NCERT Solutions for Class 11th: Ch 7 Natural Hazards and Disasters Indian Physical Environment


Page No: 93


(i) Which one of the following states of India experiences floods frequently?
(a) Bihar
(b) West Bengal
(c) Assam
(d) Uttar Pradesh
► (c) Assam

(ii) In which one of the following districts of Uttaranchal did Malpa Landslide
disaster take place?
(a) Bageshwar
(b) Champawat
(c) Almora
(d) Pithoragarh
► (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
► (d) Tamil Nadu

(iv) In which of the following rivers is the Majuli River Island situated?
(a) Ganga
(b) Brahmaputra
(c) Godavari
(d) Indus
► (b) Brahmaputra

(v) Under which type of natural hazards do blizzards come?
(a) Atmospheric
(b) Aquatic
(c) Terrestrial
(d) Biological
► (a) Atmospheric

2. Answer the following questions in less than 30 words.

(i) When can a hazard become a disaster?


A hazard can become a disaster when it becomes active. A disaster causes losses to property and life on a large scale.

(ii) Why are there more earthquakes in the Himalayas and in the north-eastern region of India?


The Indian plate is moving at a speed of one centimetre per year towards the north and northeastern direction and the movement of plates is being constantly obstructed by the Eurasian plate from the north. This result 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 in the Himalayas and in the north-eastern region of India

(iii) What are the basic requirements for the formation of a cyclone?


The basic requirements for the formation of a cyclone are:
• Large and continuous supply of warm and moist air that can release enormous latent heat.
• Strong Coriolis force that can prevent filling of low pressure at the centre.
• Unstable condition through the troposphere that creates local disturbances around which a cyclone develops.
• Absence of strong vertical wind wedge, which disturbs the vertical transport of latent heat.

(iv) How are the floods in Eastern India different from the ones in Western India?


The flood occur more in Eastern India as compared to Western India because of high rainfall in eastern India than western India. Also, the floods of eastern India are more disastrous in comparison to western India.

(v) Why are there more droughts in Central and Western India?


Central and Western India experiences less rainfall because the intensity of monsoon winds becomes weak as they reach in these areas.


(i) Identify the Landslide-prone regions of India and suggest some measures to mitigate the disasters caused by these.


The Landslide-prone regions of India are:
• 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.
• 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.
• Landslides due to the mining and subsidence are most common in the states like Jharkhand, Orissa, Chhattisgarh, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka etc.

Some measures to mitigate the disasters are:
• Restriction on the construction and other developmental activities such as roads and dams, limiting
agriculture to valleys.
• Areas with moderate slopes, and control on the development of large settlements in the high vulnerability zones, should be enforced.
• Terrace farming should be encouraged in the northeastern hill states where Slash and Burn/Shifting
Cultivationis still prevalent.

(ii) What is vulnerability? Divide India into natural disaster vulnerability zones based on droughts and suggest some mitigation measures.


Vulnerability means the risk becoming victim to the disaster.

On the basis of severity of droughts, India is divided into following regions:

• Extreme Drought Affected Areas: Most parts of Rajasthan, particularly areas to the west of the Aravali hills, i.e. Marusthali and Kachchh regions of Gujarat. 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.

Some mitigation measures are:

• Identification of ground water potential in the form of aquifers.
• Transfer of river water from the surplus to the deficit areas.
• Planning for inter-linking of rivers and construction of reservoirs and dams.
• 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.

(v) When can developmental activities become the cause of disasters?


There are many times when developmental 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 created due to developmental activities done by humans. 

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.

The human-made disasters have increased both in their numbers and magnitudes over the years and serious efforts are necessary are on at various levels to prevent and minimise their occurrences.

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