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Before landslide hazard mapping and risk assessment are reviewed, it is important to define terms and concepts closely in order to avoid the confusion and misuse that has occurred in some previously reported case histories. The most widely accepted and basic definitions in landslide studies are those provided by Varnes (1984).

Natural Hazard: the probability of occurrence within a specified period of time and within a given area of a potentially damaging phenomenon.

Vulnerability: the degree of loss to a given element or set of elements resulting from the occurrence of a natural phenomenon of a given magnitude. It is expressed on a scale from 0 (no damage) to 1 (total loss).

Specific Risk: the expected degree of loss due to a particular natural phenomenon. It may be expressed by the product of Hazard and Vulnerability.

Elements at Risk: the population, properties, economic activities, including public services, etc., at risk in a given area.

Total Risk: the expected number of lives lost, persons injured, damage to property or disruption of economic activity due to a particular natural phenomenon. It is therefore the product of Specific Risk and Elements at Risk.

These definitions have been expanded by the International Union of Geological Sciences (IUGS) Working Party on Landslides through its committee on Risk Assessment (IUGS 1997) but the main elements are essentially the same.

Hazard, therefore, defines the potential to cause damage. With respect to landslides it is necessary

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