42  Natural Hazards and Disasters

A hazard is a natural or human-made phenomenon that may cause damage. A disaster is the actual event in which the hazard causes serious disruption — loss of life, livelihood, or property — that exceeds local capacity to cope.

TipHazard vs Disaster
  • Hazard — the threat (an earthquake fault).
  • Disaster — the consequence when the hazard strikes vulnerable populations (an earthquake that kills thousands).

Risk = Hazard × Vulnerability × Exposure ÷ Capacity.

42.1 Classification of Disasters

TipDisaster Categories
Category Examples
Geological / Geophysical Earthquakes, volcanic eruptions, landslides, tsunamis
Hydrological Floods, cyclones, storm surges, glacial-lake outburst floods
Meteorological Cyclones, typhoons, tornadoes, hailstorms, droughts
Climatological Heat waves, cold waves, droughts, wildfires
Biological Pandemics, epidemics, locust attacks
Anthropogenic Industrial accidents, oil spills, nuclear accidents, terrorism

42.2 Earthquakes

Earthquakes occur when accumulated stress in the Earth’s crust is released suddenly along a fault.

TipEarthquake Vocabulary
  • Focus / Hypocentre — the point inside the Earth where rupture begins.
  • Epicentre — the point on the surface directly above the focus.
  • Seismic waves — P-waves (primary, fastest), S-waves (secondary), surface waves (most damaging).
  • Magnitude — energy released; Richter scale (logarithmic, open-ended) and the more modern Moment Magnitude (Mw) scale.
  • Intensity — felt effects; Mercalli scale (I to XII).
  • Tsunami — sea waves triggered by underwater earthquakes.
TipIndian Seismic Zones

India is divided into four seismic zones by the Bureau of Indian Standards (IS 1893):

  • Zone V — highest risk (Kashmir, Himalayan region, Northeast, parts of Gujarat).
  • Zone IV — high (Delhi, parts of Himachal, parts of Maharashtra).
  • Zone III — moderate (Kerala, parts of Gujarat, parts of MP).
  • Zone II — low (most of central and southern peninsula).

Note: Zone I has been merged into Zone II in modern revisions.

42.3 Floods, Cyclones, and Storm Surges

TipIndian Cyclone Vocabulary
  • Cyclone — large-scale low-pressure system with strong winds. Called hurricane in the Atlantic, typhoon in the Pacific, cyclone in the Indian Ocean.
  • Indian cyclone seasons — pre-monsoon (April-June) and post-monsoon (October-December).
  • IMD cyclone categories by wind speed:
    • Depression: 31-49 km/h
    • Deep depression: 50-61 km/h
    • Cyclonic storm: 62-87 km/h
    • Severe cyclonic storm: 88-117 km/h
    • Very severe cyclonic storm: 118-165 km/h
    • Extremely severe cyclonic storm: 166-220 km/h
    • Super cyclonic storm: 221+ km/h

The Indian Meteorological Department (IMD) issues colour-coded warnings (Green, Yellow, Orange, Red) for hazardous weather.

42.4 Droughts

TipThree Types of Drought
  • Meteorological drought — rainfall deficit over an extended period.
  • Hydrological drought — depletion of streams, lakes, reservoirs.
  • Agricultural drought — soil-moisture deficit affecting crops.

A socio-economic drought is sometimes added — combined effect on supply and demand of water-dependent goods.

42.5 Landslides

Landslides occur in hilly regions when slope stability is lost — heavy rain, earthquakes, deforestation, road construction. Major Indian regions: Western Ghats, Eastern Himalaya, Northeast.

42.6 Tsunamis

Tsunamis are long ocean waves triggered by underwater earthquakes, volcanic eruptions, or landslides. The 2004 Indian Ocean Tsunami (Boxing Day, 26 December 2004) killed approximately 230,000 across 14 countries — among the deadliest natural disasters in history. India established the Indian Tsunami Early Warning System (ITEWS) at INCOIS, Hyderabad.

42.7 Wildfires

Wildfires (forest fires) destroy biodiversity, release CO₂, and threaten communities. India sees significant fires in dry deciduous forests of central and northeast India during summer.

42.8 Disaster Management Cycle

TipFour Phases of Disaster Management
Phase What it does When
Mitigation Reduce risk through structural and non-structural measures Before disaster
Preparedness Plans, training, drills, early warning systems Before
Response Search & rescue, relief, evacuation, medical aid During and immediately after
Recovery Reconstruction, livelihood restoration, resilience-building After 

flowchart LR
  M[Mitigation] --> P[Preparedness]
  P --> R[Response]
  R --> RC[Recovery]
  RC --> M
    classDef default fill:#003366,color:#ffffff,stroke:#ffcc00,stroke-width:3px,rx:10px,ry:10px;

42.9 Indian Disaster Management Framework

TipKey Bodies and Acts
  • Disaster Management Act, 2005 — primary legislation.
  • NDMA — National Disaster Management Authority — chaired by the Prime Minister.
  • State Disaster Management Authority (SDMA) — chaired by the Chief Minister.
  • District Disaster Management Authority (DDMA) — chaired by the District Collector.
  • NDRF — National Disaster Response Force — operational arm.
  • NIDM — National Institute of Disaster Management — capacity-building and research.
  • IMD — India Meteorological Department.
  • INCOIS — Indian National Centre for Ocean Information Services (Hyderabad) — tsunami warnings.
  • CDRI — Coalition for Disaster Resilient Infrastructure (India-led, 2019).

42.10 Sendai Framework for Disaster Risk Reduction (2015–2030)

The Sendai Framework, adopted at the third UN World Conference (Sendai, Japan, 2015) is the global blueprint for disaster risk reduction (replacing the Hyogo Framework 2005-2015).

TipSendai’s Four Priorities
  1. Understanding disaster risk.
  2. Strengthening disaster risk governance.
  3. Investing in disaster risk reduction for resilience.
  4. Enhancing disaster preparedness for effective response — and to “Build Back Better”.
TipSendai’s Seven Targets

By 2030, substantial reduction in (1) global mortality, (2) affected people, (3) economic loss, (4) damage to infrastructure, plus increase in (5) countries with national/local DRR strategies, (6) international cooperation, (7) availability of warning systems.

42.11 Practice Questions

Q 01 DM Act Easy

India's Disaster Management Act was enacted in:

  • A1990
  • B2000
  • C2005
  • D2015
View solution
Correct Option: C
The Disaster Management Act, 2005 is the primary legislation, enacted after the 2004 Indian Ocean Tsunami.
Q 02 NDMA Easy

The National Disaster Management Authority (NDMA) is chaired by:

  • APresident of India
  • BPrime Minister of India
  • CHome Minister
  • DVice President
View solution
Correct Option: B
NDMA is chaired by the Prime Minister; SDMA by the Chief Minister; DDMA by the District Collector.
Q 03 Earthquake Medium

The point on the Earth's surface directly above the focus of an earthquake is called the:

  • AHypocentre
  • BEpicentre
  • CMagnitude
  • DIntensity
View solution
Correct Option: B
The epicentre is the surface point directly above the focus (hypocentre).
Q 04 Sendai Framework Medium

The Sendai Framework for Disaster Risk Reduction covers the period:

  • A2005–2015
  • B2010–2020
  • C2015–2030
  • D2020–2050
View solution
Correct Option: C
The Sendai Framework covers 2015–2030, replacing the Hyogo Framework (2005–2015).
Q 05 Tsunami Medium

The Indian Tsunami Early Warning System (ITEWS) is operated by:

  • AIMD, New Delhi
  • BINCOIS, Hyderabad
  • CISRO, Bengaluru
  • DNDMA, New Delhi
View solution
Correct Option: B
ITEWS is operated by INCOIS (Indian National Centre for Ocean Information Services) at Hyderabad.
Q 06 Cyclone Medium

A tropical cyclone is called a *hurricane* in:

  • AIndian Ocean
  • BNorthwest Pacific
  • CAtlantic and Eastern Pacific
  • DAntarctic Ocean
View solution
Correct Option: C
Atlantic and Eastern Pacific → hurricane; Northwest Pacific → typhoon; Indian Ocean → cyclone.
Q 07 DM Cycle Easy

The four phases of the disaster management cycle are:

  • AMitigation, Preparedness, Response, Recovery
  • BPlan, Prevent, Predict, Pacify
  • CAssess, Alert, Act, Audit
  • DSurvey, Save, Salvage, Settle
View solution
Correct Option: A
The four phases: Mitigation, Preparedness, Response, Recovery.
Q 08 Seismic Zones Hard

India is divided into how many seismic zones (under IS 1893)?

  • AThree
  • BFour (Zones II to V)
  • CSix
  • DEight
View solution
Correct Option: B
India has four seismic zones (II to V; Zone I merged into II in modern revisions). Zone V is highest risk.
ImportantQuick recall
  • Hazard vs Disaster (consequence). Risk = Hazard × Vulnerability ÷ Capacity.
  • Earthquake: Focus / Epicentre / Magnitude (Richter, Mw) / Intensity (Mercalli). Indian seismic zones: II to V.
  • Cyclone names: Atlantic = hurricane; NW Pacific = typhoon; Indian Ocean = cyclone.
  • DM cycle: Mitigation → Preparedness → Response → Recovery.
  • Indian framework: DM Act 2005; NDMA (PM-chaired), SDMA (CM), DDMA (DC), NDRF, NIDM, IMD, INCOIS, CDRI (2019).
  • Sendai Framework 2015–2030 — 4 priorities, 7 targets; replaced Hyogo 2005–2015.
  • 2004 Indian Ocean Tsunami → ITEWS at INCOIS Hyderabad.