Natural Hazards and Disasters
NCERT Solutions • Class 11 Geography (India) • Chapter 61. Multiple Choice Questions
(i) Which one of the following states of India experiences floods frequently?
(c) Assam
Reason: While Bihar is also flood-prone, Assam experiences floods almost annually due to the unstable nature of the Brahmaputra river and heavy rainfall.
Reason: While Bihar is also flood-prone, Assam experiences floods almost annually due to the unstable nature of the Brahmaputra river and heavy rainfall.
(ii) In which one of the following districts of Uttaranchal did Malpa Landslide disaster take place?
(d) Pithoragarh
Reason: The tragic Malpa landslide occurred in the Pithoragarh district of Uttarakhand (formerly Uttaranchal) in 1998, wiping out the village of Malpa.
Reason: The tragic Malpa landslide occurred in the Pithoragarh district of Uttarakhand (formerly Uttaranchal) in 1998, wiping out the village of Malpa.
(iii) Which one of the following states receives floods in the winter months?
(d) Tamil Nadu
Reason: Tamil Nadu receives the bulk of its rainfall from the retreating (Northeast) monsoon during winter (November-December), which often leads to flooding.
Reason: Tamil Nadu receives the bulk of its rainfall from the retreating (Northeast) monsoon during winter (November-December), which often leads to flooding.
(iv) In which of the following rivers is the Majuli River Island situated?
(b) Brahmaputra
Reason: Majuli, the world’s largest inhabited river island, is located in the Brahmaputra river in Assam.
Reason: Majuli, the world’s largest inhabited river island, is located in the Brahmaputra river in Assam.
(v) Under which type of natural hazards do blizzards come?
(a) Atmospheric
Reason: Blizzards are severe snowstorms with high winds, which are atmospheric weather phenomena.
Reason: Blizzards are severe snowstorms with high winds, which are atmospheric weather phenomena.
2. Short Answer Questions
(i) When can a hazard become a disaster?
A hazard becomes a disaster when it strikes a populated area and causes significant loss of life, property, and livelihood, overwhelming the local capacity to cope. If a hazard occurs in an uninhabited desert, it remains just a hazard, not a disaster.
(ii) Why are there more earthquakes in the Himalayas and in the north-eastern region of India?
This region lies along the convergent plate boundary where the Indian Plate is subducting (colliding) under the Eurasian Plate. The intense tectonic stress and geological instability make it a “Very High Damage Risk Zone” (Zone V).
(iii) What are the basic requirements for the formation of a cyclone?
- Large and continuous supply of warm moist air (Sea surface temp $> 27^\circ C$).
- Presence of strong Coriolis force to create cyclonic rotation.
- Unstable atmosphere producing a Low-Pressure center.
- Absence of strong vertical wind shear.
(iv) How are the floods in Eastern India different from the ones in Western India?
- Eastern India (Ganga-Brahmaputra): Floods are annual and predictable. They are caused by river overflow due to heavy monsoon rains and siltation.
- Western India (Gujarat/Maharashtra): Floods are often “Flash Floods” caused by sudden, extremely heavy rainfall in a short duration and poor urban drainage, rather than river overflow.
(v) Why are there more droughts in Central and Western India?
These regions (Rajasthan, Gujarat, Marathwada) lie in the Rain Shadow Zone of the Western Ghats or are far from the sea (Continentality). They receive low and erratic rainfall, and high evaporation rates due to heat exacerbate the water scarcity.
3. Long Answer Questions
(i) Identify Landslide-prone regions of India and suggest mitigation measures.
Regions:
- Very High Vulnerability: Himalayas, Andaman & Nicobar, Western Ghats, and Nilgiris. (Young folded mountains with steep slopes and heavy rain).
- High Vulnerability: North-eastern states (Assam, Meghalaya) due to seismic activity and shifting cultivation.
- Restriction on construction in hazard-prone areas.
- Afforestation to hold the soil together.
- Building Retaining Walls to stop land slippage.
- Terrace farming to reduce slope instability.
(ii) What is vulnerability? Divide India into drought vulnerability zones and suggest mitigation.
Vulnerability: It is the inability to resist a hazard or to respond when a disaster has occurred.
Drought Zones:
Drought Zones:
- Extreme Drought: Rajasthan (West of Aravalli), Kutch region of Gujarat.
- Severe Drought: Parts of Eastern Rajasthan, Interior Karnataka, Andhra Pradesh, and Marathwada.
- Moderate Drought: Parts of Northern India, Maharashtra, and Jharkhand.
- Rainwater Harvesting: Storing water in tanks/kunds.
- Inter-linking of rivers and canals (e.g., Indira Gandhi Canal).
- Using drought-resistant crops (Millets).
- Drip and sprinkler irrigation.
(iii) When can developmental activities become the cause of disasters?
Development becomes a disaster trigger when it ignores ecological balance:
- Unplanned Urbanization: Blocking natural drainage channels leads to Urban Floods (e.g., Mumbai, Chennai).
- Deforestation: Clearing forests for industry/agriculture increases soil erosion, leading to Landslides.
- Large Dams: Construction in seismic zones can induce earthquakes (Reservoir Induced Seismicity) or cause downstream ecological damage.
- Construction on Slopes: Building roads/hotels on fragile Himalayan slopes destabilizes them.
Project Work
Project Ideas Guidance
(Select one topic to prepare a report)
Example: (viii) Rooftop Rainwater Harvesting Model
Example: (viii) Rooftop Rainwater Harvesting Model
- Objective: To conserve water in urban/rural homes.
- Materials: Cardboard (house), Straws/Pipes (conduits), Plastic Bottle (storage tank), Filter (gravel/sand).
- Process: Rain falls on the roof $\rightarrow$ Flows through pipes $\rightarrow$ Passes through filter $\rightarrow$ Collected in the tank/recharge pit.
- Benefits: Raises groundwater level, provides water for dry season.