Indian Coastal Plains, Islands and Lakes Notes for UPSC

India has a long coastline, two large island groups and many types of lakes. These features affect the climate, the economy, the defence and the life of millions of people. In the UPSC Prelims, you will see questions on the western and eastern coastal plains, the names of channels and passes, the island groups, the biggest lagoon and lakes. In the Mains, the coastal regulation, the blue economy and the vulnerability of the coast to cyclones and sea-level rise are important. This note explains the Indian coast, the islands and the lakes in simple language, with tables for quick revision.

India's Coastline at a Glance

India's coastline is about 7,516 km long, including the islands: nearly 6,100 km of the mainland coast and the rest in the island territories. The mainland coast touches nine States: Gujarat, Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Odisha and West Bengal. The Union Territories with a coast are Puducherry, Lakshadweep, Andaman and Nicobar Islands, and Dadra and Nagar Haveli and Daman and Diu. Gujarat has the longest coastline among the States (about 1,600 km), followed by Andhra Pradesh. Under the law of the sea, India has a territorial sea of 12 nautical miles, a contiguous zone of 24 nautical miles and an Exclusive Economic Zone (EEZ) of 200 nautical miles, where it has the right to use the resources of the sea.

The Western Coastal Plain

The western coastal plain lies between the Western Ghats and the Arabian Sea. It is narrow and is a submerged coast, since the sea has covered part of the land, so the coast has many natural harbours but few deltas. The rivers on this side, such as the Narmada and the Tapi, flow into the sea through estuaries and not deltas, because they are short, fast and flow through rift valleys. It is divided into four parts:

• Gujarat coast: The Kachchh and Kathiawar region, with the Rann of Kachchh, a salt marsh, and many gulfs (Gulf of Kachchh and Gulf of Khambhat).
• Konkan coast: From Daman to Goa, in Maharashtra and Goa, with a rocky coast and many creeks.
• Kanara coast: The coast of Karnataka from Goa to Mangalore, with small rivers and estuaries.
• Malabar coast: The Kerala coast, with backwaters (kayals), lagoons and sand bars, and the Vembanad lake.

The Eastern Coastal Plain

The eastern plain lies between the Eastern Ghats and the Bay of Bengal. It is wider than the western plain and is an emergent coast (where the land has risen from the sea), so it has few natural harbours, but large deltas formed by the big rivers: the Mahanadi, Godavari, Krishna and Kaveri. Because the deltas are fertile, the region is a major rice-growing area. It has three parts: the Utkal plains (Odisha), the Andhra plains (also called the Northern Circars) and the Coromandel coast in Tamil Nadu, which gets the rain from the retreating monsoon in winter and is hit often by the cyclones of the Bay of Bengal. Important lagoons are Chilika in Odisha and Pulicat on the Andhra-Tamil Nadu border.

Island Groups of India

Andaman and Nicobar Islands (Bay of Bengal)

The group has more than 500 islands. The Ten Degree Channel separates the Andaman group in the north from the Nicobar group in the south. The Duncan Passage lies between South Andaman and Little Andaman. The highest peak is Saddle Peak in North Andaman. Barren Island is India's only active volcano, and Narcondam is a dormant volcano. Indira Point on Great Nicobar is the southernmost point of India. The islands have dense tropical forests, mangroves and coral reefs, and they are very important for the defence of the Indian Ocean region. The capital is Port Blair (now called Sri Vijaya Puram).

Lakshadweep (Arabian Sea)

Lakshadweep is a group of about 36 islands, which are coral atolls formed by the coral polyps on the submerged volcanic peaks. The capital is Kavaratti. The Eight Degree Channel separates Minicoy island from the Maldives, and the Nine Degree Channel separates Minicoy from the main Lakshadweep group. Andrott is the largest island by area. The islands are famous for the coconut, fishing and tourism.

Other Important Islands

• Majuli: The largest river island in the world, in the Brahmaputra in Assam.
• Sriharikota: The island of the main launch centre of ISRO in Andhra Pradesh.
• Pamban: Links Rameswaram with the mainland by the Pamban bridge.
• Elephanta: Island near Mumbai with the cave temples, a World Heritage Site.
• Diu and Salsette: Islands on the west coast.

Lakes of India

Coastal Ecosystems and Their Protection

The Indian coast has rich ecosystems. Mangroves, such as the Sundarbans in West Bengal (the largest mangrove forest in the world) and Bhitarkanika in Odisha, protect the coast from storms and are the nursery of fish. Coral reefs are found in the Gulf of Mannar, the Gulf of Kachchh, Lakshadweep and the Andaman and Nicobar Islands. Olive Ridley turtles nest on the Odisha coast at Gahirmatha. Threats are cyclones, sea-level rise, pollution, sand mining and unplanned construction. The government regulates the coastal development through the Coastal Regulation Zone (CRZ) notification, first issued in 1991 and later revised in 2011 and 2019, which restricts construction near the shore. The Integrated Coastal Zone Management programme and the idea of the blue economy aim to use the sea in a sustainable manner.

Economic Importance of the Coast and Islands

The coast supports fishing, ports, shipbuilding, salt production, tourism and offshore oil and gas. About 95 per cent of India's trade by volume goes by sea, and the Sagarmala programme aims to improve port-led development. The coastal plains of the east are a rice bowl, and the backwaters of Kerala attract tourists from all over the world. The islands are strategically important: the Andaman and Nicobar group guards the entrance to the Strait of Malacca, while Lakshadweep lies on the busy sea lanes of the Arabian Sea. Future growth is expected from the blue economy, including deep-sea mining, marine biotechnology, offshore wind energy and sustainable aquaculture, but it must be balanced with the protection of the fragile coastal ecology and the rights of the fishing communities.

Mains Angle: Why Are the Eastern Coast Cyclones More Frequent?

The Bay of Bengal has warm sea surface water, which supplies the energy for the cyclones. The shape of the bay acts as a funnel, and the many rivers bring fresh water, which keeps the surface layer stable and warm. The flat eastern coastal plain and the dense population in the deltas increase the damage. Compared to this, the Arabian Sea is cooler, so it has fewer cyclones, though their number has recently increased with global warming. Mention early warning by the IMD, cyclone shelters and mangrove belts as the solutions.

Memory Tip

Remember the east-west contrast with the letters "W-S-E" and "E-E-D": the West coast is Submerged and has Estuaries; the East coast is Emergent and has Deltas. For the channels, remember the numbers in order from the north: Ten (Andaman-Nicobar), Nine (Lakshadweep-Minicoy) and Eight (Minicoy-Maldives).

Practice Questions

• Q1. Which channel separates the Andaman from the Nicobar group? Answer: The Ten Degree Channel.
• Q2. Which is the largest brackish water lagoon of India? Answer: Chilika.
• Q3. Which is India's only active volcano? Answer: Barren Island.
• Q4. Which State has the longest coastline? Answer: Gujarat.

Read it along with our notes on the physiographic divisions of India and the lakes and national parks of India.

Quick Revision

• Coastline about 7,516 km; Gujarat has the longest coast; 9 coastal States.
• Western plain: narrow, submerged, estuaries; Eastern plain: wide, emergent, deltas.
• Ten Degree Channel (Andaman-Nicobar); Eight and Nine Degree Channels (Lakshadweep-Maldives).
• Barren Island: active volcano; Indira Point: southernmost point; Majuli: river island.
• CRZ rules: 1991, 2011, 2019.

Frequently Asked Questions (FAQ)

How long is the coastline of India?

India's coastline is about 7,516 km including the islands, and about 6,100 km on the mainland.

Which State has the longest coastline?

Gujarat has the longest coastline among the States.

Why is the western coastal plain narrow?

It is narrow because the Western Ghats lie close to the sea, and the coast is a submerged one.

Why does the eastern coast have deltas?

The large rivers like the Mahanadi, Godavari, Krishna and Kaveri flow slowly through a wider plain and form deltas before entering the Bay of Bengal.

Which channel separates the Andaman and Nicobar islands?

The Ten Degree Channel separates the Andaman group from the Nicobar group.

Where is Indira Point?

Indira Point is on Great Nicobar Island and is the southernmost point of India.

Which is the active volcano of India?

Barren Island in the Andaman Sea is India's only active volcano.

What are the Lakshadweep islands made of?

They are coral atolls formed on submerged volcanic peaks.

Which is the largest river island in the world?

Majuli in the Brahmaputra river in Assam is the largest river island.

Which is the largest brackish water lagoon in India?

Chilika Lake in Odisha is the largest brackish water lagoon.

What is the CRZ notification?

The Coastal Regulation Zone notification regulates the construction and activities along the coast, first issued in 1991 and revised in 2011 and 2019.

How large is India's EEZ limit?

India's Exclusive Economic Zone extends 200 nautical miles from the coast.