GS1 – Geography
Context
In 2023–24, India’s coastline was officially revised, increasing from 7,516.6 km to 11,098.81 km, a 47.7% rise.
The number of islands also rose to 1,389 — comprising 1,298 offshore islands and 91 inshore islands.
Who Conducted the Revision?
- Survey of India (Ministry of Science & Technology)
- National Hydrographic Office (Ministry of Defence)
- Coordinated by the National Maritime Security Coordinator (Ministry of Home Affairs)
This updated coastline will now be reviewed every 10 years using modern geospatial technologies.
Reasons for the Increase
- Improved Mapping Resolution:
- Adoption of 1:250,000 scale allowed for finer identification of coastal features like creeks and inlets.
- GIS-Based Techniques:
- Geospatial systems helped in tracing the actual coastline, avoiding generalisations.
- Inclusion of Previously Unmapped Islands:
- Offshore islands and coastal rock formations, earlier omitted, are now accounted for.
- Updated Tidal Boundaries:
- Measurements based on High Water Line (HWL) using updated 2011 NHO tidal data.
- Use of Advanced Tools:
- Drones, satellite altimetry, and remote sensing improved accuracy of shoreline mapping.
- New Measurement Method:
- Replaced the earlier straight-line method with contour-following techniques for precision.
Coastline Paradox
- The Coastline Paradox explains why a coastline’s length increases with finer measurement scale.
- Fractal Geometry: Coastlines exhibit repeating irregular patterns at all scales.
- Scale Dependency: More detailed measurement tools capture additional inlets, increasing total length.
- Not Unique to Coasts: Also applies to rivers, mountains, and other irregular natural boundaries.
Key Findings
Top Rankings (Coastline Length)
- States:
- 1st: Gujarat (2,340.62 km)
- 2nd: Tamil Nadu (surpassing Andhra Pradesh)
- UTs:
- 1st: Andaman & Nicobar Islands (3,083.50 km)
- 2nd: Lakshadweep (144.80 km)
Summary: Combined Rankings (States + UTs)
| Category | Highest | Second Highest | Lowest |
| Coastline Length | Andaman & Nicobar | Gujarat | Puducherry |
| Coastline Increase (km) | Gujarat | Andaman & Nicobar | Puducherry |
| Coastline Increase (%) | West Bengal | Goa | Puducherry |
| Offshore Islands | Andaman & Nicobar | Gujarat | — |
| Inshore Islands | Gujarat | Maharashtra | — |