Atmospheric phenomena such as rainfall and evapotranspiration contribute to slope movements in unsaturated soils, the study of which requires fully coupled numerical methods, combined with realistic boundary conditions and appropriate mechanical and hydraulic soil properties. This paper focuses on the effect of the hydraulic behaviour, and in particular of the modelling of the soil-water retention curve and the permeability on slope movements, with the aim of identifying which model parameters are critical and, therefore, require careful experimental identification.