In this paper we present a modified version of an existing, physically-based model for shallow landslide susceptibility analysis over large area. In general, the potentially unstable soil cover is considered uniform and homogeneous, over impervious underlying bedrock. In several case studies, this was proven to be unrealistic. The possibility of taking into account the detailed configuration of the soil cover allows having a more accurate estimate of the potentially unstable volumes, which determine the intensity of the considered phenomena. The newly–implemented tool was tested by comparing its results with those obtained from a Finite Element (FE) commercial code, solving the same 1D problem. Then, a parametric analysis was carried out by varying the permeability ratio between the two layers, with the aim of examining the influence of such parameter on the pore-pressure distribution along the vertical profile. As expected, as the permeability ratio increases, the underlying layer tends to behave as an impervious boundary. This increases the chance that only the most superficial soil layer fails. An analysis of the routine performance and efficiency was also done to investigate the response of the model with various tolerances and different spatial discretizations along the vertical profile. As main result, it is shown that the variability in ground conditions may highly affect the pore water pressures and the proposed seepage model can be successfully whether detailed stratigraphy site investigations are available.