2. The Indus – Ganga – Brahmaputra plain:
The fertile northern plain of India has been formed by the depositional work of the Indus, the Ganga and the Brahmaputra rivers. That is why it is called the Indus – Ganga – Brahmaputra plain. It stretches from the river Satluj all the way across to the Ganga delta in an east – west direction and has a length of about 2400 kilometres. This plain is extremely fertile and is used for agricultural purposes on a large scale.
Relief features of the Plain:
Depending on the surface relief the plain is divided into four divisions. These features or divisions have their own unique characteristics.
- The Bhabar:
It lies along the foot of the ‘Shiwaliks’. It is a narrow belt with a width of about 16 kilometres and is made up of porous rocks and pebbles. This bed or belt has streams running through it. The porosity of this region is so high that the streams running through it disappear. It is not suitable for agriculture either.
- The Terai:
It runs along the south of the ‘Bhabar’ and is parallel to it. It is marked by the appearance of the underground streams of the ‘Bhabar’ belt. Fine alluvium is deposited in this region making it marshy due to the re – emergence of the underground streams. Thick forests with rich wild life are found in this region. Most of area has been reclaimed and has significant agricultural value.
- The Bhangar:
This is an alluvial terrace located above the flood plains or the marsh. It consists of old alluvium and has huge deposits of calcareous concretions known as ‘Kankar’.
- The Khadar:
The flood plain which has new or fresh alluvium is called ‘Khadar’. New layers of alluvium are deposited every year by the rivers making this area fertile.
Regional divisions of the plain: Although this region is considered to be featureless there are variations in local relief. The plain is consequently divided into the following sub – divisions.
- The Rajasthan plain:
This arid area lies between the Aravali range in the east and the alluvial plain of the Indus in the west. This region consists of sandy ridges and dunes. The average altitude or elevation of the sand dunes in this area varies from 10 – 30 metres. This plain receives low rainfall which is less than 25 centimetres per annum. Hence this area does not have any vegetation.
- The Punjab – Haryana plain:
This part of the plain was formed by the alluvial deposits brought down by five rivers namely the Satluj, the Beas, the Ravi, the Chenab and the Jhelum. It is also known as the land of the five rivers. It mostly consists of ‘Doabs’ which is the land or area between two rivers. The northern part of this plain adjoining the ‘Shiwaliks’ has been subjected to gully erosion by the five rivers mentioned above.
- The Ganga plain:
This plain lies in Uttar Pradesh, Bihar and West Bengal. Certain deltaic parts of this plain lie in Bangladesh too. This plain was formed due to the depositional work of the Ganga and its tributaries like the Yamuna and the ‘Kosi’. This plain slopes towards the east and south – east with local variations in the slope. Depending on geographical variations the plain is divided into three parts.
- The upper plain
- The middle plain
- The lower plain
- The Brahmaputra Plain:
This plain is also known as the Assam plain. It has an average width of 100 kilometres. This plain was formed due to the depositional work of the Brahmaputra and its tributaries.
Significance of the plains:
These plains have rich alluvial soils, perennial rivers and good climate. It supports a huge population and due to its agricultural value agro- based economies thrive in this region.