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Classification Glossary

Definitions of Disaster Types

EM-DAT’s definitions related to the group of natural hazards mainly refer to the IRDR Peril Classification and Hazard Glossary (see A Brief History of the EM-DAT Classification System). These are reported in the following sections by disaster subgroups.

EM-DAT definitions related to the groups of complex disasters and technological hazards are listed separately in the Complex and Technological Hazards section. These are legacy definitions from the EM-DAT project and do not refer to a particular glossary serving as an international standard.

1 - Biological Hazards

Term Level Definition Source
Biological hazard Subgroup A hazard caused by exposure to living organisms and/or their toxic substances (e.g., venom, or mold) or vector-borne diseases that they may carry. Examples are venomous wildlife and insects, poisonous plants, algae blooms, and mosquitoes carrying agents that causes disease such as parasites, bacteria, or viruses (e.g., malaria). IRDR
Animal incident Type Subtype Human encounters with dangerous or exotic animals in both urban and rural environments. IRDR
Epidemic Type Either an unusual, often sudden, increase in the number of cases of an infectious disease that already existed in the region (e.g., flu, or E. coli) or the appearance of an infectious disease previously absent from the region (e.g., plague, or polio). EM-DAT1
Infectious disease Subtype (General) Either an unusual, often sudden, increase in the number of cases of an infectious disease that already existed in the region (e.g., flu, or E. coli) or the appearance of an infectious disease previously absent from the region (e.g., plague, or polio). IRDR1
Bacterial disease Subtype An unusual increase in the number of cases caused by exposure to bacteria either through skin contact, ingestion, or inhalation. Examples include salmonella, Methicillin-Resistant Staphylococcus Aureus (MRSA), and cholera, among others. IRDR2
Parasitic disease Subtype An unusual increase in the number of cases caused by exposure to a parasite, i.e., an organism living on or in a host. Exposure to parasites occurs mostly through contaminated water, food, or contact with insects, animals, etc. Examples are malaria, Chagas disease, giardiasis, and Trichinellosis. IRDR2
Viral disease Subtype
Fungal disease Subtype An unusual increase in the number of cases caused by exposure to fungi either through skin contact, ingestion, or inhalation of spores. Examples are fungal pneumonia, fungal meningitis, etc. IRDR2
Prion disease Subtype A type of biological hazard caused by prion proteins. Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of rare progressive neurodegenerative disorders that affect both humans and animals. They are characterized by long incubation periods and neural loss. Examples are Bovine Spongiform Encephalopathy (BSE), Creutzfeldt-Jakob Disease (CJD), Kuru, etc. IRDR2
Infestation Type Subtype (General) The pervasive influx, swarming and/or hatching of insects, worms, or other animals affecting humans, animals, crops, and perishable goods. IRDR3
Grasshopper infestation Subtype Infestation of grasshoppers (insects). IRDR3
Locust infestation Subtype Infestation of locusts (insects). IRDR3
Worm Infestation Subtype Infestation of worms. IRDR3

  1. The “Infectious disease” definition corresponds to the definition of “Disease” in the IRDR glossary. The same definition is used to define “Epidemic” in the EM-DAT glossary. ↩︎ ↩︎

  2. With minor modifications. ↩︎ ↩︎ ↩︎ ↩︎

  3. These definitions have been adapted and derived from the IRDR definition of “Insect infestation”. ↩︎ ↩︎ ↩︎ ↩︎

2 - Climatological Hazards

Term Level Definition Source
Climatological hazard Subgroup A hazard caused by long-lived, meso- to macro-scale atmospheric processes ranging from intra-seasonal to multi-decadal climate variability. IRDR
Drought Type Subtype An extended period of unusually low precipitation that produces a shortage of water for people, animals, and plants. Drought is different from most other hazards in that it develops slowly, sometimes even over the years, and its onset is generally difficult to detect. Drought is not solely a physical phenomenon because its impacts can be exacerbated by human activities and water supply demands. Drought is therefore often defined both conceptually and operationally. Operational definitions of drought, i.e., the degree of precipitation reduction that constitutes a drought, vary by locality, climate, and environmental sector. IRDR
Glacial lake outburst flood Type Subtype These floods occur when water held back by a glacier or moraine is suddenly released. Glacial lakes can be at the front of the glacier (marginal lake) or below the ice sheet (sub-glacial lake). IRDR1
Wildfire Type Subtype (General) Any uncontrolled and non-prescribed combustion or burning of plants in a natural setting such as a forest, grassland, brush land or tundra, which consumes natural fuels and spreads based on environmental conditions (e.g., wind, or topography). Wildfires can be triggered by lightning or human actions. IRDR
Forest fire Subtype A type of wildfire in a wooded area. IRDR
Land fire (Brush, Bush, Pasture) Subtype A type of wildfire in a brush, bush, pasture, grassland, or other treeless natural environment. IRDR2

  1. The definition of “Glacial lake outburst flood” corresponds to the definition of “Glacial lake outburst” in the IRDR glossary. ↩︎

  2. Not defined in the IRDR glossary but adapted from the “Wildfire” and “Forest fire” definitions. ↩︎

3 - Extra-terrestrial Hazards

Term Level Definition Source
Extra-terrestrial hazard Subgroup A hazard caused by asteroids, meteoroids, and comets as they pass near to the Earth, enter the Earth’s atmosphere, and/or strike the Earth, and by changes in interplanetary conditions that effect the Earth’s magnetosphere, ionosphere, and thermosphere. IRDR
Impact Type A type of extra-terrestrial hazard caused by the collision a meteoroid, asteroid, or comet with the Earth. IRDR
Airburst Subtype An explosion of a comet or meteoroid within the Earth’s atmosphere without striking the ground. IRDR
Collision Subtype An impact caused by the collision of a meteoroid, asteroid, or comet with the Earth’s ground. IRDR1
Space weather Type A general term for extra-terrestrial weather conditions driven by solar eruptions such as geomagnetic storms, radio disturbances, and solar energetic particles. IRDR
Energetic particles Subtype Emissions from solar radiation storms consisting of pieces of matter (e.g., protons and other charged particles) moving at very high speed. The magnetosphere and atmosphere block (solar) energetic particles (SEP) from reaching humans on Earth but they are damaging to the electronics of space-borne technology (such as satellites) and pose a radiation hazard to life in space and aircraft traveling at high altitudes. IRDR
Geomagnetic storm Subtype A type of extra-terrestrial hazard caused by solar wind shockwaves that temporarily disturb the Earth’s magnetosphere. Geomagnetic storms can disrupt power grids, spacecraft operations, and satellite communications. IRDR
Shockwave Subtype A shockwave carries energy from a disturbance through a medium (solid, liquid, or gas) similar to the action of a wave, though it travels at much higher speed. It can be a type of extra-terrestrial hazard caused by the explosion (airburst) or impact of meteorites that generate energy shockwaves capable of shattering glass, collapsing walls, etc. IRDR
Radio disturbance Subtype Triggered by x-ray emissions from the Sun hitting the Earth’s atmosphere and causing disturbances in the ionosphere such as jamming of high and/or low frequency radio signals. This affects satellite radio communication and Global Positioning Systems (GPS). IRDR

  1. The “Collision” definition is derived from the IRDR “Impact” and “Airburst” definitions. ↩︎

4 - Geophysical Hazards

Term Level Definition Source
Geophysical hazard Subgroup A hazard originating from solid earth. This term is used interchangeably with the term geological hazard. IRDR
Earthquake Type Sudden movement of a block of the Earth’s crust along a geological fault and associated ground shaking. IRDR
Ground movement Subtype Surface displacement of earthen materials due to ground shaking triggered by earthquakes or volcanic eruptions. IRDR
Tsunami Subtype A series of waves (with long wavelengths when traveling across the deep ocean) that are generated by a displacement of massive amounts of water through underwater earthquakes, volcanic eruptions, or landslides. Tsunami waves travel at very high speed across the ocean, but as they begin to reach shallow water they slow down, and the wave grows steeper. IRDR
Mass movement (dry) Type Any type of downslope movement of earth materials under hydrological dry conditions. IRDR1
Avalanche (dry) Subtype A large mass of loosened earth material, snow, or ice that slides, flows, or falls rapidly down a mountainside under the force of gravity. Debris Avalanche: The sudden and very rapid downslope movement of a mixed mass of rock and soil. There are two general types of debris avalanches. A cold debris avalanche usually results from an unstable slope suddenly collapsing whereas a hot debris avalanche results from volcanic activity leading to slope instability and collapse. IRDR
Landslide (dry) Subtype Any kind of moderate to rapid soil movement incl. lahars, mudslides, and debris flows (under dry conditions). A landslide is the movement of soil or rock controlled by gravity and the speed of the movement usually ranges between slow and rapid, but it is not very slow. It can be superficial or deep, but the materials must make up a mass that is a portion of the slope or the slope itself. The movement has to be downward and outward with a free face. EM-DAT
Rockfall (dry) Subtype
Sudden subsidence (dry) Subtype Sinking of the ground due to groundwater removal, mining, dissolution of limestone (e.g., karst sinkholes), extraction of natural gas, and earthquakes. In this case, the sinking occurs under dry conditions as a result of a geophysical trigger. IRDR2
Volcanic activity Type Subtype (General) A type of volcanic event near an opening/vent in the Earth’s surface including volcanic eruptions of lava, ash, hot vapor, gas, and pyroclastic material. IRDR
Ash fall Subtype Fine (less than 4 mm in diameter) unconsolidated volcanic debris blown into the atmosphere during an eruption; can remain airborne for long periods of time and travel a considerable distance from the source. IRDR
Lava flow Subtype The ejected magma that moves as a liquid mass downslope from a volcano during an eruption. IRDR
Pyroclastic flow Subtype Extremely hot gases, ash, and other materials with a temperature of more than 1,000 degrees Celsius that rapidly flow down the flank of a volcano (at more than 700 km/h) during an eruption. IRDR
Lahar Subtype Hot or cold mixture of earthen material flowing down the slope of a volcano either during or between volcanic eruptions. IRDR

  1. The definition of “Mass movement (dry)” is adapted from the “Mass movement” IRDR definition. ↩︎

  2. The first definition sentence of “Sudden subsidence (dry)” is the definition of “Subsidence” in the IRDR glossary. The second sentence has been added to distinguish this class from “Sudden subsidence (wet)” in the hydrological group. ↩︎

5 - Hydrological Hazards

Term Level Definition Source
Hydrological hazard Subgroup A hazard caused by the occurrence, movement, and distribution of surface and subsurface freshwater and saltwater. IRDR
Flood Type Subtype (General) A general term for the overflow of water from a stream channel onto normally dry land in the floodplain (riverine flooding), higher-than-normal levels along the coast (coastal flooding) and in lakes or reservoirs as well as ponding of water at or near the point where the rain fell (flash floods). IRDR
Coastal flood Subtype Higher-than-normal water levels along the coast caused by tidal changes or thunderstorms that result in flooding, which can last from days to weeks. IRDR
Flash flood Subtype Heavy or excessive rainfall in a short period of time that produces immediate runoff, creating flooding conditions within minutes or a few hours during or after the rainfall. IRDR
Riverine flood Subtype A type of flooding resulting from the overflow of water from a stream or river channel onto normally dry land in the floodplain adjacent to the channel. IRDR
Ice jam flood Subtype The accumulation of floating ice restricting or blocking a river’s flow and drainage. Ice jams tend to develop near river bends and obstructions (e.g., bridges). IRDR
Mass movement (wet) Type Types of mass movement that occur when heavy rain or rapid snow/ice melt send large amounts of vegetation, mud, or rock down a slope driven by gravitational forces. IRDR1
Avalanche (wet) Subtype A large mass of loosened earth material, snow, or ice that slides, flows, or falls rapidly down a mountainside under the force of gravity. Snow Avalanche: Rapid downslope movement of a mix of snow and ice. IRDR
Landslide (wet) Subtype Any kind of moderate to rapid soil movement incl. lahars, mudslides, and debris flows (under wet conditions). A landslide is the movement of soil or rock controlled by gravity and the speed of the movement usually ranges between slow and rapid, but it is not very slow. It can be superficial or deep, but the materials must make up a mass that is a portion of the slope or the slope itself. The movement has to be downward and outward with a free face. EM-DAT
Rockfall (wet) Subtype
Sudden subsidence (wet) Sinking of the ground due to groundwater removal, mining, dissolution of limestone (e.g., karst sinkholes), extraction of natural gas, and earthquakes. In this case, the sinking occurs under wet conditions as a result of a hydrological trigger (e.g., rain). IRDR2
Mudslide Subtype
Wave action Type Wind-generated surface waves that can occur on the surface of any open body of water such as oceans, rivers, or lakes. The size of the wave depends on the strength of the wind and the distance traveled (fetch). IRDR
Rogue wave Subtype An unusual single crest of an ocean wave far out at sea that is much higher and/or steeper than other waves in the prevailing swell system. IRDR
Seiche Subtype A standing wave of water in a large semi- or fully-enclosed body of water (lakes or bays) created by strong winds and/or a large barometric pressure gradient. IRDR

  1. The “Mass movement (wet)” definition is adapted from the IRDR definition of “Debris flow, mud flow, rock fall”. ↩︎

  2. The first definition sentence of “Sudden subsidence (wet)” is the definition of “Subsidence” in the IRDR glossary. The second sentence has been added to distinguish this class from “Sudden subsidence (dry)” in the geophysical group. ↩︎

6 - Meteorological Hazards

Term Level Definition Source
Meteorological hazard Subgroup A hazard caused by short-lived, micro- to meso-scale extreme weather and atmospheric conditions that last from minutes to days. IRDR
Extreme temperature Type A general term for temperature variations above (extreme heat) or below (extreme cold) normal conditions. IRDR
Cold wave Subtype A period of abnormally cold weather. Typically, a cold wave lasts for two or more days and may be aggravated by high winds. The exact temperature criteria for what constitutes a cold wave may vary by location. EM-DAT
Heat wave Subtype A period of abnormally hot and/or unusually humid weather. Typically, a heat wave lasts for two or more days. The exact temperature criteria for what constitutes a heat wave may vary by location. EM-DAT
Severe winter conditions Subtype Damage caused by snow and ice. Winter damage refers to damage to buildings, infrastructure, traffic (esp. navigation) inflicted by snow and ice in the form of snow pressure, freezing rain, frozen waterways etc. EM-DAT
Fog Type Subtype Water droplets that are suspended in the air near the Earth’s surface. Fog is, in fact, simply a cloud that is in contact with the ground. IRDR1
Storm Type Subtype (General)
Derecho Subtype Widespread and usually fast-moving windstorms associated with a convection/convective storm. Derechos include downburst and straight-line winds. The damage from derechos is often confused with the damage from tornadoes. IRDR
Hail Subtype Solid precipitation in the form of irregular pellets or balls of ice more than 5 mm in diameter. IRDR
Lightning / Thunderstorms Subtype A high-voltage, visible electrical discharge produced by a thunderstorm and followed by the sound of thunder. IRDR2
Sand/Dust storm Subtype Strong winds carrying particles of sand aloft, but generally confined to less than 50 feet (15 m), especially common in arid and semi-arid environments. A dust storm is also characterized by strong winds but carries smaller particles of dust rather than sand over an extensive area. IRDR
Storm surge Subtype An abnormal rise in sea level generated by a tropical cyclone or other intense types of storm. IRDR
Tornado Subtype A violently rotating column of air that reaches the ground or open water (waterspout). IRDR
Winter storm/Blizzard Subtype A low-pressure system in winter months with significant accumulations of snow, freezing rain, sleet, or ice. A blizzard is a severe snowstorm with winds exceeding 35 mph (56 km/h) for three or more hours, producing reduced visibility (less than 0.25 miles (400 m)). IRDR
Extra-tropical storm Subtype A type of low-pressure cyclonic system in the middle and high latitudes (also called a mid-latitude cyclone) that primarily gets its energy from the horizontal temperature contrasts (fronts) in the atmosphere. When associated with cold fronts, extra-tropical cyclones may be particularly damaging (e.g., European winter/windstorm, or Nor’easter). IRDR
Tropical cyclone Subtype A tropical cyclone originates over tropical or subtropical waters. It is characterized by a warm-core, non-frontal synoptic-scale cyclone with a low-pressure center, spiral rain bands and strong winds. Depending on their location, tropical cyclones are referred to as hurricanes (Atlantic, Northeast Pacific), typhoons (Northwest Pacific), or cyclones (South Pacific and Indian Ocean). IRDR
Severe weather Subtype

  1. Note: the only “Fog” entry in EM-DAT is the Great London SMOG, 1952, which was also accompanied by air pollution. ↩︎

  2. The “Lightning/Thunderstorm” definition corresponds to the definition of “Lightning” in the IRDR glossary. ↩︎

7 - Complex and Technological Hazards

Term Level Definition Source
Complex disaster Group Subgroup Type Subtype Major famine situation for which drought was not the main causal factor. Removed from EM-DAT in September 2023. EM-DAT
Industrial accident Subgroup Type Subtype (General) Disaster type term used in EM-DAT to describe technological accidents of an industrial nature/involving industrial buildings (e.g. factories). EM-DAT
Miscellaneous accident Subgroup Type Subtype (General) Disaster type term used in EM-DAT to describe technological accidents of a non-industrial or transport nature (e.g., involving houses). EM-DAT
Chemical spill Type Subtype Accident release occurring during the production, transportation, or handling of hazardous chemical substances. EM-DAT
Collapse (Industrial) (Miscellaneous) Type Subtype Accident involving the collapse of a building or structure. Can either involve industrial structures or domestic/non-industrial structures. EM-DAT
Explosion (Industrial) (Miscellaneous) Type Subtype Explosions involving buildings or structures. Can involve industrial structures. EM-DAT
Fire (Industrial) (Miscellaneous) Type Subtype Urban fire involving buildings or structures. Can involve industrial structures. EM-DAT1
Gas leak Type Subtype
Oil spill Type Subtype
Poisoning Type Subtype Poisoning of atmosphere or water courses due to industrial sources of contamination. EM-DAT
Radiation Type Subtype
Transport accident Subgroup Disaster type term used to describe technological transport accidents involving mechanized modes of transport. It comprises four disaster subtypes (i.e., Air, Water, Rail, and Road). EM-DAT
Air Type Subtype Transport accidents involving airplanes, helicopters, airships, and balloons. EM-DAT
Water Type Subtype Transport accidents involving sailing boats, ferries, cruise ships, and other vessels. EM-DAT
Rail Type Subtype Transport accidents involving trains. EM-DAT
Road Type Subtype Transport accidents involving motor vehicles on roads and tracks. EM-DAT

  1. Urban fire is a former class that is now either described as “Fire (industrial)” or “Fire (miscellaneous).” ↩︎