The Terai is a plain landscape south of the outer foothills of the Himalaya, the Siwalik Hills, and north of the Indo-Gangetic Plain of the Ganges, Brahmaputra and their tributaries. This lowland belt is characterised by tall grasslands, scrub savannah, sal forests and clay rich swamps. In northern India, the Terai spreads eastward from the Yamuna River across Himachal Pradesh, Haryana, Uttarakhand, Uttar Pradesh and Bihar. The Terai is part the Terai-Duar savanna and grasslands ecoregion. Corresponding parts in West Bengal, Bangladesh, Bhutan and Assam east to the Brahmaputra River are called 'Dooars'. In Nepal, the Terai lies at an altitude of between 67 and 300 m (220 and 984 ft) and comprises more than 50 wetlands. North of the Terai rises the Bhabhar, a narrow but continuous belt of forest about 8–12 km (5.0–7.5 mi) wide.
In Sanskrit, the region is called तराई tarāī meaning "foot-hill". In Nepali, the region is called तराइ tarāi meaning "the low-lying land, plain" and especially "the low-lying land at the foot of the Himālayas". The region's name in Urdu is ترای tarāʼī meaning "lands lying at the foot of a watershed" or "on the banks of a river; low ground flooded with water, valley, basin, marshy ground, marsh, swamp; meadow".
The Terai is crossed by the large perennial Himalayan rivers Yamuna, Ganges, Sarda, Karnali, Narayani and Kosi that have each built alluvial fans covering thousands of square kilometres below their exits from the hills. Medium rivers such as the Rapti rise in the Mahabharat Range. The geological structure of the region consists of old and new alluvium, both of which constitute as alluvial deposits mainly of sand, clay, silt, gravels and coarse fragments. The new alluvium is renewed every year by fresh deposits brought down by active streams, which engage themselves in fluvial action. Old alluvium is found rather away from river courses, especially on uplands of the plain where silting is a rare phenomenon.
A large number of small and usually seasonal rivers flow through the Terai, most of which originate in the Siwalik Hills. The soil in the Terai is alluvial and fine to medium textured. Forest cover in the Terai and hill areas has decreased at an annual rate of 1.3% between 1978 and 1979, and 2.3% between 1990 and 1991. With deforestation and cultivation increasing, a permeable mixture of gravel, boulders and sand evolves, which leads to a sinking water table. But where layers consist of clay and fine sediments, the groundwater rises to the surface and heavy sediment is washed out, thus enabling frequent and massive floods during monsoon, such as the 2008 Bihar flood.
The reduction in slope as rivers exit the hills and then transition from the sloping Bhabhar to the nearly level Terai causes current to slow and the heavy sediment load to fall out of suspension. This deposition process creates multiple channels with shallow beds, enabling massive floods as monsoon-swollen rivers overflow their low banks and shift channels. Many areas show erosion such as gullies. 20 of the 75 districts of Nepal are situated in this region.
|Biratnagar, 26°N, 87°E|
|Climate chart (explanation)|
|Chandigarh, 30°N, 77°E|
|Climate chart (explanation)|
- Moving inland and away from monsoon sources in the Bay of Bengal, the climate becomes more continental with a greater difference between summer and winter.
- In the far western Terai, which is five degrees latitude further north, the coldest months' average is 3 °C (37 °F) cooler.
- Total rainfall markedly diminishes from east to west. The monsoon arrives later, is much less intense and ends sooner. However, winters are wetter in the west.
Terai in Nepal
The Terai in Nepal is differentiated into "Inner" and "Outer" Terai.
The Inner Terai refers to the river valleys in the lowlands of southern Nepal located between the Mahabharat and Shivalik ranges. In Nepali, they are called 'bhitri madhes'. The Inner Terai comprises five elongated valleys extending from north-west to south-east parallel to the enclosing hilly ranges:
- Surkhet Valley (Nepali: सुर्खेत) is in the Surkhet district, north of the Kailali and Bardiya districts;
- Dang Valley (Nepali: दाङ) is in the Dang Deokhuri district;
- Deukhuri Valley (Nepali: देउखुरी) is located south of the Dang Valley in the Dang Deokhuri district;
- Chitwan Valley (Nepali: चितवन) comprises the Chitwan and Makwanpur districts;
- Kamala Valley, also called Udayapur Valley (Nepali: उदयपुर) is in the Udayapur district north of the Siraha and Saptari districts.
Most of these valleys are five to ten kilometers wide (north-south) and up to a hundred kilometers long (east-west).
The 2001 national census counted 2.3 million population (10% of the national total) in these seven Inner Terai districts (counting Banke district as Outer Terai). Adding 45% in the outer Terai gives 55% of Nepal's population living in its Terai districts.
The Outer Terai begins south of the Siwalik Hills and extends to the Indo-Gangetic plain. In the Far-Western Region, Nepal it comprises the Kanchanpur and Kailali districts, and in the Mid-Western Region, Nepal Bardiya and Banke districts. These were once called the Naya Muluk and lay on the periphery of the Awadh dynasty. After Nepal lost the Anglo–Nepalese War (1814–1816), these districts were annexed by the British in the Sugauli Treaty and returned in 1860 as reward for Nepal's military aid in the Indian Rebellion of 1857. Farther east, the Outer Terai comprises the Kapilvastu, Rupandehi, Nawalparasi, Parsa, Bara, Rautahat, Sarlahi, Mahottari, Dhanusa, Siraha, Saptari, Sunsari, Morang and Jhapa districts.
East of Banke the Nepalese Outer Terai is interrupted where the international border swings north and follows the edge of the Siwaliks adjacent to Deukhuri Valley. Here the Outer Terai is entirely in Uttar Pradesh's Shravasti and Balrampur districts. East of Deukhuri the international border extends south again and Nepal has three more Outer Terai districts.
The 2001 national census counted 10.3 million population (45% of the national total) in the Outer Terai districts.
Until the mid 18th century, the Terai was divided into several smaller kingdoms, and the forests were little disturbed. Forest stands comprised mainly Sal. Heavy logging began in the 1920s. Extracted timber was exported to India to collect revenues. Cleared areas were subsequently used for agriculture.
Inner Terai valleys historically were agriculturally productive but extremely malarial. Some parts were left forested by official decree during the Rana dynasty as a defensive perimeter called Char Kose Jhadi, meaning 'four kos forest'; one kos equals about 3 km (1.9 mi). A British observer noted, "Plainsmen and paharis generally die if they sleep in the Terai before November 1 or after June 1." British travelers to Kathmandu went as fast as possible from the border at Raxaul to reach the hills before nightfall.
Malaria was eradicated using DDT in the mid-1950s. Subsequently, people from the hills migrated to the Terai. Timber export continued to 1969. In 1970, the king granted land to loyal ex-army personnel in the districts of Jhapa, Sunsari, Rupandehi and Banke, where seven colonies were developed for resettling about 7,000 people. They acquired property rights over uncultivated forest and 'waste' land, thus accelerating the deforestation process in the Terai.
Tharu people are the traditional inhabitants of the Terai forests. They were semi-nomadic, practised shifting cultivation and collected wild fruits, vegetables and medicinal herbs. They have been living in the Terai for many centuries and reputedly had an innate resistance to malaria. Following the malaria eradication program using DDT in the 1960s, a large and heterogeneous non-Tharu population settled in the region.
Pahari farmers from the mid-hills moved to the plains in search of arable land including Bahun, Chhetri and Newar. In the rural parts of the Terai, distribution and value of land determine economic hierarchy to a large extent. High caste migrants from the hills and traditional Tharu landlords who own agriculturally productive land constitute the upper level of the economic hierarchy. The poor are the landless or near landless Terai Dalits, including the Musahar and Chamar, as well as the traditional fishermen, the Mallaah, and some of the Hill Dalits. In particular the Musahars rarely get other work than hard farm labor.
The Terai is the most productive region in Nepal with the majority of the country's industries. Agriculture is the basis of the economy. Major crops include rice, wheat, pulses, sugarcane, jute, tobacco, and maize. In the eastern districts from Parsa to Jhapa they support agro-based industries: jute factories, sugar mills, rice mills and tobacco factories.
Cities over 50,000 population in Nepal's Terai include:
|Biratnagar||Morang||166,674||agro-industry, education, trade/transport Hub|
|Birganj||Parsa||112,484||trade/transport hub, agro and other industry|
|Dharan||Sunsari||95,332||tourism hub and destination, education, financial services|
|Bharatpur||Chitwan||89,323||agro-industry and food processing, tourism, health care, education|
|Bhim Dutta||Kanchanpur||80,839||transport hub, education, health services|
|Butwal||Rupandehi||75,384||transport hub, retailing, agro-industry, health care, education|
|Hetauda||Makwanpur||68,482||transport hub, cement factory, large and small-scale industry|
|Janakpur||Dhanusa||67,192||transport hub, agro-industry, education, health care, pilgrimage site|
|Nepalganj||Banke||57,535||transport hub, retailing, financial services, health services|
|Siddharthanagar||Rupandehi||52,569||trade/transport hub, retailing, tourist and pilgrim services|
Mahendra Highway crosses the Nepal Terai from Kankarbhitta on the eastern border in Jhapa District, Mechi Zone to Mahendranagar near the western border in Kanchanpur District, Mahakali Zone. It is the only motor road spanning the country from east to west.
Tourist attractions in the Terai include:
- Lumbini, birthplace of Lord Buddha (near Siddharthanagar)
- Bardia National Park (near Nepalganj)
- Chitwan National Park (near Bharatpur)
- Janakpur, the birthplace of Sita, wife of Rama in the Ramayana.
Terai in India
This section requires expansion. (April 2011)
In India, the valleys in the inner Terai are called Dūn (Hindi: दून). The Terai extends over the states of Uttar Pradesh and Uttarakhand. These are mostly the districts of these states that are on the Indo-Nepal border:
- Uttar Pradesh: Pilibhit, Gonda district, Ballia, Bahraich, Balrampur, Siddharthnagar, Maharajganj
- Uttarakhand: Udham Singh Nagar district
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