Morphological evolution and dynamics of a large, sand braid‐bar, Jamuna River, Bangladesh

The initiation and evolution of a kilometre‐scale, sand braid‐bar was monitored during a 28‐month survey period from 1993 to 1996 in one of the world’s largest braided rivers, the Jamuna River, Bangladesh. Repeated bathymetric surveys through two monsoon flood seasons, combined with bar‐top surveys during exposure of the bar at low flow, provide the most detailed chronology of braid‐bar growth yet compiled for a large sand‐bed river. During rising and peak flow of the 1994 monsoon flood, a 1·5‐km‐long, 0·5‐km‐wide, 12‐m‐high, symmetrical mid‐channel bar was deposited in the centre of a major channel downstream of a zone of flow convergence and significant bank erosion. Initial deposition and growth of the bar core were probably caused by amalgamation of dunes that…