Syllabus Section: Disaster Management/ GS Paper III


What is a disaster?

A disaster is a sudden, calamitous event that seriously disrupts the functioning of a community or society and causes human, material, and economic or environmental losses that exceed the community’s or society’s ability to cope using its own resources. Though often caused by nature, disasters can have human origins.


The combination of hazards, vulnerability and inability to reduce the potential negative consequences of risk results in disaster.

What is Hazard?

A hazard is a process, phenomenon or human activity that may cause loss of life, injury or other health impacts, property damage, social and economic disruption or environmental degradation.

 Hazards may be natural, anthropogenic or socionatural in origin.

The classification schemes for hazards vary across different research institutions and governments, but these can be divided into (UNSIDR, 2017):

Biological hazards

• They are of organic origin or conveyed by biological vectors, including pathogenic microorganisms, toxins and bioactive substances.

• Examples are bacteria, viruses or parasites, as well as venomous wildlife and insects, poisonous plants and mosquitoes carrying disease-causing agents.

Environmental hazards

• It includes chemical, natural and biological hazards.

• They can be created by environmental degradation or physical or chemical pollution in the air, water and soil.

• However, many of the processes and phenomena that fall into this category may be termed drivers of hazard and risk rather than hazards in themselves, such as soil degradation, deforestation, loss of biodiversity, salinization and sea-level rise.

Geological or geophysical hazards

• It originates from internal earth processes.

• Examples are earthquakes, volcanic activity and emissions, and related geophysical processes such as mass movements, landslides, rockslides, surface collapses and debris or mud flows.

• Hydro meteorological factors are important contributors to some of these processes.

• Tsunamis are difficult to categorize: although they are triggered by undersea earthquakes and other geological events, they essentially become an oceanic process that is manifested as a coastal water-related hazard.

Hydro meteorological hazards

• They are of atmospheric, hydrological or oceanographic origin.

• Examples are tropical cyclones (also known as typhoons and hurricanes); floods, including flash floods; drought; heat waves and cold spells; and coastal storm surges. Hydro meteorological conditions may also be a factor in other hazards such as landslides, wild land fires, locust plagues, epidemics and in the transport and dispersal of toxic substances and volcanic eruption material.

Technological hazards

• It originates from technological or industrial conditions, dangerous procedures, infrastructure failures or specific human activities.

• Examples include industrial pollution, nuclear radiation, toxic wastes, dam failures, transport accidents, factory explosions, fires and chemical spills. Technological hazards also may arise directly as a result of the impacts of a natural hazard event

Difference between Hazard and Disaster:




  • Vulnerability is the inability to resist a hazard or to respond when a disaster has occurred. For instance, people who live on plains are more vulnerable to floods than people who live higher up.
  • Vulnerability depends on several factors such as people's age and state of health, local environmental and sanitary conditions, as well as on the quality and state of local buildings and their location with respect to any hazards.
  • Families with low incomes often live-in high-risk areas around cities, because they can't afford to live in safer (and more expensive) places, this is what we call economic vulnerability
  • Similarly, a wooden house is sometimes less likely to collapse in an earthquake, but it may be more vulnerable in the event of a fire or a hurricane. This is what we call physical vulnerability.
  • Risk
  • Risk (or more specifically, disaster risk) is the potential disaster losses (in terms of lives, health status, livelihoods, assets and services) which could occur to a particular community or a society over some specified future time period.
  • It considers the probability of harmful consequences, or expected losses (deaths, injuries, property, livelihoods, economic activity disrupted or environmentally damaged) resulting from interactions between natural or human induced hazards and vulnerable conditions.   
  • Risk = Probability of Hazard x Degree of Vulnerability.



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