BharatNotes Tsunamis — Understanding the Mechanism
A tsunami (Japanese: "harbour wave") is a series of ocean waves generated by large-scale disturbances of the ocean floor. Unlike wind-driven waves that affect only the surface, tsunamis involve the entire water column from surface to seabed, giving them immense energy.
How Tsunamis Are Generated
| Cause | Mechanism |
|---|---|
| Earthquakes | Vertical displacement of the ocean floor along subduction-zone faults — accounts for over 80% of all tsunamis |
| Submarine landslides | Underwater mass movement triggers displacement of water column |
| Volcanic eruptions | Caldera collapse or pyroclastic flows entering ocean (e.g., Krakatoa 1883, Hunga Tonga 2022) |
| Meteorite impact | Extremely rare; theoretical models suggest catastrophic wave generation |
Characteristics of Tsunami Waves
| Feature | Open Ocean | Near Coast |
|---|---|---|
| Wave height | 0.3 to 1 metre (barely noticeable) | Can exceed 10-30 metres |
| Wavelength | 100 to 200 km | Compressed as depth decreases |
| Speed | 600 to 900 km/h (jet aircraft speed) | Slows to 30-50 km/h |
| Period | 10 to 60 minutes between waves | Multiple waves over hours |
For Prelims: Tsunami speed in open ocean follows the formula v = square root of (g x d), where g is gravitational acceleration and d is ocean depth. This is why tsunamis travel faster in deeper water.
Tsunami vs. Storm Surge — Key Differences
| Parameter | Tsunami | Storm Surge |
|---|---|---|
| Cause | Seismic or volcanic event | Cyclone/hurricane wind and pressure |
| Warning time | Minutes to hours depending on distance | Hours to days (weather forecasting) |
| Duration | Multiple waves over several hours | Sustained flooding for 6-12 hours |
| Inland penetration | Can travel kilometres inland | Usually limited to low-lying coastal strip |
| Recurrence | Episodic, unpredictable | Seasonal, linked to cyclone season |
The 2004 Indian Ocean Tsunami — A Turning Point
The Event
On 26 December 2004, a magnitude 9.1 undersea earthquake struck off the west coast of northern Sumatra, Indonesia. It was the third-largest earthquake ever recorded on a seismograph and the largest in the Indian Ocean region.
| Parameter | Detail |
|---|---|
| Magnitude | 9.1 on the Richter scale |
| Epicentre | Off the west coast of Sumatra, Indonesia (3.316 degrees N, 95.854 degrees E) |
| Depth | Approximately 30 km below the ocean floor |
| Rupture length | About 1,300 km along the Sunda megathrust fault |
| Energy released | Equivalent to 23,000 Hiroshima-type atomic bombs |
| Countries affected | 14 countries across the Indian Ocean rim |
Death Toll and Devastation
| Country | Deaths (approximate) |
|---|---|
| Indonesia | 167,000+ |
| Sri Lanka | 35,000+ |
| India | 10,749 confirmed; 5,640 missing |
| Thailand | 8,200+ |
| Maldives | 82 |
| Total (all countries) | Approximately 228,000 |
Impact on India
| Region | Impact |
|---|---|
| Tamil Nadu | Nearly 7,000 deaths — Nagapattinam district worst hit with over 6,000 deaths |
| Andaman and Nicobar Islands | 1,310 confirmed dead, approximately 5,600 missing; waves up to 15 metres in southern Nicobar Islands |
| Andhra Pradesh | Over 100 deaths along the coast |
| Kerala | Approximately 170 deaths |
| Pondicherry | Over 100 deaths |
For Mains: The 2004 tsunami exposed a critical gap — the Indian Ocean had no tsunami warning system, unlike the Pacific. India lost over 10,000 lives partly because there was no mechanism to translate the earthquake detection (which happened within minutes) into a public warning. This institutional failure became the catalyst for building the ITEWS.
Lessons Learned
- No early warning system existed — The Pacific Tsunami Warning Centre detected the earthquake but had no protocol to warn Indian Ocean nations
- Coastal communities lacked awareness — Many victims ran toward receding waters out of curiosity rather than fleeing inland
- Indigenous knowledge saved lives — The Onge and Jarawa tribes of Andaman Islands survived by moving to higher ground based on traditional knowledge of sea behaviour
- Mangroves provided protection — Coastal areas with intact mangroves (e.g., Pichavaram in Tamil Nadu) suffered significantly fewer casualties
- Need for multi-hazard approach — Tsunami preparedness cannot be separated from cyclone and coastal flood preparedness
Indian Tsunami Early Warning System (ITEWS)
Establishment and Mandate
The Government of India established the Indian Tsunami Early Warning System (ITEWS) in 2007, operated by the Indian National Centre for Ocean Information Services (INCOIS) in Hyderabad, under the Ministry of Earth Sciences (MoES).
| Feature | Detail |
|---|---|
| Established | October 2007 (operational) |
| Nodal agency | INCOIS, Hyderabad |
| Ministry | Ministry of Earth Sciences (MoES) |
| Coverage | Entire Indian Ocean region |
| International role | Designated as a Tsunami Service Provider (TSP) by IOC-UNESCO for the Indian Ocean |
| Alert generation time | Less than 10 minutes after a major earthquake |
Sensor Network
| Component | Details |
|---|---|
| Seismic stations | 17 broadband seismic stations transmitting real-time data via V-SAT to CRSs at IMD New Delhi and INCOIS Hyderabad |
| Bottom Pressure Recorders (BPRs) | 4 deep-ocean BPRs deployed in the Indian Ocean to detect tsunami waves in the open ocean |
| Tide gauges | 50 real-time tide gauge stations along the Indian coastline and island territories |
| DART buoys | Deep-ocean Assessment and Reporting of Tsunamis buoys for real-time sea-level monitoring |
| Coastal radar stations | Radar-based coastal monitoring stations to track wave approach and storm surges |
| Satellite communication | INSAT-based communication for rapid data transmission and warning dissemination |
How the Warning System Works
- Earthquake detection — Seismic network detects earthquake within minutes; events above magnitude 6 in the Indian Ocean trigger analysis
- Tsunamigenic assessment — Automated algorithms assess whether the earthquake has tsunami-generating potential based on magnitude, depth, and location
- Ocean monitoring — BPRs and tide gauges confirm whether a tsunami has been generated and its characteristics
- Bulletin generation — INCOIS issues bulletins to national and international agencies within 10 minutes
- Warning dissemination — Alerts sent to NDMA, SDMAs, coastal district administrations, and media via multiple channels (SMS, fax, email, GTS)
- All-clear — System continues monitoring until the threat has passed; issues cancellation bulletin
For Prelims: INCOIS is headquartered in Hyderabad and is a Tsunami Service Provider (TSP) for the Indian Ocean, designated by IOC-UNESCO. It can detect any earthquake above magnitude 6 in the Indian Ocean in less than 12 minutes of occurrence.
International Cooperation — IOC-UNESCO Framework
| Initiative | Detail |
|---|---|
| IOTWMS | Indian Ocean Tsunami Warning and Mitigation System — established in 2005 under IOC-UNESCO after the 2004 tsunami |
| TSP system | Three Tsunami Service Providers: India (INCOIS), Australia (JATWC), Indonesia (BMKG) |
| IOWave exercises | Regular Indian Ocean-wide tsunami warning exercises (IOWave16, IOWave18, IOWave20, IOWave23) |
| UNESCO Tsunami Ready | Community-based preparedness programme recognising tsunami-ready communities |
| ICG/IOTWMS | Intergovernmental Coordination Group meets biennially to review warning protocols |
Coastal Vulnerability in India
India's Coastal Profile
| Parameter | Detail |
|---|---|
| Total coastline | 7,516 km (5,422 km mainland + 2,094 km island territories) |
| Coastal states and UTs | 9 states and 4 union territories |
| Coastal districts | Over 70 districts |
| Population in Low Elevation Coastal Zone | Over 170 million people live within 50 km of the coast |
| Percentage of GDP | Coastal economy contributes approximately 14% of India's GDP |
| Fishing communities | Over 4 million fisherfolk and their families directly dependent on the coast |
Note: Recent re-measurement using advanced geospatial technologies has revised India's total coastline to approximately 11,099 km — nearly 50% more than the earlier estimate of 7,516 km. The revision reflects more precise measurement of inlets, creeks, and indentations rather than any physical change.
Coastal Hazards
| Hazard | Description | Vulnerable Areas |
|---|---|---|
| Cyclones | Bay of Bengal generates over 80% of India's cyclones; east coast more vulnerable | Odisha, Andhra Pradesh, Tamil Nadu, West Bengal |
| Storm surge | Wind-driven rise in sea level during cyclones; can exceed 5 metres | Sundarbans, Odisha coast, Krishna-Godavari delta |
| Tsunamis | Subduction zones in Indian Ocean, particularly Andaman-Nicobar trench | Andaman and Nicobar Islands, Tamil Nadu, Andhra Pradesh, Kerala |
| Coastal erosion | Over 33% of India's coastline is affected by erosion | Kerala (67% eroding), West Bengal, Puducherry |
| Sea-level rise | 1.3 mm/year average rise along Indian coast (IPCC estimates) | Low-lying deltas, Mumbai, Kolkata, Chennai |
| Flooding | Combination of high tide, heavy rainfall, and storm surge in coastal cities | Mumbai, Chennai, Kolkata |
| Salinisation | Saltwater intrusion into freshwater aquifers and agricultural land | Gujarat coast, Sundarbans, Krishna delta |
Storm Surge — Major Events
| Cyclone | Year | Storm Surge | Key Impact |
|---|---|---|---|
| Odisha Super Cyclone | 1999 | 7-9 metres | Over 10,000 deaths; devastated Jagatsinghpur and surrounding districts |
| Cyclone Nargis (Myanmar) | 2008 | 3.6 metres | 138,000+ deaths — showed catastrophic potential of surge in deltaic areas |
| Cyclone Fani | 2019 | 1.5 metres | 89 deaths in India; 155 mph winds — strongest pre-monsoon cyclone in Bay of Bengal since 1991; Odisha's early warning and evacuation of 1.2 million people minimised casualties |
| Cyclone Amphan | 2020 | 5 metres | 103 deaths in India; over USD 14 billion damage — costliest North Indian Ocean cyclone at the time; 15-foot surge at Digha, West Bengal |
| Cyclone Yaas | 2021 | 2-4 metres | Severe flooding in Odisha and West Bengal coastal areas |
For Mains: Cyclone Fani (2019) is a textbook example of successful disaster risk reduction. Despite being an extremely severe cyclonic storm, Odisha's early warning system and massive evacuation of 1.2 million people limited deaths to 64 in the state — compared to over 10,000 deaths in the 1999 super cyclone. This demonstrates the value of institutional preparedness.
Coastal Erosion
Scale of the Problem
| Statistic | Detail |
|---|---|
| Eroding coastline | Approximately 33% of India's coastline is experiencing erosion |
| Worst affected | Kerala (67% of coastline eroding), West Bengal, Puducherry, Tamil Nadu |
| Accretion areas | Parts of Gujarat and Odisha coast are accreting (gaining land) |
| Annual land loss | Estimated hundreds of hectares lost annually to coastal erosion |
Causes of Coastal Erosion
| Natural Causes | Anthropogenic Causes |
|---|---|
| Wave action and longshore drift | Sand mining from rivers and beaches |
| Storm surge and cyclone damage | Construction of harbours and breakwaters disrupting sediment flow |
| Sea-level rise | Damming of rivers reducing sediment supply to coast |
| Tectonic subsidence | Destruction of mangroves and coastal vegetation |
| Natural sediment deficit | Groundwater extraction causing land subsidence |
Mitigation Measures
| Measure | Description |
|---|---|
| Hard engineering | Seawalls, groynes, breakwaters, revetments — protect specific areas but can cause erosion elsewhere |
| Soft engineering | Beach nourishment, sand dune restoration, managed retreat |
| Bioshields | Mangrove plantation, coastal shelterbelt forestry (casuarina, coconut, pandanus) |
| Regulation | CRZ notification restricting construction in erosion-prone areas |
| Shoreline management plans | Integrated plans considering entire coastal sediment cells rather than piecemeal intervention |
Mangroves and Coastal Disaster Risk Reduction
How Mangroves Reduce Disaster Impact
| Protection Function | Mechanism |
|---|---|
| Wave attenuation | Mangrove roots and dense canopy reduce wave height by 13-66% per 100 metres of mangrove width |
| Storm surge reduction | Surge height reduced by 5-50 cm per kilometre of mangrove forest |
| Coastal erosion prevention | Root systems bind sediment and trap new sediment, building up coastline |
| Wind speed reduction | Dense canopy acts as windbreak, reducing wind damage to inland areas |
| Flood buffering | Mangrove wetlands absorb and slow floodwaters from both marine and terrestrial sources |
Evidence from the 2004 Tsunami
| Location | Finding |
|---|---|
| Pichavaram, Tamil Nadu | Villages behind dense Pichavaram mangroves suffered significantly fewer casualties than adjacent unprotected villages |
| Cuddalore, Tamil Nadu | Areas protected by mangroves experienced less damage compared to exposed stretches |
| Andaman Islands | Islands with intact mangrove belts recorded lower inundation levels |
Evidence from Cyclones
| Event | Finding |
|---|---|
| 1999 Odisha Super Cyclone | A PNAS study found that villages with wider mangroves between them and the coast experienced significantly fewer deaths than those with narrow or no mangroves in Kendrapara district |
| Cyclone Bulbul (2019) | Sundarbans mangroves broke the cyclone's force, limiting damage to inland areas |
| Cyclone Amphan (2020) | Areas of Sundarbans with intact mangroves had less flooding than degraded areas |
Limitation: Large tsunamis exceeding 4 metres in depth can damage and destroy mangroves, reducing their protective function. Mangroves are most effective against moderate events and as part of a multi-layered defence system, not as standalone protection.
Mangrove Cover in India
| Statistic | Detail |
|---|---|
| Total mangrove cover | 4,992 sq km (India State of Forest Report 2023) |
| Top states | West Bengal (2,114 sq km — mostly Sundarbans), Gujarat (1,175 sq km), Andaman and Nicobar Islands (616 sq km) |
| Sundarbans | World's largest contiguous mangrove forest (shared between India and Bangladesh); approximately 10,000 sq km total, with Indian portion about 4,200 sq km |
| Trend | Mangrove cover has shown gradual increase over the last two decades due to conservation efforts |
Conservation Measures
| Measure | Detail |
|---|---|
| CRZ regulations | Mangroves classified under CRZ-I (ecologically sensitive) — no development permitted |
| Mangrove plantation drives | State-level programmes for mangrove restoration in degraded areas |
| CAMPA funds | Compensatory Afforestation Fund used for mangrove plantation |
| Community participation | Joint mangrove management with coastal fishing communities |
| International frameworks | Ramsar Convention (wetland protection), CBD, UNFCCC recognise mangrove role in coastal protection and carbon sequestration |
Coastal Regulation Zone (CRZ) Framework
Evolution of CRZ Regulations
| Notification | Key Features |
|---|---|
| CRZ 1991 | First notification under Environment Protection Act 1986; classified coast into CRZ-I to CRZ-IV; established 500m No Development Zone |
| CRZ 2011 | Revised classification; introduced concept of hazard line mapping; addressed island territories separately |
| CRZ 2019 | Current notification — reduced NDZ in densely populated areas; promoted sustainable tourism; addressed climate change adaptation |
CRZ Classification (2019 Notification)
| Zone | Description | Key Restrictions |
|---|---|---|
| CRZ-I | Ecologically sensitive areas — mangroves, coral reefs, sand dunes, turtle nesting grounds | No new construction except facilities for monitoring and navigation |
| CRZ-II | Developed urban areas within existing municipal limits | Development permitted as per approved Coastal Zone Management Plan |
| CRZ-III | Rural and undeveloped areas | CRZ-IIIA (population density above 2,161/sq km): NDZ of 50m from HTL; CRZ-IIIB (below threshold): NDZ of 200m from HTL |
| CRZ-IV | Water area from Low Tide Line to 12 nautical miles seaward | No untreated sewage, solid waste dumping; no discharge of effluents |
For Prelims: The CRZ 2019 notification reduced the No Development Zone (NDZ) in CRZ-III areas with high population density (above 2,161 persons per sq km) from 200m to 50m from the High Tide Line.
Hazard Line Mapping
The CRZ framework mandates hazard line mapping along the entire Indian coastline. The hazard line demarcates the area that is likely to be inundated due to sea-level rise and associated coastal hazards. Survey of India (SOI) has been tasked with mapping the hazard line using scientific methods.
Coastal Shelter Belts and Bioshields
Types of Coastal Protection Plantations
| Type | Description | Species Used |
|---|---|---|
| Mangrove bioshields | Dense mangrove plantations along estuaries and tidal flats | Rhizophora, Avicennia, Sonneratia, Bruguiera |
| Shelterbelt plantations | Rows of trees parallel to the coastline to reduce wind speed and wave energy | Casuarina equisetifolia, coconut palms, Pandanus, Thespesia |
| Sand dune stabilisation | Vegetation to prevent sand dune erosion and movement | Ipomoea pes-caprae, Spinifex littoreus |
NDMA Guidelines on Bioshields
NDMA recommends a robust techno-legal regime through efficient land-use practices, bioshields, shelterbelt plantation, and mangrove regeneration with community involvement. Key recommendations include:
- Maintaining and restoring coastal vegetation as first line of defence
- Multi-species, multi-row shelterbelt plantations along vulnerable stretches
- Integration of bioshields with structural measures (seawalls, embankments)
- Community-based plantation and maintenance programmes
- Scientific monitoring of bioshield health and effectiveness
Nuclear Plant Coastal Risks
Context
Several of India's nuclear power plants are located along the coastline, raising specific concerns about tsunami and coastal hazard vulnerability.
| Plant | Location | Coastal Concern |
|---|---|---|
| Kudankulam Nuclear Power Plant | Tamil Nadu coast | Post-2004 tsunami, additional safety assessments conducted; backup diesel generators elevated; seawall height increased |
| Kalpakkam (Madras Atomic Power Station) | Tamil Nadu coast | Was operational during the 2004 tsunami; seawater entered the pump house but reactor was safely shut down |
| Tarapur | Maharashtra coast | Cyclone and storm surge risk assessment updated post-Fukushima |
| Jaitapur (proposed) | Maharashtra coast | Seismic and tsunami risk assessment part of environmental clearance process |
Post-Fukushima Safety Measures
After the 2011 Fukushima disaster in Japan (triggered by a tsunami following a magnitude 9.0 earthquake), India's Atomic Energy Regulatory Board (AERB) conducted comprehensive safety reviews of all coastal nuclear installations.
| Measure | Detail |
|---|---|
| Stress tests | All coastal nuclear plants subjected to beyond-design-basis stress tests |
| Backup systems | Additional backup power systems (diesel generators, batteries) placed at elevated positions |
| Seawall upgrades | Coastal protection barriers strengthened and raised |
| Emergency protocols | Revised emergency operating procedures incorporating tsunami-specific scenarios |
| Flood protection | Waterproofing of critical safety systems and control rooms |
NDMA Guidelines on Tsunami Management
Key Components
| Area | NDMA Recommendation |
|---|---|
| Risk assessment | Scientific assessment of tsunami-prone coastal areas using probabilistic and deterministic methods |
| Early warning | Strengthening ITEWS infrastructure; ensuring last-mile connectivity for warning dissemination |
| Structural mitigation | BIS standards for tsunami-resistant construction; elevated structures in vulnerable zones |
| Land-use planning | Integration of tsunami risk into coastal zone management plans; no critical infrastructure in high-risk zones |
| Bioshields | Mangrove and shelterbelt plantation as first line of defence |
| Evacuation planning | Pre-identified evacuation routes and shelters; signage and public awareness |
| Mock drills | Regular community-level tsunami mock drills; participation in IOC-UNESCO IOWave exercises |
| Capacity building | Training of local administration, fishing communities, and tourist facilities |
Tsunami-Ready Community Programme
UNESCO's "Tsunami Ready" programme recognises communities that have achieved a minimum level of tsunami preparedness through 12 indicators covering risk assessment, standard operating procedures, community preparedness, and response capability. INCOIS is implementing this programme along India's coastline.
India's Comprehensive Coastal Disaster Management Approach
Multi-Hazard Early Warning System
India has moved toward an integrated multi-hazard approach rather than treating each coastal hazard separately.
| Component | Agency | Function |
|---|---|---|
| Cyclone warning | IMD | Cyclone track prediction, wind and rainfall warnings |
| Tsunami warning | INCOIS | Seismic monitoring, tsunami bulletin generation |
| Storm surge prediction | INCOIS + IMD | Numerical modelling of storm surge for cyclone events |
| Ocean state forecast | INCOIS | Wave height, sea state, and coastal inundation forecasts |
| Coastal flooding | CWC + INCOIS | Integrated riverine and coastal flood warnings |
Key Institutional Framework
| Institution | Role in Coastal Disaster Management |
|---|---|
| NDMA | Policy, guidelines, and coordination at national level |
| INCOIS | Tsunami early warning, ocean state forecasts |
| IMD | Cyclone tracking and warnings |
| Indian Navy and Coast Guard | Maritime search and rescue, coastal surveillance |
| NDRF | Specialised coastal disaster response teams |
| Survey of India | Hazard line mapping, coastal topographic surveys |
| National Institute of Ocean Technology (NIOT) | Coastal engineering, ocean observation systems |
| State Disaster Management Authorities | State-level plans, local coordination, evacuation management |
Recent Developments (2024–2026)
Cyclone Dana — Odisha's Zero-Casualty Response Model (October 2024)
Severe Cyclonic Storm Dana (October 2024) made landfall near Bhitarkanika, Odisha on 24–25 October 2024. Despite being a severe cyclonic storm with wind speeds of 100–110 km/h, Odisha's pre-landfall evacuation of over 7 lakh people from coastal districts resulted in minimal human casualties — validating the state's celebrated "zero-casualty" disaster model built over 25 years following the catastrophic 1999 super-cyclone.
Odisha's preparedness ecosystem includes: 879 multi-purpose cyclone and flood shelters (accommodating 8–10 lakh people); the Odisha State Disaster Management Authority (OSDMA) with 24/7 control room; ODRAF (Odisha Disaster Rapid Action Force) supplementing NDRF; and deep community-level awareness through "Cyclone Mitras" — trained local volunteers. The 25 NDRF teams (11 Odisha, 14 West Bengal) were pre-positioned before landfall based on IMD's 5-day advance forecast.
UPSC angle: Prelims — Cyclone Dana October 2024; landfall Bhitarkanika, Odisha; 7 lakh evacuated; OSDMA; Cyclone Mitras. Mains (GS3) — Odisha cyclone model as global best practice; pre-positioned infrastructure; community-institutional integration; comparison with cyclone Ockhi (2017) response failure.
Indian Tsunami Early Warning Centre — Operational Upgrades (2024)
The Indian Tsunami Early Warning Centre (ITEWC) — operated by INCOIS, Hyderabad — underwent significant upgrades in 2024. INCOIS expanded its buoy network (DART buoys — Deep-ocean Assessment and Reporting of Tsunamis) in the Indian Ocean, adding 4 new stations in collaboration with Australia and Sri Lanka. The ITEWC now provides tsunami bulletins within 10 minutes of a seismic event exceeding M7.5 in the Indian Ocean.
INCOIS also enhanced the TSUNAMI portal — a public-facing real-time monitoring platform — with improved visualisation of seismic events, wave height modelling, and inundation zone mapping for coastal India. A new "Inundation Simulation Tool" allows coastal district disaster managers to visualise tsunami wave heights specific to their coastline geography for different earthquake scenarios, enabling better evacuation planning.
UPSC angle: Prelims — ITEWC (INCOIS, Hyderabad); DART buoys; 10-minute bulletin turnaround; M7.5 threshold. Mains (GS3) — early warning as life-saving infrastructure; international cooperation in Indian Ocean tsunami monitoring; last-mile communication challenge.
Coastal Vulnerability and Mangrove Restoration — 2024 Progress
India's coastline continues to face significant erosion, sea-level rise, and storm surge risks. The National Centre for Coastal Research (NCCR) 2024 data shows that approximately 33% of India's coastline (total ~7,500 km) is experiencing erosion — highest in West Bengal (76%), Kerala (67%), and Puducherry (58%). The Coastal Regulation Zone (CRZ) Notification 2019 — which relaxed some coastal development restrictions — is under judicial review for its environmental implications.
The MISHTI (Mangrove Initiative for Shoreline Habitats & Tangible Incomes) scheme — launched in Budget 2023–24 — aims to expand mangrove cover along India's coastline through convergence between the MGNREGS and CAMPA (Compensatory Afforestation Fund). By 2025, MISHTI had planted mangroves in Odisha, West Bengal, Gujarat, and Maharashtra coastal areas. Mangrove restoration directly reduces storm surge damage — validated by data showing reduced wave energy in Bhitarkanika (Odisha) during Cyclone Dana compared to unprotected coastlines.
UPSC angle: Prelims — MISHTI scheme (Budget 2023-24); NCCR; CRZ 2019; 33% India coastline eroding. Mains (GS3) — nature-based solutions for coastal disaster risk; mangroves as green infrastructure; CRZ reform debate.
Key Terms for UPSC
| Term | Definition |
|---|---|
| Tsunami | Series of ocean waves caused by large-scale displacement of water, typically from undersea earthquakes |
| Storm surge | Abnormal rise in sea level during a cyclone, caused by wind and low atmospheric pressure |
| ITEWS | Indian Tsunami Early Warning System, operated by INCOIS Hyderabad |
| INCOIS | Indian National Centre for Ocean Information Services — nodal agency for tsunami warnings |
| CRZ | Coastal Regulation Zone — regulatory framework governing development along India's coast |
| Bioshield | Coastal vegetation belt (mangroves, casuarina) acting as natural barrier against waves and wind |
| Hazard line | Demarcation of area likely to be inundated by sea-level rise and coastal flooding |
| DART buoy | Deep-ocean Assessment and Reporting of Tsunamis — real-time sea-level monitoring system |
| Subduction zone | Where one tectonic plate dives beneath another — primary source of tsunami-generating earthquakes |
| IOC-UNESCO | Intergovernmental Oceanographic Commission — coordinates global tsunami warning systems |
Exam Strategy
Prelims Focus: Tsunami generation mechanism, ITEWS sensor network, INCOIS mandate, CRZ classification and NDZ distances, 2004 tsunami facts (magnitude, death toll), mangrove wave attenuation statistics.
Mains Connections: Link tsunami preparedness to disaster management institutional framework (GS3). Connect mangrove protection to environmental conservation (GS3). Relate CRZ regulations to coastal development vs. environmental protection debate. Use 2004 tsunami and Cyclone Fani as case studies for before-and-after institutional capacity comparison.
Essay Potential: "When the ocean speaks, are we listening?" — covering the journey from 2004 vulnerability to building one of the world's most comprehensive tsunami early warning systems.
