2) , Jean-Louis Boillat (3) and Anton J. Schleiss (4) (1), (2), (3),(4) Laboratory of Hydraulic Constructions (LCH), Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 18, CH-1015 Lausanne, Switzerland, phone: +41 21 693 2385, fax: +41 21 693 2264 e-mail: (1) email@example.com, (2) firstname.lastname@example.org , (3) email@example.com and (4) firstname.lastname@example.org ABSTRACT ... [Show full abstract] Understanding the complex three-dimensionality of flow and the interaction of flow patterns with the fluvial dynamics of confluences is important in river rehabilitation projects. Despite recent advances, sediment transport and morphological dynamics in confluences are still not fully understood. Systematic experiments are performed in a confluence where the main channel is 8.5 m long and 0.50 m wide. A second channel (tributary) of 4.90 m length and 0.15 m wide is connected with an angle of 90°, 3.60 m downstream of the inlet of the main channel. Three tests with different momentum flux ratios M r (ρQU tributary /ρQU main) are compared. Tests are run with a constant solid discharge at the tributary. With the increase of M r , the discordance between the tributary and main channel, the penetration of the tributary into the main channel and the deposition at the separation zone are reduced. Moreover, grain sorting can be observed at the confluence zone.