Classification and characteristics of disasters in India

CLASSIFICATION OF DISASTERS IN INDIA

The Indian subcontinent is among the world’s most disaster prone areas.

It is vulnerable to wind storms spawned in the Bay of Bengal and the Arabian Sea, earthquakes caused by active crustal movement in the Himalayan mountains, floods brought by monsoons, and droughts in the country’s arid and semi-arid areas.

Most of the frequently occurring disasters in India fall in two categories.

1. Hydro-meteorological disasters and 
2. Geological disasters

Hydro-meteorology refers to the transfer of water and energy between land surface and the lower atmosphere. 

Examples of hydro-meteorological disasters are:

1. Floods
2. Tropical cyclones
3. Drought and
4. Desertification

Geological disasters are also called geophysical disasters that originate from the solid Earth. They are interchangeably used with the term geophysical hazard. Examples of geological hazards are:

1. Earthquakes
2. Mass movements and
3. Volcanic activity

Other types of disasters are:

1. Meteorological disasters are short lived and caused by micro to meso-scale extreme weather and atmospheric conditions that last from minutes to days for example:
1. Extreme temperature
2. Fog
3. Storm
2. Hydrological disasters that are caused by occurrence, movement and distribution of surface and sub-surface freshwater and saltwater.
3. Climatological disasters are caused by long-lived meso to macro-scale atmospheric processes ranging from intra-seasonal to multi-decadal climate variability for example:
1. Drought
2. Glacial lake outburst
3. Wildfires
4. Biological hazards are caused due to exposure to living organisms and their toxic substances (Ex: venom)
5. Extraterrestrial hazards caused by extra-terrestrial objects as they pass near the Earth, strike the Earth and affect the Earth's Ionosphere, magnetosphere and thermosphere. Ex: Meteorites and asteroids. Another example of extraterrestrial hazard is "Magnetic storms" that are caused by solar flares from the sun or Coronal Mass Ejections (CME). This causes disruption of communication and navigation systems, damage to communication satellites, power outages, radiation poisoning in human beings leading to chromosomal damage, cancer and other health problems.

Characteristics of disasters in India

The most common natural disasters occurring in India are:

1. Earthquakes
2. Cyclones
3. Floods and
4. Famine

The characteristics of the above listed natural disasters are discussed  with regard to the following parameters.

1. Predictability
2. Initial lethality
3. Scope and
4. Onset delay

Among the above listed natural disasters, Earthquakes cannot be predicted while cyclones can be predicted with reasonable accuracy. However, cyclones give a very small window of opportunity (time) to people so that they can escape. Floods can be predicted well in advance so that necessary measures for mitigation can be put into place thereby preventing loss to life and property. Famine is a natural disaster that can be predicted accurately with modern computer modelling and simulation techniques.

Owing to the destructive nature of Earthquakes, it is considered to have the highest initial lethality among the natural hazards being discussed. Next comes cyclones followed by floods. Cyclones have a higher destructive potential than floods as they comprise of very fast winds that move in a circular fashion destroying everything coming in their way. A flood is defined as land that is normally dry being inundated due to excessive rains leading to disruption in daily activities. 

Earthquakes affect a relatively small region and hence the scope of damage caused is relatively low. Cyclones occur mainly along coasts. Hence, the scope of the damage caused is greater than Earthquakes. Floods occur over a large area and hence they have a relatively greater scope for damage than cyclones. A famine refers to an extended period of drought. Lack of water for an extended duration causes severe destruction in the community

The term 'on-set delay' refers to the time lag before the occurrence of a disaster. This short time should be used as a window of opportunity to rescue people from the potentially dangerous situation. As Earthquakes occur at any random instant, the on-set delay is low in this case. In case of cyclones, the on-set delay is greater than that mentioned in the case of Earthquake as they can be predicted a few days in advance with the help of satellite images. Floods have greater on-set delay (except in case of FLASH FLOODS) than cyclones as flooding of any area takes place gradually and provides sufficient time for evacuation operations. Famine is a disaster with the greatest 
on-set delay as it develops extremely slowly and provides several indicators well in advance.