Indo Ganga Brahmaputra Plain, also known as the North Indian River Plain, is a fertile plain that encompasses the Indian subcontinent's northern areas, including much of northern and eastern India. The region is called for the rivers Indus, Brahmaputra and Ganges, and it includes a number of big metropolitan centres. The Himalayas, which feed the plain's numerous rivers and are the source of the rich alluvium deposited throughout the region by the two river systems, border it on the north. The Chota Nagpur Plateau marks the plain's southern boundary. This article will explain to you about the Indo-Ganga-Brahmaputra Plain which will be helpful in Geography preparation for the UPSC Civil service exam.

Indo-Ganga-Brahmaputra Plain

• The Indo-Gangetic-Brahmaputra plain is sometimes referred to as the Northern lowlands of India or the Great Plain of India.
• It is a transitional zone between the northern Himalayas and Peninsular India. The Indo-Gangetic-Brahmaputra Plain is the world's biggest alluvial tract.
• The Great Plain of North India is located to the south of the Himalayas and to the north of the Peninsula.
• It is an aggradational plain produced by the depositional action of three main river systems, including the Indus, Ganga, and Brahmaputra.
• This elongated plain is also known as the Indo-Gangetic-Brahmaputra Plain.
• This plain's northern boundary is strongly defined by the Shivalik foothills, while its southern limit is a wavy irregular line along the northern edge of Peninsular India.
• Rivers running across this plain, particularly those originating in the Himalayas, have deposited a thick layer of alluvium over its length and width.
• As a result, it is a classic example of an aggradational plain.
• However, the thickness of the alluvium deposit varies from location to location, and several estimations have been given.

Indo-Ganga-Brahmaputra Plain

Indo-Ganga-Brahmaputra Plain - Formation

• The formation of the Indo-Ganga-Brahmaputra Plain is linked to the formation of the Himalayas.
• This vast plain is almost widely perceived to have originated as a result of the depositional action of rivers flowing from the Peninsular and Himalayan areas filling a deep depression between these two landmasses.
• Rivers that used to flow into the Tethys sea deposited massive amounts of sediments in the Tethys Geosyncline.
• The Himalayas are produced from these sediments, which were raised, folded, and crushed when the Indian Plate moved northward.
• The Indian Plate's northern shift generated a trough to the south of the Himalayas.
• A "foredeep" emerged in front of high crust-waves of the Himalayas when they were slowed in their southerly approach by the Peninsula's inflexible solid landmass.
• This foredeep was similar to a vast syncline where alluvium from the Himalayan and Peninsular rivers was deposited.
• This was eventually filled with alluvium, resulting in the formation of the Great Plain of North India.
• It is supported by strong and crystalline rocks that connect the area to the Himalayan and Peninsular blocks.

Depositional Activities in the Great Plain of India

• During the early phases of sediment upliftment, existing rivers altered channels multiple times and were revitalised each time (perpetual youth stage of rivers).
• The rejuvenation is accompanied by intensive headward and vertical downcutting of the soft strata that lies under the harder rock stratum.
• Headward and vertical erosion of the river valley in the early phases, followed by lateral erosion, produced a massive amount of conglomerates (detritus) (rock debris, silt, clay, etc.) that were transported downslope.
• Headward erosion - Erosion at the stream channel's origin that causes the origin to migrate away from the direction of the streamflow, causing the stream channel to extend.
• These conglomerates were formed in the depression between peninsular India and the convergent boundary (the base of the geosyncline is hard crystalline rock).

Alluvium Deposition

• Many new rivers were formed as a result of the rising of the Himalayas and the consequent creation of glaciers.
• These rivers, in conjunction with Glacial erosion, contributed more alluvium, hastening the filling of the depression.
• The Tethys sea began to recede as additional sediments (conglomerates) were deposited.
• Over time, the depression was entirely filled with alluvium, gravel, and rock debris, and the Tethys vanished, leaving behind a monotonous aggradational plain.
• Upper peninsular rivers have also played a minor role in the creation of plains.
• Depositional work of three main river systems, namely the Indus, Ganga, and Brahmaputra, has been prominent in recent times (since a few million years).
• As a result, this curving plain is also known as the Indo-Gangetic-Brahmaputra Plain.

Indo-Ganga-Brahmaputra Plain - Features

• The Indo-Gangetic-Brahmaputra Plain is the world's biggest alluvial tract.
• It runs 3,200 kilometres from the mouth of the Indus to the mouth of the Ganga. The Indian plain has a total length of 2,400 kilometres.
• The Shiwaliks form the northern boundary, while a wavy irregular line runs down the northern edge of Peninsular India to indicate the southern boundary.
• The Sulaiman and Kirthar mountains form the western border. The plains are bounded on the east by the Purvanchal hills.
• The breadth of the plain varies depending on area. It is at its broadest in the west, where it runs for nearly 500 kilometres. Its breadth narrows to the east.
• The thickness of the alluvium deposits varies from place to place as well. The highest depth of alluvium up to foundation rocks is approximately 6,100 m.
• The cones or alluvial fans of Kosi in the north and Son in the south have larger alluvial thickness, although the deposits within the cones are somewhat shallower.
• The boring plain's main feature is its extreme horizontality.
• It has an average elevation of roughly 200 metres above sea level, with the highest point being 291 metres above sea level near Ambala.
• From Saharanpur to Kolkata, the average gradient is just 20 cm per km, and it drops to 15 cm per km from Varanasi to the Ganga delta.

Indo-Ganga-Brahmaputra Plain - Geomorphological Features

Bhabhar Region

• Cobbles, pebbles, gravels, boulders, and coarse sand are found adjacent to the Shivalik foothills.
• The Indo-Gangetic plain's northernmost portion is small and permeable.
• It's around 8-16 kilometres wide and runs east-west along the Shiwaliks' foothills (alluvial fans).
• From the Indus to the Tista, they display amazing continuity.
• Rivers descending from the Himalayas dump their burden in the shape of alluvial fans along the slopes.
• The bhabar belt is made up of these alluvial fans that have melded together.
• The porosity of bhabar is its most distinguishing characteristic.
• The porosity is caused by a large amount of pebbles and rock debris being deposited over the alluvial fans.
• Due to the porosity, the streams vanish once they reach the bhabar zone.
• As a result, save during the rainy season, the land is defined by dry river channels.
• The Bhabar belt is narrow in the east and wide in the western and northwestern mountainous regions.
• The Bhabar Zone runs from Punjab to the Himalayas of Assam.
• This belt is unsuitable for cultivation, and only giant trees with deep roots flourish here.

Terai Region

• From Punjab to Assam, marshy regions near the Bhabar zone, exceedingly flat marshy lands, extensively deforested and parallel to the Himalayas.
• To the south of Bhabar, the Terai is a narrow, ill-drained, wet (marshy) and densely wooded region that runs parallel to it.
• The Terai is around 15-30 kilometres wide.
• It is widest in Bihar and eastern Uttar Pradesh, while it is smallest in the east.
• The Bhabar belt's subsurface streams resurface in this belt.
• The Terai is more noticeable in the east than in the west because the east receives a larger quantity of rainfall.
• The majority of the area has been deforested for agricultural purposes.
• Tarai soils are nitrogen-rich and humus-rich.
• The majority of Terai terrain, particularly in Punjab, Uttar Pradesh, and Uttarakhand, has been converted to agricultural land, producing good crops of sugarcane, rice, and wheat.

Bangar Region

• It encompasses the whole Gangetic plain.
• The Bhangar is the older alluvium that forms terraces higher than the flood plain along the river banks.
• The terraces are frequently encrusted with calcareous concretions known as 'Kankar.'
• Regional variants of Bhangar include the 'Barind plains' in Bengal's deltaic area and the 'bhur formations' in the middle Ganga and Yamuna doab.
• Bhur refers to an elevated portion of land located along the Ganga river's banks, particularly in the upper Ganga-Yamuna Doab.
• This was produced as a result of wind-blown sand buildup during the hot, dry months of the year.
• Bhangar is home to fossils of creatures such as rhinoceros, hippopotamus, and elephants.
• It has Kankar deposits, which are Limestone pieces that provide natural base additions to the soil.
• It has been severely damaged in certain parts of UP where it is known as Usar (infertility owing to salinization).

Khadar Region

• The flood plains along the river banks are formed by the Khadar, which is made up of recent alluvium.
• Almost every year, a fresh layer of alluvium is deposited by a river flood. These deposits are often restricted to the region of current river courses.
• The cluys contain less kankar, and the organic remains entombed in them are from still-living animals.
• The khadar blends invisibly with prehistoric deltaic and other accumulations.
• Reh or Kollar is made up of salty efflorescences from arid portions of Haryana.
• With more irrigation, reh regions have developed in recent years.

Regional Divisions of the Great Indian Plain

• Although the Great Plain of North India is viewed as a geographical unit because of its low height and mild slope.
• This enormous expanse displays diverse fluvial patterns, flow directions, and geomorphology in different sections, allowing it to be split into the four primary regions listed below.
  • Rajasthan Plain
  • Punjab Plain
  • Gangetic Plain
  • Brahmaputra Plain

Rajasthan Plain

• The Ghagar valley in the north and the Aravallis in the east
• It is a portion of the Thar desert, yet it has Indus and its tributaries alluvial deposits.
• Following the upliftment of the Himalayas, these routes migrated westward.
• This plain is an undulating (wave-like) plain with an average elevation of around 325 metres above mean sea level.
• The plain is divided into marusthali in the west and Rajasthan Bagar in the east by a 25cm isohyet.
• Marusthali is a desert characterised by changing sand dunes known as Dhrian.
• The whole Marushatli area receives 25cm of rainfall, and the lone tree is Khejri (the Bishnoi tribe is associated with it).
• Thali is a sandy desert to the north of Luni.
• There is an interior drainage with many saline lakes north of the Luni. They are a source of common salt as well as a variety of other salts.
• Some of the prominent lakes include Sambhar, Didwana, Degana, Kuchaman, and so on. The Sambhar lake in Jaipur is the biggest.

Punjab Plain

• This plain is formed by the Indus system's five major rivers.
• The plain is mostly made up of 'doabs,' which are the lands between two rivers.
• There are five doabs (Chaj, Rechna, Bist, Bari and Sindsagar).
• The river's depositional process has combined these doabs, giving them a uniform look.
• Plains that are extremely rich yet have inadequate drainage and are prone to flooding.
• This plain covers an area of around 1.75 lakh square kilometres.
• The plain's average elevation is roughly 250 metres above mean sea level.
• It is limited by a 291-metre contour line that runs along to the Delhi–Ambala ridge, separating it from the Gangetic basin.
• The underlying Delhi-Aravali ridge marks the eastern limit of the Punjab Haryana plain.
• The northern half of this plain has been heavily degraded by several Chos streams. This has resulted in a massive gully.
• The Malwa plain in Punjab is to the south of the Satluj river.
• The area between the Ghaggar and Yamuna rivers in Haryana is known as the 'Haryana Tract.' It serves as a water divider between the Yamuna and Sutlej rivers.
• The only river between the Yamuna and the Satluj is the Ghaggar, which is said to be the modern-day successor of the mythological Saraswati.

Gangetic Plain

• This is the longest unit of India's Great Plains, running from Delhi to Kolkata (about 3.75 lakh sq km).
• The Ganga, together with its numerous tributaries that originate in the Himalayas, transported massive amounts of alluvium from the mountains and deposited it here to form this vast plain.
• The peninsular rivers that enter the Ganga river system, such as Chambal, Betwa, Ken, Son, and others, have also contributed to the creation of this plain.
• The overall slope of the plain is to the east and south east. It is said to be the modern-day successor to the fabled Saraswati River.
• Rivers run slowly in the lower portions of the Ganges, resulting in local prominences such as levees, bluffs, oxbow lakes, marshes, ravines, and so on. Fluvial Landforms and Arid Landforms
• Almost all of the rivers are constantly changing their courses, leaving this area prone to regular flooding. In this regard, the Kosi River is well-known. It has long been known as the "Sorrow of Bihar."

Brahmaputra Plain

• As most of the Brahmaputra valley is located in Assam, it is also known as the Assam Valley or Assam Plain.
• The Indo-Bangladesh border, as well as the lower Ganga Plain's boundary, comprise its western limit.
• Purvanchal hills define the state's eastern border.
• It is an aggradational plain formed by the Brahmaputra and its tributaries' depositional action.
• The Brahmaputra river's numerous tributaries from the north generate a variety of alluvial fans.
• As a result, the tributaries split into numerous channels, resulting in river meandering and the formation of the ox-bow lakes.

Ganga Brahmaputra Delta

• This is the world's biggest delta.
• In the delta, the Ganga river splits into multiple rivers. The ground here has a slope of only 2 cm per kilometre.
• Two-thirds of the land area is less than 30 metres above mean sea level.
• The delta's seaward edge is dotted with estuaries, mud flats, mangrove swamps, sandbanks, islands, and forelands.
• Tidal woods comprise a substantial portion of the coastal delta. Because of the Sundri tree's dominance here, these are known as the Sunderbans.

Significance of Indo Ganga Brahmaputra Plain

• Half of India's population lives on just one-fourth of the country's area.
• Fertile alluvial soils, a level terrain, slow-moving perennial rivers, and a pleasant climate make intensive farming possible.
• Punjab, Haryana, and the western section of Uttar Pradesh have become India's granary thanks to substantial irrigation (Prairies are called the granaries of the world).
• Except for the Thar Desert, the whole plain has a well-connected network of roads and trains, allowing for large-scale manufacturing and urbanisation.
• Cultural tourism, There are several religious sites along the banks of sacred rivers such as the Ganga and the Yamuna that Hindus revere.
• Budha and Mahavira faiths, as well as Bhakti and Sufism movements, flourished here.

Conclusion

The Indo-Ganga-Brahmaputra Plain, commonly known as the North Indian River Plain, is a rich plain that stretches throughout the northern half of the Indian subcontinent, including much of northern and eastern India. The Great Plains of North India are a vast expanse of land in northern India. Intensive farming is possible thanks to fertile alluvial soils, flat terrain, slow-moving perennial rivers, and a pleasant environment. Thanks to extensive irrigation, Punjab, Haryana, and the western part of Uttar Pradesh have become India's granary.