3.1.5.1 - Hazard risk, perception and responses

From a physical hazard to disaster risk

Hazard describes a potential source of harm; risk describes the possible losses when that hazard meets exposed and vulnerable people or assets.

Geophysical hazards arise from Earth processes, such as earthquakes, volcanic eruptions and slope failure. Atmospheric hazards involve weather, such as tropical-storm winds; hydrological hazards involve water movement or storage, such as river flooding. The categories can overlap: a storm produces atmospheric winds, hydrological flooding and slope failure. Classify the process you are explaining rather than forcing an entire disaster into one box.

An offshore earthquake far from settlement may have little direct human impact. The same shaking beside weakly built housing can cause collapse, injury and interrupted services. A tsunami could extend exposure to a distant coast. Primary impacts follow directly from the physical event; secondary impacts arise through subsequent processes, such as business closures after transport damage. Environmental, social, economic and political effects overlap: water contamination harms ecosystems, health and the authorities responsible for safe supply.

Keep measures distinct. Magnitude describes the event's overall size, for example earthquake moment magnitude. Intensity describes effects or strength at a particular location, such as local shaking. Incidence concerns occurrence, often a count or rate over a defined period; frequency similarly needs a time interval and event threshold. Distribution identifies where events or exposure occur. A record of ten floods in ten years is uninterpretable without knowing which area, flood threshold and reporting method it covers. A low-frequency extreme event may overwhelm a defence designed for frequent smaller events.

In an original comparison, two towns experience the same peak river level. One has elevated homes and a working evacuation route; another has ground-floor bedrooms and one bridge already submerged. Equal physical intensity does not imply equal risk. Development may fund resistant buildings and warnings, but valuable concentrated assets, inequality and poor maintenance can still produce large losses. Use the UNDRR risk terminology to distinguish these interacting elements.

Perception, resources and choices

Hazard perception is how people understand and judge a threat, and it can differ from an agency's probability estimate.

Experience may increase awareness after a disaster, but surviving earlier warnings can also normalise danger or weaken trust. Information is interpreted through language, education, social networks and cultural meanings. A warning signal associated with one hazard may be misunderstood during another. Religious or cultural explanations can encourage fatalism, meaning a belief that outcomes are inevitable or beyond human control. They can also motivate collective protection: never assume that a religion or community is uniformly fatalistic.

Economic conditions affect both judgement and the choices available. An insured business owner may tolerate disruption because losses are partly recoverable. A tenant with no savings or transport may recognise danger yet be unable to relocate. A farmer may weigh evacuation against lost crops and income. Remaining in a risky place is therefore not automatic evidence of ignorance, indifference or fatalism. Housing costs, jobs, family ties and trust in defences matter alongside the perceived chance of an event.