Disasters, Its Characteristic and Impact


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- Define disasters
- Classify and describe the different types of disasters
- Describe its impact to the community


“A serious disruption of the functioning of a society, causing widespread human, material of environmental losses which exceed the ability of the affected society to cope using only its own resources”

To simplify, a disaster can be defined as

“Any events that overwhelms existing societal systems”

Declaration of disaster occurs when local needs exceed resources

Classification of Disaster

1. Natural
E.g. Earthquake, Landslides, typhoon, flood, tsunami, volcano, disease outbreaks, drought etc.

2. Man Made
E.g. War conflicts, industrial, chemical, biological and nuclear incidents, deforestation etc.

3. Complex
E.g. Combination of the above, e.g. War conflict during draught causing population displacement, malnutrition and an outbreak of diseases.

Phases of a Disaster


  • An earthquake is caused by a sudden slip on a fault in the earth’s crust. This layer has broken apart into oceanic and continental plates. The relative movement of these thin, rigid plates to each other causes the build-up of tensions along the boundaries, which are released in the form of earthquakes.
  • Richter Scale –describes the energy released and the amplitude waves measured by a seismograph
  • Magnitude, distance from epicenter and soil condition determine how you feel and its impact.

Measurement of an earthquake

  • There are however other ways to measure earthquake. the Mercalli Scale is used to measure the intensity, and the Moment Scale is to measure the size of the earthquake where the Richter Scale may not be accurate
  • The “Ring of Fire”


  • Massively destroy infrastructure: medical facilities, comm., transportation, gas, electrical, water supply and sewage sys.
  • Search and rescue missions important but dangerous. Requires heavy equipment
  • Medical response: Orthopaedic injuries e.g. crush injuries; public and primary health care.
  • Pitfalls: Slow response, poor comm. and coordination.

Casualties result from

  • falling bricks and plaster
  • splintering glass
  • toppling furniture, collapsing walls, falling debri
  • rock slides on mountains and hillsides
  • fallen power lines
  • sea waves generated by earthquakes
  • fire resulting from broken gas lines and spillage of gasoline and other flammables-a danger which may be aggravated by lack of water due to broken mains
  • rarely from drastic human actions resulting from panic


  • Due to gravity induced land movements causing rock falls, avalanches and mud flows.
    • Contributing factors
    • Steep slopes
    • Heavy rainfall
    • Erosions from river, snow or infrastructure development
    • Earthquakes and volcanic eruptions
  • Pitfall in relief: Mortality and morbidity high. Requires expertise and trained personnel in search and rescue during the initial phase.

Tornado and Cyclone

  • violent rotating columns of wind extending from sky to the ground
  • speed > 250 mph causes extensive damage
  • Severity: Fujita-Pearson scale: F0 – F5
  • EWS and education helps reduce injury
  • Injuries: Contaminated soft tissue wounds, fractures and head injuries


  • Most common natural disaster (40%)
  • Cause: poor drainage system, development of wetlands, failure or release of water from dam
  • Usually can be predicted, thus preparedness and mitigation program can be implemented
    • Impact
    • Drowning, traumatic and burns injuries from debris and electrical faults, water chemical contamination and vector borne illness
    • Pitfalls: Unprepared, rescue personnel’s safety, Delayed evacuation and poor camp management and rehabilitation


  • The word tsunami came from Japanese word which means ‘harbor waves’
  • Causes: Earthquake, landslide and sub-sea explosion
  • Characteristics: Initially water recedes or even rise, then a series of waves (ripples) 60- 500mph shallow-deep water with a height of 1-2 feet in deep sea. As it reaches shore the waves increases in height (‘run up’) and energy

    • Impact
    • Greatest over coastal areas, danger areas: 50-100 feet above sea level and 1 mile of the coast (distant origin)
    • Initial seismic activity already causes damage followed by tsunami
    • Pitfalls: Devastating damage and injuries, slow response due to severe damage


  • There is lack of access to food resulting from natural or man-made disasters. Malnutrition, dehydration and even death may follow.
  • Usually happens in complex disaster where there is massive population displacement, staying in cramp shelters, poor hygiene and lack of security and safety measures.
  • Vulnerable groups are children below 5 years old, pregnant and lactating mothers, elderly and the disabled.
  • Assessment methods include identification of communicable diseases (e.g. measles, typhoid, cholera) and crude mortality rate (CMR)
  • Relief activities should include clean water supply, nutritious food and cooking utensils

War conflict

  • May lead to complex disasters
  • Political and cultural influences
  • Safety of relief workers are highly concerned since they are vulnerable to attacks, mine injuries and violence.
  • May cause chemical, biological and radiation injuries to the affected population and relief workers.


  • Each types of disaster has its own characteristics and impacts
  • There has been an increasing in frequency and impact of disasters in the world
  • Recognizing the different characteristics will help in the management

Question: Choose the single best answer

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