Expanded Coastline of India

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

1. Improved Mapping Resolution:
   • Adoption of 1:250,000 scale allowed for finer identification of coastal features like creeks and inlets.
2. GIS-Based Techniques:
   • Geospatial systems helped in tracing the actual coastline, avoiding generalisations.
3. Inclusion of Previously Unmapped Islands:
   • Offshore islands and coastal rock formations, earlier omitted, are now accounted for.
4. Updated Tidal Boundaries:
   • Measurements based on High Water Line (HWL) using updated 2011 NHO tidal data.
5. Use of Advanced Tools:
   • Drones, satellite altimetry, and remote sensing improved accuracy of shoreline mapping.
6. 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	—