Chapter - 8 - Natural Hazards, Disasters and their Management ( Part -1) - Environment UPSC Notes | EduRev

Environment and Additional Topics for UPSC Prelims

UPSC : Chapter - 8 - Natural Hazards, Disasters and their Management ( Part -1) - Environment UPSC Notes | EduRev

The document Chapter - 8 - Natural Hazards, Disasters and their Management ( Part -1) - Environment UPSC Notes | EduRev is a part of the UPSC Course Environment and Additional Topics for UPSC Prelims.
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The “cradle of civilisation” in the Middle East eventually became a desert due to the neglect of natural assets and environment.

Change is the law of nature. It is a continuous process that goes on uninterruptedly involving phenomena, big and small, material and nonmaterial that make our physical and socio-cultural environment. Change can be a gradual or slow process like the evolution of landforms and organisms. Changes have different meanings for different people. It depends upon the perspective one takes while trying to understand them. From the perspective of nature, changes are value-neutral. But from the human perspective, these are value-loaded.

There are some changes that are desirable and good like the change of seasons, ripening of fruits, while there are others like earthquakes, floods and wars that are considered bad and undesirable. Changes which are considered bad and have haunted humankind for a long time are our point of discussion here.

What is a natural hazard? Changes that affect humans adversely are called natural hazards. Natural Hazards are elements of circumstances in the Natural environment that have the potential to cause harm to people or property or both. These may be swift or permanent aspects of the respective environmental settings like currents in the oceans or extreme climatic conditions in deserts etc.

Natural hazards become natural disasters when people’s lives and livelihoods are destroyed. As compared to natural hazards, natural disasters are relatively sudden and cause large scale, widespread death, loss of property and disturbance to social systems and life over which people have a little or no control. Thus, any event can be classed as disaster when the magnitude of destruction and damage caused by it is very high.



Hazard is a threat. A hazard is a dangerous physical condition or event.

Disaster is an event. It is a calamity or tragedy or a consequence of a hazard. Natural hazards that cause great loss to human life and economy are called disasters and cat astrophes. A disaster disrupts the normal function of the society.

Earthquakes, floods, volcanic erruption, landslides, droughts etc. are called natural hazards before they cause great loss of life and damage to property.

It causes damage to property and loss of life but it also disrupts the opportunities of employment.

Small number of people are effected

A large number of people are effected

It may cause injury, loss of life or damage of property.

It causes wide spread loss to life and property.

Earthquakes, floods, volcanoes, tsunami, land slide, drought etc. are natural hazards

It affects the society to such an extent that external aid becomes sate the losses.

Table 1 – Difference between Natural Hazard and Disaster


Every disaster is unique in terms of the local socio-environmental factors that control it, the social response it generates, and the way each social group negotiates with it. There are three observations on disasters which are as follows:
 The magnitude, intensity, frequency and damages caused by natural disasters have increased over the years.
 There is a growing concern among people the world over to deal with the menace created by these so that the loss of human life and property can be minimised.
 Significant changes have taken place in the pattern of natural disasters over the years.

Man has been bearing the brunt of natural disasters since ancient times. There are many disasters which man in unable to face or prevent from happening. They are destined to bring their tragic consequences of human
destruction. Due to human intervention in the natural processes, the destructive power and frequency of natural disasters have increased considerably. According to UN statistics, natural disasters kill 1,00,000 persons on an average and cause property damage worth of billions of dollar per year. Among the top ten natural disaster-prone countries, India stands second after China.

People used to correlate hazards and disasters. Areas prone to natural hazards were more vulnerable to disasters. Hence, people avoided tampering with the delicate balance that existed in a given ecosystem. People avoided intensification of their activities in such areas and that is how disasters were less damaging.

With the advent of technology and rise in population density in certain parts of the world, human beings tend to intensify their activities into disaster prone areas increasing their vulnerability to disasters. Colonization of flood plains and seaward extension of port cities etc. make them vulnerable to the occurrence of floods, cyclones, hurricanes and tsunamis.

What is vulnerability ?
Vulnerability may be defined as “The extent to which a community, structure, services or geographic area is likely to be damaged or disrupted by the impact of particular hazard, on account of their nature, construction and proximity to hazardous terrains or a disaster prone area.” Vulnerabilities can be categorized into physical and socio-economic vulnerability. Disasters occur when hazards meet vulnerability.

India is vast and diverse in terms of its physical and socio-cultural attributes. It is largely due to its vast geographical area, environmental diversities and cultural pluralities, India is struggling with disasters from many years. Its vastness in terms of natural attributes combined with its prolonged colonial past, continuing various forms of social discriminations and also equally large population have enhanced its vulnerability to natural disasters. Killer waves (tsunami) struck the coastal parts of India on 26th December 2004 or the morning of 26th January 2001, when western part of India was badly affected by earthquake or recent flashflood in the Uttrakhand or Cyclone Phalin at Odisha coast. These are just few examples. We always listen such kind of news in print or electronic media that one part of India is affected by flood where as another faces drought. Due to vulnerability of different kinds of disasters, it is said that India is a disaster prone country, the reasons are:
 85% vulnerable to single or multiple disasters
 12% is flood prone,
 8% is vulnerable to cyclones and
 57% of area lies in high seismic zones
 40 million hectare prone to flood = ~12% of total area
 8% area vulnerable to cyclone
 68% area is susceptible to drought
 Out of 35 states and UTs- 27 are prone to one or more of these events
 Some areas are vulnerable to industrial, chemical and biological disasters


Researchers have been studying disasters for more than a century. The studies reflect a common opinion when they argue that all disasters can be seen as being human-made, their reasoning being that human actions before the strike of the hazard can prevent it developing into a disaster. All disasters are hence the result of human failure to introduce appropriate disaster management measures Hazards are routinely divided into natural or human-made, although complex disasters, where there is no single root cause, are more common in developing countries.

(1) Man-made Disasters: Disasters caused by human action, negligence, error, or involving the failure of a system are called human-made disasters. Human-made disasters are in turn categorized as technological or sociological. Technological disasters are the results of failure of technology, such as engineering failures, transport disasters, or environmental disasters. Sociological disasters have a strong human motive, such as criminal acts, stampedes, riots, and war.

(2) Natural Disasters:
Broadly, natural disasters can be classified under four categories (Table 2).

IAS,UPSC,Natural Hazards,Ecology,Disaster Management

An earthquake is a phenomenon that occurs without warning and involves violent shaking of the ground and everything over it. It results from the release of accumulated stress of the moving lithospheric or crustal plates. The occurrence of an earthquake in a populated area may cause numerous casualties and injuries as well as extensive damage to property. Earthquakes are by far the most unpredictable and highly destructive of all the natural disasters. Earthquakes that are of tectonic origin have proved to be the most devastating and their area of influence is also quite large. As compared to these, the earthquakes associated with volcanic eruption, rock fall, landslides, subsidence, particularly in the mining areas, impounding of dams and reservoirs, etc. have limited area of influence and the scale of damage. There is a geographic pattern of earthquake around the world at the tectonic plate margins. There are instances where earthquake occurs within the plate also.
India's increasing population and extensive unscientific constructions mushrooming all over, including multistoried luxury apartments, huge factory buildings, gigantic malls, supermarkets as well as warehouses and masonry buildings keep - India at high risk. During the last 15 years, the country has experienced 10 major earthquakes that have resulted in over 20,000 deaths. As per the current seismic zone map of the country, over 59 per cent of India’s land area is under threat of moderate to severe seismic hazard. In fact, the entire Himalayan belt is considered prone to great earthquakes of magnitude exceeding 8.0-; and in a relatively short span of about 50 years, four such earthquakes have occurred: 1897 Shillong (M8.7); 1905 Kangra (M8.0); 1934 Bihar-Nepal (M8.3); and 1950 Assam-Tibet (M8.6). Himalayas is the region of convergence of Indian and Eurasian plates. The Indian plate is moving at a speed of one centimetre per year towards the north and northeastern direction. In the recent past, even inter-plate boundary areas have experienced devastating earthquakes, albeit of lower magnitude than the Himalayan earthquakes. The Koyna earthquake in 1967 led to revision of the seismic zoning map. The occurrence of the Killari earthquake in 1993 resulted in further revision of the seismic zoning map.

IAS,UPSC,Natural Hazards,Ecology,Disaster Management

The North-Eastern part of the country continues to experience moderate to large earthquakes at frequent intervals including the two great earthquakes. On an average, the region experiences an earthquake with a magnitude greater than 6.0 every year. The Andaman and Nicobar Islands are also situated on an inter-plate boundary and frequently experience damaging earthquakes.

India is divided into following four earthquake zones as shown in figure 1. There was a change in the earthquake map of India where Very low risk zone and Low risk zone were merged into single ‘low risk zone’. Zone IV and Zone V had experienced some of the most devastating earthquakes in India. Areas vulnerable to these earthquakes are the North-east states, areas to the north of Darbhanga and Araria along the Indo-Nepal border in Bihar, Uttaranchal, Western Himachal Pradesh (around Dharamshala) and Kashmir Valley in the Himalayan region and the Kuchchh (Gujarat). Most of the areas that can be considered safe are from the stable landmass covered under the Deccan plateau.

IAS,UPSC,Natural Hazards,Ecology,Disaster Management

Socio-Environmental Consequences of Earthquakes
Earthquake is often associated with fear and horror due to the scale, magnitude and suddenness at which it spreads disasters on the surface of the earth without discrimination. It becomes a calamity when it strikes the areas of high density of population. Following are major impact of earthquake:
 Damage of property: when earthquake occurs, all buildings from cottage to
palaces and stronger skyscrapers are greatly damaged or totally destroyed.
Underground pipelines and railway lines are damaged or broken. Dams on river collapse, resultant floods cause havoc.
 Human loss: Duration of tremors of earthquake is normally of only few seconds, but thousands of people may die in this short period. Bihar earthquake of 1934 and Kangra earthquake of 1905, 10,000 and 20,000 people died respectively. The destruction of property was tremendous and could not be estimated properly and exactly.
 Changes in river courses: Sometimes river channels are blocked or their courses are changed due to the impact of earthquake.
 Tsunamis: are caused by earthquake. It wreaks havoc on settlement of coastal areas. It sinks large ships. Tsunami that occurred on 26-12-2004 near coast of Sumatra (Indonesia) damaged property worth billions of rupees.
 Fountains of mud: Due to the intense impact of earthquake hot water and mud appear on the surface and take a form of fountains. In Bihar earthquake of 1934 some cracks and fissures had developed. The fields of farmer were covered by knee-deep mud and the crops were destroyed.
 Landslides and avalanches are triggered
 Different effects of earthquake are shown in table 3.

On Ground

On Manmade Structures

On water





Earth Pressure

Possible Chain effects






Possible China effects


Hydro-Dynamic Pressure


Possible China effects


 Earthquake Hazard Mitigation

Since earthquake also destroys most of the transport and communication links, providing timely relief to the victims becomes difficult. It is not possible to prevent the occurrence of an earthquake; hence, the next best option is to emphasis on disaster preparedness and mitigation rather than curative measures such as:

 Establish earthquake monitoring centres (seismological centres) for regular monitoring and fast dissemination of information among the people in the vulnerable areas.

 Preparing a vulnerability map of the country and dissemination of vulnerability risk information among the people and educating them about the ways and means minimising the adverse impacts of disasters.

 Community preparedness: Community preparedness is vital for mitigating earthquake impact. The most effective way to save you even in a slightest shaking is 'DROP, COVER and HOLD'.

 Planning: The Bureau of Indian Standards has published building codes and guidelines for safe construction of buildings against earthquakes. Before the buildings are constructed the building plans have to be checked by the Municipality, according to the laid down bylaws. Many existing lifeline buildings such as hospitals, schools and fire stations may not be built with earthquake safety measures. Their earthquake safety needs to be upgraded by retrofitting techniques. The analysis of data from major earthquakes establishes the fact that the casualties here in India are primarily due to building collapse while the similar intensity earthquakes in US or Japan does not lead to such enormous loss of lives as the structures in these countries are built with structural mitigation measures and earthquake-resistant features

 Public education is educating the public on causes and characteristics of an earthquake and preparedness measures. It can be created through sensitization and training programme for community, architects, engineers, builders, masons, teachers, government functionaries teachers and students. by preparation of disaster management plans by schools, malls, hospitals etc. and carrying out a mock drill, by preparing documentation on lessons from previous earthquakes and widely disseminating it

 Engineered structures: Buildings need to be designed and constructed as per the building by laws to withstand ground shaking. Architectural and engineering inputs need to be put together to improve building design and construction practices. The soil type needs to be analyzed before construction. Building structures on soft soil should be avoided. Buildings on soft soil are more likely to get damaged even if the magnitude of the earthquake is not strong as shown. Similar problems persist in the buildings constructed on the river banks which have alluvial soil.

 Risk transfer instruments – These should be developed in collaboration with the insurance companies and financial institutions.

 Encouraging use of Indigenous methods – Indigenous earthquake-resistant houses like the bhongas in the Kutch Region of Gujarat, dhajji diwari buildings in Jammu & Kashmir, brick-nogged wood frame constructions in Himachal Pradesh and ekra constructions made of bamboo in Assam are increasingly being replaced with modern Reinforced Cement Concrete (RCC) buildings, often without incorporating earthquake resistant features and without compliance to building codes and bye-laws. It is thus necessary to empower communities to ensure the seismic safety of the built environment by encouraging the use of simple, easy and affordable technical solutions and institutional arrangements and making use of indigenous technical knowledge and locally available materials in the construction of earthquake-resistant buildings in suburban and rural areas.

 Quick and effective response – Although NDRF battalions have been set up by the government, experience has shown that over 80% search and rescue is carried out by communities itself before the intervention of state machineries and specialized rescue and relief forces. Thus there is a need to give basic training to the community members as it is always the first responder after any disaster.

 Early Earthquake Warning and Security System - Chennai-based Structural Engineering Research Centre (CSIR-SERC), a pioneer advanced seismic testing and research laboratory under the Council of Scientific & Industrial Research (CSIR), has completed the testing of the German-developed “Early Earthquake Warning and Security System”, which was launched for the first time in India early this year.

 Participation of community at local level in planning, implementation and monitoring process.

Challenges for India in mitigation
 Inadequate numbers of trained and qualified civil engineers, structural engineers, architects and masons proficient in earthquake-resistant design and construction of structures.
 Need for imparting training in earthquake-resistant design and construction to faculty members in professional colleges, for revising the curriculum in professional courses
 Creating public awareness on seismic risk reduction features in non-engineered construction in earthquake-prone areas.
 Carrying out structural safety audit of existing critical lifeline infrastructure and their strengthening and seismic retrofitting in earthquake prone areas.
 Mobilisation of resources including funds and their management

Some Dos and Don’ts during and after the earthquake:

 Have a disaster emergency kit ready which includes torch, radio, first aid kit, emergency food, chlorine tablets for water purifier, cash and cards etc.
 Inside the house - Don’t run outside, set your family into-doorways, under table or if they are bedridden, move them under the beds; keep away from windows and chimneys.  Outside the house - Don’t go near the buildings, high walls, or electric wires.  While driving - If an earthquake occurs stop driving and keep sitting in the vehicle.  To be done immediately o Put off domestic fire, and all electrical switches. o Leave the house if possible and go to open space.
o Leave the house if a gas leak is detected after the gas is turned off. o Save water
o Untie and free pets and domestic animals (dogs, cats and cattles)
 If trapped under debris
o Do not light a match.
o Do not move about or kick up dust.
o Cover your mouth with a handkerchief or clothing.
o Tap on a pipe or wall so rescuers can locate you.

8.3.2. TSUNAMI
Earthquakes and volcanic eruptions that cause the sea-floor to move abruptly resulting in sudden displacement of ocean water in the form of high vertical waves are called tsunamis (harbour waves) or seismic sea waves. Normally, the seismic waves cause only one instantaneous vertical wave.

The speed of wave in the ocean depends upon the depth of water. It is more in the shallow water than in the ocean deep. As a result of this, the impact of tsunami is less over the ocean and more near the coast where they cause large-scale devastations. When a tsunami enters shallow water, its wave-length gets reduced and the period remains unchanged, which increases the wave height. Sometimes, this height can be up to 15m or more, which causes large-scale destructions along the shores. Thus, these are also called Shallow Water Waves.

After reaching the coast, the tsunami waves release enormous energy stored in them and water flows turbulently onto the land destroying port-cities and towns, structures, buildings and other settlements. The loss of life and property is likely to be much higher by a tsunami as compared to other natural hazards in the coastal areas due to high population density and centre of economic activities. Whole coastline of mainland India along with Islands in both oceans is prone to Tsunami disaster.

Combined efforts at the international levels are the possible ways of dealing with these disasters as has been in the case of the tsunami that occurred on 26th December 2004 in which more than 300,000 people lost their lives. India has volunteered to join the International Tsunami Warning System after the December 2004 tsunami disaster.

The Government of India has put in place an Early Warning System for mitigation of such oceanogenic disasters under the control of Indian National Center for Ocean Information Services (INCOIS), Hyderabad. A state-of-the-art early warning centre was established with the necessary computational and communication infrastructure that enables reception of real-time data from sensors, analysis of the data, generation and dissemination of tsunami advisories following a standard operating procedure. Seismic and sea-level data are continuously monitored in the Early Warning Centre using custom-built software application that generates alarms/alerts in the warning centre whenever a pre-set threshold is crossed. Tsunami warnings/watches are then generated based on pre-set decision support rules and disseminated to the concerned authorities for action, as per pre-decided standard operating procedure. The efficiency of this end-to-end system was proved during the large under-sea earthquake of 8.4 M that occurred on September 12, 2007 in the Indian Ocean.

Ministry of Environment and Forests is also implementing Integrated Coastal Zone Management Program, which cohesively considers several coastal problems, such as erosion, pollution, tourism and sediment discharge from rivers and demarcating the vulnerability lines along coastal stretches. It should be emphasized that the island states must have their own coping capacities and adequate capabilities to respond to any emergency, without waiting for assistance from the Central Government. Cyclone-cum-tsunami shelters need to be designed and built in such away that it addresses multi-purpose uses. One other area to be stressed for the mitigation og effects of Tsunami is enhancing the area under mangroves forests as they provde buffer against it. Thus plantations need to be closely monitored to ensure their survival and growth using state-of-the-art remote sensing technologies.

Dos and Don’ts for Protection from Tsunami

 Before Tsunami

 Know the height of your street above sea level and the distance of your street from the coast or other high-risk waters.

 Plan evacuation routes from your home, school, workplace, or any other place you could be where tsunamis present a risk. If possible, pick areas (30 meters) above sea level or go as far as 3 kilometres inland, away from the coastline.
 Use a Weather Radio or stay tuned to a local radio or television station to keep informed of local watches and warnings.

 During Tsunami
 If you feel an earthquake that lasts 20 seconds or longer when you are in a coastal area, you should drop, cover, and hold on. You should first protect yourself from the earthquake damages
 Gather members of your household and move quickly to higher ground away from the coast.
 Move immediately to higher ground, DO NOT wait for a tsunami warning to be announced. Stay away from rivers and streams that lead to the ocean

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