<P> Between Dibrugarh and Lakhimpur Districts, the river divides into two channels--the northern Kherkutia channel and the southern Brahmaputra channel . The two channels join again about 100 km (62 mi) downstream, forming the Majuli island, which is the largest river island in the world . At Guwahati, near the ancient pilgrimage centre of Hajo, the Brahmaputra cuts through the rocks of the Shillong Plateau, and is at its narrowest at 1 km (1,100 yd) bank - to - bank . Because of the river's narrow width, the Battle of Saraighat was fought here in March 1671 . The first combined rail / road bridge across the Brahmaputra was opened to traffic in April 1962 at Saraighat . </P> <P> The environment of the Brahmaputra floodplains in Assam have been described as the Brahmaputra Valley semi-evergreen forests ecoregion . </P> <P> In Bangladesh, the Brahmaputra is joined by the Teesta River (or Tista), one of its largest tributaries . Below the Tista, the Brahmaputra splits into two distributary branches . The western branch, which contains the majority of the river's flow, continues due south as the Jamuna (Jomuna) to merge with the lower Ganga, called the Padma River (Pôdda). The eastern branch, formerly the larger, but now much smaller, is called the lower or old Brahmaputra (Brommoputro). It curves southeast to join the Meghna River near Dhaka . The Padma and Meghna converge near Chandpur and flow out into the Bay of Bengal . This final part of the river is called Meghna . </P> <P> The Brahmaputra enters the plains of Bangladesh after turning south around the Garo Hills below Dhuburi, India . After flowing past Chilmari, Bangladesh, it is joined on its right bank by the Tista River and then follows a 240 km (150 - mi) course due south as the Jamuna River . (South of Gaibanda, the Old Brahmaputra leaves the left bank of the main stream and flows past Jamalpur and Mymensingh to join the Meghna River at Bhairab Bazar .) Before its confluence with the Ganga, the Jamuna receives the combined waters of the Baral, Atrai, and Hurasagar Rivers on its right bank and becomes the point of departure of the large Dhaleswari River on its left bank . A tributary of the Dhaleswari, the Buriganga ("Old Ganga"), flows past Dhaka, the capital of Bangladesh, and joins the Meghna River above Munshiganj . </P>

What does brahmaputra form after its meeting with the ganga