequate state of the institutional disposals, at all levels, to prevent, mitigate, prepare for, face and recover from disasters.

– Technical v.: inadequate knowledge and/or use of risk management techniques.

-Political v. : weakness of the political powers, their legitimacy and control which hinders risk management.

-Socio-economic v.: social and economical elements which raise the susceptibility of undergoing disasters and lower the capacities of self protection

Ex: : socio-spatial segregation, large inequalities of wealth and of access to the security disposals, misery, anomie and social disorganization, poor social position and social isolation of exposed people, existence of higher social risks undergone by people.

– Psychological and cultural v.: inadequate security paradigm or risk perceptions; cultural anomie or weakness; attachment to risk zones or risky behavior, non-willingness or incapacity to protect oneself.

• The overall vulnerability of a stake is a mix of some or all these vulnerabilities

• This analysis can be applied at any level (individual, household, collective)

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