Risk is a forward-looking concept, as opposed to a present situation or a past event. It aims to assess the final result of combining the following measurable items: hazard, exposure and vulnerability.
Disaster risk can be understood as the likelihood (or probability) of loss of life, injury or destruction and damage from a disaster in a given period of time. Or, more clearly: disaster risk is the consequence of the interaction between a hazard and the characteristics that make people and places vulnerable and exposed.
- Hazard: a dangerous event that may cause loss of life, injury or other health impacts, as well as damage and loss to property, infrastructure, livelihoods and services, social and economic disruption and, or environmental damage; as a component of risk, it is the probability of experiencing a certain intensity of hazard (eg. earthquake, cyclone, etc.) at a specific location and is usually determined by a historical or user-defined scenario, probabilistic hazard assessment, or other methods. Some hazard modules can include secondary perils (such as soil liquefaction or fires caused by earthquakes, or storm surge associated with a cyclone).
- Exposure: the presence and number of people, property, livelihoods, systems or other elements in hazard areas (and so thereby subject to potential losses); as a component of risk, it represents the stock of property and infrastructure exposed to a hazard, and it can include socioeconomic factors.
- Vulnerability: the set of characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard; as a component of risk, it accounts for the susceptibility to damage of the assets exposed to the forces generated by the hazard. Fragility and vulnerability functions estimate the damage ratio and consequent loss respectively, and/or the social cost (e.g., number of injured, homeless, and killed) generated by a hazard, according to a specified exposure.
- Open-ended Intergovernmental Expert Working Group on Indicators and Terminology Relating to Disaster Risk Reduction: https://www.preventionweb.net/drr-framework/open-ended-working-group/