Coastal Plains – UPSC Indian Geography Notes

Coastal Plains are flat, low-lying lands adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and a piedmont area.

The Coastal Plains of India lie on either side of the Deccan Plateau, along the western and eastern coasts of India. They extend for about 6,150 km from the Rann of Kutch in the west to West Bengal in the east.

The Indian coastline, which is 7516.6 km long, covers 6100 km of mainland coastline along with the Andaman, Nicobar, and the Lakshadweep islands.

The straight and regular coastline of India is the result of the faulting of the Gondwana land during the Cretaceous period.

The coastline of India touches 13 states and Union Territories. The western coastal plains are along the Arabian Sea, whereas the eastern coastal plains are located along the Bay of Bengal.

Coastal Plains of India are broadly divided into the Western Coastal Plains and the Eastern Coastal Plains.

Coastal Plains of India – West Coast

The west coast strip extends from the Gulf of Cambay (Gulf of Khambhat) in the north to Cape Comorin (Kanniyakumari).

The Western Coastal Plain is a narrow strip of land sandwiched between the Western Ghats and the Arabian Sea, ranging from 50 to 100 km (31 to 62 mi) in width.

It extends from Gujarat in the north and extends through Maharashtra, Goa, Karnataka, and Kerala.

West Coast:

• Divided from north to south into
  • (i) the Konkan coast,
  • (ii) the Karnataka coast, and
  • (iii) the Kerala coast.

Mostly originating in the Western Ghats, the rivers are fast-flowing, usually perennial, and empty into estuaries. Major rivers flowing into the sea are the Tapti, Narmada, Mandovi, and Zuari.

It is made up of alluvium brought down by the short streams originating from the Western Ghats.

It is dotted with a large number of coves (a very small bay), creeks (a narrow, sheltered waterway such as an inlet in a shoreline or channel in a marsh), and a few estuaries. The estuaries of the Narmada and the Tapi are the major ones.

The Kerala coast (Malabar Coast) has some lakes, lagoons, and backwaters, the largest being the Vembanad Lake.

Vegetation is mostly deciduous, but the Malabar Coast moist forests constitute a unique ecoregion.

Western Coastal Plains of India

From the Rann of Kachchh in the north to Kanniyakumari in the south, these are narrow plains with an average width of about 65 km.

Western coast plains are mainly divided into four categories:

1. Kachchh and Kathiawar coast
2. Konkan coast
3. Kanada coast
4. Malabar coast

Kutch and Kathiawar region

Kutch and Kathiawar, although an extension of the Peninsular plateau (Kathiawar made of Deccan Lava and Kutch with tertiary rocks), are considered an integral part of the Western Coastal Plains due to recent leveling.

The Kutch Peninsula was initially an island surrounded by seas and lagoons. Sediment from the Indus River filled these waters over time. However, lack of recent rainfall has transformed it into an arid and semi-arid landscape.

To the north of Kutch is the salt-soaked plain known as the Great Rann, and its southern continuation, the Little Rann, lies on the coast and southeast of Kachchh.

The Kathiawar Peninsula, south of Kachchh, features a central highland, the Mandav Hills, from which small streams radiate (Radial Drainage). The highest point, Mt. Girnar (1,117 m), is of volcanic origin.

The southern part of the Kathiawar Peninsula houses the Gir Range, covered in dense forests and renowned as the home of the Gir lion.

Gujarat Plain

The Gujarat Plain is situated east of Kachchh and Kathiawar and slopes towards the west and southwest.

Formed by the rivers Narmada, Tapi, Mahi, and Sabarmati, the plain encompasses the southern part of Gujarat and the coastal areas of the Gulf of Khambhat.

The eastern part of this plain is fertile, supporting agriculture. However, the greater part near the coast is covered by windblown loess (heaps of sand).

Konkan Plain

• The Konkan Plain, south of the Gujarat plain, extends from Daman to Goa (50 to 80 km wide).
• Features of marine erosion: cliffs, shoals, reefs, and islands in the Arabian Sea.
• The Thane creek around Mumbai is a significant embayment providing an excellent natural harbor.

Karnataka Coastal Plain

• Extends from Goa to Mangalore.
• Narrow plain with an average width of 30-50 km (max 70 km near Mangalore).
• Streams from the Western Ghats descend along steep slopes, creating waterfalls.
• The Sharavati forms the impressive Gersoppa (Jog) Falls, 271 m high.

Malabar Plain (Kerala Plain)

• The Kerala Plain, also known as the Malabar Plain, lies between Mangalore and Kanniyakumari.
• Wider than the Karnataka plain, it is a low-lying plain.
• Significant features include lakes, lagoons, backwaters, spits, etc.
• Backwaters (kayals) are shallow lagoons or inlets parallel to the coastline.
• The largest, Vembanad Lake, is about 75 km long, 5-10 km wide, giving rise to a 55 km long spit.

Coastal Plains of India – East Coast

East Coast:

• Located between the Eastern Ghats and the Bay of Bengal.
• Extends from the Ganga delta to Kanniyakumari.
• Marked by deltas of rivers: Mahanadi, Godavari, Krishna, and Cauvery.

Geographical Features:

• Chilka lake and the Pulicat lake (lagoon) are significant features.

Climate:

• Coastal regions often experience temperatures exceeding 30 °C (86 °F) with high humidity.

Monsoons:

• Receives both the northeast monsoon and southwest monsoon rains.
• Southwest monsoon splits into two branches: Bay of Bengal branch and Arabian Sea branch.
• Bay of Bengal branch moves northwards, crossing northeast India in early June.
• Arabian Sea branch moves northwards, discharging most rain on the windward side of Western Ghats.

Rainfall and Plains:

• Annual rainfall averages between 1,000 and 3,000 mm (39 and 118 in).
• Plains’ width varies between 100 and 130 km (62 and 81 mi).

Divisions:

• The plains are divided into six regions:
  • The Mahanadi delta
  • The southern Andhra Pradesh plain
  • The Krishna-Godavari deltas
  • The Kanyakumari coast
  • The Coromandel Coast
  • Sandy coastal areas.

Eastern Coastal Plains of India

Geographical Stretch:

• Extending from the Subarnarekha river along the West Bengal-Odisha border to Kanniyakumari.

Formation and Rivers:

• Major part formed by the alluvial fillings of the littoral zone by rivers: Mahanadi, Godavari, Krishna, and Cauvery.
• These rivers contribute to some of the largest deltas in the region.

Plain Characteristics:

• In contrast to the West Coastal Plains, these are extensive plains with an average width of 120 km.

Divisions:

• Known as the Northern Circars between the Mahanadi and the Krishna rivers and Carnatic between the Krishna and the Cauvery rivers.

Eastern Coast Categories:

• The eastern coast is divided into three categories:
  • Utkal coast
  • Andhra coast
  • Coromandel coast

Utkal Plain

• The Utkal Plain encompasses the coastal areas of Odisha.
• It includes the Mahanadi delta.

Prominent Features:

• The most prominent physiographic feature is the Chilka Lake.
• Largest lake in the country.
• Area varies between 780 sq km in winter to 1,144 sq km in the monsoon months.

Geographical Characteristics:

• South of Chilka Lake, low hills dot the plain.

Andhra Plain

• South of the Utkal Plain, extending up to Pulicat Lake.
• Pulicat Lake barred by a long sand spit known as Sriharikota Island (ISRO launch facility).
• Delta formation by the rivers Godavari and Krishna is a significant feature.
• The two deltas have merged into a single physiographic unit.
• The combined delta has advanced about 35 km towards the sea in recent years.
• Notable change reflected in the current location of Kolleru Lake, which was once a lagoon at the shore but now lies far inland.
• This part of the plain has a straight coast and lacks good harbors, except for Vishakhapatnam and Machilipatnam.

Tamil Nadu Plain

• The Tamil Nadu Plain stretches for 675 km from Pulicat Lake to Kanniyakumari along the coast of Tamil Nadu.
• Average width is 100 km.
• Most important feature is the Cauvery delta, where the plain is 130 km wide.
• Fertile soil and large-scale irrigation facilities have made the Cauvery delta the granary of South India.

FAQs on Coastal Plains

Q1: What constitutes the coastal plains of India?

Coastal plains refer to flat, low-lying lands adjacent to a sea coast. The Coastal Plains of India are situated on both sides of the Peninsular Plateau, along the western and eastern coasts of the country.

Q2: Why do coastal plains hold significance?

The coastal regions of India play a crucial role in various aspects such as agriculture, trade, industrial centers, tourism, fishing, and salt production. They serve as vital hinterlands for major ports. Many areas in the Indian coastal plains boast rich and fertile soil, supporting the cultivation of a diverse range of crops alongside rice.

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