The paper tackles some important issues regarding the dynamics of mixtures of gains and water, on the basis of a series of experiments on uniform channel flows of non-cohesive particles and water. Precise measurements of the granular concentration, temperature, velocity, normal and shear stresses are presented. The experiments show the existence of an unstable stratification of collisional and frictional regimes, and, with reference to the time integrated variables, to a relatively smooth transition between the two regimes. The experimental data were interpreted following Bagnold's theory and the kinetic theories. Finally, the paper presents and discusses global relationships in uniform flow condition among depth-integrated parameters (slope, solid and liquid average concentrations, average velocity, water and grains flow depth). (C) 2007 Elsevier B.V. All fights reserved.