Chapter 10
CHAPTER NO.10 DISASTEARS
The word disaster has been derived from the French
word ‘desastre’ which means a bad or evil star, Disaster is a suciden event
that causes a great damage to human life, plants, animals and
property.According to the World Health Organization (WHO), disaster is an
occurrence that causes economic
destruction, loss of human life, deterioration of
health and health services on a scale sufficient to elicit an extraordinary
response from the people outside the affected community in the area, The recent
disas-ters faced by the modem industrialized world are of greater magnitude and
more devastating than those occurred in the past. Disasters are of two types,
the natural disasters and the man made disasters.
NATURAL DISASTERS
Natural disasters happen due to certain natural
causes or forces. These include earthquakes,droughts, floods, cyclones and
landslides. The natural forces responsible for these disasters are
beyond man's control. The important natural
disasters are briefly explained here :
EARTHQUAKE :
Any sudden violent shaking or trembling of the earth's crust due to a natural
cause is known as an earthquake. It is one of the most terrifying natural
disasters that cause
great loss of life and property. The energy
associated with a single major earthquake may be more than several thousand
atom bombs. The major natural cause responsible for earthquake is move-ment of
molten rocks present beneath the earth surface. This results in sudden slipping
of the por-tions of earth's crust past each other, producing strong vibrations.
The place of origin of these vibra-tions within the earth is known as seismic
focus. The point on earth's surface exactly above the
centre of seismic focus is known as epicentre of the
earthquake. The strength of an earthquake is measured by the Richter Scale which
ranges from 0 to 8. Eruption of volcanoes is another cause of earthquakes.
Underground nuclear tests also generate minor earthquakes. The strength of
vibrations
can be measured by using an instrument known as
seismograph. Earthquakes cause tremendous damage to life and property. The
Assam earthquake of June 12, 1897 was one of the most terrifying
earthquake of the world. In 1935, the Quetta
earthquake caused more then 25000 death. The earthquake of Bhuj and Ahmedabad
in Gujarat on January 26, 2001 destroyed 8 lakh houses killing
20000 te 30000 people. More recently, the earthquake
of October 10, 2005 bas caused death of more than 40000 people in Pakistan. The
tremors during an earthquake result in collapse of mud
and brick houses, twisting of railway lines, out
breaking of fire and damage to underground water supply system. Earthquakes
also cause landslides in mountainous regions. Strong tsunami waves are
generated by earthquakes, which have their origin in the oceans.
The causes responsible for earthquakes are beyond
control of man. However, the damage caused by earthquakes can be mitigated. It
has been observed that the performance of man made buildings, electric and
water supply lines is very poor during the earthquakes. This is primarily due
to faulty structural designs, lack of symmetry and poor quality of construction
material. This can be avoided by adopting proper structural designs. The
participation of community and Non-Govern-ment Organizations (NGOs) is very
essential in different earthquake mitigation programmes. In addi-tion to
technological skills, the disaster preparedness also involves awareness and
consciousness among masses, Better communication facilities, rescue operations
and accurate planning can mini-mize the losses during earthquakes.
DROUGHTS : It can defined
as a drying up condition of land due to unusual scarcity of water in an area,
where a normal rainfall is expected. A drought may last for from a few days to
many years. During the drought period, the different
water reservoirs dry up. The conditions of the weather remain dry for long
period. More severe droughts generally occur in the regions between
latitudes of 15°-20°. In India, the states of
Rajasthan, Gujarat, Tamilnadu, Jharkhand, Chhattisgarh,Karnataka and
Maharashtra are drought prone areas. Changing rainfall patterns due to global
warm-ing, deforestation, industrialization etc. are contributing towards this
natural disaster.
Dry conditions of land during the drought period
destroy the fertile topsoil rendering it useless for cultivation. This is known
as desertification of land. The acute shortage of water, food and fodder
causes starvation and death of animals and human
beings. Drought also causes soil erosion, famine,health problems and
unemployment.
Conservation of water is very essential to mitigate
the harmful effects of drought. This can be achieved through rainwater
harvesting and canal irrigation systems. Emergency water storage tanks should
be constructed. The practice of sowing drought resistant crop varieties following
improved
agricultural methods can prove helpful in coping
with dry weather conditions. Plantation of more and more trees in the drought
prone areas helps in percolation of the rainwater under ground. The people in
drought-hit areas should be provided with emergency water supply and adequate
resources.
FLOODS : A flood refers to the inundation of a large land area for several days. It is the
most frequent natural disaster that has been destroying and damaging human
life and property since times immemorial. Floods are commonly due to excessive
rains in a particular area. The other causes
of floods include bursting of dams and sudden
release of pent up waters of a river choked by landslides. Earthquakes
occurring in oceans beds also generate serious flash floods in the coastal
areas. Many a times, natural bursting of clouds in
mountainous regions also results in flash floods.Anthropogenic activities such
as deforestation, changes in land use pattem, agricultural
practices,construction of bridges etc. also intensify the magnitude of the
disaster. In India, the Himalayan rivers
like the Ganges, the Brahmaputra, the Satluj etc.
are responsible for 70 percent of the flood dam-ages (Fig. 10.1). In many
Indian states such as Assam, Bihar and West Bengal, floods are a routine affair
every year during the monsoon season.
Floods causes huge loss of life and property.
Thousands of people are displaced and become homeless. Floods destroy the
agricultural field leading to shortage of food and fodder. The telephone
service, water supply, electricity supply and transportation are badly hit and
get interrupted. The
natural habitats of different wild animals are
destroyed. This leads to death or migration of these animals, The erosion of
upper fertile layer of soil also takes place. After the floods, many infectious
diseases may spread in the flood affected areas. The weather forecast made on
the basis of data
collected by meteorological department seems to be
useful in mitigating this natural disaster. On basis of these warnings, the
people can move to safe areas before the disaster occurs. The construction of
check dams or water reservoirs and afforestation help in reducing floods. It is
quite unfortunate that our wetlands are shrinking at a rapid rate. The restoration
of these wetlands can partially play a significant role in control of floods.
The timely public health services can prevent the chances of an can minimize
the losses caused by floods.
CYCLONES : Cyclones are low
pressure systems that develop over the surface of oceans in tropical and
subtropical regions. These are known as hurricanes in West Indies,
willy-willies in from.
50 km to 300 kun. The pressure in the centre of the
cyclone is quite low and fast winds blow in a spiral manner around it. The wind
speed in a cyclone may be 120 km per hour. In India, the cy-clones develop over
the surface of the Arabian Sea and the Bay of Bengal Cyclones follow the
direction of regular wind and strike suddenly. They generally remain active on
surface of oceans.
After leaving the ocean surface, they loose their
strength. When a cyclone approaches an area, the sky becomes dull and over
clouded. There is heavy rain, thunder and lightening,Cyclones cause great
damage to human life, crops, general vegetation and buildings. The strong winds
uproot trees and liit roofs of houses. Heavy rains brought by a cyclone may
cause flooding of
an area and subsequent spread of infectious diseses.
Cyclones also damage ships and other installa-tions in the coastal areas. In
India, cyclones are an annual feature, occuring mostly in October and November.
The Orissa cyclone of 1999 caused huge damage to property and loss of more than
10000 human lives.
Development of cyclones over ocean surface is beyond
our control. But unlike earthquakes, the approach of cyclones to an area can be
predicted through different techniques. Weather sensing satellites are used for
this purpose. These are also helpful in evacuating people to safer areas. The
better structural designs of buildings, information
technology, rescue operations, community aware-ness and disaster preparedness
can prove helpful in mitigating this disaster.
LANDSLIDES :
Landslide is the sudden sliding of mass of rocks or earth down a mountain slope
under action of gravity (Fig. 10.2). These are caused by heavy rains or melting
of snow. The running water softens the upper soil and triggers sliding of
rocks. Blasting and cutting of rocks for construction or widening of roads and
deforestation also adds to this problem. Sometimes, the trem-ors of an
earthquake are strong enough to cause landslides.
The massive landslides may destroy the human
settlements along the mountain slopes. Buildings and plantations are buried
under mud and debris. The roads are blocked and this disturbs the trans-
port network. Pent up waters of a river or stream
blocked due to landslides may result in flash floods. All this results in huge
economic losses. In India, the landslides are very common in the
north-east and north-west Himalayan regions.
The mountain ecosystem is very fragile (fig. 10.3).
The frequency of landslides can be reduced by adopting proper protection
measures. More and more trees should be planted in landslide prone
areas. The rocts of trees consolidate the surface
soil of mountain slopes. The construction of wired stone blocks along roadside
and near river bridges also provides support to the rocks and reduces sliding
of slopes. Trained manpower should be employed and an appropriate quantity of
explosive
should be used to blast the rocks for road construction.
Proper drainage of surface waters during rainy season can also minimize the
magnitude of this problem.
MAN MADE DISASTERS
Man made disasters are associated with human
activities. These include nuclear accidents, leak-age of toxic chemicals, out
breaking of fire, air crashes, accidents, collapsing of bridges and tunnels
etc. Most of man made disasters are attributed to human errors and are
generally unpredictable.
TECHNOLOGICAL AND INDUSTRIAL DISASTERS
:
Technological and industrial di-sasters are the most important man made
disasters. These are caused due to lack of proper installa-tions, flawed
structural designs and improper handling of hazardous wastes and substances.
Many-a-times, technical errors resulting from lack of adequate technical training
also lead to technological disasters. The effects of these disasters become
more pronounced when the operators lack aware-ness and are not well equipped
with appropiate safety measures.
Several such disasters have been witnessed in the
modem times. The Chemobyl nuclear disas-ter is the worst accident ever to occur
at a nuclear power plant. It took place at the Chernobyl Nuclear Plant in teh
former Soviet Union on April 26, 1986. A nuclear reactor exploded and ex-
pelled about 50 tonnes of radioactive substances in
the atmosphere. The effects of the accident were not restricted to the local
area, but the radiation quickly spread across a large area of northern
hemisphere. A number of fire workers died from exposure to high levels of
dangerous radiation.
More than 116000 people living within a 30 km radius
around the nuclear plant were evacuated to safer areas. The accident caused
death of 31 persons on the spot. As many as 24000 persons
received an excessive dose of radiation. When the
clean up operations were over, the damaged building of the reactor was covered
under 300000 tonnes of concrete. Later on, the investigations made to identify
the causes of this accident, revealed that the reactor was not housed in a
contain-ment building and was unstable at low temperature. Many of the plant
operators lacked the full
technical know-how.
On 3” December 1984, the world's worst industrial
disaster took place at the Union Carbide pesticide plant located in Bhopal,
India. The highly toxic methyl isocyanate gas (used in manufacture
of pesticides) leaked from the storage tank. It
caused death more than 2300 people. About 14000 persons suffered serious
inuries and health disorders.
These typical examples highlight the magnitude of
huge damage which can be caused by tech-nological and industrial disasters. The
exposure to radiation can cause skin burns, cataract, sterility
and cancer of different body tissues. It can induce
hanmful changes in the genetic material. These changes may get inherited to
future generations. Similarly, exposure to harmful chemicals may causes
blindness, deafness, nervous disorders, sterility, kidney and liver
dysfunctions. The governments of
different nations, the scientists, the rescue
workers, the engineers and the doctors have leamt a lot from these disasters,
The aspect of nuclear power is being taken more seriously by different
coun-tries now. Proper safety measures are being developed and incorporated in
the newly constructed
nuclear power plants and other industries. The better
safety measures, adequate technical training,
EXERCISE
(A) Very short answer type questions (1
mark each) :
1.What is a disaster ?
2.How many types of disasters are there?
3. What is seismic focus ?
4, What is epicentre 7
5. Name the instrument used for measuring strength
of an earthquake.
6. Write about the major cause of floods.
7. In which season of the year the floods occur more
frequently ?
8. What is the speed of wind in a cyclone ?
9. What is a landslide ?
10. When did the Chemobyl nuclear disaster happen ?
(B) Short answer type questions (2
marks each) :
1. Differentiate between the natural and man-made
disasters.
2. What is acyclone ?
3. How can cyclone be predicated 7
4. What is desertification of land ?
5. Give two preventive measures for control of
landslides.
6. Name two important man-made disasters.
7. What were the important causes of Chernobyl
nuclear disaster ?
8. Write about the harmful effects of radiation
exposure.
9. What is drought ?
(C) Short answer type questions (4
marks each):
1, How does an earthquake originate ?
2. What is the impact of drought ?
3. What should be done to prevent an control drought
7
4. How do the floods affect animal life ?
5. How does a cyclone cause devastation of human
life ?
6. What are different causes of landslides ?
Long answer type questions: (5 marks
each):
1. Wiite about causes, impact and mitigation of
earthquakes.
2. Discuss floods as a natural disaster.
3. Describe important types of man-made disasters.
4. Howcan different natural disasters be mitigated ?
