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Hazards Definitions And Characteristics

Hazards Definitions And Characteristics. Definitions. Hazard : A threat ( whether natural or human) that has the potential to cause loss of life , injury , property damage , socio- economic disruption , or environmental degradation .

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Hazards Definitions And Characteristics

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  1. HazardsDefinitions And Characteristics

  2. Definitions • Hazard: A threat (whether natural or human) that has thepotentialto cause loss of life, injury, propertydamage, socio-economicdisruption, orenvironmentaldegradation. • HazardEvent: Theoccurrence (realization) of a hazard, theeffects of whichchangedemographic, economic, and/orenvironmentalconditions.

  3. Definitions • Disaster: A major hazard event that causes widespread disruption to a community or region, with significant demographic, economic and/or environmental losses, and which the effected community is unable to deal with adequately without outside help. • Vulnerability: The geographic conditions that increase the susceptibility of a community to a hazard or to the impacts of a hazard event. • Risk: The probability of a hazard event causing harmful consequences.

  4. Types

  5. What Happens Where? (Some)

  6. Characterising Hazards • Magnitude: The size of the event e.g. Force 10 on the Beaufort Scale, Maximum Height or Discharge of a Flood, or the size of an Earthquake on the Richter Scale. • Frequency: How often an event of a certain size occurs. For example a flood 1m high may occur, on average, every year. By contrast in the same stream a flood of 2m might occur only every 10 years. The frequency is sometimes called the recurrence interval (Gumbel’s Laws). The larger the event, the less frequently it occurs. However it is the very large events that do most of the damage (to the physical environment, to people, properties, and livlihoods).

  7. Characterising Hazards • Duration: The length of time that an environmental hazard exists. This varies from a matter of hours, such as with urban smog, to decades, in the case of drought, for example. • Areal Extent: The size of the area covered by the hazard. This can range from very small scale, such as an avalanche chute, to continental, as in the case of drought. • Spatial Concentration/Dispersion: Is the distribution of hazards over space; whether they are concentrated in certain areas, such as tectonic plate boundaries, coastal locations and valleys etc.

  8. Characterising Hazards • Speed Of Onset: This is rather like the lag-time in a flood hydrograph. It is the time difference between the start of the event and the peak of the event. It varies from rapid events, such as the Kobe Earthquake, to slow time-scale events such as drought in the Sahel of Africa. • Regularity: (or temporal spacing). Some hazards, such as cyclones, are regular; whereas others, such as earthquakes and volcanoes, are much more random.

  9. Activity 1 Look at the “Natural Hazards” Worksheet and… • Try to work out what type of hazard it is. • A place in the world it could happen. • Whether it is natural or human induced.

  10. Activity 2 Look at the “What Is A Natural Hazard?” Worksheet and answer the following… • What would be your definition of an “Extreme Natural Event” and why? • What is a “Vulnerable Population” and what makes them vulnerable? • Explain the interaction/consequences of the interaction between an “Extreme Natural Event” and a “Vulnerable Population”. • Is the definition of a Natural Hazard justified? Is there anything that could be added?

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