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A Supplementary Textbook in Geography for Class XI
UNIT 11 : Natural Hazards and Disasters
Published By: The Secretary, Central Board of Secondary Education,
2, Community Centre, Preet Vihar, Delhi-110092
Design, Layout and Illustration By: Chandu Press, D-97, Shakarpur, Delhi-110092
Printed By: Chandu Press, D-97, Shakarpur, Delhi-110092
y CBSE Advisors:
ο Shri Ashok Ganguly, Chairman, CBSE.
ο Shri G. Balasubramanian, Director (Academics), CBSE.
y Editor:
ο Shri M.P Sajnani, Advisor Disaster Management & Dy. National Project Director,
GOI-UNDP, DRM Programme.
y Authors:
ο Ms. Balaka Dey, Programme Associate, GoI – UNDP, DRM Programme.
ο Dr. R.B Singh, Reader, Dept. of Geography, Delhi School of Economics,
University of Delhi, Delhi – 110007.
y Review Team:
ο Prof. Noor Mohammad, Dept. of Geography, Delhi School of Economics,
University of Delhi, Delhi – 110007.
ο Shri S.S Rastogi, Retd. Principal, Directorate of Education, Delhi
y Coordinator: Ms. Sugandh Sharma, Education Officer (Commerce), CBSE
Page Nos.
Foreword (i)
For Students (ii)
Chapter 1: 1
Introduction to Disaster Management
Chapter 2:
Natural Hazards: causes, distribution pattern,
consequences and mitigation measures for :
y Earthquake 10
y Tsunami 17
y Cyclone 23
y Flood 30
y Drought 34
y Landslide 39
The recurrent occurrences of various natural and manmade disasters like the December
2004 Tsunami, the bomb blasts in the cinema halls of Delhi and many such incidences
have diverted our focus towards safety of one’s own life. In the previous class of VIII, IX
and X as students you must have read about various natural and manmade hazards –
their preparedness and mitigation measures. In class XI, the Board had introduced frontline
curriculum on Disaster Management in Unit 11 of the Geography syllabus. In supplementary
textbook on Disaster Management in Geography the Board intends to explain in detail
various concepts used in Disaster Management and discussed about the causes, distribution
pattern, consequences and mitigation measures for various natural hazards like earthquake,
tsunami, flood, cyclone, landslide and drought which are a recurrent phenomena in our
I hope this book will help all students of Geography, who are the future citizens, to have a
better understanding of the subject so that they are well prepared to combat it. Being
senior students of the school I would appreciate if all of you (including teachers) as
responsible citizens and as volunteers take up the initiative of preparing the school disaster
management plan and also educate the younger students of the school on various safety
measures that need to be taken up for a better living.
I would like to thank Ministry of Home Affairs for their support and guidance in the preparation
of the course material and helping the Board in carrying out training programmes for the
teachers across the country. I would also like to extend my sincere thanks to the Geography
Department, University of Delhi for the support they have extended to come up with the
course outline for the Board and also helping in the development of the textbook. My
sincere thanks to the UNDP team who have contributed the most and have tirelessly put
all their effort in development of the textbook and also carrying out training programmes
for the teachers and the school principals across the country without whose support the
initiative would have been difficult to continue. I am grateful to the teachers who have
played a key role in making the subject so interesting and demanding. Their understanding
and interest have made teachers, students and other staff members of the school design
the school disaster management plans which have made the schools a better and safer
Last but not the least my sincere thanks and appreciation to Shri G. Balasubramanian
(Director, Academics) who has always guided the team while developing the textbook and
introducing innovative ways to make the subject as a necessary life skill than a mere
Ashok Ganguly
Chairman, CBSE
For the Students………………
Some of you must have encountered one or the other natural or manmade hazard which
has caused a huge loss to life and property and have disrupted the normal life of the
people. Those who have had the opportunity to undergo certain training on safety like first
aid or search and rescue would have helped those in misery but then all of you are not well
equipped with both theoretical and practical knowledge. As a young responsible citizen
you can take up initiatives to prepare the community and make the community a safer
place to live.
The Board in its endeavor to make the students good managers and volunteers and effec-
tive carrier of messages, have introduced Disaster Management at various levels starting
from Standard VIII with effect from the academic year 2003. The Standard VIII textbook on
“Together Towards a Safer India – Part I” focuses on various natural and manmade
hazards and its preparedness measures. Taking it forward the Standard IX textbook “To-
gether Towards a Safer India – Part II” explains explicitly on the mitigation measures
that need to be taken up to save lives, livelihood and property. Apart from understanding it
as a subject, CBSE has felt the need to understand the subject as a necessary life skill.
Standard X textbook “Together Towards a Safer India – Part III” looks disaster manage-
ment from a different perspective of making the students and teachers help in preparation
of Disaster Management Plans for the school and the community and also making them
understand the various First Aid and Search and Rescue techniques and also on the role
of government, NGOs and others in managing disasters.
Those who have had the opportunity to read these books are by now better equipped but,
as a student the Board doesn’t refrain you from gaining knowledge and have a basic
understanding of the subject. In this textbook we have tried to give some basic
understanding about various natural hazards from the geography point of view. Apart from
various concepts the chapter tries to analyse various hazards prevalent in our country.
Understanding the causes, distribution pattern, consequences and mitigation measures
will help you to get better prepared.
Natural Hazards & Disaster Management
Chapter 1
Objectives of the chapter: Background:
The main objective of this chapter is to The global context:
have a basic understanding of various
Disasters are as old as human history but
concepts used in Disaster Management.
the dramatic increase and the damage
The concepts explained here are: caused by them in the recent past have
Disaster, Hazard, Vulnerability, Capacity, become a cause of national and international
Risk and Disaster Management Cycle. concern. Over the past decade, the number
Apart from the terminologies, the chapter of natural and manmade disasters has
also tries to explain various types of climbed inexorably. From 1994 to 1998,
disasters. In standard VIII, IX and X reported disasters average was 428 per year
many of you have already been but from 1999 to 2003, this figure went up to
introduced to some of these concepts. an average of 707 disaster events per year
This chapter has been designed showing an increase of about 60 per cent
to upgrade your knowledge and skill over the previous years. The biggest rise was
so as to have a better understanding of in countries of low human development,
natural hazards, disasters and their which suffered an increase of 142 per cent.
management. The figure 1.1 shows the deadliest disasters
of the decade (1992 – 2001). Drought and
After reading this chapter the
famine have proved to be the deadliest
students and the teachers will be disasters globally, followed by flood,
able to have a basic understanding technological disaster, earthquake, winds-
of the concepts and should be able torm, extreme temperature and others. Global
to differentiate between them with economic loss related to disaster events
suitable examples. average around US $880 billion per year.
Fig : 1.1 World Scenario: Reported Deaths from all
Disasters (1992-2001)
Natural Hazards & Disaster Management
Indian scenario: affected millions across the country
leaving behind a trail of heavy loss of life,
The scenario in India is no different from property and livelihood. Table 1.1 shows
the global context. The super cyclone of a list of some of the major disasters that
Orissa (1999), the Gujarat earthquake have caused colossal impact on the
(2001) and the recent Tsunami (2004) community.
Table 1.1 Major disasters in India since 1970
Sl. No Disaster Impact
1 29th October 1971, Orissa Cyclone and tidal waves killed 10,000
2 19th November, 1977, Cyclone and tidal waves killed 20,000
Andhra Pradesh people
3 29th and 30th October 1999, Cyclone and tidal waves killed 9,000 and
Orissa 18 million people were affected
4 20th October 1991 Uttarkashi An earthquake of magnitude 6.6 killed
723 people
5 30th September 1993 Latur Approximately 8000 people died and
there was a heavy loss to infrastructure
6 22 May 1997 Jabalpur 39 people dead
7 29th March 1997, Chamoli 100 people dead
8 26th January, 2001, Bhuj, More than 10,000 dead and heavy loss
Gujarat to infrastructure
9 July 1991, Assam 300 people killed, heavy loss to roads
and infrastructure
10 August 1993, Nagaland 500 killed and more than 200 houses
destroyed and about 5kms. Road
11 18th August 1998, Malpa 210 people killed. Villages were washed
12 1978 Floods in North East India 3,800 people killed and heavy loss to
13 1994 Floods in Assam, More than 2000 people killed and
Arunachal Pradesh, Jammu and thousands affected
Kashmir, Himachal Pradesh,
Panjab, Uttar Pradesh, Goa,
Kerala and Gujarat
Natural Hazards & Disaster Management
While studying about the impact we need to origin to the French word “Desastre” which
be aware of potential hazards, how, when is a combination of two words ‘des’ meaning
and where they are likely to occur, and the bad and ‘aster’ meaning star. Thus the term
problems which may result of an event. In refers to ‘Bad or Evil star’. A disaster can
India, 59 per cent of the land mass is be defined as “A serious disruption in the
susceptible to seismic hazard; 5 per cent of functioning of the community or a society
the total geographical area is prone to floods; causing wide spread material, economic,
8 per cent of the total landmass is prone to social or environmental losses which exceed
cyclones; 70 per cent of the total cultivable the ability of the affected society to cope
area is vulnerable to drought. Apart from this using its own resources”.
the hilly regions are vulnerable to avalanches/
landslides/hailstorms/cloudbursts. Apart from A disaster is a result from the combination
the natural hazards, we need to know about of hazard, vulnerability and insufficient
the other manmade hazards which are capacity or measures to reduce the potential
frequent and cause huge damage to life and chances of risk.
property. It is therefore important that we are
A disaster happens when a hazard impacts
aware of how to cope with their effects.
on the vulnerable population and causes
We have seen the huge loss to life, property damage, casualties and disruption. Fig: 1.2
and infrastructure a disaster can cause but would give a better illustration of what a
let us understand what is a disaster, what disaster is. Any hazard – flood, earthquake
are the factors that lead to it and its impact. or cyclone which is a triggering event along
with greater vulnerability (inadequate access
What is a Disaster ? to resources, sick and old people, lack of
awareness etc) would lead to disaster
Almost everyday, newspapers, radio and causing greater loss to life and property. For
television channels carry reports on disaster example; an earthquake in an uninhabited
striking several parts of the world. But what desert cannot be considered a disaster, no
is a disaster? The term disaster owes its matter how strong the intensities produced.
Fig: 1.2
Natural Hazards & Disaster Management
An earthquake is disastrous only when it 1. Natural hazards are hazards which are
affects people, their properties and activities. caused because of natural phenomena
Thus, disaster occurs only when hazards (hazards with meteorological, geological or
and vulnerability meet. But it is also to be even biological origin). Examples of natural
noted that with greater capacity of the hazards are cyclones, tsunamis, earth-
individual/community and environment to quake and volcanic eruption which are
face these disasters, the impact of a hazard exclusively of natural origin. Landslides,
reduces. Therefore, we need to understand floods, drought, fires are socio-natural
the three major components namely hazard, hazards since their causes are both natural
vulnerability and capacity with suitable
and man made. For example flooding may
examples to have a basic understanding of
be caused because of heavy rains, landslide
disaster management.
or blocking of drains with human waste.
What is a Hazard ? How is it clas- 2. Manmade hazards are hazards which
sified ? are due to human negligence. Manmade
hazards are associated with industries or
Hazard may be defined as “a dangerous energy generation facilities and include
condition or event, that threat or have the explosions, leakage of toxic waste, pollution,
potential for causing injury to life or damage dam failure, wars or civil strife etc.
to property or the environment.” The word
‘hazard’ owes its origin to the word ‘hasard’ The list of hazards is very long. Many occur
in old French and ‘az-zahr’ in Arabic frequently while others take place
meaning ‘chance’ or ‘luck’. Hazards can be occasionally. However, on the basis of their
grouped into two broad categories namely genesis, they can be categorized as
natural and manmade. follows:
Table 1.2: Various types of hazards
Types Hazards
Geological Hazards 1. Earthquake 4. Landslide
2. Tsunami 5. Dam burst
3. Volcanic eruption 6. Mine Fire
Water & Climatic Hazards 1. Tropical Cyclone 6. Cloudburst
2. Tornado and Hurricane 7. Landslide
3. Floods 8. Heat & Cold wave
4. Drought 9. Snow Avalanche
5. Hailstorm 10. Sea erosion
Environmental Hazards 1. Environmental pollutions 3. Desertification
2. Deforestation 4. Pest Infection
Biological 1. Human / Animal Epidemics 3. Food poisoning
2. Pest attacks 4. Weapons of Mass
Natural Hazards & Disaster Management
Types Hazards
Chemical, Industrial and 1. Chemical disasters 3. Oil spills/Fires
Nuclear Accidents 2. Industrial disasters 4. Nuclear
Accident related 1. Boat / Road / Train 3. Building collapse
accidents / air crash 4. Electric Accidents
Rural / Urban fires 5. Festival related
Bomb /serial bomb disasters
blasts 6. Mine flooding
2. Forest fires
What is vulnerability ? proximity, location and nature of the hazard.
It also relates to the technical capability of
Vulnerability may be defined as “The extent building and structures to resist the forces
to which a community, structure, services acting upon them during a hazard event.
or geographic area is likely to be damaged
or disrupted by the impact of particular Figure 1.3 shows the settlements which are
hazard, on account of their nature, located in hazardous slopes. Many landslide
construction and proximity to hazardous and flooding disasters are linked to what you
terrains or a disaster prone area.” see in the figure 1.3. Unchecked growth of
settlements in unsafe areas exposes the
Vulnerabilities can be categorized into people to the hazard. In case of an earth-
physical and socio-economic vulnerability. quake or landslide the ground may fail and
the houses on the top may topple or slide
Physical Vulnerability: It includes notions of and affect the settlements at the lower level
who and what may be damaged or even if they are designed well for earthquake
destroyed by natural hazard such as earth- forces.
quakes or floods. It is based on the physical
condition of people and elements at risk, Socio-economic Vulnerability: The degree
such as buildings, infrastructure etc; and their to which a population is affected by a hazard
Figure 1.3 : Site after pressures from population growth and urbanization
Natural Hazards & Disaster Management
will not merely lie in the physical components safe areas and their houses are built with
of vulnerability but also on the socio- stronger materials. However, even when
economic conditions. The socio-economic everything is destroyed they have the
condition of the people also determines the capacity to cope up with it.
intensity of the impact. For example, people
who are poor and living in the sea coast don’t Hazards are always prevalent, but the
have the money to construct strong concrete hazard becomes a disaster only when there
houses. They are generally at risk and is greater vulnerability and less of capacity
loose their shelters when ever there is to cope with it. In other words the frequency
strong wind or cyclone. Because of their or likelihood of a hazard and the vulnerability
poverty they too are not able to rebuild their of the community increases the risk of being
houses. severely affected.
What is capacity ? What is risk ?
Capacity can be defined as “resources, Risk is a “measure of the expected losses
means and strengths which exist in due to a hazard event occurring in a given
households and communities and which area over a specific time period. Risk is a
enable them to cope with, withstand, function of the probability of particular
prepare for, prevent, mitigate or quickly hazardous event and the losses each
recover from a disaster”. People’s capacity would cause.” The level of risk depends
can also be taken into account. Capacities upon:
could be:
y Nature of the hazard
Physical Capacity: People whose houses
y Vulnerability of the elements which are
have been destroyed by the cyclone or crops
have been destroyed by the flood can
salvage things from their homes and from y Economic value of those elements
their farms. Some family members have
A community/locality is said to be at ‘risk’
skills, which enable them to find employment
when it is exposed to hazards and is
if they migrate, either temporarily or
likely to be adversely affected by its
impact. Whenever we discuss ‘disaster
Socio-economic Capacity: In most of the management’ it is basically ‘disaster risk
disasters, people suffer their greatest losses management’. Disaster risk management
in the physical and material realm. Rich includes all measures which reduce disaster
people have the capacity to recover soon related losses of life, property or assets by
because of their wealth. In fact, they are either reducing the hazard or vulnerability
seldom hit by disasters because they live in of the elements at risk.
Natural Hazards & Disaster Management
Disaster Risk Reduction can take place in the following ways:
1. Preparedness
This protective process embraces measures which enable governments, communities
and individuals to respond rapidly to disaster situations to cope with them effectively.
Preparedness includes the formulation of viable emergency plans, the development
of warning systems, the maintenance of inventories and the training of personnel.
It may also embrace search and rescue measures as well as evacuation plans for
areas that may be at risk from a recurring disaster.
Preparedness therefore encompasses those measures taken before a disaster event
which are aimed at minimising loss of life, disruption of critical services, and damage
when the disaster occurs.
2. Mitigation
Mitigation embraces measures taken to reduce both the effect of the hazard and the
vulnerable conditions to it in order to reduce the scale of a future disaster. Therefore
mitigation activities can be focused on the hazard itself or the elements exposed to
the threat. Examples of mitigation measures which are hazard specific include water
management in drought prone areas, relocating people away from the hazard prone
areas and by strengthening structures to reduce damage when a hazard occurs.
In addition to these physical measures, mitigation should also aim at reducing the
economic and social vulnerabilities of potential disasters
Disaster Management Cycle community level etc. Such risk reduction
measures taken under this stage are termed
Disaster Risk Management includes sum as mitigation and preparedness activities.
total of all activities, programmes and
measures which can be taken up before, 2. During a disaster (disaster
during and after a disaster with the purpose occurrence).
to avoid a disaster, reduce its impact or
recover from its losses. The three key stages Initiatives taken to ensure that the needs and
of activities that are taken up within disaster provisions of victims are met and suffering is
risk management are: minimized. Activities taken under this stage
are called emergency response activities.
1. Before a disaster (pre-disaster).
3. After a disaster (post-disaster)
Activities taken to reduce human and
property losses caused by a potential Initiatives taken in response to a disaster
hazard. For example carrying out aware- with a purpose to achieve early recovery and
ness campaigns, strengthening the existing rehabilitation of affected communities,
weak structures, preparation of the disaster immediately after a disaster strikes. These are
management plans at household and called as response and recovery activities.
Natural Hazards & Disaster Management
Reference: Are you prepared? Learning from the Great Hanshin-Awaji
Earthquake Disaster - Handbook for Disaster Reduction and Volunteer activities
Figure 1.4 : Disaster Management
In the subsequent chapters we would Times of Disaster. UNESCO and West view
Press, Inc., Colorado.
discuss in detail some of the major hazards
prevalent in our country its causes, impact, 3. Anderson M. Vulnerability to Disaster and
preparedness and mitigation measures that Sustainable Development: A General
need to be taken up. Framework for Assessing Vulnerability.
4. UNDP Disaster Management Training
Reference for further reading: Programme.1992. An Overview of Disaster
1. Reading materials of 11th Community Based
5. International Federation of Red Crescent
Disaster Risk Management Course, Societies World Disaster Report: Focus on
Bangkok, Thailand July 21 – August 1, 2003. Community resilience.
2. Anderson, M. and P. Woodrow. 1989. Rising 6. http://www.unisdr.org/eng/library/lib-
from the Ashes: Development Strategies in terminology
Natural Hazards & Disaster Management
Exercise 3) Define risk and suggest two ways of
reducing risk with appropriate
1) Explain with examples the difference examples.
between hazard, and vulnerability. How
does capacity influence vulnerability? 4) Briefly discuss the Disaster
2) Explain in detail the vulnerability Management Cycle with suitable
profile of our country. examples.
Natural Hazards & Disaster Management
Chapter 2
The discussion on various terminologies has kilometers under the sea to 65 kilometers
helped us in having a basic understanding under the continents. The crust is not one
of disaster management. However, each piece but consists of portions called ‘plates’
hazard has its own characteristics. To which vary in size from a few hundred to
understand the significance and implications thousands of kilometers (Fig 2.1.1). The
of various types of hazards we must have a ‘theory of plate tectonics’ holds that the
basic understanding about the nature, plates ride up on the more mobile mantle,
causes and effects of each hazard type and and are driven by some yet unconfirmed
the mitigation measures that need to be mechanisms, perhaps thermal convection
taken up. In this chapter, we would discuss currents. When these plates contact each
the following hazards namely earthquake, other, stress arises in the crust (Fig 2.1.2).
tsunami, landslide, flood, cyclone and
drought that we normally face in our country. These stresses can be classified according
to the type of movement along the plate’s
2.1 Earthquake a) pulling away from each other,
Earthquake is one of the most destructive b) pushing against one another and
natural hazard. They may occur at any time c) sliding sideways relative to each other.
of the year, day or night, with sudden impact
and little warning. They can destroy buildings All these movements are associated with
and infrastructure in seconds, killing or earthquakes.
injuring the inhabitants. Earthquakes not
only destroy the entire habitation but may The areas of stress at plate boundaries
de-stabilize the government, economy and which release accumulated energy by
social structure of the country. But what is slipping or rupturing are known as 'faults'.
an earthquake? It is the sudden shaking of The theory of 'elasticity' says that the crust
the earth crust. The impact of an earthquake is continuously stressed by the movement
is sudden and there is hardly any warning, of the tectonic plates; it eventually reaches
making it impossible to predict. a point of maximum supportable strain. A
rupture then occurs along the fault and the
Cause of Earthquake : rock rebounds under its own elastic stresses
until the strain is relieved. The fault rupture
The earth’s crust is a rocky layer of varying generates vibration called seismic (from the
thickness ranging from a depth of about 10 Greek 'seismos' meaning shock or
Natural Hazards & Disaster Management
Fig. : 2.1.1 : Tectonic Plates
Seven major plates and several minor ones- They move a few inches a year,
riding on semi-molten layers of rock underneath the crust
Fig. : 2.1.2 : Tectonic Plates
Natural Hazards & Disaster Management
Table 2.1.1 Different types of plate movement
Plate Motions Examples Illustrations
Divergent - where new The Mid-Atlantic Ridge,
crust is generated as the which splits nearly the entire
plates pull away from each Atlantic Ocean north to
other. south, is probably the best-
known and most-studied
example of a divergent-plate
boundary. The rate of
spreading along the Mid-
Atlantic Ridge averages
about 2.5 centimeters per
year (cm/yr), or 25 km in a
million years. Mid Atlantic Ridge
2. Convergent - where Ring of Fire and The
crust is destroyed as one Himalayan mountain range
plate dives under another. dramatically demonstrates
one of the most visible and
spectacular consequences
of plate tectonics.
3. Transformational - where The San Andreas fault
crust is neither produced slicing through the Carrizo
nor destroyed as the plates Plain in the Temblor Range
slide horizontally past each east of the city of San Luis
other. Obispo
San Andreas fault,
California, U.S.A
Natural Hazards & Disaster Management
earthquake) waves, which radiates from the ♦ Deep:- 300 to 700 kms from the earth
focus in all directions. surface
The point of rupture is called the 'focus' and ♦ Medium:- 60 to 300 kms
may be located near the surface or deep
below it. The point on the surface directly ♦ Shallow: less than 60 kms
above the focus is termed as the 'epicenter'
The deep focus earthquakes are rarely
of the earthquake (see Fig 2.1.3).
destructive because by the time the waves
reach the surface the impact reduces.
Shallow focus earthquakes are more
common and are extremely damaging
because of their proximity to the surface.
Measuring Earthquakes
Earthquakes can be described by the use
of two distinctively different scales of
measurement demonstrating magnitude
and intensity. Earthquake magnitude or
Fig 2.1.3 amount of energy released is determined
by the use of a seismograph’ which is an
General characteristics instrument that continuously records ground
vibration. The scale was developed by a
Earthquake vibrations occur in a variety of seismologist named Charles Richter. An
frequencies and velocities. The actual earthquake with a magnitude 7.5 on the
rupture process may last for a few seconds Richter scale releases 30 times the energy
to as long as one minute for a major than one with 6.5 magnitudes. An earthquake
earthquake. The ground shaking is caused of magnitude 3 is the smallest normally felt
by ‘body waves’ and ‘surface wave’. by humans. The largest earthquake that has
been recorded with this system is 9.25
Body waves (P and S waves) penetrate (Alaska, 1969 and Chile, 1960).
the body of the earth, vibrating fast. ‘P’
waves travel about 6 kilometers per hour The second type of scale, the earthquake
and ‘S’ waves travel with a speed of 4 intensity scale measures the effects of an
kilometers per hour. earthqua

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