<title>Use of GPR in developing a facies model for a large sandy braided river, Brahmaputra River, Bangladesh</title>

A large (2 km X 1 km) sand bar has been surveyed using ground penetrating radar (GPR), augmented by vibracoring and trenching, to investigate the sedimentary structures and three-dimensional alluvial architecture. Around 8 Km of GPR profiles were collected with nine survey lines running transversely across the bar at 250 m intervals with a profile along the bar. Profiles image structures beneath the water table to depths of up to 15 m. Reflectors from GPR profiles are interpreted as sets of cross-stratification, channel erosion surfaces, bar slipface accretion, mud-drapes, upstream accretion surfaces and the water table. Elements of upstream, downstream, lateral and cross-channel accretion are identified. Apart from the preservation of a range of dunes, the dominant style of deposition…