“…In many cases of slow slope movements involving colluvial covers, a close correlation between the piezometric levels time evolution and the displacement rates inside the landslide bodies can be observed (Manfredini et al, 1981;Nakamura, 1984;Sangrey et al, 1984;Morgenstern, 1985;Bertini et al, 1986;Cascini et al, 1986;Iverson et al, 1987;Cartier et al, 1988;Sirangelo et al, 1992;Davis et al, 1993;Pouget et al, 1994;Desai et al, 1995;Urciuoli, 1998;Alonso et al, 1999;Russo et al, 1999;Vulliet, 1999;Pellegrino et al, 2000Pellegrino et al, , 2002Piscitelli et al, 2001;Crosta et al, 2003). So it should be taken into account in the numerical analysis: piezometric level variations during time can be obtained introducing the piezometric level time dependence, h w (t), in the Mohr-Coulomb-Terzaghi criterion used to represent τ lim (t), the soil yielding resistance:…”