The Brahmaputra floodplain is the broad, braided river valley that the Brahmaputra builds across Assam in northeastern India and then northern Bangladesh, where the river is called the Jamuna. In Assam the valley runs roughly 1,000 km long and 80 to 100 km wide, and the river follows a 700 km braided course through it, spreading more than 8 km from bank to bank in the monsoon. It is a landscape of shifting sand islands (chars), oxbow lakes called beels, tall grassland and rice fields. Part of it is protected: Kaziranga National Park, a reserve forest since 1905 and now a UNESCO World Heritage Site, and Deepor Beel near Guwahati, a Ramsar Wetland of International Importance since November 2002. Above all, it is a floodplain where millions of people live. Assam alone had 31.2 million people in the 2011 census, and they and the char dwellers of Bangladesh farm, fish, weave and trade on ground that the river remakes every year.
Mising Villages and the Satras of Majuli
The clearest place to see how people adapt to the river is Majuli, an island between the main Brahmaputra channel and an anabranch to its north, reached by ferry from Jorhat. Guinness World Records lists it as the world's largest inland river island. In 2016 it became the first island in India to be made a district. More than 150,000 people live in its 144 villages, about 300 people per square kilometre. The Mising make up about 41% of the population, alongside Deori, Sonowal Kachari and caste-Hindu Assamese communities, and the island's main languages are Mising, Assamese and Deori.
The Mising are a Tibeto-Burman people whose language belongs to the Tani group, related to communities in the hills of Arunachal Pradesh. They probably came down to the plains around the 13th or 14th century looking for fertile land, and today they live mostly in Dhemaji, Lakhimpur and Majuli, which are among the most flood-prone districts on the north bank. The 2001 census counted 587,310 Mising, which made them Assam's second-largest tribe after the Bodo. Mising organisations put the real figure nearer 1.2 million. Their traditional village answer to the flood is the chang ghar, a house raised on posts so that floodwater and silt pass underneath.
Majuli is also the religious heart of the valley. In the 16th century the reformer Srimanta Sankardev and his disciple Madhavdev spread neo-Vaishnavism here and founded monasteries called satras. These became centres of Assamese religion, art and culture, and Majuli has been on UNESCO's Tentative List as a cultural site since March 2004. The river, though, keeps eating the island. Majuli covered about 1,300 km² in the 1790s and about 1,255 km² in the early 20th century. By 2024 it was down to about 880 km². Land that a family farmed a generation ago can now be riverbed.
Aus and Aman Rice, Assam Tea and Sualkuchi Silk
Most farmers on the floodplain depend on a "normal" flood, one that wets the soil and lays down fresh silt. Two of the region's three seasonal rice crops, aus and aman, cannot grow without floodwater. The river has two high-water seasons: snowmelt from the eastern Himalayas raises it in early summer, and monsoon runoff raises it again in late summer. Its average discharge of about 22,000 m³/s can reach roughly 103,000 m³/s in flood. At Pandu, near Guwahati, the highest daily discharge on record was 72,726 m³/s, in August 1962. Snow and glacier melt supplies about 27% of the river's yearly runoff.
The valley's best-known crop grows on the higher ground along both banks. Assam is the world's largest tea-growing region by production, and its tea comes from a native variety, Camellia sinensis var. assamica. The Singpho people were already brewing it when the Scottish trader Robert Bruce was shown the plant in 1823. After British companies were allowed to rent land from 1839, estates spread through Upper Assam, and planters brought in workers from central and eastern India. That migration changed the valley's population, and the poor conditions of tea labourers outlasted Indian independence.
Weaving is the third pillar. Sualkuchi, on the north bank about 35 km from Guwahati, is known as the "Manchester of Assam" because so many of its households run handlooms. It weaves muga and pat silk into mekhela chadors and gamosas that are sold across India. Assam silk and Assam tea are both registered Geographical Indications. Oil, discovered in the region in 1867 and drilled from 1889, gave the valley its other long-running industry.
Deepor Beel and the Fishing Economy of the Beels
Fish caught on flooded fields and in floodplain ponds are the main source of protein for many rural families on the floodplain, in Assam and in Bangladesh. The beels are central to this. They are oxbow lakes and abandoned channels left behind as the river moves. As the monsoon water drains away, fish are trapped in them, and villagers catch them with bamboo traps and nets on poles. The Ahom king Pratap Singha is said to have praised the fish of Kaziranga in the 17th century, and that meal is one of the oldest records of the park's name.
Deepor Beel, 13 km southwest of Guwahati, shows the way a city and a wetland depend on each other. It lies in a former channel of the Brahmaputra. In the dry season it holds about 10.1 km² of open water, and in floods it spreads to about 40.1 km², rising to about four metres deep before falling back to about one metre. It is the only major storage basin for Guwahati's storm drainage, which makes it the city's flood buffer as well as a fishery. Assam declared 4.1 km² of it a wildlife sanctuary in 1989, and it was listed under the Ramsar Convention in November 2002. Even so, a remote-sensing study reported that its wetland area shrank between 1990 and 2002, and only 414 hectares of the wider beel are protected as a bird sanctuary.
Guwahati, Saraighat and the Bridges of Assam
Guwahati sits at the river's narrowest point. There the Brahmaputra cuts through the rocks of the Shillong Plateau and is about 1 km from bank to bank, compared with up to 20 km elsewhere in Assam. Pragjyotishpura, a capital of the ancient kingdom of Kamarupa, stood here. In 1671 the Ahom commander Lachit Borphukan defeated a much larger Mughal force under Ram Singh I in the Battle of Saraighat, a naval battle fought on the river at Guwahati. It ended the last major Mughal attempt to take Assam. Today Guwahati is the largest city in Northeast India, with 962,334 people in the 2011 census. The state capital, Dispur, lies within its urban area, and the city is also home to Kamakhya Temple.
The width of the river has always made it hard to cross. The Saraighat road-and-rail bridge at Guwahati, completed in 1962, was the first in Assam. Others followed at Tezpur (Kolia Bhomora Setu, 3,025 m) and Bongaigaon (Naranarayan Setu). The Bogibeel road-and-rail bridge near Dibrugarh, at 4,940 m, is the longest on the river. Even so, most people on the islands still rely on boats. Majuli's ferry to Jorhat runs six times a day.
Char Dwellers of the Jamuna in Bangladesh
After turning south around the Garo Hills below Dhubri, the river enters Bangladesh. Below its meeting with the Teesta, most of its water flows south as the Jamuna. This channel is new. Between about 1776 and 1850 the main stream shifted about 80 km west of the Madhupur Tract, leaving the Old Brahmaputra past Jamalpur and Mymensingh as a minor branch. The Jamuna is a textbook braided river, and its sandbars, the chars, form in one flood and are washed away in the next. About 600,000 people live on such river islands. They farm the fresh silt while it lasts and move when the current takes it.
Because the chars keep moving, even district boundaries are uncertain. The border between Sirajganj and Pabna on one bank and Mymensingh, Tangail and Dhaka on the other has never been fixed precisely. When a char breaks up or a new one appears, the result is often violence and lawsuits over who owns it. Bank erosion slowed from about 150 m a year in 1973–1992 to about 30 m a year, but it has already made about 0.7 million people homeless. The Bangabandhu Bridge, opened in June 1998 at a narrow point in the braid belt, is 4.8 km long. It carries road, rail, gas, power and telecom lines across a river that defeats most permanent structures.
The Floods of 1998, 2004 and 2012
The same water that feeds the rice can also destroy it. In 1998, a flood lasting from July to September covered more than 70% of Bangladesh, affected 31 million people and killed 918. In 2004, 36 million people in Bangladesh were affected and about 800 died. Some 952,000 houses were destroyed, and 1.1 million hectares of rice went under water before harvest. In 2012 an unprecedented flood along the Brahmaputra and its tributaries in India, Bangladesh and Myanmar killed 124 people and displaced about six million, with Assam the worst hit. In Kaziranga, where floodwater covers 70–80% of the park for 5 to 10 days at a time in a big flood, 540 animals died.
Kaziranga shows the trade-off between people and wildlife most sharply. It holds the world's largest populations of the Indian rhinoceros (2,401) and wild water buffalo (1,666). During floods, most animals leave for higher, forested ground beyond the park's southern border, such as the Mikir Hills, which means crossing land that people use. Tourism has brought jobs and income to the villages on the park's fringe. That is the pattern across the whole floodplain: a living taken from the river, and losses when it floods. The river's full course, from the Tibetan plateau to the sea, is traced in our Brahmaputra River guide. What happens where it joins the Ganges is covered in the Ganges–Brahmaputra Delta article, and the wider setting of the char lands is explained in our look at the geography of Bangladesh.