In this study the results of Baseline Explicit Algebraic Reynolds Stress model (BSL EARSM), Baseline Reynolds Stress model (BSL RSM) and Speziale-Sarkar-Gatski Reynolds Stress model (SSG RSM) of turbulent flow in an asymmetric compound channel are presented. The numerical results are validated with experimental measurements of Tominaga & Nezu (1991). Secondary flows are captured by all turbulence models at the step-junction between the main channel and the floodplain, where a strong bulging of velocity isolines towards the free surface is observed. The Reynolds stresses are predicted with relatively close agreement to the corresponding experimental data. The turbulence anisotropy and generation of streamwise vorticity are presented and their role in promoting secondary flows is discussed. The results are also analysed in order to evaluate the influence of the underlying hypotheses of each closure model.