Coastal Plains, Indian Islands, Drainage System Part 5

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Coastal Plains

The Great Plateau of India is surrounded by plains on all sides. In the north lies the Great Northern Plain and in south, along the east and west lie the Coastal Plains.

The East Coastal Plain extends along the coast of the Bay of Bengal from the Ganga Delta in the north to Kanyakumari in the south. This plain is broader than the western coastal Plains. The plain includes the deltas of the rivers Mahanadi, Godavari, Krishna, and Kaveri. Some of the famous lakes or the lagoons are located in this plain.

These lakes have been formed by enclosing small parts of the Bay of Bengal behind sand bars. Lake Chilka is situated south of the delta of Mahanadi. The lake measures 75 km in length. Lake Pulicut is situated north of Chennai city. Koluru lake is situated between the deltas of the Godavari and Krishna rivers. The east coastal plain is very fertile where rice grows in plenty.

West Coastal Plain extends along the Arabian Sea from the Rann of Kachchh in the north to Kanyakumari in the south. Except for the Gujarat plain, the western coastal plains are narrower than the eastern coastal plain. From southern Gujarat up to Mumbai this plain is comparatively broader, but it narrows southwards of Mumbai. Occasionally rocky domes and hills are visible in the plains of Gujarat, the Rann of Kachchh, and the plains of Kathiawar.

The plains of Gujarat are made up of black soil. The coastal strip extending for about 500 km between Daman in the north and Goa in the south is called Konkan. This region is highly dissected and the coast line is indented or irregular with several natural harbours. A number of small and seasonal rivers flow through this region. The coast from Goa to Mangalore is called the Karnataka coast. The coast from Mangalore up to Kanyakumari is called the Malabar coast.

Here the coastal plain is wider. There are a number of long and narrow lagoons found for example 80 km long Vembanad lake in Kerala. Kochi port is situated on one of the lagoons.

Indian Islands

There are two small groups of islands. One of these situated in the Bay of Bengal, off the coast of Myanmar known as the Andaman and Nicobar Islands. The other is known as Lakshadweep situated in the Arabian Sea, off the coast of Kerala. The Andaman Islands consists of North, Middle, South, and Little Andaman Islands. Port Blair is the capital city of the entire Union Territory and is located in South Andaman Island. This island group is separated by the Ten Degree Channel. To its south are situated the Nicobar Islands. They include Car Nicobar, Little Nicobar, and Great Nicobar Islands from north to south. The southernmost point of the Indian Union lies in Great Nicobar Island and has been named after Indira Gandhi. These islands represent a submerged chain of mountains. The Barren Island in the Andamans is India’s only active volcano.

Lakshadweep and Andaman and Nicobar Islands

Lakshadweep and Andaman and Nicobar Islands

Lakshadweep and Andaman and Nicobar Islands

Lakshadweep Islands are situated in the Arabian Sea, off the coast of Kerala. All these islands are of coral origin. They have been built up by corals, the microscopic polyps. The islands are very small in size. The largest island among these, the Minicoy, has an area of 4.5 square km only. Kavarati is the capital city of this island group.

Drainage System

The drainage pattern or system of an area refers to the system of flow of surface water mainly through the rivers and basins forms. The drainage system studies streams and the directions in which they carry the surface water of an area. The drainage system is related to a number of factors, such as the slope of land, geological structure, amount of volume of water, and velocity of water. The surface run off of India is carried by a number of small and large rivers. The drainage system of our country can be studied with reference to two parts:

Drainage System of North India

The Himalayas play an important role in the drainage system of the north India. This is because the rivers have their sources in these mountains and beyond. These rivers differ from those of south India as they are still deepening their valleys rather rapidly. The debris eroded by these rivers are carried to the plains and seas and deposited there. This deposition is caused by the reduced velocity of river waters in the plains and deltas.

The Great North Indian plain has been formed by the silt brought down by these rivers. Some of the Himalayan rivers are older than the Himalayas themselves. As the ranges of the Himalayas had been rising upwards, these rivers were equally busy in downward cutting forming deep gorges and valleys. The depth of the Indus gorge near Bunji in Jammu and Kashmir is 5200 metres. Sutlej and Brahmaputra have also formed such gorges.

The drainage system of northern India can be further sub-divided into three subsystems Indus System, Ganga System, and Brahmaputra System.

The major rivers of Indus basin are the Indus, Jhelum, Chenab, Ravi, Beas and Sutlej. The Ganga basin includes Ramganga, Ghaghra, Gomti, Gandak, Kosi, Yamuna along with its southern tributaries, Son and Damodar rivers. The major rivers of Brahmaputra basin are Dibang and Lohit in Arunachal Pradesh and Assam, Tista in Sikkim, West Bengal and Bangladesh and Meghna, draining north-eastern part of Bangladesh.

Major Rivers of of India

Major Rivers of of India

Major Rivers of of India

Drainage System of Southern India

The Peninsular India is an ancient landmass. Therefore, the streams flowing through this region are in their old stage. They have almost attained their base level of erosion. Their capacity to erode valleys vertically has almost come to a negligible stage. Now these streams are eroding their sides at a slow pace. This is resulting in broadening of their valleys. Consequently, during flood their waters spread over a large area. It is believed that at the time of the Himalayan orogeny, due to the movements associated with the mountain building processes, the Peninsular block had a slight tilt towards east. This is why, barring Narmada and Tapi, all the major rivers of south India flow towards east. Narmada and Tapi, both flow through fault or rift valleys. The major rivers of the drainage system of southern India are Mahanadi, Godavari, Krishna, Pennar, Kaveri, and Vaigai.

The slope of the northern part of the southern peninsula is towards north. Consequently, some of the streams originating in the Vindhyas, flow towards north and join Yamuna and Ganga. Among these, Chambal, Ken, Betwa, Sind and Son are more important.

The difference between the Himalayan rivers and Peninsular rivers can be summarised as:

The rivers which have their origin in the Himalayas are perennial. These rivers are fed by the melting of ice and snow lying near the tongue of glaciers of the Great Himalayan Range or Himadri. In the rivers of South India, the flow of water is highly fluctuating. While the rivers are in spate during the monsoons, they are almost dry during the long rainless months. Some of these rivers at many places become totally dry.

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