“…We test different FS formulations (Table 1) to 20 investigate the role of different conditions of the slope instability in the following states: dry infinite slope, submerged infinite slope, infinite slope with seepage parallel to slope and infinite slope with seepage and tree roots (Cruikshank, 2002;Lambe and Whitman, 1969;Turner and Schuster, 1996;Budhu, 2000;Abramson et al, 1995). The following parameters are involved in the quantification of FS: C, cohesion of dry soil; C, cohesion of saturated soil; t, thickness of the slide; d, vertical distance of the sliding body; γ, unit weight of dry soil; θ, slope gradient; ϕ, angle of internal friction of dry soil; γ t, total unit 25 weight material; γ w, unit weight of water; ϕ, angle of internal friction of saturated soil, (Jibson, 2007). Landslides are initiated at locations that exceed D N = 15 cm (Jibson et al, 2000).…”