The Terai or Tarai is a lowland region in northern India and southern Nepal that lies south of the outer foothills of the Himalayas, the Sivalik Hills, and north of the Indo-Gangetic Plain. This lowland belt is characterised by tall grasslands, scrub savannah, sal forests and clay rich swamps. In North India, the Terai spreads from the Yamuna River eastward across Haryana, Uttarakhand, Uttar Pradesh, Bihar and West Bengal. The Terai is part of the Terai-Duar savanna and grasslands ecoregion. The corresponding lowland region in West Bengal, Bangladesh, Bhutan and Assam in the Brahmaputra River basin is called 'Dooars'. In Nepal, the term is applied to the part of the country situated north of the Indo-Gangetic Plain. Nepal's Terai stretches over , about 23.1% of Nepal's land area, and lies at an elevation of between . The region comprises more than 50 wetlands. North of the Terai rises the Bhabar, a narrow but continuous belt of forest about wide. Etymology The Urdu word तराई tarāʼī means "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". In Hindi, the region is called 'tarāī' meaning "foot-hill". In Nepali, the region is called 'tarāi' meaning "the low-lying land, plain" and especially "the low-lying land at the foot of the Himālayas". It has been described as "low, marshy ground". Geology 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 alluvial deposits of mainly 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 Sivalik 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