Natural Hazards & Disaster Management – NDA Geography Notes

Introduction

India is one of the most disaster-prone countries in the world. Its diverse geography makes it vulnerable to earthquakes in the Himalayan and northeastern zones, cyclones along the eastern coast, floods in river plains, droughts in dry regions, landslides in hilly areas, and tsunamis along coastal zones.

NDA tests this chapter through questions on seismic zones, types of natural hazards, specific disaster characteristics (cloudbursts, sheet floods), disaster management institutions, and the distinction between natural and man-made hazards.

This chapter is moderate in frequency — but when questions appear, they are direct and reward students who understand geography clearly.

Understand the Topic

What is a Natural Hazard?

A natural hazard is a naturally occurring event that threatens human lives and property. When a natural hazard affects a community and causes loss of life, property, or livelihoods, it becomes a natural disaster.

The same event may be a hazard in one place and a disaster in another — depending on how many people live there and how prepared they are.

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Types of Natural Disasters in India

India faces several types of natural disasters:

1. Earthquakes
2. Cyclones and storms
3. Floods
4. Droughts
5. Landslides
6. Tsunamis
7. Cloudbursts and flash floods
8. Avalanches
9. Heatwaves and cold waves

Earthquakes

What causes earthquakes?

Earthquakes are caused by the sudden release of energy stored in the Earth’s crust. This energy is released when rocks along fault lines suddenly slip. The point underground where the earthquake starts is called the focus (or hypocenter). The point directly above it on the surface is called the epicenter.

India lies in a seismically active region. The Himalayan zone and the northeastern states are among the most earthquake-prone regions in the world. This is because the Indian tectonic plate is still pushing northward against the Eurasian plate.

Seismic Zones of India

India is divided into four seismic zones based on earthquake risk:

Zone	Risk Level	Areas
Zone V	Very High Risk	Northeast India (Assam, Manipur, Mizoram), J&K, Himachal Pradesh, Uttarakhand, parts of Gujarat (Kutch), Andaman & Nicobar Islands
Zone IV	High Risk	Delhi, parts of J&K, Himachal Pradesh, UP, Bihar, West Bengal, parts of Maharashtra (Mumbai)
Zone III	Moderate Risk	Kerala, Goa, Lakshadweep, parts of UP, Gujarat, West Bengal, Punjab, Rajasthan, MP, Bihar
Zone II	Low Risk	Parts of peninsular India, south Tamil Nadu, Karnataka, AP

City-Zone Matching:

• Guwahati = Zone V (very high risk — in Northeast India) [NDA tested via CDS]
• Kolkata = Zone IV (high risk) [NDA tested via CDS]
• Delhi = Zone IV (high risk) [NDA tested via CDS]
• Chennai = Zone III (moderate risk) [NDA tested via CDS]

Pithoragarh (Uttarakhand) is in a high seismic zone — Zone V — and is at MORE risk from earthquake hazard than Secunderabad, Indore, or Bhubaneswar. [NDA tested via CDS]

Factors influencing earthquake damage:

• Strength of the earthquake
• Population density
• Type of building construction
• Climate of the area does NOT influence earthquake damage. [NDA tested via CDS]

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Cyclones

Cyclones are intense low-pressure weather systems with strong rotating winds. They develop over warm ocean water.

Bay of Bengal branch is more active than the Arabian Sea in producing cyclones that hit India.

India’s eastern coast (Andhra Pradesh, Odisha, West Bengal, Tamil Nadu) is more cyclone-prone than the western coast.

Retreating monsoon season (October-November) is when most cyclones hit the eastern coast of India.

Blizzards:
A blizzard is a severe snow storm with strong winds, low temperatures, and poor visibility. Blizzards affect high altitude mountainous regions. If travelling to Arunachal Pradesh (high altitude, snowy areas), protection from blizzards is advised. Assam, Tripura, and Odisha are not prone to blizzards. [NDA tested via CDS]

Floods

Floods are the most common natural disaster in India. They affect large parts of the country every year during the monsoon.

Most flood-prone regions:

• Brahmaputra Valley (Assam) — Brahmaputra is a braided river; massive floods every monsoon
• Bihar — Kosi River causes devastating floods; Kosi is called the “Sorrow of Bihar”
• Odisha and Andhra Pradesh coastal areas — cyclone-induced floods
• West Bengal — delta floods and cyclones
• Uttar Pradesh and Punjab — Ganga and Yamuna plain flooding

Flash floods and cloudbursts:
A cloudburst is a very heavy precipitation event in a short period of time in a limited geographical area. According to the Indian Meteorological Department, two key features of a cloudburst: [NDA 2022-I]

1. Heavy precipitation in short period of time in a limited geographical area — TRUE
2. It occurs generally during the monsoon period and triggers flash floods and landslides — TRUE
   Both statements are correct. [NDA 2022-I]

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Sheet Floods in Rajasthan

A sheet flood is a thin sheet of fast-moving water that spreads across a flat surface during or after heavy rain. It occurs in western Rajasthan.

Causes of sheet floods in western Rajasthan: [NDA 2014-I]

1. Scanty rainfall (very little rain overall) — TRUE
2. Sudden high intensity rain (when it rains, it rains heavily in a short time) — TRUE
3. Loose sandy soil with scanty vegetation (water cannot be absorbed; no plant roots to hold soil or water) — TRUE

All three are correct causes. [NDA 2014-I]

Droughts

A drought occurs when an area receives significantly less rainfall than normal over an extended period.

Most drought-prone regions of India:

• Rajasthan — especially western Rajasthan
• Parts of Andhra Pradesh, Telangana, Maharashtra
• Parts of Karnataka and Tamil Nadu

Semi-arid tracts from eastern Rajasthan to south-central Tamil Nadu are agriculturally less productive — TRUE. This region has poor rainfall and dry conditions. The statement that this region is the “homeland of a large number of central Indian scheduled tribes” is also true — but it does NOT explain why agriculture is less productive. The two statements are separately true but one does not explain the other. [NDA 2011-II]

For an area to be excluded from the drought-prone category, at least 30% or more of its gross cropped area should be under irrigation. [NDA 2020-I]

Variability of monsoon rainfall is a major cause of droughts. Rajasthan has high rainfall variability — some years get almost normal rain, others get very little. [NDA tested via CDS]

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Landslides

Landslides occur when masses of rock, soil, or debris move down a slope. They are common in:

• Himalayan states — J&K, Himachal Pradesh, Uttarakhand, Sikkim
• Northeastern states — Arunachal Pradesh, Meghalaya, Nagaland, Manipur
• Western Ghats — Kerala, Karnataka

Causes:

• Heavy rainfall saturating slopes
• Earthquakes triggering slope failure
• Human activities — road cutting, deforestation, construction

Tsunamis

A tsunami is a series of ocean waves caused by a sudden displacement of water — usually due to an underwater earthquake, volcanic eruption, or landslide.

The 2004 Indian Ocean Tsunami (26 December 2004) was one of the deadliest natural disasters in recorded history. It was caused by a massive earthquake (magnitude 9.1) off the coast of Sumatra, Indonesia. It devastated coastal areas of Tamil Nadu, Andhra Pradesh, Kerala, Andaman and Nicobar Islands, and Sri Lanka.

Indira Point on Great Nicobar Island partially submerged after the 2004 tsunami.

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Avalanches

An avalanche is a mass of snow and ice rapidly sliding down a mountain slope. It is a type of terrestrial disaster. [NDA tested via CDS]

Avalanches are common in:

• High Himalayan regions — J&K, Himachal Pradesh, Uttarakhand
• Siachen Glacier area

Indian Monsoon Rainfall — Key Disaster Connections

Monsoonal rainfall characteristics: [NDA 2017-I]

1. Largely governed by topographical features — TRUE (Western Ghats, Himalayas affect distribution)
2. Regional and seasonal variation in rainfall distribution — TRUE
3. Heavy downpour resulting in considerable runoff — TRUE
4. Beginning and end of rain is regular and on time — FALSE (monsoon onset and withdrawal are unpredictable)

Statements 1, 2, and 3 are correct. [NDA 2017-I]

Tamil Nadu and J&K do NOT receive most of their rainfall from the Southwest Monsoon during June-September. Tamil Nadu gets most rain from the Northeast Monsoon. J&K gets rain from Western Disturbances in winter. [NDA 2009-I]

Ganga basin rainfall pattern decreases from East to West and South to North — meaning the eastern and southern parts of the Ganga basin get more rain than the western and northern parts. [NDA tested via CDS]

Maharashtra receives rainfall from BOTH the Arabian Sea branch and the Bay of Bengal branch of the monsoon — it sits between the two branches. [NDA tested via CDS]

Interior Maharashtra receives less rain because it lies in the rain shadow of the Western Ghats. [NDA tested via CDS]

Minimum rainfall in India: Leh receives the minimum rainfall in India. [NDA tested via CDS]

Disaster Management in India

National Disaster Management Authority (NDMA):

• The NDMA functions under the Ministry of Home Affairs. [NDA tested via CDS]
• It is headed by the Prime Minister of India.
• It was established under the Disaster Management Act, 2005.

State Disaster Management Authorities (SDMAs):
Set up in each state, headed by the Chief Minister.

National Disaster Response Force (NDRF):
A specialised force for disaster response in India. Equipped to handle earthquakes, floods, cyclones, chemical disasters, and nuclear emergencies.

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Seismic Zones — Detailed

India is divided into seismic zones to guide earthquake-resistant construction.

The most dangerous zones are in:

• Northeast India (Assam, Manipur, Nagaland, Mizoram, Arunachal Pradesh, Meghalaya, Tripura, Sikkim) — Zone V
• Parts of Jammu & Kashmir, Himachal Pradesh, Uttarakhand — Zone V
• Kutch (Gujarat) — Zone V (after 2001 Bhuj earthquake)
• Andaman & Nicobar Islands — Zone V
• Delhi — Zone IV

A person at Pithoragarh (Uttarakhand) is at more risk from earthquake than at Secunderabad, Indore, or Bhubaneswar — because Pithoragarh is in a high seismic zone (Zone V in the Kumaon Himalayas). [NDA tested via CDS]