This paper describes an application of Large Eddy Simulation methods to the flow in a laboratory-style confluence of parallel channels of unequal depths (Reynolds No. ≈ 13,500), and a natural river channel confluence that also exhibits pronounced bed discordance (Reynolds No ≈ 100,000). The aim is to investigate the formation of periodic flow features inherent in the flow dynamics in river confluences. The laboratory-style confluence predictions are compared with experimental data, and suggest that the simulation was capable of capturing some of the key flow periodicities. The model provides detailed flow and mixing data which help inform understanding of the production and evolution of large scale turbulence features in confluences.