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The coastal plains and the islands

Physiography of India · Part 4 / 4 · Fact-checked on 8 November 2026 · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

India's coastline and its 2024-25 re-measurement; the western coastal plain from Kachchh and Kathiawar through the Konkan and Kanara coasts to the Malabar backwaters; the eastern coastal plain with the Northern Circars, the Coromandel coast, the four great deltas and the Chilika and Pulicat lagoons; the two coasts and their ports compared; the Andaman and Nicobar Islands and Lakshadweep with their channels; and how the six divisions fit together.

The first three parts climbed the Himalaya, crossed the plains and the desert, and walked over the Peninsular Plateau. This last part goes to the edges of the country: the strips of low land between the plateau and the sea, and the two groups of islands far out in the Bay of Bengal and the Arabian Sea. Coasts matter for ports, fishing, salt, tourism and naval security, and they are also where cyclones and tsunamis strike first. For decades India's coastline was quoted as 7,516.6 km. A fresh measurement by the National Hydrographic Office and the Survey of India, reported by the Ministry of Home Affairs in 2024-25, put it at 11,098.81 km. The coast had not grown; it was simply traced at a finer scale that follows every bay and creek. Among the states, Gujarat has the longest coastline.

Hemmed in by the Western Ghats on one side and the Arabian Sea on the other, the western coastal plain runs all the way from Gujarat's Rann of Kachchh down to Kanyakumari. Outside Gujarat it is narrow, often only a few tens of kilometres wide, because the steep seaward face of the Ghats stands close to the shore. Geographers usually call it a submerged coast: parts of the old land edge sank below the sea, so sea water reaches into river mouths and fills drowned valleys. Its rivers are short and fast, dropping straight off the Ghats, and over such short courses they cannot pile up much sediment. The two large west-flowing rivers, the Narmada and the Tapi, flow through rift valleys and end in a broad tidal mouth, an estuary, rather than a delta. Offshore the continental shelf is wide, which is why the Mumbai High oil field lies far out at sea.

The northern stretch, in Gujarat, is the widest part of the west coast. It takes in the Kachchh peninsula, bordered on the north by the salt flats of the Rann, and the Kathiawar peninsula, also called Saurashtra, to its south. Two gulfs bite into the land here. The Gulf of Kachchh, between Kachchh and Kathiawar, shelters a Marine National Park with coral reefs and mangroves, and the large ports of Deendayal (Kandla, renamed in 2017) and Mundra stand on its shores. The Gulf of Khambhat, between Kathiawar and mainland Gujarat, narrows like a funnel; the incoming tide is squeezed as it moves in and rises very high, which makes the gulf one of the few places in India studied for tidal power. The Sabarmati, Mahi, Narmada and Tapi all reach the sea in or near this gulf, so it is a good map landmark.

South of Daman begins the Konkan coast of Maharashtra and Goa. It is rocky and broken: cliffs and headlands alternate with small bays, creeks and sandy beaches, and the hills of the Ghats send short spurs almost to the water. Mumbai grew on what were once seven islands, later joined by reclamation, around a deep and sheltered natural harbour; Jawaharlal Nehru Port on the mainland side of the same harbour is one of India's main container ports. Mormugao in Goa ships iron ore mined on the plateau behind it. Further south lies the Kanara or Karavali coast of Karnataka, another narrow strip, where rivers such as the Sharavati, which plunges over Jog Falls in the Ghats, reach the sea after a short, steep run. New Mangalore is the chief port of this stretch. Along the whole Konkan and Kanara coast, flat land is scarce, so towns and paddy fields crowd the river mouths.

The Malabar coast of Kerala is lower and a little wider than the stretches to its north. Its signature feature is a chain of backwaters, called kayals: shallow lagoons that run parallel to the shore, cut off from the sea by long sandbars and linked to one another by rivers and canals. Vembanad, the largest, opens to the sea at Kochi, where a gap in the bar gives one of the finest natural harbours on the west coast. The backwaters are also a waterway; the West Coast Canal from Kottapuram to Kollam is National Waterway 3. They support fishing, coir making and tourism. Near the southern tip, the deep-water Vizhinjam International Seaport near Thiruvananthapuram, dedicated to the nation in 2025, uses naturally deep water close to the shore to handle very large container ships. With the Malabar coast the western plain ends at Kanyakumari, where the two coasts meet.

The eastern coastal plain runs from West Bengal and Odisha down to Kanyakumari, between the Eastern Ghats and the Bay of Bengal. It is much broader than the western plain, often 100 km or more, and it slopes gently, because large rivers have spread their alluvium over it for a very long time. Geographers usually call it an emergent coast: the land has risen relative to the sea, leaving a fairly straight, smooth shoreline with sandbars, beach ridges and few natural inlets. Its northern stretch, lying from the Mahanadi to the Krishna, carries the name Northern Circars; the southern part, mostly in Tamil Nadu, is the Coromandel coast. This coast faces the tropical cyclones of the Bay of Bengal, and much of Tamil Nadu gets its main rain from October to December, during the north-east monsoon, when most of India is dry.

Four great rivers of the Peninsula, the Mahanadi, Godavari, Krishna and Kaveri, cross the plateau eastward and each builds a delta where it meets the sea. The Godavari and Krishna deltas lie side by side in Andhra Pradesh, with the shallow freshwater Kolleru lake between them, and the sedimentary basin beneath and offshore, the Krishna-Godavari basin, yields natural gas. The Kaveri delta around Thanjavur is an old rice-growing heartland. Between and beside the deltas, sandbars have closed off lagoons. Chilika in Odisha, just south of the Mahanadi delta, is India's largest brackish-water lagoon; in 1981 it became one of India's first two Ramsar wetlands, and it is famous for wintering birds and Irrawaddy dolphins. Pulicat, on the Andhra Pradesh–Tamil Nadu border, is the second largest; the long barrier island of Sriharikota that separates it from the sea is home to the Satish Dhawan Space Centre.

Set side by side, the two coasts are almost opposites. The west is narrow, indented and very wet in summer, with an estuary at each large river mouth, cliffs, backwaters and good natural harbours; the east is wide, smooth and fertile, with a delta at each large river mouth, a lagoon here and there and long sandy beaches. This difference shaped their ports. On the west, deep sheltered water let Mumbai, Mormugao and Kochi grow naturally. On the east, a straight shore with few shelters meant that Chennai's harbour had to be built with breakwaters, while Visakhapatnam lies in a natural harbour guarded by a headland. Kolkata, far up the Hooghly, is a river port that needs constant dredging, with Haldia downstream for larger ships; Paradip in Odisha and V.O. Chidambaranar (Thoothukudi) in Tamil Nadu are other major ports on this side. The table below sums up the contrast.

Far out in the Bay of Bengal, the Andaman and Nicobar Islands form an archipelago of more than 500 islands strung out over roughly 800 km from north to south. They are the summits of a drowned mountain range that continues the Arakan Yoma of Myanmar, folded up by the same plate collision that raised the Himalaya; the Andaman Sea lies to their east. The Andaman group in the north is separated from the Nicobar group in the south by the Ten Degree Channel. Saddle Peak in North Andaman, about 730 m high, is the highest point of the islands. Lying to the east of the main chain, Barren Island holds the distinction of being the one active volcano in India; Narcondam, to its north, is a dormant one. Indira Point on Great Nicobar is the southernmost point of India. The islands are hot, humid and thickly forested, and the tsunami of 26 December 2004 struck them hard. Their capital, Port Blair, was renamed Sri Vijaya Puram in 2024.

Lakshadweep, in the Arabian Sea about 220 to 440 km off the Kerala coast, is a very different kind of island group. Its 36 islands, of which ten are inhabited, are low islands of coral sand and limestone, most of them sitting on an atoll, a ring of coral reef that encloses a shallow lagoon. With only about 32 sq km of land, it is India's smallest union territory by area, and Kavaratti is its capital. The northern islands are known as the Amindivi group. Minicoy, in the far south, is separated from the rest by the Nine Degree Channel and from the Maldives by the Eight Degree Channel. Because the islands rise only a few metres above the sea, rising sea levels and coral bleaching are serious threats. India also has many small islands close to the mainland, such as those of the Gulf of Mannar and Pamban island with Rameswaram, from which a chain of shoals called Adam's Bridge (Ram Setu) runs towards Sri Lanka.

Taken together, the six divisions work like parts of one system. The Himalaya store snow and send down rivers and silt; the Northern Plains turn that silt into farmland that feeds a large share of the people; the Peninsular Plateau holds most of the coal, iron ore and other minerals; the Thar is a dry fringe with its own resources of salt and sun; the coastal plains add rice-growing deltas, fisheries, salt pans and the ports through which most of India's foreign trade by volume passes; and the island groups extend India's exclusive economic zone far into two seas and sit beside busy shipping lanes near the Strait of Malacca and the Nine and Eight Degree Channels. Each division has a different age and shape, from the ancient rocks of the plateau to the newest silt of the deltas, yet each depends on the others: rivers born in the mountains end in the deltas of the coasts. The next chapter follows those rivers in detail.

Exam traps

• The Northern Circars are on the EAST coast (Andhra Pradesh and Odisha, between the Mahanadi and the Krishna), not in the north of India. The Coromandel coast is also on the east coast, mainly in Tamil Nadu.
• Konkan, Kanara and Malabar are WEST-coast names, in that order from north to south (Maharashtra-Goa, Karnataka, Kerala).
• Estuaries are typical of the west coast (Narmada, Tapi); deltas of the east coast (Mahanadi, Godavari, Krishna, Kaveri). Kolleru, between the Godavari and Krishna deltas, is a freshwater lake, not a lagoon.
• Chilika (Odisha) is India's largest brackish-water lagoon; Pulicat (Andhra Pradesh-Tamil Nadu border) is the second largest, with Sriharikota as its barrier island. Vembanad is a Kerala backwater, on the west coast.
• Barren Island is India's only active volcano; Narcondam is dormant. Both are in the Andaman Sea, not in Lakshadweep.
• The Ten Degree Channel separates the Andamans from the Nicobars; the Nine Degree Channel lies within Lakshadweep (Minicoy from the rest); the Eight Degree Channel separates Minicoy from the Maldives.
• Indira Point (Great Nicobar) is India's southernmost point; Kanyakumari is the southern tip of the mainland only.
• The coastline rose from 7,516.6 km to 11,098.81 km in the 2024-25 figures because of a finer measuring scale, not because land was added. Gujarat has the longest coastline among the states.

Recap

• India's coastline: 11,098.81 km in the 2024-25 re-measurement (earlier 7,516.6 km); Gujarat has the longest among the states.
• Western coastal plain: narrow, submerged, from Kachchh to Kanyakumari; Kachchh-Kathiawar, Konkan, Kanara and Malabar.
• West coast features: estuaries of the Narmada and Tapi, the Gulfs of Kachchh and Khambhat, natural harbours, and the Kerala backwaters (kayals) such as Vembanad.
• Eastern coastal plain: broad, emergent; Northern Circars (Mahanadi to Krishna) and Coromandel; deltas of the Mahanadi, Godavari, Krishna and Kaveri.
• Lagoons of the east: Chilika (largest, Ramsar 1981) and Pulicat (Sriharikota); Kolleru is a freshwater lake between two deltas.
• Ports: natural harbours on the west (Mumbai, Mormugao, Kochi); on the east Visakhapatnam is natural, Chennai artificial, Kolkata a river port.
• Andaman and Nicobar: drowned extension of the Arakan Yoma; Ten Degree Channel; Saddle Peak; Barren Island (active volcano); Indira Point.
• Lakshadweep: 36 coral islands on atolls, 10 inhabited, about 32 sq km; Kavaratti; Minicoy between the Nine and Eight Degree Channels.
• The six divisions complement one another: mountains give water and silt, plains food, the plateau minerals, the coasts ports and fish, the islands sea area.

Practice questions

Sources

• Ministry of Home Affairs, Annual Report 2024-25, and Press Information Bureau: revised length of India's coastline (11,098.81 km, earlier 7,516.6 km) computed by the National Hydrographic Office and the Survey of India — https://www.mha.gov.in
• Survey of India, Department of Science and Technology: physical and political maps of India, the coastal plains, the island groups, Saddle Peak and Indira Point — https://surveyofindia.gov.in
• Chilika Development Authority, Government of Odisha: Chilika Lake, the largest brackish-water lagoon in India, Ramsar site since 1981, Irrawaddy dolphins and migratory birds — https://www.chilika.com
• Ministry of Ports, Shipping and Waterways and Press Information Bureau: major ports of India, the renaming of Kandla Port as Deendayal Port (2017), and the Vizhinjam International Seaport dedicated to the nation (2025) — https://shipmin.gov.in
• Inland Waterways Authority of India: National Waterway 3, the West Coast Canal (Kottapuram to Kollam) in the Kerala backwaters — https://iwai.nic.in
• Andaman and Nicobar Administration: geography of the islands, the Ten Degree Channel, Barren and Narcondam islands, Indira Point, and the renaming of Port Blair as Sri Vijaya Puram (2024) — https://andaman.gov.in
• Union Territory of Lakshadweep Administration: 36 islands, 10 inhabited, about 32 sq km of land, Kavaratti, the Amindivi group and Minicoy — https://lakshadweep.gov.in
• Geological Survey of India, Ministry of Mines: the Andaman-Nicobar arc as a continuation of the Arakan Yoma, the volcanoes of Barren Island and Narcondam, and the coastal geology of India — https://www.gsi.gov.in
• India Meteorological Department, Ministry of Earth Sciences: the north-east monsoon season (October to December) over Tamil Nadu and tropical cyclones of the Bay of Bengal — https://mausam.imd.gov.in
• Directorate General of Hydrocarbons, Ministry of Petroleum and Natural Gas: the Mumbai offshore basin (Mumbai High) and the Krishna-Godavari basin — https://dghindia.gov.in
• ISRO National Remote Sensing Centre and India-WRIS: river basins, deltas and estuaries of the east- and west-flowing rivers — https://www.nrsc.gov.in
• Ministry of New and Renewable Energy: ocean energy, including the tidal-energy potential of the Gulf of Khambhat and the Gulf of Kachchh — https://mnre.gov.in
• Ministry of Environment, Forest and Climate Change: Ramsar sites of India (Chilika and Keoladeo, 1981), the Marine National Park in the Gulf of Kachchh and the Gulf of Mannar — https://moef.gov.in
• NOAA Coral Reef Conservation Program: atolls, fringing and barrier reefs, and coral bleaching (US government) — https://coralreef.noaa.gov