Tarai

Also called: Terai · Topic: Structure and Physiography of India: Himalayas, Plains, Peninsula, Coasts and Islands · NCERT: Class 11, Ch 2 "Structure and Physiography"; Class 11, Ch 6 "Natural Hazards and Disasters: Causes, Consequences and Management"

Meaning

Tarai (also spelt Terai) is a wet, marshy belt of land 10-20 km wide, just south of the bhabar. Here, streams that disappeared underground in the bhabar come back to the surface. They have no proper channels, so the land becomes swampy, with thick forest, tall grassland and rich wildlife.

It is a key part of the north-to-south order of zones in the Northern Plain. Its story also shows a big environmental change: swamp forest was cleared for farming after 1950, and the protected areas left over now hold some of India's most important tiger habitat.

Explanation

How the tarai forms (cause → process → result)

• Cause: the bhabar soaks up the water
• Rivers come out of the Shiwalik hills and reach a break of slope (the point where steep hills suddenly meet flat ground).
• They slow down and drop their heaviest load first: boulders, pebbles and gravel. This makes the bhabar, a belt 8-10 km wide.

• This coarse material is very porous (full of gaps that let water through). Small streams sink into it and vanish.

• Process: the water comes back up

• The water that sank into the bhabar flows south underground.
• Further south, the sediment is finer and less porous. Water cannot pass through it easily.

• So the underground water is pushed back up to the surface.

• Result: a marshy belt

• The streams that reappear have no proper channels.
• They spread out over the land and form marshes and swamps.
• Constant wetness supports thick forest, tall grassland and rich wildlife.

Main features

• Width: 10-20 km. It is wider than the bhabar (8-10 km).
• Position: it runs parallel to the Shiwalik foothills, between the bhabar to the north and the bhangar/khadar alluvial plain to the south.
• Soil and water: finer sediment than the bhabar, a high water table and waterlogged ground.
• Vegetation: dense forest and tall grasslands. The grasslands shelter many ungulates (hoofed animals such as deer) and the predators that hunt them [3].
• Landform type: it is part of the piedmont alluvial plain (a plain "at the foot of the mountain", built where rivers leave the hills and drop sediment), together with the bhabar.

Land-use change after 1950

• Clearing for farms
• Much of the tarai was cleared for farming after 1950.

• Refugees and other settlers were resettled there, for example in Udham Singh Nagar (Uttarakhand) and in the Uttar Pradesh tarai.

• Effect

• The tarai became a productive farming belt.
• But the swamp forest was broken into pieces, and only scattered protected areas remain.

Protected tarai today

• Dudhwa Tiger Reserve (UP) is a typical tarai ecosystem. It is made up of Dudhwa National Park, Kishanpur Wildlife Sanctuary and Katerniaghat Wildlife Sanctuary [3].
• Dudhwa is the only place in India with a likely viable population of the nominate (original) sub-species of the northern swamp deer [3].
• Valmiki Tiger Reserve is Bihar's only tiger reserve. It joins Chitwan National Park in Nepal and connects with Sohagi Barwa Wildlife Sanctuary in UP [4].
• The Terai Arc Landscape is a forest-grassland belt that crosses the India-Nepal border. It includes Corbett, Dudhwa and Valmiki and supports tigers, elephants and rhinos [2].

Where it occurs

• India: a strip along the foot of the Shiwalik hills, on the northern edge of the Ganga plain.
• Uttarakhand: Udham Singh Nagar, a tarai district resettled after 1950.
• Uttar Pradesh: the UP tarai, with Dudhwa Tiger Reserve and Sohagi Barwa Wildlife Sanctuary [3][4].

• Bihar: Valmiki Tiger Reserve, on the Nepal border [4].

• Nepal: the tarai continues across the border into Nepal's southern lowlands. Chitwan National Park is joined to Valmiki [4].

• Across the border: the Terai Arc Landscape links protected areas in India and Nepal [2].
• Related belt further east: the Duars of north Bengal and Assam are another piedmont plain. They are known for tea gardens.

Don't confuse with

• Bhabar: lies to the north of the tarai, is 8-10 km wide and is made of coarse, porous pebbles and gravel. Streams disappear in the bhabar and re-emerge in the tarai. The bhabar is dry; the tarai is wet. Corbett lies in the bhabar tract, not the tarai [2].
• Khadar: newer alluvium on floodplains, renewed by river floods almost every year. The tarai is wet because underground water comes back up, not because of yearly floods.
• Bhangar: older alluvium on raised terraces above flood level, with kankar (lime nodules). It lies south of the tarai and is dry and well drained.
• Duars: also a foothill piedmont plain, but in north Bengal and Assam, and known for tea gardens. "Tarai" is the name used for the belt along the Ganga plain from Uttarakhand to Bihar.

Prelims Hooks

• North to south order: Shiwalik → Bhabar → Tarai → Bhangar → Khadar. Streams disappear in the bhabar and re-emerge in the tarai.
• Widths: bhabar 8-10 km, tarai 10-20 km. The tarai is the wider belt.
• Reserve–zone matches: Corbett → bhabar (Uttarakhand); Dudhwa → tarai, northern swamp deer (UP); Valmiki → Bihar's only tiger reserve, next to Chitwan in Nepal [2][3][4].
• Dudhwa Tiger Reserve = Dudhwa National Park + Kishanpur Wildlife Sanctuary + Katerniaghat Wildlife Sanctuary [3].
• Terai Arc Landscape: a cross-border (India-Nepal) belt that includes Corbett, Dudhwa and Valmiki and supports tigers, elephants and rhinos [2].
• Trap: the tarai is marshy because underground streams re-emerge without proper channels, not because of yearly river floods (that is khadar) or heavy rainfall alone.

Mains Points

• Tarai transformation (GS-III, environment):
• After 1950, swamp forest was cleared to resettle refugees and other settlers, for example in Udham Singh Nagar and the UP tarai.
• The tarai became a rich farming belt, but wildlife habitat was broken into small patches.

• Only scattered protected areas such as Dudhwa and Valmiki remain [3][4].

• Cross-border corridors (GS-III):

• The Terai Arc Landscape links Corbett, Dudhwa and Valmiki with Nepal's parks, such as Chitwan [2][4].

• Tigers, elephants and rhinos move across the border, so conservation in India and Nepal has to work together.

• Physiography and land use (GS-I):

• The order bhabar (dry, porous) → tarai (wet, marshy) → bhangar/khadar (fertile alluvium) shows how sediment size and water movement shape soils and land use at the foot of the Himalayas.
• It explains why the bhabar is poor for farming, why the tarai first needed clearing and draining, and why the khadar is the best farmland in the plain.

Related concepts

• Indo-Ganga-Brahmaputra plain
• Bhabar
• Bhangar
• Khadar
• Piedmont alluvial plains
• Riverine island
• Majuli
• Ganga-Brahmaputra delta

Read more

• The Northern Plain: bhabar, tarai, bhangar, khadar and the deltas