This dataset contains numerical model output of a morphodynamic and sedimentological simulation of a large river confluence based loosely on the Jamuna-Ganges junction in Bangladesh. The work was carried out as part of a joint project between the Universities of Birmingham, Southampton and Exeter. "The sedimentology of fluvial megascours" was a scientific research project funded by NERC. One aspect of the project was to undertake numerical simulations (the data described here) with which to compare with river bed bathymetry data (collected using a multibeam echosounder) and sub bottom seismic profiling data (collected using a surface tow boomer and chirp system). The data has been accepted for a publication in the journal 'Sedimentology' which will be published in 2018 with the title 'The Sedimentology of channel confluences'.