10.6 Natural Hazards, Disasters & Mitigation Strategies
Key Takeaways
- A hazard is a potentially damaging event, a disaster is the realised event that overwhelms local coping capacity, and disaster risk is conventionally modelled as hazard multiplied by vulnerability and divided by capacity.
- The Disaster Management Act, 2005 created a three-tier institutional structure — the National Disaster Management Authority chaired by the Prime Minister, State Authorities chaired by Chief Ministers, and District Authorities chaired by the District Magistrate or Collector.
- The disaster management cycle runs pre-disaster (prevention, mitigation, preparedness), through response, to post-disaster recovery, rehabilitation and reconstruction; within it, structural mitigation modifies the physical environment through engineering while non-structural mitigation uses law, land-use zoning, insurance, early warning and education without construction.
- India's hazard profile is severe: 58.6 per cent of the landmass is prone to earthquakes of moderate to very high intensity, about 12 per cent is flood-prone, close to 5,700 kilometres of the 7,516-kilometre coastline is exposed to cyclones and tsunamis, and around 68 per cent of the cultivable area is drought-vulnerable.
- The Sendai Framework for Disaster Risk Reduction 2015–2030, adopted in March 2015, succeeded the Hyogo Framework for Action and sets four priorities for action and seven global targets.
Natural Hazards, Disasters & Mitigation Strategies
Quick Answer: Unit 9 lists "Natural hazards and disasters: Mitigation strategies" as its own bullet. The vocabulary is examined precisely: a hazard is a potential damaging event; a disaster is the realised event that exceeds local coping capacity; vulnerability is susceptibility to harm; capacity is the resources available to resist it. Risk is modelled as Risk = (Hazard × Vulnerability) ÷ Capacity. India's statutory architecture is the Disaster Management Act, 2005, and the international framework is the Sendai Framework 2015–2030.
1. Core Vocabulary
| Term | Definition | Worked Illustration |
|---|---|---|
| Hazard | A potentially damaging physical event, phenomenon or human activity | An earthquake of magnitude 7.0 |
| Exposure | People, assets and systems located in hazard-prone areas | A city of two million situated on the fault |
| Vulnerability | Characteristics that make exposed elements susceptible to damage | Unreinforced masonry housing, no building-code enforcement |
| Capacity | Resources, skills and institutions available to cope and recover | Trained response force, hospital surge capacity, insurance penetration |
| Disaster | A hazard event whose impact overwhelms local coping capacity | The earthquake causing mass casualties and requiring external assistance |
| Risk | Expected loss, a function of the four above | Modelled as Risk = (Hazard × Vulnerability) ÷ Capacity |
[!WARNING] The highest-frequency conceptual item. A hazard does not become a disaster merely by occurring. An earthquake of identical magnitude in an uninhabited desert is a hazard event, not a disaster; in a densely populated city with poor construction it is a disaster. The disaster is produced by the intersection of hazard with vulnerability and exposure — which is why disaster risk reduction targets vulnerability, the only variable a state can actually control.
2. Classification of Disasters
Natural disasters are conventionally grouped by originating process:
- Geophysical / Geological: earthquakes, tsunamis, volcanic eruptions, landslides, avalanches.
- Hydrological: floods, flash floods, river erosion, glacial lake outburst floods.
- Meteorological: tropical cyclones, storms, cloudbursts, lightning, hailstorms.
- Climatological: droughts, heat waves, cold waves, forest fires.
- Biological: epidemics, pandemics, pest and locust infestations.
Human-induced (anthropogenic) disasters include industrial and chemical accidents, nuclear and radiological emergencies, building collapses, transport accidents, oil spills, dam failures, and conflict-related emergencies.
[!NOTE] Many events are hybrid. A landslide is geological in mechanism but is frequently triggered by deforestation, slope cutting for roads and unregulated construction, all anthropogenic. Urban flooding similarly arises where a meteorological hazard meets encroached drainage and paved catchments. The syllabus links this directly to the anthropogenic-impact bullet treated in Section 10.2.
3. The Disaster Management Cycle
PRE-DISASTER DISASTER POST-DISASTER
------------------ ---------- -------------------------
1. Prevention → 4. Response → 5. Recovery
2. Mitigation (rescue, 6. Rehabilitation
3. Preparedness relief, 7. Reconstruction
evacuation) ↓
feeds back into
Prevention & Mitigation
- Prevention — eliminating the hazard or the exposure entirely, for example prohibiting settlement in a floodway.
- Mitigation — reducing the severity of impact when the hazard cannot be prevented.
- Preparedness — planning, stockpiling, drills, early warning, and capacity building before the event.
- Response — search and rescue, evacuation, emergency relief, medical care in the immediate aftermath.
- Recovery, rehabilitation and reconstruction — restoring services, livelihoods and infrastructure, ideally to a "Build Back Better" standard that reduces vulnerability to the next event rather than reproducing the original exposure.
The defining shift in modern policy is from a relief-centric to a prevention-and-mitigation-centric paradigm — the explicit premise of the 2005 Act.
4. Structural and Non-Structural Mitigation
This distinction is examined more often than any other item in the bullet.
| Structural Mitigation | Non-Structural Mitigation | |
|---|---|---|
| Nature | Physical construction and engineering intervention | Policy, law, knowledge and financial instruments |
| Examples | Seismic retrofitting of buildings; base isolation; flood embankments and levees; check dams; cyclone shelters; sea walls; slope stabilisation and retaining walls; afforestation and mangrove belts | Land-use zoning and floodplain regulation; building codes and their enforcement; hazard mapping and micro-zonation; early warning systems; disaster insurance; public awareness and school education; evacuation planning and mock drills; legal and institutional reform |
| Cost profile | High capital cost, ongoing maintenance | Comparatively low cost, high governance demand |
| Failure mode | Catastrophic if the design threshold is exceeded; can induce complacency and increase floodplain settlement | Ineffective where enforcement capacity or public compliance is weak |
[!NOTE] The levee effect. Structural works can increase long-run risk by encouraging settlement behind them, so that when the design threshold is eventually exceeded the loss is greater than it would have been without the structure. This is the standard argument for pairing every structural measure with non-structural land-use control.
5. India's Statutory Architecture
The Disaster Management Act, 2005 established a three-tier structure:
- National Disaster Management Authority (NDMA) — chaired by the Prime Minister; lays down policies, plans and guidelines and approves the National Plan.
- National Executive Committee (NEC) — chaired by the Union Home Secretary; the implementing and coordinating arm.
- State Disaster Management Authority (SDMA) — chaired by the Chief Minister of the state.
- District Disaster Management Authority (DDMA) — chaired by the District Magistrate or Collector; the operational planning unit.
- National Institute of Disaster Management (NIDM) — training, research, documentation and capacity building.
- National Disaster Response Force (NDRF) — a specialist multi-disciplinary force for threatening or actual disaster situations.
The Act also provides for the National Disaster Response Fund and National Disaster Mitigation Fund, with corresponding state and district funds. Administratively, disaster management sits with the Ministry of Home Affairs, other than drought, which is handled by the Ministry of Agriculture.
6. India's Hazard Profile and Zoning
The figures published by the NDMA are directly examinable:
- 58.6 per cent of the landmass is prone to earthquakes of moderate to very high intensity (the National Policy on Disaster Management figure; many secondary sources round this to 59 per cent).
- Over 40 million hectares, roughly 12 per cent of the land area, is prone to floods and river erosion.
- Of a coastline of 7,516 kilometres, close to 5,700 kilometres is exposed to cyclones and tsunamis.
- About 68 per cent of the cultivable area is vulnerable to drought.
- Hilly regions face landslides and avalanches, and the Himalayan belt carries additional glacial-lake outburst risk.
Seismic zonation. India is divided into four seismic zones — II, III, IV and V — under the Bureau of Indian Standards code IS 1893. Zone V carries the highest expected intensity and covers areas including the north-eastern states, parts of Jammu and Kashmir and Himachal Pradesh, Uttarakhand, the Rann of Kachchh and the Andaman and Nicobar Islands. Zones I and II were merged, so Zone I no longer exists — a frequently tested detail.
Early warning agencies: the India Meteorological Department for cyclones, heavy rainfall and heat waves; the Indian National Centre for Ocean Information Services (INCOIS) for tsunami warning; the Central Water Commission for flood forecasting; the Geological Survey of India as nodal agency for landslides; and the Snow and Avalanche Study Establishment for avalanches.
7. The International Framework
| Instrument | Period | Content |
|---|---|---|
| International Decade for Natural Disaster Reduction | 1990–1999 | The United Nations decade that established disaster reduction as a distinct policy field |
| Yokohama Strategy | 1994 | First global blueprint for disaster prevention, preparedness and mitigation |
| Hyogo Framework for Action | 2005–2015 | Five priorities for action; adopted after the 2004 Indian Ocean tsunami |
| Sendai Framework for Disaster Risk Reduction | 2015–2030 | Adopted at Sendai, Japan in March 2015; successor to Hyogo; four priorities for action and seven global targets |
The four Sendai priorities: (1) understanding disaster risk; (2) strengthening disaster risk governance to manage disaster risk; (3) investing in disaster risk reduction for resilience; (4) enhancing disaster preparedness for effective response and to "Build Back Better" in recovery, rehabilitation and reconstruction.
Sendai is one of the three 2015 global agreements, alongside the Sustainable Development Goals (Section 10.1) and the Paris Agreement (Section 10.5); the three are designed to be mutually reinforcing, since climate change alters the frequency and intensity of the hydro-meteorological hazards that Sendai governs. India additionally articulated a ten-point agenda on disaster risk reduction at the Asian Ministerial Conference held in New Delhi in 2016, opening with the principle that all development sectors must imbibe disaster-resilience principles.
An earthquake of magnitude 7.0 occurs beneath an uninhabited desert, causing no casualties or property loss. How should this event be classified in disaster management terminology?
A state government responds to recurrent flooding by enacting floodplain zoning regulations, mandating hazard disclosure in property transactions, and funding a school-based awareness programme. These measures are best classified as which form of mitigation?
Under the Disaster Management Act, 2005, who chairs the National Disaster Management Authority and who chairs the District Disaster Management Authority respectively?
Which statement about India's seismic zoning under the Bureau of Indian Standards code is correct?