Divisions of Indo - Gangetic And Brahmaputra Plains
The Northern Plains form an important geographical feature of India, covering over 7 lakh sq.km. There are divisions within the Northern Plains based on the rivers that drain the region, the kind of alluvial soil present in the region and also the geographical location of the region.
Division of Indo-Gangetic And Brahmaputra Plains
Starting from the west, moving towards the east, the plain has the following divisions
- Sindh plain
- Rajasthan plain
- Punjab plain
- Ganga plain
- Ganga - Brahmaputra delta
- Brahmaputra plain
- It comprises the older alluvium deposited by the Indus and its tributaries. Hence, these are considered to be Bhangar plains.
- The two important features of these plains are Dhor and Dhand. Dhors are long, narrow depressions which are considered to be the remnants of an old river. Dhands are alkaline lakes which are usually found within the Dhors.
- It is mostly located in Pakistan. The city of Karachi is found in this region
- With an average elevation of 325m above the mean sea level (MSL), this region is among the highest places in the Northern plains.
- This plain is mostly occupied by the Great Indian Desert or the Thar desert.
- This is an undulating plain or a rolling plain, with a wave-like topography of ups and downs.
- The desert is also known by its regional name of Marusthali and forms a part of the Marwar plain.
- Geologically, it's a part of the Peninsular plateau. Hence, low lying rock formations (outcrops) can be found at distant intervals on these plains. They mostly contain peninsular rocks such as granite, schist, and gneiss.
- However, on the surface, it looks like a depositional/aggradational plain.
- The eastern part of the Marusthali is rocky in general, but the western part comprises sand dunes which regularly shift their shape under the influence of local winds. They are locally known as Dhrian.
- Rajasthan Bagar is a semi-arid plain which occupies the intervening space between the Thar desert until the Aravalli range.
- Unlike, the Marusthali region, the plains of Rajasthan have fertile lands which support agriculture because a number of short streams which are seasonal in nature and originate from the Aravallis drain the region.
- One such short coursed river is Luni which is an ephemeral river flowing into the Rann of Kutchch.
- This plain is formed by the deposition of sediments by the tributaries of Indus viz., Jhelum, Chenab, Sutlej, Beas, and Ravi
- This region is characterized by Doabs - the area in between two rivers.
- This plain has an average elevation of 250 m above the MSL
- Apart from deposition, this plain also experienced intensive erosion due to numerous streams flowing from the Shiwaliks termed as Chos. This gave rise to a gully landform, characteristic of an arid region.
- Malwa plain is a part of the Punjab plains and lies to the south of the Sutlej.
- Delhi ridge (the northernmost extent of Aravallis) forms the eastern boundary of these plains.
- Ghaggara is a river which is considered to be the present day remnant of the legendary river Saraswati. It lies in Haryana, in between Sutlej and Yamuna.
- With an area of around 3.75 lakh sq.km, this is the largest section of the Northern Plains.
- This region includes sediments brought down and deposited by the Himalayan rivers as well as the Peninsular rivers. Himalayan rivers include the Ganga and its tributaries such as Yamuna, Gandak, Kali, Kosi etc. and Peninsular rivers include such as Chambal, Ken, Betwa, Son etc.
- Since the plain is gently sloping towards the southeast, most of the rivers that flow through this region drain into the Bay of Bengal.
- The lower reaches of Ganga and its tributaries are characterized by various landforms such as oxbow lakes, marshes, etc. due to a slow movement of rivers leading to extensive sediment deposition which can alter the courses of these rivers over a period.
- Kosi is considered to be the "sorrow of Bihar" due to frequent floods in its catchment area. These occur because it flows from great heights onto a plain accompanied by deposition of huge amounts of sediments along its riverbed. This causes the river to change its course frequently, flooding the areas along its course.
- This is true for other rivers of this region too, though they do not cause floods as severe as those along the Kosi floodplains.
- The region is further divided into - Rohilkhand plain, Awadh plain, Mithila plain, and Magadh plain
- It is formed by the deposition/aggradation of sediments by the Brahmaputra and its tributaries.
- It is mostly situated in Assam, in the Brahmaputra valley in Assam. The region is bounded by the Purvanchal hills on its east and the Gangetic plain on its west
- Due to the huge sediments brought down by the Brahmaputra, the river bed gets filled causing it to split into a number of braided channels in this region. Majuli is the largest river island in the world and is situated in the Brahmaputra valley of Assam
- The tributaries of Brahmaputra also bring down a large volume of sediments. This results in a number of depositional landforms such as oxbow lakes, river islands etc.
- Apart from these, the region also has a number of marshy tracts, giving rise to terai like conditions.
Ganga - Brahmaputra Delta
- The largest delta in the world, formed by the joining of the two largest rivers of the Indian subcontinent - Ganga and Brahmaputra.
- This is an aggradational landform in which the merged river of Ganga and Brahmaputra, known as the Padma, flows in the form of a number of channels.
- This a low lying region, with some of the delta lying up to 30m below the MSL. This makes the region highly vulnerable to climate change (sea level rise).
- Towards the mouth of the delta, there is a large mangrove forest famous for its Sundari trees and is known as the Sunderbans.
Characteristics of Indo - Gangetic - Brahmaputra plains
- The narrow belt of the plains at the foothills of Himalayas comprises boulders and pebbles brought by the rivers, making it a porous region is known as Bhabar. Most of the streams disappear in this region, flowing under the rocky layer. This region is not suited for crop cultivation.
- Adjacent to Bhabar is a region comprising newer alluvium and finer sediments. This is the Terai region and is a densely forested marshland. At present, the Terai is extensively cultivated and densely populated. Rice, wheat, sugarcane, maize, pulses, and oilseeds are some of the important crops cultivated in this region
- Calcareous deposits or kankar make up a very large area of the plains. This region contains the older alluvium, along with the terraces of the floodplains and is known as Bhangar. Since the old alluvium is rich in humus, it is one of the most productive agricultural regions of India.
- The region next to the old alluvium is the region of Khadar, which comprises new alluvium. It is made of sand, silt, clay and fine mud. It is an extensively cultivated region, similar to Bhangar.
- The fertile tracts of land, availability of water, and vibrant cultivation of crops makes the region a highly populated one. The Indo - Gangetic plains have a dense network of roads and railways crisscrossing them, facilitating the growth of many industries.