Hazards and disasters can be classified as either natural or human-made (anthropogenic – resulting from human activity).
Natural hazards and disasters are divided into six major groups:
Human-made hazards and disasters are divided into five main categories:
Hazards can also be categorized in terms of their spatial extent, predictability, frequency, magnitude, duration, speed of onset, and effects.
- Duration: The length of time that a hazard lasts for. As a general rule the longer the hazard the more severe it is likely to be. For example and earthquake that lasts 1 minute is likely to be more severe than one that last two seconds and a drought that lasts ten years is likely to be more severe than one that last three months.
- Magnitude: This is the strength of a hazard. Most hazards are measured on a scale e.g. the Richter scale or the volcanic explosivity index (VEI). Generally speaking, the stronger the hazard the more severe the hazard is.
- Predictability: Some hazards are easier to predict than others. For example, volcanoes normally give warning signs before they erupt and tropical storms can be tracked from development to landfall. However, others like earthquakes are much harder to predict. Generally speaking hazards that hit with no warning are going to be more serious.
- Regularity: If hazards happen often and in quick succession e.g. a earthquake followed by multiple aftershocks then the severity is likely to be greater. During hurricane seasons, countries can be hit by repeated storms each causing greater damage because it has not been possible to recover from previous damage.
- Frequency: The return interval of hazards of certain sizes. For example earthquakes with a magnitude of over 8.0 happen on average once a year, but earthquakes of only 3 or 4 happen many times a day. If the hazard is a less frequent strong event, then it is going to have a bigger impact.
- Speed of onset: If the peak of the hazard arrives first or arrives quickly e.g. an earthquake, then the affects are likely to be worse than one that arrives slowly e.g. a drought.
- Spatial concentration: Where hazards are located or centred. For example earthquakes tended to be focused along plate boundaries, whereas tropical storms tend to be located in coastal areas in the tropics. Hazards that are located in known areas can be better prepared for and managed better.
- Areal extent: If a hazard covers a large area e.g. a drought covering the whole of East Africa, then the severity of the hazard is likely to be more severe, than a flood hitting just one village.
- Intentionality: Intentional or accidental.
Timing and Predictably Classifications
Hazards can be further classified by their timing and predictability durations:
|Quick Timing||Predictable||Tropical Storms, Hurricanes, Floods, Wildfires, Storms, Extreme Heat, Pandemics|
|Quick Timing||Unpredictable/Sudden||Earthquakes, Volcanoes, Tsunamis, Landslides, Avalanches, Tornados|
|Slow Timing||Predictable||Droughts, Famines|
- Image Source: http://blog.usa.gov/post/3880552826/how-to-safely-donate-to-disaster-relief [Accessed August 16, 2014]