Sedimentary structures exposed in bar tops in the Brahmaputra River, Bangladesh

Abstract The Brahmaputra River is one of the world’s largest sand-bed braided rivers with a channel belt up to 15 km wide, a mean channel depth of 5 m and maximum scour depths of up to 40 m. The recorded discharge varies by around 60 000 cumecs every year following the annual monsoon, producing dramatic stage fluctuations with the water level falling between 7 and 8 m from bankfull to low flow stage. In the dry season large areas of bar top and channel bed are exposed and low flow channels cut natural sections through bar tops exposing the internal stratification. Elements of upstream, downstream and lateral accretion are identified, although the high width/depth ratio of channels (up to 500:1)…