Unit 5: Disaster management

A disaster is an event that overwhelms a community's capacity to cope using its own resources, causing widespread human, material, economic or environmental loss. Disaster management (the discipline formalised in India by the Disaster Management Act, 2005) is the organised effort to reduce these losses across the full event cycle.

• Hazard vs disaster: A hazard is the potential threat (a fault line, a cyclone); a disaster is the hazard realised on a vulnerable population. Disaster = Hazard × Vulnerability ÷ Capacity.
• Vulnerability: The conditions (poverty, weak buildings, floodplain settlement) that increase exposure to harm.
• Disaster cycle: Four phases — mitigation (reducing risk), preparedness (planning, drills), response (rescue, relief), recovery (rehabilitation, reconstruction).
• Classification: Split into natural (geophysical/hydro-meteorological origin) and manmade/anthropogenic (technological or human-triggered).

II. Natural Disasters — Hydro-meteorological and Geological Origin

Natural disasters arise from Earth's physical processes; they are grouped by the sphere that drives them — water, air or the solid Earth.

A. Water-related disasters

Hydrological events caused by excess, shortage or displacement of water.

• Types: Floods, droughts, tsunamis, cloudbursts, and glacial-lake outburst floods (GLOFs).
• Driver: Imbalance in the hydrological cycle — precipitation, runoff and storage.
• Example: The 2004 Indian Ocean tsunami, triggered by a magnitude-9.1 undersea earthquake, killed over 230,000 people across coastal water-related impact.

B. Floods and drought

Two opposite extremes of water availability.

1. Floods: Inundation when water volume exceeds channel or land capacity.
   • Causes: Heavy/prolonged rainfall, dam failure, poor drainage, embankment breach.
   • Impact: Drowning, crop loss, waterborne disease (cholera), displacement.
   • Anchor: The Ganga–Brahmaputra basin causes recurrent flooding in Bihar and Assam.
2. Drought: Prolonged deficiency of water over an extended period.
   • Types: Meteorological (rainfall < 75% of normal), hydrological (depleted reservoirs/groundwater), agricultural (soil moisture insufficient for crops).
   • Impact: Famine, livestock death, migration, land degradation.

C. Air-related disasters

Atmospheric events driven by pressure, temperature and moisture gradients.

• Types: Cyclones, tornadoes, hailstorms, heat waves, cold waves.
• Driver: Steep pressure differences generate high-velocity winds; the Coriolis effect gives them rotation.
• Anchor: A heat wave is declared when maximum temperature exceeds 40 °C in the plains and departs ≥ 4.5 °C from normal.

D. Cyclones and storms

Intense rotating low-pressure systems formed over warm oceans.

• Formation: Sea-surface temperature above ~26.5 °C supplies latent heat; converging warm moist air spirals inward.
• Structure: Calm central eye, surrounding eye wall of strongest winds, spiral rain bands.
• Naming: Called cyclones in the Indian Ocean, hurricanes in the Atlantic, typhoons in the Pacific.
• Hazards: Storm surge (dome of seawater) is the biggest killer, plus wind damage and flooding.
• Anchor: Cyclone in the Bay of Bengal are more frequent and severe than in the Arabian Sea; the 1999 Odisha Super Cyclone had winds near 260 km/h.

E. Earth-related disasters

Geological events originating in the lithosphere.

• Types: Earthquakes, landslides, avalanches, volcanic eruptions.
• Driver: Movement of tectonic plates, gravity on slopes, and internal magmatic pressure.
• Anchor: India lies on the Indian Plate colliding with the Eurasian Plate, making the Himalayas seismically active (Zones IV–V).

F. Earthquakes

Sudden ground shaking from the release of accumulated strain energy in the crust.

• Mechanism: Stress along a fault exceeds rock strength; rupture releases seismic waves (P, S, surface).
• Terms: Focus/hypocentre (origin below surface); epicentre (point directly above on surface).
• Measurement: The Richter scale measures magnitude (energy, logarithmic); the Mercalli scale measures intensity (felt effects).
• Zonation: India divided into seismic Zones II–V, Zone V being the highest risk.
• Anchor: The 2001 Bhuj (Gujarat) earthquake measured Mw 7.7 and killed about 20,000.

G. Landslides

Downslope movement of rock, debris or soil under gravity.

• Causes: Slope steepness, deforestation, heavy rain saturating soil, road cutting, earthquakes.
• Types: Falls, slides, flows (mudflows/debris flows), and creep.
• Mitigation: Retaining walls, terracing, afforestation, proper drainage to reduce pore pressure.
• Anchor: The 2013 Kedarnath (Uttarakhand) disaster combined cloudburst, flooding and landslides.

H. Avalanches

Rapid flow of a large mass of snow down a mountainside.

• Cause: Accumulation of snow on steep slopes (30°–45°) exceeding the friction holding it; triggered by fresh snowfall, temperature rise or vibration.
• Types: Loose-snow avalanches (point release) and slab avalanches (a cohesive block detaches).
• Anchor: The upper Himalayas — Siachen, and passes in Jammu & Kashmir and Himachal — face frequent avalanches endangering troops and travellers.

I. Volcanic eruptions

Ejection of magma, ash and gases from a vent in Earth's crust.

• Mechanism: Magma rising through weak crust; dissolved gases expand and drive explosive or effusive eruption.
• Products: Lava flows, pyroclastic flows, volcanic ash, and toxic gases (SO₂, CO₂).
• Effects: Local destruction plus global cooling from ash veiling sunlight.
• Anchor: India's only active volcano is on Barren Island in the Andaman Sea; it erupted most recently in the 21st century.

III. Manmade Disasters — Technological and Anthropogenic Origin

Manmade disasters result from human action, negligence, or failure of technology and can occur alongside natural triggers.

A. Nuclear disasters

Uncontrolled release of radioactive material from nuclear installations or weapons.

• Causes: Reactor core meltdown, cooling failure, explosion, or weapon detonation.
• Radiation effects: Acute radiation sickness at high doses; cancers, genetic mutation and long-lived environmental contamination at chronic exposure.
• Anchor: The 1986 Chernobyl meltdown and the 2011 Fukushima disaster (triggered by an earthquake and tsunami) show both negligence and cascading causes.

B. Chemical disasters

Accidental release of toxic chemicals harming people and the environment.

• Causes: Industrial leaks, storage failure, transport spills, explosions.
• Effects: Poisoning, burns, respiratory damage, soil and water contamination.
• Anchor: The Bhopal Gas Tragedy (1984) leaked methyl isocyanate (MIC) from the Union Carbide plant, killing thousands — the world's worst industrial chemical disaster.

C. Biological disasters

Outbreaks of disease or release of biological agents affecting large populations.

• Sources: Epidemics and pandemics, bioterrorism, contaminated food or water.
• Agents: Bacteria (plague), viruses (COVID-19, influenza), and toxins (anthrax spores).
• Response tools: Quarantine, vaccination, surveillance, and vector control.
• Anchor: The COVID-19 pandemic demonstrated rapid global spread and health-system overload.

D. Transport accidents

Disasters from failure or collision in road, rail, air or water transport.

• Causes: Human error, mechanical failure, overloading, poor maintenance, bad weather.
• Impact: Mass casualties, hazardous-material spills, infrastructure damage.
• Anchor: Rail collisions and road accidents cause the largest transport death toll in India, with over 150,000 road deaths yearly.

IV. National Disaster Management Framework

India's institutional structure for managing disasters, established under the Disaster Management Act, 2005.

A. Statutory framework

The Act created a three-tier hierarchy for coordinated action.

• NDMA (National Disaster Management Authority): Apex body chaired by the Prime Minister; lays down policies, plans and guidelines.
• SDMA (State Disaster Management Authority): Chaired by the Chief Minister at state level.
• DDMA (District Disaster Management Authority): Chaired by the District Collector/Magistrate, executing plans on the ground.

B. Operational and support agencies

Dedicated bodies deliver response and capacity-building.

• NDRF (National Disaster Response Force): Specialised, trained force for rescue and relief operations.
• NIDM (National Institute of Disaster Management): Handles training, research and documentation.
• Shift in approach: From a relief-centric (post-disaster) model to a holistic approach stressing prevention, mitigation and preparedness.

V. Roles in Disaster Response — Comparative

Effective response depends on coordinated action by state, civil society and information channels; each actor fills a distinct role.

A. Role of governmental agencies in disaster response

Government provides the authority, resources and coordination backbone.

• Response: Deploying NDRF, armed forces and police for search, rescue and evacuation.
• Relief: Setting up shelters, distributing food, water and medical aid; releasing funds from the NDRF/SDRF (disaster response funds).
• Coordination: Early-warning dissemination (via IMD for cyclones), rebuilding infrastructure, enforcing building codes.

B. Role of NGOs in disaster response

Non-governmental organisations supplement official effort with flexibility and reach.

• Relief delivery: Rapid distribution of food, clothing, shelter and medicines to remote areas.
• Specialised aid: Medical camps, trauma counselling, and sanitation (Red Cross, Oxfam, Goonj).
• Advantage: Faster mobilisation and community trust where bureaucracy is slow.

C. Role of community-based organizations in disaster response

Local groups are the true first responders, acting before external help arrives.

• Immediate action: Neighbours perform the first rescues within the "golden hours."
• Local knowledge: Awareness of safe routes, vulnerable people, and local resources.
• Preparedness: Forming and training village/ward-level disaster-management committees and volunteer teams.

D. Role of media in disaster response

Media shapes information flow before, during and after a disaster.

• Warning: Broadcasting early warnings and evacuation orders through TV, radio and mobile alerts.
• Awareness: Educating the public on safety measures and mobilising relief donations.
• Accountability: Reporting ground realities, tracking relief delivery, and highlighting government or agency lapses; must avoid sensationalism and misinformation.