Natural Hazards and Disasters in India

Introduction

India is among the world's most disaster-prone countries — 59% of its landmass is earthquake-prone, 12% flood-prone, 68% of its coastline is cyclone-prone, and nearly 70% of cultivated land faces drought risk.

Natural Hazard vs Disaster

India's disaster vulnerability is high because of:

1. High population density in hazard-prone zones (coastal, river flood plains, Himalayan foothills).
2. Poverty → low adaptive capacity in affected communities.
3. Rapid urbanisation on unsuitable land (flood plains, steep slopes).
4. Climate change increasing frequency and intensity of extreme events.

---

1. Cyclones

Nature and Formation

A tropical cyclone is an intense low-pressure system over warm tropical oceans (SST ≥ 26.5°C) with circular wind rotation:

• Northern Hemisphere: Anti-clockwise (Coriolis force).
• Southern Hemisphere: Clockwise.
• Wind speed classification (IMD): Cyclone ≥ 63 km/h; Severe ≥ 89 km/h; Very Severe ≥ 102 km/h; Super Cyclonic Storm ≥ 221 km/h.

Bay of Bengal vs Arabian Sea Cyclones

Why Bay of Bengal cyclones are more frequent:

• Bay of Bengal is relatively enclosed → no cold water upwelling → SST remains high.
• Large freshwater input from major rivers → low salinity layer reduces mixing → sustains warm SST.

Major Cyclone-Prone Coasts

• Eastern coast (highly vulnerable): Odisha coast, Andhra Pradesh coast, West Bengal coast.
• Western coast (less frequent but intensifying): Gujarat, Maharashtra, Arabian Sea.

Major Recent Cyclones

Trend: Arabian Sea cyclones are intensifying faster and lasting longer — linked to positive Indian Ocean Dipole and rising sea surface temperatures (SST rose 1.2°C in north Arabian Sea, 2000–2024).

Cyclone Warning System (India)

• IMD issues Cyclone Watch (96 hrs), Cyclone Alert (48 hrs), Cyclone Warning (24 hrs), Post-Landfall Outlook.
• INCOIS (Indian National Centre for Ocean Information Services) — wave and storm surge modelling.
• NDRF (National Disaster Response Force) — pre-positioned for evacuation.
• Early warning success: Odisha model — mass evacuation of 1.2 million before Cyclone Fani (2019) → only 64 deaths vs 10,000+ in 1999 Odisha Super Cyclone.

---

2. Earthquakes

Seismicity of India

India is highly seismic because:

1. Ongoing Himalayan collision — Indian Plate still pushing northward at ~5 cm/year.
2. Old fault lines in Peninsular India — reactivated by neotectonic stress.
3. Induced seismicity — reservoir-triggered earthquakes (e.g., Koyna, Maharashtra).

Seismic Zones of India (IS 1893:2016)

India is divided into 4 seismic zones (Zone II to Zone V):

Note: India no longer uses Zone I. Zones II to V are current.

Zone V facts:

• Entire NE India (due to subduction at Burmese plate boundary + Himalayan collision).
• Entire Andaman & Nicobar Islands (active subduction zone — 2004 tsunami epicentre nearby).
• Rann of Kutch (2001 Bhuj earthquake occurred here).
• North Bihar (Himalayan frontal thrust zone).

Major Historical Earthquakes

Earthquake Risk Reduction

• Bureau of Indian Standards IS 1893 — seismic design codes.
• National Building Code mandates seismic resistance.
• Early Warning: Under development — NDMA has installed seismograph networks; real-time alert system piloted in Delhi.

---

3. Floods

Types of Floods in India

Flood-Prone Rivers

• Brahmaputra — carries the highest sediment load; regular flooding in Assam; flash floods from Meghalaya tributaries.
• Kosi (Bihar) — "Sorrow of Bihar"; shifts its course frequently (avulsions); devastating floods in North Bihar.
• Damodar (West Bengal) — historically called "Sorrow of Bengal"; controlled by DVC dams.
• Godavari — peninsular floods; Polavaram dam area.

Flood-prone states (by frequency): Assam, Bihar, UP, West Bengal, Odisha.

Recent Major Floods

GLOF Risk (Critical UPSC Topic)

• Glacial Lake Outburst Floods: When ice-dammed or moraine-dammed glacial lakes breach suddenly.
• India has ~4,000+ glacial lakes in the Himalayas (Space Applications Centre estimate).
• High-risk state: Sikkim (South Lhonak Lake, GLOF 2023 — one of India's worst).
• Uttarakhand — repeated events: Chorabari (2013), Rishiganga (2021).
• Climate change is expanding glacial lakes as glaciers retreat → increasing GLOF frequency.
• NDMA has issued GLOF-specific guidelines; SAC/ISRO monitors 200+ high-risk lakes via satellite.

---

4. Droughts

Types of Droughts

Drought-Prone Regions

• Highly drought-prone: Rajasthan, Gujarat (western), Maharashtra (Marathwada, Vidarbha), Karnataka (northern), Andhra Pradesh (Rayalaseema), Tamil Nadu (interior).
• Criterion: Districts with rainfall <750 mm and significant rainfall variability.
• ~33% of India's land area classified as drought-prone (33 cm isohyet to 75 cm isohyet zone).

UPSC PYQ: Rainfall-Drought Link

The 'drought-prone area' is typically defined as areas receiving < 750 mm annual rainfall AND with high coefficient of variation in annual rainfall (>30%). — Drought-prone area is NOT simply dry area; it's the combination of low AND variable rainfall.

Drought Management

• National Drought Management Policy (NDMP, 2016) — shift from reactive relief to proactive risk reduction.
• IMD — early warning through Standardized Precipitation Index (SPI) and ENSO forecasting.
• Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) — micro-irrigation, "Har Khet Ko Pani."
• Atal Bhujal Yojana — groundwater management in drought-prone states.

---

5. Landslides

Why India is Vulnerable

India has one of the world's highest rates of landslide occurrence, primarily because:

• Steep, fragile Himalayan slopes (geologically young and unstable).
• High rainfall (orographic) on unstable slopes.
• Earthquakes triggering slope failures.
• Deforestation, road construction, and unplanned development on hill slopes.

Landslide-Prone Zones

Most landslide-prone state: Mizoram (77% of land area) — steep terrain + high rainfall.

Recent Major Landslides

Wayanad 2024 context: Twin landslides at Mundakkai and Chooralmala (July 30, 2024) — two consecutive landslides struck within 2 hours of each other; 400+ deaths, 200+ missing; attributed to intense rainfall from a low-pressure system over Bay of Bengal.

Landslide Early Warning

• NRSC (National Remote Sensing Centre) — satellite-based monitoring.
• GSI (Geological Survey of India) — national landslide susceptibility map.
• NDMA guidelines include land-use zoning for landslide-prone areas.

---

6. Tsunamis

Mechanism

A tsunami is a series of ocean waves generated by a sudden displacement of the ocean floor — primarily by:

• Submarine earthquakes (most common in India's context).
• Submarine landslides.
• Volcanic eruptions (rare in Indian context).

India's Tsunami Vulnerability

• Andaman & Nicobar Islands — highest risk; located on an active subduction zone (Burma Plate subducting under Indian Plate).
• Eastern coast — Tamil Nadu, Andhra Pradesh, Odisha have low-lying coastal plains vulnerable to tsunami inundation.
• Western coast — lower risk but not immune (scenario studies show Arabian Sea tsunami from Makran subduction zone could affect Gujarat/Maharashtra coast in <2 hours).

2004 Indian Ocean Tsunami (UPSC Important)

Consequence: India established the Indian Tsunami Early Warning Centre (ITEWC) at INCOIS, Hyderabad — now provides 7–20 minute warning for coastal India.

Indian Tsunami Early Warning System

• ITEWC (INCOIS, Hyderabad) — 24/7 monitoring since 2007.
• Bottom Pressure Recorders (BPR) — 12 sensors in the Indian Ocean detect tsunami waves.
• Warning chain: INCOIS → Coastal District Collectors → Sirens and SMS alerts.
• Works together with Pacific Tsunami Warning Center (PTWC) and Japan Meteorological Agency.

---

7. Cold Waves and Heat Waves

Cold Waves

• Definition (IMD): Temperature ≤ 4.5°C in plains; temperature ≤ 10°C with departure of ≥ 4.5°C from normal.
• Season: December–February, occasionally March.
• Most affected: Punjab, Haryana, Delhi, UP, Bihar, Rajasthan.
• Cause: Surge of cold polar/continental air from Siberian High down through Pakistan → NW India.
• Intensified by Western Disturbance absence — clear nights radiate heat rapidly.
• Mortality: Cold waves kill 1,500–2,000 people annually in India (mainly poor, homeless, outdoor workers).

Heat Waves

• Definition (IMD): Temperature ≥ 40°C in plains and ≥ 4.5°C above normal.
• Season: March–June (peak: April–May).
• Most affected: Rajasthan, UP, MP, Bihar, Jharkhand, Telangana, Andhra Pradesh.
• Climate change link: Heat wave frequency has increased — 15.4 heat wave days/year (2010–2020) vs 4.9 days/year (1981–1990).

Notable heat waves:

2024 heat wave: Delhi recorded 52.9°C at Mungeshpur (May 29, 2024) — highest ever recorded in Delhi (though under review for sensor error; Safdarjung reference station recorded 44.9°C).

---

8. Disaster Management Framework in India

Key Legislation: Disaster Management Act, 2005

Enacted after the 2004 Indian Ocean Tsunami — India's first comprehensive DM legislation.

Established the three-tier structure:

NDMA (National Disaster Management Authority)

• Established: 2005; headquartered in New Delhi.
• Chairman: Prime Minister of India (ex-officio).
• Functions: Approve national plans, set minimum standards of relief, coordination with states, promote R&D in DRR.
• National Disaster Response Fund (NDRF) — under Finance Ministry; state-level SDRF.

NDRF (National Disaster Response Force)

• India's dedicated disaster response force — 16 battalions (as of 2024).
• Drawn from paramilitary (BSF, CRPF, ITBP, CISF, SSB).
• Specialised in search & rescue (USAR — Urban Search And Rescue), flood rescue, mountain rescue.
• Pre-positioned before major cyclones/floods.

Sendai Framework (2015–2030)

India is signatory to the Sendai Framework for Disaster Risk Reduction — global framework with 4 priorities:

1. Understanding disaster risk.
2. Strengthening disaster risk governance.
3. Investing in disaster risk reduction.
4. Enhancing disaster preparedness for effective response.

India's target: Reduce disaster mortality, affected population, economic losses, and infrastructure damage by 2030.

NDMP (National Disaster Management Plan, 2016)

• India's first national DM plan after 2005 Act.
• Aligned with Sendai Framework.
• Covers all 4 phases: Mitigation → Preparedness → Response → Recovery.

---

Disaster Vulnerability Map Summary

---

UPSC Corner

High-Frequency Prelims Topics

• Seismic Zone V states: NE India (all states), J&K, Uttarakhand foothills, N Bihar, Rann of Kutch.
• 2004 Tsunami epicentre: Sunda Trench (off Sumatra) — 9.1 Mw earthquake — December 26, 2004.
• NDRF: 16 battalions; Chairman NDMA = Prime Minister of India.
• Bay of Bengal cyclones: ~80% of all Indian cyclones; peak season Oct–Dec.
• ITEWC: Indian Tsunami Early Warning Centre — INCOIS, Hyderabad (not Delhi).
• "Kosi" = Sorrow of Bihar; "Damodar" = Sorrow of Bengal.
• Wayanad 2024: Deadliest landslide in India in recent decades.
• Sendai Framework: 2015–2030 (not 2005; that's the DM Act).

UPSC Mains GS3 Angles

1. "Examine why the Himalayan region is becoming more prone to compound disasters (GLOF + flash floods + landslides)." [Use Sikkim 2023, Wayanad 2024]
2. "Critically evaluate India's disaster preparedness using the Odisha cyclone model vs the Bihar flood model."
3. "The Disaster Management Act 2005 has transformed India's approach from reactive relief to proactive risk reduction. Discuss."
4. "Urban India is increasingly vulnerable to floods. Explain the reasons and suggest solutions." [Chennai 2015, Bengaluru 2022]
5. "Climate change is converting hazards into disasters at an unprecedented rate. Discuss with reference to Indian examples."

GS1 Geography Angles

1. "Why is India's northeastern region seismically most active? Explain the tectonic factors."
2. "Bay of Bengal cyclones are more frequent than Arabian Sea cyclones. Explain the reasons."
3. "Discuss the factors responsible for the high vulnerability of Himalayan rivers to flash floods."

MCQ Trap Awareness

• Trap: "Zone I is the least seismic zone" → Zone I was discontinued; Zone II is now the lowest.
• Trap: "All of J&K is in Zone V" → Incorrect; J&K has areas in Zone IV and V; not entire state in V.
• Trap: "NDMA Chairman is Home Minister" → Incorrect; Chairman = Prime Minister.
• Trap: "Arabian Sea cyclones are more frequent" → Incorrect; Bay of Bengal has ~80% frequency.
• Trap: "2004 Tsunami epicentre was in the Indian Ocean" → More precisely: Sunda Trench, off northern Sumatra.

---

Current Affairs 2023–2026

---

Key Facts at a Glance

• Seismic zones: II to V (Zone I discontinued)
• Zone V states: NE India, J&K/Ladakh (parts), Uttarakhand foothills, N Bihar, Rann of Kutch, Andaman & Nicobar
• Cyclone season: Pre-monsoon (Apr–Jun) and Post-monsoon (Oct–Dec)
• Bay of Bengal cyclones: ~80% of all Indian cyclones
• 2004 Tsunami: 9.1–9.3 Mw; 16,000 deaths in India
• ITEWC: INCOIS, Hyderabad (established 2007)
• NDMA Chairman: Prime Minister of India
• NDRF: 16 battalions
• Sendai Framework: 2015–2030
• DM Act: 2005
• "Sorrow of Bihar": Kosi River
• "Sorrow of Bengal": Damodar River
• Worst recent landslide: Wayanad, Kerala (July 2024) — 400+ deaths