Revision summary
Coastal erosion is net loss of shore from waves, storms, sea-level rise and human interruption of sand. Dams, seawalls, ports, sand mining and mangrove clearance are the main human causes in India. Effects include lost villages and roads, saline intrusion, habitat loss and higher cyclone damage. Soft and nature-based methods (nourishment, dunes, mangroves) treat the sand budget; hard structures protect a point and often starve the next beach. CRZ, ICZM, sand bypassing and, where needed, managed retreat are the planning tools.
Model answer
Introduction
India’s long coastline is not a fixed line. Coastal erosion is the net loss of beach and cliff to waves, currents, storms and human structures. Some stretches accrete; many, especially after a port or a seawall, retreat. Management is a choice between hard armour, soft beaches, and moving people back.
Body
Causes
- Natural: monsoon wave climate, cyclones and storm surge, longshore drift that starves a downdrift beach, sea-level rise, and river-mouth shifts that cut sand supply.
- Sediment starvation: dams on east- and west-flowing rivers trap sand that used to feed deltas and beaches.
- Hard structures: groynes, seawalls and breakwaters on one plot rob sand from the next; unplanned ports and inlets do the same at larger scale.
- Mangrove and dune destruction for shrimp ponds, real estate and sand mining removes the buffer.
- Relative sea-level rise from warming plus local subsidence (groundwater, compaction) worsens inundation and erosion.
- Inlet and creek training can focus currents that scour banks.
Effects
- Loss of land, houses and roads in fishing villages; saltwater in wells and fields.
- Habitat: nesting beaches for turtles, dunes, and mangroves shrink.
- Livelihoods: landing spaces and drying yards disappear; tourism beaches narrow.
- Infrastructure: ports, coastal roads, and defence installations need recurrent repair.
- Disaster risk: a thinner beach means waves reach inland sooner in a cyclone.
Coastal management techniques
- Hard engineering: seawalls, revetments, groynes, offshore breakwaters, tetrapods. They protect a specific asset but often shift erosion alongshore. Use where a city or port cannot retreat.
- Soft engineering: beach nourishment (placing sand), dune fencing and vegetation, and living shorelines. They need a sand budget and repetition.
- Nature-based: mangrove and shelter-belt restoration, coral and wetland buffers, and protecting dune corridors. India’s National Coastal Mission / CAMPA-type and mangrove programmes sit here.
- Hybrid: a low revetment with a nourished beach and a mangrove belt in front.
- Planning instruments: Coastal Regulation Zone (CRZ) rules, setback lines, ban on sand mining in sensitive reaches, and Integrated Coastal Zone Management (ICZM) projects (World Bank-supported in some States).
- Managed retreat: relocating the most exposed hamlets; politically hard, physically honest where the sediment budget is gone.
- Sediment management: dam flushing where feasible, bypassing sand around ports, and stopping illegal mining.
- Science: shoreline mapping (NCSCM and Survey of India-type products), monsoon monitoring, and not building in the active profile.
Principle
- Erosion is often a sand-budget problem. A wall without sand is a delay, not a cure.
Flow diagram
flowchart TD
N[Waves cyclones sea-level] --> E[Erosion]
H[Dams ports seawalls mining] --> E
E --> L[Land habitat livelihood loss]
S[Soft nourishment mangroves CRZ] --> E
W[Hard walls groynes] --> E
W --> X[Downdrift shift]
Conclusion
Indian coastal erosion comes from waves and storms plus dams, walls, mining and mangrove loss. Effects are lost land, salt and livelihoods. Management should prefer sand, dunes and mangroves, use hard armour only for vital assets, and keep CRZ setbacks. Shifting the scar down the coast is not protection.
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Next question in the 2022 paper (Q19). View answer →
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Do seawalls always save the coast?
They may save the plot behind them and increase erosion next door by reflecting waves and blocking sand.
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Is sea-level rise the only cause?
No. Local sand starvation from dams, walls and mining often dominates a given Indian stretch.
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