The Northern Plains | Part 1

Let’s move on to the next physiographic unit: The Northern Plains.

Article Outline:

  • Location and Extent
  • Formation of Northern Plains
  • Chief Characteristics
  • Physiographic Division
    • The Bhabar
    • The Terai
    • The Bhangar
    • The Khadar
  • Regional Divisions
  • Significance of this region

Location and Extent:

Northern plains are the youngest physiographic feature in India. They lie to the south of the Shivaliks, separated by the Himalayan Frontal Fault (HFF). The southern boundary is a wavy irregular line along the northern edge of the Peninsular India. On the eastern side, the plains are bordered by the Purvanchal hills.

The Northern Plains | Part 1

The Northern Plains | Part 1

Formation of Northern Plains:

Due to the uplift of the Himalayas in the Tethys Sea, the northern part of the Indian Peninsula got subsided and formed a large basin.

That basin was filled with sediments from the rivers which came from the mountains in the north and from the peninsula in the south. These extensive alluvial deposits led to the formation of the northern plains of India.

Chief Characteristics:

  • The northern plain of India is formed by three river systems, i.e. the Indus, the Ganga and the Brahmaputra; along with their tributaries.
  • The northern plains are the largest alluvial tract of the world. These plains extend approximately 3200 km from west to east.
  • The average width of these plains varies between 150 and 300 km. In general, the width of the northern plains increases from east to west (90-100km in Assam to about 500km in Punjab).
  • The exact depth of alluvium has not yet been fully determined. According to recent estimates, the average depth of alluvium in the southern side of the plain varies between 1300-1400m, while towards the Shiwaliks, the depth of alluvium increases. The maximum depth of over 8000m has been reached in parts of Haryana.
  • The extreme horizontality of this monotonous plain is its chief characteristic (200m – 291m). The highest elevation of 291 m above mean sea level near Ambala forms a watershed between Indus system and Ganga system).
  • The monotony of the physical landscape is broken at the micro level by the river bluffs, levees etc.
    • [Floodplain – That part of a river valley, adjacent to the channel, over which a river flows in times of a flood.
    • Levee – An elevated bank flanking the channel of the river and standing above the level of the flood plain.
    • Bluff – A river cut cliff or steep slope on the outside of a meander. A line of bluffs often marks the edge of a former floodplain.]

The Northern Plains

Physiographic Divisions of the Northern Plains:

From the north to the south, the northern plains can be divided into three major zones:

  1. The Bhabar
  2. The Tarai
  3. The alluvial plains.

The alluvial plains can be further divided into the Khadar and the Bhangar as illustrated below:

Let’s understand these divisions one by one:

Bhabar:

  • Bhabar is a narrow belt (8-10km wide) which runs in the west-east direction along the foot of the Himalayas from the river Indus to Teesta

  • Rivers which descend from the Himalayas deposit their load along the foothills in the form of alluvial fans.
  • These fans consisting of coarser sediments have merged together to build up the piedmont plain/the Bhabar.
  • The porosity of the pebble-studded rock beds is very high and as a result, most of the streams sink and flow underground. Therefore, the area is characterized by dry river courses except in the rainy season.
  • The Bhabar tract is not suitable for cultivation of crops. Only big trees with large roots thrive in this region.
  • The Bhabar belt is comparatively narrow in the east and extensive in the western and north-western hilly region.

Tarai:

  • It is a 10-20 km wide marshy region in the south of Bhabar and runs parallel to it.
  • The Tarai is wider in the eastern parts of the Great Plains, especially in the Brahmaputra valley due to heavy rainfall.
  • It is characterized by the re-emergence of the underground streams of the Bhabar belt.
  • The reemerged water transforms large areas along the rivers into badly drained marshy lands.
  • Once covered with dense forests, most of the Tarai land (especially in Punjab, Uttar Pradesh and Uttarakhand) has been reclaimed and turned into agricultural land over a period of time.

Bhangar:

  • It is the older alluvium along the river beds forming terraces higher than the flood plain.
  • Dark in colour, rich in humus content and productive.
  • The soil is clayey in composition and has lime modules (called kankar)
  • Found in doabs (inter-fluve areas)
  • ‘The Barind plains’ in the deltaic region of Bengal and the ‘bhur formations’ in the middle Ganga and Yamuna doab are regional variations of Bhangar. [Bhur denotes an elevated piece of land situated along the banks of the Ganga river especially in the upper Ganga-Yamuna Doab. This has been formed due to accumulation of wind-blown sands during the hot dry months of the year]
  • In relatively drier areas, the Bhangar also exhibits small tracts of saline and alkaline efflorescence known as ‘Reh’, ‘Kallar’ or ‘Bhur’. Reh areas have spread in recent times with increase in irrigation (capillary action brings salts to the surface).
  • May have fossil remains of even those plants and animals which have become extinct.

Khadar:

  • Composed of newer alluvium and forms the flood plains along the river banks.
  • Light in colour, sandy in texture and more porous.
  • Found near the riverbeds.
  • A new layer of alluvium is deposited by river flood almost every year. This makes them the most fertile soils of Ganges.
  • In Punjab, the Khadar rich flood plains are locally known as ‘Betlands’ or ‘Bets’.
  • The rivers in Punjab-Haryana plains have broad flood plains of Khadar flanked by bluffs, locally known as Dhayas. These bluffs are as high as 3metres.

 

That’s it for this part! In the next article, we will look at the regional divisions of the Northern Plains.

The Northern Plains | Part 2

  1. Punjab Plains:
  • The Punjab plains form the western part of the northern plain.
  • In the east, the Delhi-Aravalli ridge separates it from the Ganga plains.
  • This is formed by the Indus and its tributaries; like Jhelum, Chenab, Ravi, Beas and Sutlej. A major portion of these plains is in Pakistan.
  • It is divided into many Doabs (do-“two” + ab- “water or river” = “a region or land lying between and reaching to the meeting of the two rivers”).
  • Important features:
    • Khadar rich flood plains known as ‘Betlands’ or ‘Bets’.
    • The rivers in Punjab-Haryana plains have broad flood plains of Khadar flanked by bluffs, locally known as Dhayas.
    • The northern part of this plane adjoining the Shivalik hills has been heavily eroded by numerous streams, which are called Chhos.
    • The southwestern parts, especially the Hisar district is sandy and characterized by shifting sand-dunes.
  1. Ganga Plains:
  • The Ganga plains lie between the Yamuna catchment in the west to the Bangladesh border in the East.
  • The lower Ganga plain has been formed by the downwarping of a part of the Peninsular India between Rajmahal hills and the Meghalaya plateau and subsequent sedimentation by the Ganga and Brahmaputra rivers.
  • The main topographical variations in these plains include Bhabar, Tarai, Bhangar, Khadar, levees, abandoned courses etc.
  • Almost all the rivers keep on shifting their courses making this area prone to frequent floods. The Kosi river is very notorious in this respect. It has long been called the ‘Sorrow of Bihar’.
  • The northern states, Haryana, Delhi, UP, Bihar, part of Jharkhand and West Bengal in the east lie in the Ganga plains.
  • The Ganga-Brahmaputra delta: the largest delta in the world. A Large part of the coastal delta is covered tidal forests called Sunderbans. Sunderbans, the largest mangrove swamp in the world gets its name from the Sundari tree which grows well in marshland. It is home to the Royal Tiger and crocodiles.
  1. Brahmaputra Plains:
  • This plain forms the eastern part of the northern plain and lies in Assam.
  • Its western boundary is formed by the Indo-Bangladesh border as well as the boundary of the lower Ganga Plain. Its eastern boundary is formed by Purvanchal hills.
  • The region is surrounded by high mountains on all sides, except on the west.
  • The whole length of the plain is traversed by the Brahmaputra.
  • The Brahmaputra plains are known for their riverine islands (due to the low gradient of the region) and sand bars.
  • The innumerable tributaries of the Brahmaputra river coming from the north form a number of alluvial fans. Consequently, the tributaries branch out in many channels giving birth to river meandering leading to the formation of bill and ox-bow lakes.
  • There are large marshy tracts in this area. The alluvial fans formed by the coarse alluvial debris have led to the formation of terai or semi-terai conditions.

Significance of this region:

  • The plains constitute less than one-third of the total area of the country but support over 40 percent of the total population of the country.
  • Fertile alluvial soils, flat surface, slow moving perennial rivers and favourable climate facilitate an intense agricultural activity.
  • The extensive use of irrigation has made Punjab, Haryana and western part of Uttar Pradesh the granary of India (Prairies are called the granaries of the world).
  • Cultural tourism: Several sacred places and centres of pilgrimage are situated in these plains e.g. Haridwar, Amritsar, Varanasi, Allahabad, Bodh Gaya etc.
  • The sedimentary rocks of plains have petroleum and natural gas deposits.
  • The rivers here have very gentle gradients which make them navigable over long distances.

Now that we are done with this part, let’s try to attempt some questions from the past UPSC examinations:

Prelims:

2000

Question: Assertion (A): The frequency of floods in North Indian plains has increased during the last couple of decades.

Reason(R): There has been reduction in the depth of river valleys due to deposition of silt.

Ans. A (Both A and B are true and R is the correct explanation of A)

 

Question: Assertion (A): Ganga plain is the most densely populated part of India.

Reason(R): Ganga is the most harnessed river of India.

Ans. C (A is true but R is false)

Mains:

Question: Write a short note on Tarai region. (2008/2marks)

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