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DMHA 101 | Disaster Management Primer

Disaster Management Overview & Definitions

What is a disaster?

The internationally accepted definition of “disaster” is:

“A serious disruption of the functioning of society which poses a significant, widespread threat to human life, health, property or the environment, whether arising from accident, nature or human activity, whether developing suddenly or as the result of long term processes, but excluding armed conflict.” [International Federation of Red Cross/Red Crescent Societies (IFRC), 2007]

Key components of this definition are:

  • There is a serious disruption of society
  • There is a widespread threat to human life, property, and the environment
  • The disaster is caused by natural or man-made hazards

For example, was Hurricane Katrina a “disaster” by this definition? Here are some facts:

Flooding resulting from Hurricane KatrinaPhoto Jocelyn Augustino / FEMA Photo 15022

Hurricane Katrina

August 29, 2005

  • Fatalities: 1,422
  • Individuals homeless: 770,000
  • Jobless: 400,000
  • No power for 2.5 M homes
  • Damages from Hurricane Katrina now estimated between $152-$200 billion


Was there a disruption of society? Was there a threat to human life, property, and environment?  Was the disaster caused by natural or man-made hazards?

Yes, Katrina definitely fits this definition.

Hazards cause disasters. Hazards can be natural, or man-made. Were the hazards which caused Katrina natural or man-made? The hurricane was clearly a natural hazard when it made landfall. But the poorly maintained levee system and building the city below sea level were clearly man-made hazards. Thus, the levees in New Orleans were the man-made hazard that became a disaster once the natural hazard of Hurricane Katrina occurred.

Disasters can be classified by timing.



Onset is immediate, without warning, such as earthquakes or explosions. It is generally unpredictable.

Example: Christchurch Earthquake

Christchurch earthquake
Photo by Sharon Davis / CC BY-NC 2.0


Onset comes with little warning, such as hurricanes. It is relatively predictable.

Example: Hurricane Katrina

 Hurricane Katrina
 Photo by Peter Stinson / CC BY-NC-SA 2.0


Onset is longer, allowing more time to foresee, such as drought or flooding. It is generally predictable.

Example: Haitian Flooding 2012

 Haitian flooding

Photo by proimos / CC BY-NC 2.0

How a disaster affects a society are a function of the hazard, vulnerability, and exposure.



  • Geophysical-earthquakes, landslides, tsunamis and volcanic activity
  • Hydrological-avalanches and floods
  • Climatological-extreme temperatures, droughts, wildfires
  • Meteorological-cyclones and storms/wave surges
  • Biological-disease epidemics and insect/animal plagues


  • Complex emergencies /conflicts
  • Famine
  • Displaced populations
  • Industrial accidents and transport accidents


The ability or resiliency of society to withstand a disaster.


Exposure refers to people, property, systems or elements present in hazard zones that are thereby subject to potential losses.

Disaster Risk Reduction through the Disaster Risk Management Cycle

Disaster risks can be reduced through systematic efforts to analyze and manage the causal factors of disasters, including through reduced exposure to hazards, lessened vulnerability of people and property, wise management of land and the environment, and improved preparedness for adverse events. This concept of “disaster risk reduction”, instead of just responding to a crisis, is embodied in the disaster risk management cycle.

The Disaster Risk Management Cycle consists of four phases.

Disaster Risk Management Cycle


The Disaster Risk Management Cycle

Response phase

Disaster response is predominantly focused on immediate and short-term needs and is sometimes called “disaster relief”. Response phase tasks may include search and rescue, firefighting, emergency medical support and evacuation. This is the phase where foreign militaries can best provide assistance.

Recovery phase

The recovery task of rehabilitation and reconstruction begins soon after the emergency phase has ended, and should be based on pre-existing strategies and policies that facilitate clear institutional responsibilities for recovery action and enable public participation. Recovery programs, coupled with the heightened public awareness and engagement after a disaster, afford a valuable opportunity to develop and implement disaster risk reduction measures and to apply the “build back better” principle. Military assistance may have an impact through the recovery and risk reduction phase based on specific activities it is conducting.

Risk reduction phase

Risk reduction minimizes the vulnerabilities and disaster risks to society. Tasks may include preventative measures to avoid future disasters, such as planting trees in deforested areas to prevent future mudslides, or mitigation efforts to lessen the impact of hazards, such as earthquake resistance building codes. Ideally, lessons learned from the latest disaster have been incorporated in risk reduction measures.

Preparedness phase

Includes activities such as training, exercises, warning systems, and stockpiling of equipment and supplies.

National Disaster Management Organization

The governments of all countries should be actively involved in all phases of the disaster risk management cycle.  National governments have a disaster management structure, generically known as a National Disaster Management Organization, or NDMO. For the United States, FEMA (Federal Emergency Management Agency) is our NDMO. NDMOs are usually replicated at provincial/state and local/municipal levels.

There are generally three models of NDMOs, as depicted below:

Exmaples of NDMO Structures

Examples of NDMO models

In certain countries, the national military plays a very significant role in disaster response. In some cases, they are the first responders and the de facto lead for disaster response.