English_Master August 7, 2016 No Comments


With the tropical climate and unstable landforms, coupled with high population density, poverty, illiteracy and lack of adequate infrastructure, India is one of the most vulnerable developing countries to suffer very often from various natural disasters, namely, drought, flood, cyclone, earthquake, landslide, forest fire, hail storm, locust, volcanic eruption, etc. which strike causing a devastating impact on human life, economy and environment.

Besides natural disasters, there are man-made disasters where the cause is an intentional or unintentional human act. These are fire-related disasters, road, rail or boat disasters, building collapses, terrorist attacks in the form of bomb blasts, etc. Accidents in which a large number of people are affected are called disasters.

Natural Disasters

Earthquake: An earthquake is a sudden movement or a fraction in the crust and the upper layer of the mantle (together called the lithosphere). This causes a series of shocks (shocks in this context means jerky movements). An earthquake may range from a mild tremor, which will only result in vibrations of the ground beneath us, to a large scale movement of the earth causing a widespread damage over a large area.

Earthquakes generally occur at plate boundaries. The plates rub against each other as they move. Faults are found at the edges of the plates where the earth’s crust is moving in different directions. Sometimes, the rocks of the plate get locked to each other. This could be because the jagged edges of the two plates get locked and prevent the plates from moving. As a result, pressure builds up against these rough edges.

As the pressure build-up continues, a point is reached when the rocks (which are locked to each other preventing the plates from moving) give way. The plates then lurch in the direction in which they were moving. This results in an earthquake. The point where the rocks give way is called the focus. The point vertically above the focus on the surface of the earth is called the epicenter.

The magnitude of an earthquake can be determined from data recorded by a seismograph. The most common scale used to measure the magnitude of an earthquake is the Richter scale. An earthquake of 2.0-4.0 on the Richter scale is not too damaging. More than 4-8 is a moderate to severe earthquake. An earthquake is greater than 8-9 would be very severe. The location of the earthquake, that is if it is in a highly populated area or in a remote area, also determines the amount of damage it can cause to human beings.

Drought: Drought is the single most important weather-related natural disaster often aggravated by human action. Drought’s beginning is subtle, its progress is insidious and its effects can be devastating. Drought may start any time, last indefinitely and attain many degrees of severity. Since it affects very large areas for months and years, it has a serious impact on the economy, destruction of iconological resources, and food shortages and starvation of millions of people.

Owing to abnormalities in the monsoon, precipitation, in terms of spatial and temporal variation especially on the late onset of monsoon, prolonged break and. early withdrawal of monsoon; drought is a frequent phenomenon over many parts of India. In India, 33 per cent of the area which receives less than 750 mm rainfall is also subject to drought once in four to five years. Thus, 67 per cent of the total sown area covering about 142 million hectares is vulnerable to drought conditions. India has faced three major droughts in this century – 1904-1905, 1965-66 and 1986-87. The 1987 drought had a lasting impact on one-third of the country.

Drought mitigation involves three phases, namely, preparedness phase, prevention phase and relief phase. In case of drought preparedness, identification of drought prone areas,-information on land use and land cover, waste lands, forest cover and soils is a prerequisite. Space borne multi-spectral measurements hold a great promise in providing such information.

Remote sensing data provides major input to all the three types of rainfall predictions; namely, such as long-term seasonal predictions, medium range predictions and short-term predictions. Global and regional atmospheric, land and ocean parameters (temperature, pressure, wind, snow, El-Nino, etc.) required for long-term prediction, could be generated from observations made by geo-stationary and polar orbiting weather satellites such as Indian National Satellite System (INSAT) and National Oceanic and Atmospheric Administration (NOAA).

Cyclone: The intense tropical storms are known in different part of the world by different names. In the Pacific Ocean, they are called ‘typhoons’, in the Indian Ocean they are called ‘cyclones’ and over North Atlantic, and they are called ‘hurricanes’. Among various natural calamities, tropical cyclones are known to claim a higher share of deaths and destruction the world over. Records show that about 80 tropical cyclones form over the globe every year. India has a vast coast line which is frequently affected by tropical cyclones causing heavy loss of human lives and property. Cyclones occur usually between April and May (called pre-monsoon cyclonic storms) and between October and December (called post-monsoon cyclonic storms). While cyclonic storms cannot be prevented, the loss of lives and damage to the properties can be mitigated if prompt action is taken after receiving timely warnings.

Meteorologists have been using satellite images for monitoring storms for about 30 years. One of the most important applications in this endeavor is to determine the strength and intensity of a storm. In the late 1960’s, meteorologists began observing tropical cyclones at more frequent intervals. The infrared sensors aboard polar orbiting satellites began providing day-and-night observations while geo-stationary satellite provided the continuous coverage during daytime. There exists a very efficient cyclone warning system in India which is comparable to the best known in the world. The approach essentially involves the prediction of the track and intensity of the cyclone using conventional as well as satellite and radar-based techniques.

Volcanic Eruption: Many times precursors of volcanic eruptions have been observed in various areas of volcanic activity. Ground deformations, changes in the compositions of gases emitting from volcanic vents, changes in the temperatures of fumaroles, hot springs and crater lakes as well as earth tremors are preceding volcanic eruptions. Thermal infrared remote sensing has been applied for volcanic hazard assessment. However, deficiencies of equipment and coverage suggest that thermal infrared has not been adequately evaluated for surveillance of volcanoes. In the last three decades, aircraft and satellite-based thermal infrared data have been used extensively to detect and monitor many of the active volcanoes around the world. Repetitive coverage, regional scale and low cost of thermal infrared images from satellites make it an alternative tool for monitoring volcanoes.

Landslides: A number of studies have been carried out in India using satellite data and aerial photographs to develop appropriate methodologies for terrain classification and preparation of maps showing landslide hazards in the Garhwali Himalayan region, Nilgiri hills in south India and in Sikkim forest area. Such studies have been carried out using mostly aerial photographs because of their high resolution enabling contour mapping with intervals of better than 2 m in height. The availability of 1 m resolution data from the future IRS mission may help generating contour maps at 2 m intervals making thereby space remote sensing a highly cost effective tool in landslide zonation.

Manmade Disasters

Fire-related Disasters: Accidents that are caused due to fire are quite common. Fire results in heavy damage both in terms of life and property. The loss of life is high if the fire is in a crowded building. Fires in building are mostly due to poor wiring and faulty electrical equipment, leakage of the cooking gas stove and carelessly thrown matches or cigarettes. We can prevent fires in our houses or places of work or any other buildings by ensuring that the source of main power supply or the fuse is in good working condition.

Nuclear Disasters: A disaster caused by the use of nuclear weapons is known as a nuclear disaster and is the worst type of man-made disaster. The progress and advancement in science and technology has created not only means of comfort but also Weapons of Mass Destruction, which can cause the breakdown and collapse of social, political and economic systems all over the world. A nuclear disaster is so bright that it blinds those who see it with naked eyes. The explosion is followed by a strong heat wave and mushroom-shaped cloud, which forms above the blast site. In nuclear disaster, radioactivity is the silent killer which lasts for years after the incident. Radioactivity is the energy released in the form of particles from radioactive elements like uranium, plutonium, etc. and spreads into the area causing nausea, dizziness, vomiting and disorientation. It is harmful to human health as it disrupts cell membranes and damages genes and chromosomes.

Chemical Disasters: Disasters that are caused by the excessive use and misuse of chemicals in industries are called chemical disasters. They are mostly caused by industrial accidents. Industries often produce hazardous substances that are life-threatening and also have an adverse impact on our environment. The irresponsible handling of harmful chemicals and poisonous gases can cause widespread devastation as they spread very fast and easily, covering large areas.

Biological Disasters: Biological disasters are caused by germs that are developed in laboratories and are released in the air. When these germs are inhaled or enter the body through a cut or wound, they infect a person. These germs can be used to kill thousands of innocent people. Even a few drops of smallpox virus or the plague virus in a town or a city or a building can cause a biological disaster killing several thousands of people. In October 2001, there was a threat of anthrax germs being used as biological weapons.

Examples of some disasters and remedial measures to be taken:

Natural Disaster

Earthquake: Many places in India fall under different categories of earthquake zones. There have been many major earthquakes in India. The damage caused by the major ones is given below:

  A powerful earthquake struck the Indo-Pakistan border on the morning of 8th October 2005. It had a magnitude of 7.6 and was felt severely in Pakistan, northern India and eastern Afghanistan. It is estimated that more than 50,000 people lost their lives due to this earthquake.  On 26th January 2001, there was a major earthquake in Gujarat. More than 20,000 people lost their lives in this earthquake.

In most cases, during an earthquake, people lose their lives because they live in unsafe buildings. Educating people about the importance of being prepared for earthquakes will go a long way in saving lives in future earthquakes. Following precautions should be taken in case there is an earthquake:

During an earthquake, if you are indoors, take cover under a heavy table or cot. Keep away from heavy objects that might fall.

If you are indoors in a public place, you should try to take cover under a sturdy object. Running to the exit may cause a stampede, and this could be very dangerous.

you are outdoors, move away from buildings, electric poles and trees, which could come down crashing.

If you are driving, stop if it is safe but stay inside your car. Stay away from bridges, overpasses and tunnels. If possible, avoid stopping under trees, light posts, power lines or sign boards.

After earthquake, look out for loose overhanging electric wires. Inform an adult so that they could be taken care of.

Man-made Disaster

Chemical Disaster: The Bhopal gas tragedy, in which the accidental leakage of the deadly poisonous gas called methyl isocyanate (MIC) from the Union Carbide factory at Bhopal in December 1984 took a heavy toll of life, is an unparalleled chemical disaster in the industrial history of the world. The pollution of the air by this poisonous leakage killed more than 2,500 people and left about 300,000 suffering from the disastrous effects of the massive poisoning. This type of chemical disaster is dangerous because it produces undesirable hereditary changes in human beings as well as other living things which can lead to the malformation of future generations.

Following precautions should be taken in case there is a chemical disaster:

  • Industries using and producing toxic chemicals and hazardous elements should be located in remote areas far away from the living population.
  • The government should make regular surveys to check out various measures taken by factories to avoid chemical disaster.
  • The government should formulate an emergency plan to deal with industrial disasters and recommend what antidotes to be used in case of the poisoning of victims.
  • Pollution levels should be checked and steps should be taken to control pollution.


Apart from loss of human lives, natural disasters inflict severe damage to ecology and economy of a region. Space technology has made significant contribution in all the three phases, i.e., preparedness, prevention and relief of disaster management. With a constellation of both INS AT and IRS series of satellites, India has developed an operational mechanism for disaster warning, especially cyclone and drought, and their monitoring and mitigation. However, prediction of certain events likes earthquake, volcanic eruption and flood is still at experimental level. Developments in space-based earth observation and weather watch capabilities in future may help refining existing models/approaches for prediction of such events and their management.