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Earth as a Fragile System: Definitions and Types of Natural Disasters…
Earth as a Fragile System: Definitions and Types of Natural Disasters
Definitions
Natural Hazard: unexpected, uncontrollable natural event. Threatens activities of people, no casualties
Natural Disaster: natural hazard event that actually results in widespread destruction of property or caused injury and/or death
Catastrophe: natural disaster associated with tremendous consequences, affects a lot of people and infrastructure. Big recovery
Magnitude: amount of energy fuelling natural process
Frequency: number of occurrences of natural processes in a period of time
Return Period: length of time between similar events
Classifications of Natural Disasters
Gelogical Hazards
Earthquakes(most deadly)
Volcanic Eruptions
Tsunamis
Landslides
Impacts with space objects
Weather-related Hazards
Thunderstorms
Floods
Droughts
Hurricanes, Cyclones, Typhoons
Tornadoes
Rapid Onset/Cataclysmic: one large scale event causes majority of damage(earthquakes,volcano,flood)
Long-term/Continuing: Situation after event remains constant or may deteriorate as time passes(drought)
Making of a Natural Disaster
The Hazard: its nature, size, intensity, and other physical properties
Human Exposure: people and property affected by the hazard, including price of affected property
Human Vulnerability/Resistance to disaster: likelihood that a community will suffer, both in fatalities and physical damage
Assessing the Risk
Risk: probability of loss due to natural hazard. Risk = Hazard x Vulnerability
Involves:
Understanding the hazard
Evaluating ability of community to survive and recover
Mapping building, highways, infrastructure subject to hazard
Effects
Environmental: damage to homes, buildings, water supply, crops
Health: widespread death, disease, famine
Social, Economic, Political: leave jobs for search and rescue or place of employment destroyed
Administrative: damage to electrical, water storage, hospitals, police stations, roads, etc.
Primary Effects: directly and immediately from hazard (ground shaking)
Secondary Effects: delayed, not always at site of hazard(tsunamis, ground failures)
Phases of a Disaster
Pre-disaster period
Focused on prevention, or tries to lessen impact, laying framework for recovery
Emergency phase
Activities during actual event, evacuation/emergency assistance
Post-disaster period:
Transitional and rehabilitation phase: reestablish sense of normalcy, infrastructure restored(water), businesses re-open
Reconstruction and Recovery Phase: replacing damaged buildings, revitalize economies, restore agricultural systems
How Natural is a Natural Disaster?
Intensity influenced by human modifications on landscape, floods(deforestation), volcanic eruptions(farming on the slopes), ocean currents/storm surge(coral reef destruction)
Human modification: doesn't change hazard, creates greater human vulnerability and exposure, leading to greater disaster
Are they predictable?
Some occur without warning(earthquakes)
Some have precursors(hurricanes, volcanic eruptions)