NCERT EXERCISES
1. Choose the
right answer from the four alternatives given below.
(i) Which one
of the following states of India experiences floods frequently?
(a) Bihar (b)
West Bengal (c) Assam (d) Uttar Pradesh
Ans. (a) Bihar
(ii) In which
one of the following districts of Uttaranchal did Malpa Landslide disaster take
place?
(a) Bageshwar
(b) Champawat (c) Almora (d) Pithoragarh
Ans. (d)
Pithoragarh
(iii) Which
one of the following states receives floods in the winter months?
(a) Assam (b)
West Bengal (c) Kerala (d) Tamil Nadu
Ans. (d) Tamil
Nadu
(iv) In which
of the following rivers is the Majuli River Island situated?
(a) Ganga (b)
Brahmaputra (c) Godavari (d) Indus
Ans. (b)
Brahmaputra
(v) Under
which type of natural hazards do blizzards come?
(a)
Atmospheric (b) Aquatic (c) Terrestrial (d) Biological
Ans. (a) Atmospheric
2.
Answer the following questions in less than 30 words.
(i) When can
a hazard become a disaster?
Ans. 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, steep slope and unstable structural features in the
Himalayas or extreme climatic conditions in deserts or glaciated areas.
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.
(ii) Why are
there more earthquakes in the Himalayas and in the north-eastern region of
India?
Ans. Earthquakes are the most unpredictable and highly destructive of all the natural disasters. There are more earthquakes in the Himalayas and in the north-eastern region of India because Himalaya is a young folded mountain of the world. Here the Indian plate is moving at a speed of one centimetre per year towards the north and northeastern direction and this movement of plates is being constantly obstructed by the Eurasian plate from the north. As a result of this, both the plates are said to be locked with each other resulting in accumulation of energy at different points of time. Excessive accumulation of energy results in building up of stress, which ultimately leads to the breaking up of the lock and the sudden release of energy, causes earthquakes along the Himalayan arch. Some of the most vulnerable regions are Jammu and Kashmir, Laddakh, Himachal Pradesh, Uttarakhand, Sikkim, and the Darjiling and subdivision of West Bengal and all the seven states of the northeast.
(iii) What
are the basic requirements for the formation of a cyclone?
Ans. Tropical cyclones are intense low-pressure areas confined to the area lying between 30° N and 30° S latitudes, in the atmosphere around which high velocity winds blow. Horizontally, it extends up to 500-1,000 km and vertically from surface to 12-14 km.
A tropical cyclone or hurricane is like a heat engine that is energised by the release of latent heat on account of the condensation of moisture that the wind gathers after moving over the oceans and seas.There are differences of opinion among scientists about the exact mechanism of a tropical cyclone.
However,
some initial conditions for the emergence of a tropical cyclone are:
(i)
Large and continuous supply
of warm and moist air that can release enormous latent heat.
(ii)
Strong Coriolis force that can prevent filling of low pressure at the centre (absence
of Coriolis force near the equator prohibits the formation of tropical cyclone
between 0°-5° latitude).
(iii)
Unstable condition through the troposphere that creates local disturbances around
which a cyclone develops.
(iv) Absence of strong vertical wind wedge, which disturbs the vertical transport of latent heat.
(vi) How are
the floods in Eastern India different from the ones in Western India?
Ans. Various
states of India face heavy loss of lives and property due to recurrent floods.
Rashtriya Barh Ayog (National Flood Commission) identified 40 million hectares
of land as flood-prone in India. In the Eastern India, Assam, West
Bengal and Bihar are among the high flood-prone states of India. In these
states Brahamputra River, Damodar River and Kosi River brings a lot of water
during rainy season every year and oucars the floods.
Apart from
these, most of the rivers in the North Western states like Rajasthan,
Gujarat, Haryana and Punjab, are also vulnerable to occasional floods. It has
been noticed that these states are also getting inundated in recent decades due
to flash floods. This is partly because of the pattern of the monsoon and
partly because of blocking of most of the streams and river channels by human
activities. Sometimes, Tamil Nadu experiences flooding during
November-January due to the retreating monsoon.
(v) Why are
there more droughts in Central and Western India?
Ans. The term ‘drought’ is applied to an extended period when there is a shortage of water availability due to inadequate precipitation, excessive rate of evaporation and over-utilisation of water from the reservoirs and other storages, including the ground water.
According to some estimates, nearly 19 per cent of the total geographical area of the country and 12 per cent of its total population suffer due to drought every year. About 30 per cent of the country’s total area is identified as drought prone affecting around 50 million people.
On the basis of severity of droughts, the most parts of western India likely - Rajasthan, Kachchh regions of Gujarat fall in Extreme Drought Affected Areas category. Eastern Rajasthan, most parts of Madhya Pradesh, eastern Maharashtra, interior parts of Andhra Pradesh and Karnataka Plateau, Telengana, northern parts of interior Tamil Nadu and southern parts of Jharkhand and interior Odisha are included in Severe Drought Prone Area category. These regions are facing severe drought every year mainly because of the large-scale variations and unpredictability in the behaviour of the monsoon in India.
3.
Answer the following questions in not more than 125 words.
(i) Identify
the Landslide-prone regions of India and suggest some measures to mitigate the
disasters caused by these.
Ans. Landslide is the rapid sliding of large mass of bedrocks. Landslides are largely controlled by highly localised factors. Hence, gathering information and monitoring the possibilities of landslide is not only difficult but also immensely cost-intensive. It is always difficult to define in a precise statement and generalise the occurrence and behaviour of a landslide.
However, on the basis of past experiences, frequency and certain causal relationships with the controlling factors like geology, geomorphic agents, slope, land-use, vegetation cover and human activities, India has been divided into a number of zones.
(a) Very High Vulnerability Zone: Highly unstable, relatively young mountainous
areas in the Himalayas and Andaman and Nicobar, high rainfall regions with
steep slopes in the Western Ghats and Nilgiris, the north-eastern regions,
along with areas that experience frequent ground-shaking due to earthquakes,
etc. and areas of intense human activities, particularly those related to
construction of roads, dams, etc. are included in this zone.
(b) High Vulnerability Zone: Areas that have almost similar conditions to
those included in the very high vulnerability zone are also included in this
category. The only difference between these two is the combination, intensity
and frequency of the controlling factors. All the Himalayan states and the
states from the north-eastern regions except the plains of Assam are included
in the high vulnerability zones.
(c) Moderate to Low Vulnerability Zone: Areas that receive less precipitation such as
Trans-Himalayan areas of Ladakh and Spiti (Himachal Pradesh), undulated yet
stable relief and low precipitation areas in the Aravali, rain shadow areas in
the Western and Eastern Ghats and Deccan plateau also experience occasional
landslides. Landslides due to mining and subsidence are most common in states
like Jharkhand, Odisha, Chhattisgarh, Madhya Pradesh, Maharashtra, Andhra
Pradesh, Karnataka, Tamil Nadu, Goa and Kerala.
Measures to
mitigate the landslides:-
It is always advisable to adopt area-specific measures to deal with landslides. Restriction on the construction and other developmental activities such as roads and dams, limiting agriculture to valleys and areas with moderate slopes, and control on the development of large settlements in the high vulnerability zones, should be enforced. This should be supplemented by some positive actions like promoting large-scale afforestation programmes and construction of bunds to reduce the flow of water. Terrace farming should be encouraged in the northeastern hill states where Jhumming (Slash and Burn/Shifting Cultivation) is still prevalent.
(ii) What is
vulnerability? Divide India into natural disaster vulnerability zones based on
droughts and suggest some mitigation measures.
Ans. Vulnerability is the inability to resist a hazard or to respond when a disaster has occurred. For instance, people who live on plains are more vulnerable to floods than people who live higher up.
The term ‘drought’ is applied to an extended period when there is a shortage of water availability due to inadequate precipitation, excessive rate of evaporation and over-utilisation of water from the reservoirs and other storages, including the ground water.
DROUGHT PRONE AREAS IN INDIA
On the basis of severity of droughts, India can be divided into
the following regions:
Extreme Drought Affected Areas : The
most parts of Rajasthan, particularly areas to the west of the Aravali hills,
i.e. Marusthali and Kachchh regions of Gujarat fall in this category. Included
here are also the districts like Jaisalmer and Barmer from the Indian desert
that receive less that 90 mm average annual rainfall.
Severe Drought Prone Area : Parts
of eastern Rajasthan, most parts of Madhya Pradesh, eastern parts of
Maharashtra, interior parts of Andhra Pradesh and Karnataka Plateau, northern
parts of interior Tamil Nadu and southern parts of Jharkhand and interior
Odisha are included in this category.
Moderate Drought Affected Area : Northern
parts of Rajasthan, Haryana, southern districts of Uttar Pradesh, the remaining
parts of Gujarat, Maharashtra except Konkan, Jharkhand and Coimbatore plateau
of Tamil Nadu and interior Karnataka are included in this category. The
remaining parts of India can be considered either free or less prone to the
drought.
CONSEQUENCES OF DROUGHT
Droughts have cascading effects on various other aspects of environment and society. Crop failure leading to scarcity of food grains (akal), fodder (trinkal), inadequate rainfall, resulting in shortage of water (jalkal), and often shortage in all the three (trikal) is most devastating.
Large-scale death of cattle and other animals, migration of humans and livestock are the most common sight to be seen in the drought-affected areas. Scarcity of water compels people to consume contaminated water resulting in spread of many waterborne diseases like gastro-enteritis, cholera, hepatitis, etc.
Some
mitigation measures:-
Droughts have both immediate as well as long-term disastrous consequences on the social and physical environments. Consequently, planning for drought has to take both aspects into consideration. Provision for the distribution of safe drinking water, medicines for the victims and availability of fodder and water for the cattle and shifting of the people and their livestock to safer places, etc. are some steps that need to be taken immediately. Identification of ground water potential in the form of aquifers, transfer of river water from the surplus to the deficit areas, and particularly planning for inter-linking of rivers and construction of reservoirs and dams, etc. should be given a serious thought. Remote sensing and satellite imageries can be useful in identifying the possible river-basins that can be inter-linked and in identifying the ground water potential. Dissemination of knowledge about drought-resistant crops and proper training to practise the same can be some of the long-term measures that will be helpful in drought-mitigation. Rainwater harvesting can also be an effective method in minimising the effects of drought
(iii) When
can developmental activities become the cause of disasters?
Ans. Disasters are
also caused by some human activities. There are some activities carried by
human beings that are directly responsible for disasters. Bhopal Gas
tragedy, Chernobyl nuclear disaster, wars, release of CFCs
(Chlorofluorocarbons) and increase of green house gases, environmental
pollutions like noise, air, water and soil are some of the disasters which are
caused directly by human actions.
There are
some other activities of human beings that accelerate or intensify disasters
indirectly. Landslides and floods due to deforestation, unscientific land
use and construction activities in fragile areas are some of the disasters that
are the results of indirect human actions.