Natural Disasters

A natural disaster is a natural hazard that causes significant loss of life, injury, or property damage. The underlying physical event, a rupture along a fault, a tropical cyclone, a river in flood, is a natural hazard. It becomes a disaster only when it intersects with exposed and vulnerable populations, infrastructure, and economic activity. This distinction is central to modern disaster science. A large earthquake in an uninhabited region is a geophysical event; the same earthquake beneath a densely populated city with vulnerable buildings is a catastrophe.

Natural disasters are conventionally classified by origin. Geological hazards include earthquakes, volcanic eruptions, tsunamis, and landslides, and arise from the internal dynamics of the Earth. Atmospheric hazards include hurricanes, typhoons, tornadoes, and severe winter storms, and arise from weather systems in the troposphere. Hydrological hazards are dominated by floods, whether from rivers, flash runoff, or coastal storm surge. Climatological hazards include droughts, heat waves, and wildfires, which unfold over weeks, months, or years. Biological hazards, chiefly epidemics and pandemics, are treated separately in disaster statistics and are covered in greater depth on the forthcoming CountryReports page on major pandemics in history.

The principal international data source on disaster impact is the Emergency Events Database, known as EM-DAT, maintained by the Centre for Research on the Epidemiology of Disasters at the Université catholique de Louvain in Belgium. EM-DAT has recorded tens of thousands of events worldwide since 1900, and its inclusion criteria require at least ten reported deaths, one hundred people affected, a declaration of a state of emergency, or a call for international assistance. Other authoritative bodies, including the United Nations Office for Disaster Risk Reduction, the World Meteorological Organization, the United States Geological Survey, and the United States National Oceanic and Atmospheric Administration, provide specialized data on particular hazard types.

Modern disaster research emphasizes that risk is a product of hazard, exposure, and vulnerability. A community can reduce risk by addressing any of the three, by avoiding the most hazardous locations, by lowering the number of people and assets exposed, or by strengthening the resilience of buildings, infrastructure, and social systems. This framing, adopted in United Nations frameworks since the 1990s, organizes most of the preparedness and mitigation work described later in this page.