Natural Hazards & Disaster Management – NDA Geography Notes

Coastal States, Gulfs, Straits, Islands and Maritime Zones of India

Indian Geography • Coastal Geography • PYQs Included

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. When questions appear, they are direct and reward students who understand the geography clearly.

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.

India faces several types of natural disasters: earthquakes, cyclones and storms, floods, droughts, landslides, tsunamis, cloudbursts and flash floods, avalanches, and heatwaves and cold waves.

Earthquakes

Causes and Terminology

Earthquakes are caused by the sudden release of energy stored in the Earth’s crust. This happens 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 northeastern states are among the most earthquake-prone regions in the world, 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: Northeast India)
Kolkata – Zone IV (high risk)
Delhi – Zone IV (high risk)
Chennai – Zone II (low risk)
Pithoragarh (Uttarakhand) – Zone V: at MORE risk from earthquake than Secunderabad, Indore, or Bhubaneswar

Factors influencing earthquake damage: Strength of the earthquake, population density, and type of building construction. Climate of the area does NOT influence earthquake damage.

Cyclones and Blizzards

Cyclones are intense low-pressure weather systems with strong rotating winds that develop over warm ocean water. The 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. The retreating monsoon season (October-November) is when most cyclones hit the eastern coast.

Blizzards are severe snowstorms with strong winds, low temperatures, and poor visibility. They affect high altitude mountainous regions. If travelling to Arunachal Pradesh (high altitude, snowy areas), protection from blizzards is relevant. Assam, Tripura, and Odisha are not prone to blizzards.

Floods

Floods are the most common natural disaster in India, affecting large parts of the country every monsoon.

Most flood-prone regions: Brahmaputra Valley (Assam): Brahmaputra is a braided river causing massive floods every monsoon. Bihar: Kosi River causes devastating floods (“Sorrow of Bihar”). Odisha and Andhra Pradesh coastal areas: cyclone-induced floods. West Bengal: delta floods and cyclones. UP and Punjab: Ganga and Yamuna plain flooding.

Cloudbursts

A cloudburst is a very heavy precipitation event, defined by the Indian Meteorological Department as intense rainfall in a short period of time in a limited geographical area. Both of the following statements about cloudbursts are correct: [NDA 2022-I]

Heavy precipitation in short period of time in a limited geographical area: TRUE. It occurs generally during the monsoon period and triggers flash floods and landslides: TRUE.

Cloudbursts are NOT restricted to mountains only. They can occur in plains as well, though mountainous terrain amplifies their destructive effects. [NDA 2022-I]

Sheet Floods in Western Rajasthan

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

All three of the following are correct causes of sheet floods in western Rajasthan: [NDA 2014-I] Scanty rainfall overall (very little rain on average): TRUE. Sudden high intensity rain (when it does rain, it comes suddenly and intensely in a short time): TRUE. Loose sandy soil with scanty vegetation (water cannot be absorbed and no plant roots hold the soil): TRUE. All three together cause the rapid runoff across the flat desert surface.

Droughts

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

Most drought-prone regions: Rajasthan (especially western Rajasthan), parts of Andhra Pradesh, Telangana, Maharashtra, and parts of Karnataka and Tamil Nadu.

The semi-arid tracts of India from eastern Rajasthan to south-central Tamil Nadu are agriculturally less productive: TRUE. This region is also the homeland of a large number of central Indian Scheduled Tribes: TRUE. But the tribal population 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, because irrigation provides a buffer against rainfall failure. [NDA 2020-I]

Variability of monsoon rainfall is a major cause of droughts. Rajasthan has high rainfall variability. Some years receive near-normal rain while others receive very little.

Landslides, Tsunamis, and Avalanches

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), and the Western Ghats (Kerala, Karnataka). Causes include heavy rainfall saturating slopes, earthquakes triggering slope failure, and human activities such as road cutting, deforestation, and construction.

Tsunamis are series of ocean waves caused by sudden underwater displacement, usually from an earthquake, volcanic eruption, or landslide. The 2004 Indian Ocean Tsunami (26 December 2004) was caused by a magnitude 9.1 earthquake off the Sumatra coast and devastated Tamil Nadu, Andhra Pradesh, Kerala, Andaman and Nicobar Islands, and Sri Lanka. Indira Point on Great Nicobar Island partially submerged after the 2004 tsunami.

Avalanches are masses of snow and ice rapidly sliding down mountain slopes, a type of terrestrial disaster. They are common in high Himalayan regions (J&K, Himachal Pradesh, Uttarakhand) and the Siachen Glacier area.

Monsoon Rainfall: Key Disaster Connections

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 most from Western Disturbances in winter. [NDA 2009-I]

Ganga basin rainfall decreases from East to West and South to North. The eastern and southern parts receive more rain than the western and northern parts.

Maharashtra receives rainfall from BOTH the Arabian Sea branch and the Bay of Bengal branch of the monsoon. Interior Maharashtra receives less rain because it lies in the rain shadow of the Western Ghats.

Minimum rainfall in India: Leh receives the minimum rainfall in India.

Disaster Management in India

National Disaster Management Authority (NDMA): Functions under the Ministry of Home Affairs. Headed by the Prime Minister of India. Established under the Disaster Management Act, 2005. It coordinates disaster preparedness, response, and mitigation across India.

State Disaster Management Authorities (SDMAs) are set up in each state and are headed by the Chief Minister.

National Disaster Response Force (NDRF) is a specialised force equipped to handle earthquakes, floods, cyclones, chemical disasters, and nuclear emergencies.

Institution	Head	Ministry
NDMA (National Disaster Management Authority)	Prime Minister	Home Affairs
SDMA (State Disaster Management Authority)	Chief Minister	State government
NDRF (National Disaster Response Force)	—	Home Affairs