Natural Disasters

Q. No. 1. Assertion (A): The frequency of floods in the North Indian plains has increased during the last couple of decades.

Reason (R): There has been a reduction in the depth of river valleys due to deposition of silt. (UPSC Civil Services Prelims, 2000)

Code:

(a) Both A and R are true, and R is the correct explanation of A

(b) Both A and R are true, but R is not the correct explanation of A

(d) A is false, but R is true

Answer: (a)

Explanation:

● A flood occurs when water inundates normally dry land because the discharge or water level exceeds the carrying capacity of the river channel, drainage system or floodplain environment. Flood risk depends not only on rainfall but also on catchment characteristics, channel capacity, sedimentation, drainage congestion, land use and human occupation of floodplains.

● The great northern plains contain large alluvial river systems such as the Ganga, Ghaghara, Gandak, Kosi and Brahmaputra-associated systems. These rivers carry substantial sediment derived from the geologically young and actively eroding Himalaya.

● Sediment deposition can cause aggradation of the channel bed. Where a channel becomes shallower, its effective conveyance capacity may decrease, so a discharge that previously remained within banks may more readily cause overbank flooding. Hence, Assertion (A) is correct.

● The Reason identifies silt deposition and reduction in effective channel depth as one factor that can increase flood susceptibility. Hence, Reason (R) is correct.

● Thus, the reduced channel capacity due to sedimentation provides a valid explanation for increased flood incidence.

Hence, option (a) is correct.

Q. No. 2. Assertion (A): East coast is more prone to cyclones than the western coast.

Reason (R): Eastern coast of India lies in the zone of north-east trade winds. (UPPCS Prelims, 2003)

(a) Both A and R are true, and R is the correct explanation of A

(b) Both A and R are true, but R is not the correct explanation of A

(d) R is true, but A is false

Answer: (b)

Explanation:

● The Bay of Bengal coast of India is climatologically more exposed to tropical cyclones than the Arabian Sea coast. IMD's cyclone climatology shows that a large proportion of Bay of Bengal tropical cyclones make landfall along India's east coast; Bay cyclones commonly affect Odisha–West Bengal, Andhra Pradesh and Tamil Nadu according to season. Hence, Assertion (A) is correct.

● The eastern coast is affected by seasonal easterly/northeasterly circulation during part of the year, so the Reason contains a broad climatic association. Hence, Reason (R) is correct.

● But the east coast's greater cyclone exposure is not caused simply by its location in the northeast-trade-wind belt.

● Cyclone occurrence depends on favourable oceanic and atmospheric conditions such as warm upper-ocean water, adequate Coriolis force, atmospheric instability, abundant moisture, relatively weak vertical wind shear and an initial cyclonic disturbance.

● The funnel-shaped northern Bay of Bengal is especially important for storm-surge amplification, not as the fundamental cause of cyclogenesis. Shallow coastal waters and coastal configuration can pile up water as a cyclone approaches.

Hence, option (b) is correct.

Q. No. 3. Which one of the following areas of India does not come under the zone of high seismic intensity? (UPPCS Prelims, 2006; Uttarakhand PCS Prelims, 2010)

(a) Uttarakhand

(b) Karnataka Plateau

(d) Himachal Pradesh

Answer: (b)

Explanation:

● India's earthquake hazard is closely related to its tectonic setting. The Himalayan belt is undergoing active convergence because the Indian Plate continues to interact with the Eurasian Plate. The northeast, Kachchh and Andaman–Nicobar regions also contain major tectonically active zones.

● The Peninsular Shield is geologically older and comparatively stable, although it is not earthquake-free. Intraplate earthquakes such as Latur and Koyna show that damaging earthquakes can occur away from active plate boundaries.

● Option (b), Karnataka Plateau, is correct as the best answer. Large parts of the stable peninsular interior fall in India's lower seismic categories compared with the Himalayan arc and Kachchh.

● As of August 2026, the Government states that the 2016 seismic-zonation standard remains operative, because the 2025 revision was withdrawn in March 2026. Current national zonation therefore again uses four zones: II, III, IV and V.

● NIDM's current earthquake-safety material describes roughly 59% of India's landmass as lying in Zones III–V and identifies Srinagar and Guwahati in Zone V, Delhi in Zone IV, and Mumbai, Kolkata and Chennai in Zone III.

Hence, option (b) is correct.

Q. No. 4. Which of the following processes is most directly capable of producing a major earthquake-generated tsunami?

(a) Horizontal surface current in the open ocean

(b) Sudden vertical displacement of the ocean floor

(d) Seasonal reversal of monsoon winds

Answer: (b)

Explanation:

● A major seismic tsunami generally requires rapid displacement of a large volume of seawater.

● Vertical displacement of the seabed, particularly during a large shallow undersea earthquake at a subduction zone, can abruptly raise or lower the overlying water column and generate long waves. Hence, option (b) is correct.

● Option (a) is incorrect because ordinary ocean currents do not suddenly displace the whole water column in the manner required.

● Option (c) is incorrect because astronomical tides arise mainly from gravitational forces of the Moon and Sun.

● Option (d) is incorrect because monsoon-wind reversal affects waves, currents and storm conditions but does not itself create a seismic tsunami.

● Landslides and volcanic activity can also generate tsunamis, so earthquakes are the most common, not the only, mechanism.

Hence, option (b) is correct.

Q. No. 5. Which of the following coasts of India was worst affected by the 2004 Tsunami? (UP RO/ARO Mains, 2014)

(a) Malabar Coast

(b) Konkan Coast

(d) Northern Circars Coast

Answer: (c)

Explanation:

A tsunami is a series of long ocean waves generated by the sudden displacement of a large volume of water. The most important cause is a large undersea earthquake involving significant vertical displacement of the sea floor, although submarine landslides and volcanic activity can also generate tsunamis.
Option (c), the Coromandel Coast, is correct. The 26 December 2004 Indian Ocean Tsunami was triggered by a magnitude 9.1–9.3 undersea earthquake off the coast of Sumatra, Indonesia.
The tsunami waves travelled across the Indian Ocean and struck the southeastern coast of India with great intensity.
The Coromandel Coast (Tamil Nadu coast) experienced the maximum damage and loss of life in mainland India.
The Andaman and Nicobar Islands were also severely affected, but among the options given, the Coromandel Coast was the worst-hit coast.
In contrast, the Malabar Coast and Konkan Coast on the Arabian Sea side experienced comparatively much less impact, and the Northern Circars Coast was less severely affected than the Coromandel Coast.

● In the deep ocean, tsunami waves may have relatively small height but extremely long wavelengths and high propagation speed. Approaching shallow coastal waters, their speed falls, wavelength shortens and wave height can increase greatly through shoaling.

Hence, option (c) is correct.

Q. No. 6. Tsunami Warning Centre in India is located in— (UPPCS Mains, 2012)

(a) Chennai

(b) Visakhapatnam

(d) Port Blair

Answer: (c)

Explanation:

● India's Indian Tsunami Early Warning Centre (ITEWC) operates at the Indian National Centre for Ocean Information Services (INCOIS), Hyderabad, under the Ministry of Earth Sciences. It became fully operational in October 2007 following development undertaken after the 2004 Indian Ocean tsunami.

● Option (c), Hyderabad, is correct.

● The system integrates seismic monitoring, tide gauges, deep-ocean pressure observations, numerical modelling and decision-support systems. INCOIS states that the centre operates continuously and can detect potentially tsunamigenic earthquakes and issue advisories to authorities.

● The distinction between detection and confirmation is important. Earthquake data identify potentially tsunamigenic events; sea-level observations help determine whether significant tsunami waves were actually generated.

Hence, option (c) is correct.

Q. No. 7. Match List-I (Natural Hazards) with List-II (Regions) and select the correct answer. (BPSC Prelims, 2005)

List-I

A. Floods

B. Earthquakes

C. Droughts

D. Cyclones

List-II

Himalayan foothill zone
Jharkhand and northern Odisha
Plains of Uttar Pradesh and Bihar
Mid-eastern India

(a) A-3, B-1, C-2, D-4

(b) A-3, B-1, C-4, D-2

(d) A-4, B-2, C-3, D-1

Answer: (b)

Explanation:

Floods → Plains of Uttar Pradesh and Bihar (3): The Ganga plain has low relief, extensive floodplains, heavy monsoon rainfall, and large river discharge, making it highly flood-prone.
Earthquakes → Himalayan foothill zone (1): The Himalayan region is an active tectonic belt formed by the collision of the Indian and Eurasian plates; therefore it is highly seismic.
Droughts → Mid-eastern India (4): This is the pairing intended in this historical BPSC question. Parts of central and eastern India experience recurrent drought conditions due to rainfall variability.
Cyclones → Jharkhand and northern Odisha (2): Bay of Bengal cyclones frequently affect Odisha and may move inland over adjoining regions such as Jharkhand as weakened cyclonic systems.

Therefore, the correct matching is A-3, B-1, C-4, D-2, so option (b) is correct.

Q. No. 8. Assertion (A): The frequency of landslides has increased in the Himalayas.

Reason (R): There has been large-scale mining in the Himalayas in recent years. (UPPCS Mains, 2003)

(a) Both A and R are true, and R is the correct explanation of A

(b) Both A and R are true, but R is not the correct explanation of A

(d) A is false but R is true

Answer: (a)

Explanation:

● A landslide is the downslope movement of rock, debris or soil under gravity. GSI identifies slope, lithology, geological structure, geomorphology and land use as important preparatory factors, while heavy rainfall and earthquakes commonly act as triggers.

● The Himalaya is intrinsically landslide-prone because it is geologically young, tectonically active, deeply dissected, steep-sloped and subject to intense monsoonal rainfall.

● GSI identifies the entire Himalayan tract, sub-Himalayan northeastern hills, Western Ghats, Nilgiris and Konkan hills among India's important landslide-prone regions. Hence, Assertion (A) is correct.

● Mining and quarrying can destabilise slopes by removing supporting material, producing fractures, modifying drainage and increasing waste/debris loads. Hence, Reason (R) is correct.

● Therefore large-scale mining can contribute to enhanced landslide susceptibility and is one of the anthropogenic reasons supporting the Assertion.

● However, it is not the only cause. Road cutting, tunnelling, hydropower construction, deforestation, unplanned settlement, slope loading and drainage alteration can increase instability.

● Heavy monsoon rainfall is one of India's most frequent immediate landslide triggers. Earthquake shaking can also reduce shear strength or dislodge already unstable material.

● Susceptibility ≠ trigger. A steep fractured slope may be susceptible for years; extreme rain or an earthquake may trigger the actual failure.

Hence, option (a) is correct.

Q. No. 9. From the following, which cyclone struck the western coast of India in the year 2021? (MPPSC Prelims, 2024)

(a) Amphan

(b) Tauktae

(d) Fani

Answer: (b)

Explanation:

● Tauktae developed over the Arabian Sea in May 2021 and became an Extremely Severe Cyclonic Storm. IMD's official archive identifies Tauktae as an Arabian Sea cyclone during 14–19 May 2021.

● Option (a), Amphan, is incorrect. Amphan was a 2020 Bay-of-Bengal cyclone associated especially with the West Bengal–Bangladesh sector.

● Option (b), Tauktae, is correct and is the key example of a major Arabian Sea/west-coast cyclone.

● Option (c), Michaung, is incorrect. It was a Bay-of-Bengal cyclone of December 2023 affecting the southeastern/eastern coastal region.

● Option (d), Fani, is incorrect. Fani was a major Bay-of-Bengal cyclone in 2019, especially associated with Odisha.

Hence, option (b) is correct.

Q. No. 10. Which of the following statements are true? (UPPCS Prelims, 2018)

Natural disasters cause maximum damage in developing countries.
Bhopal gas tragedy was man-made.
India is a disaster-free country.
Mangroves reduce the impact of cyclones.

Code:

(a) 1, 2 and 3

(b) 2, 3 and 4

(d) 1, 3 and 4

Answer: (c)

Explanation:

● Disaster losses depend heavily on exposure, vulnerability and coping capacity. Poor housing, inadequate infrastructure, limited early-warning access, poverty and weak preparedness can convert a similar physical hazard into much larger human consequences. UNDRR therefore treats disaster risk as a function of hazard, exposure, vulnerability and capacity rather than hazard magnitude alone.

● Statement 1 reflects this vulnerability-based logic. It refers to the disproportionate impact that hazards can have on vulnerable developing societies. Hence, statement 1 is correct.

● The Bhopal gas disaster was a technological/industrial disaster produced by the release of toxic methyl isocyanate from an industrial facility. It was therefore anthropogenic rather than a natural disaster. Hence, statement 2 is correct.

● India is exposed to multiple hazards, including earthquakes, floods, droughts, tropical cyclones, landslides, avalanches, tsunamis and heat waves. Hence, statement 3 is incorrect.

● Mangroves can reduce coastal hazard impacts by increasing surface roughness, dissipating wave energy, binding sediment and forming an ecological buffer. They do not make a coast cyclone-proof, but they can contribute to risk reduction. Hence, statement 4 is correct.

● The broader concept is ecosystem-based disaster risk reduction: mangroves, wetlands, dunes and healthy floodplains can provide natural protective functions alongside engineered measures.

Hence, option (c) is correct.

Q. No. 11. Which one of the following causes is responsible for rainfall during winters in the north-western part of India? (UPPCS Prelims, 2021)

(a) Retreating Monsoon

(b) Cyclonic depression

(d) South-West Monsoon

Answer: (c)

Explanation:

Western Disturbances are extra-tropical cyclonic systems that originate in the Mediterranean region and move eastward towards India under the influence of the westerly winds.
During the winter season (December–March), they bring rainfall to north-western India (Punjab, Haryana, Delhi, Rajasthan, western Uttar Pradesh) and snowfall to the western Himalayas (Jammu & Kashmir, Himachal Pradesh, and Uttarakhand).
This winter precipitation is important for rabi crops, especially wheat and mustard.

Why other options are incorrect

Retreating Monsoon mainly affects the south-eastern coast (Tamil Nadu) during October–December.
Cyclonic depressions generally produce rainfall in other seasons and regions, especially over the Bay of Bengal.
South-West Monsoon causes rainfall mainly during June–September.

Disaster relevance

Western Disturbances can sometimes cause heavy rain and snowfall, leading to avalanches, landslides, flash floods, and disruption of transport and communication in the western Himalayan region.

Hence, option (c) is correct.

Q. No. 12. Which combination provides the most favourable conditions for tropical-cyclone development?

(a) Cold sea surface, strong vertical wind shear and air crossing the equator

(b) Warm ocean water, moist unstable atmosphere, sufficient Coriolis force and relatively weak vertical wind shear

(d) Warm ocean water directly over the equator with no pre-existing disturbance

Answer: (b)

Explanation:

Tropical cyclones develop under a combination of favourable oceanic and atmospheric conditions:
Warm ocean water (generally sea-surface temperature above about 26.5°C) provides heat and moisture.
Moist and unstable atmosphere promotes deep convection and cloud development.
Sufficient Coriolis force is necessary to generate and maintain cyclonic rotation; therefore cyclones rarely form within about 5° latitude of the equator.
Relatively weak vertical wind shear allows the storm’s vertical structure to remain organized and intensify.
A pre-existing low-pressure disturbance usually acts as the initial trigger for cyclogenesis.

● Option (a) Cold water and strong wind shear suppress cyclone formation.

● Option (b) contains the favourable combination.

● Option (c) describes anticyclonic rather than cyclonic conditions.

● Option (d) is incorrect because Coriolis force approaches zero at the equator.

● Bay of Bengal cyclone activity has historically been substantially greater than Arabian Sea activity, though the difference reflects multiple atmospheric and oceanic controls rather than temperature alone.

Hence, option (b) is correct.