Multi-phase flows encountered in nature or industry (landslides, mudflows, powder mixtures, ...) exhibit non trivial rheological properties, that can be understood better thanks to model materials and appropriate rheometers. Unsaturated wet granular materials, between dry granular and immersed ones (dense granular suspensions), are one example of multi-phase materials, which rheology was not studied much. We realize for the first time to our knowledge, experiments of wet granular flows over a rough inclined plane : our results show steady uniform flows for a wide range of parameters (the inclination angle and the mass flow-rate). We demonstrate the relevance of the cohesion stress τc well defined in the cohesive Mohr-Coulomd yield criterion τ = τc + μ0 P , with τ and P , the maximal values of the shear and pressure stresses respectively, and μ0 the static internal friction coefficient, for rapid flows. Thus this yield threshold should be extended to the rheology of rapid wet granular flows, by allowing the internal friction μ 6 = μ0 to differ from its static value μ0, after having understood its variations with the experimental parameters.