Risk probability

Risks are often quantified in generalized ways. For example, there is a probability of an individual dying in any one year of: 1 in 200 if he or she smokes 10 cigarettes a day; 1 in 23,000 in an earthquake in Iran; and 1 in 10,000,000 of being hit by lightning in the USA. Such gross risk estimates can be useful for comparative purposes, but usually conceal large variations in the risk to individuals or different regions. In the case of Iran, people who live closer to an earthquake fault are at greater risk than those that live far away. Similarly, people who live in poorly constructed masonry houses near a fault are more at risk than those who may live nearby in well built wood structures.

The first step in risk management, therefore, is quantifying the probability of the risk. The second step is evaluating the risk, that is, passing judgment on how serious it is. The importance a community places on the risk of a disaster is likely to be influenced by the type and level of other everyday risks it faces. Even if the risk from a natural hazard is quite significant, it is unlikely to compare, for example, with the risk of child mortality in a society with minimal primary health care. Villages in the hazardous mountain valleys of Northern Pakistan, regularly afflicted by floods, earthquakes, and landslides, do not perceive disaster mitigation to be one of their priorities. Their priorities are protection against the greater risks of disease and irrigation failures.

As societies develop economically, risk reduction is likely to assume greater importance to them. Development itself can increase the likelihood of disasters, but as societies become richer more resources can be made available to invest in some degree of protection. Protection of the development process itself becomes a disaster mitigation issue.