During the stage of reservoir filling in a dam located in the north of Mexico, the presence of a series of cracks was reported along a hillside. The rock mass is this slope began a process of moving at a rate of 4 cm/day, decline until 0.5 cm/day at the last measurement step. Due the rate of apparent continuity in the movement of the rock mass, it was necessary to assess whether it was feasible the abrupt failure of the slope, whose volume is approximately three million cubic meters, which should slide surf that would provoke at risk the safety of the dam. From a series of studies aimed at defining the geomechanical characterization of the slope, it was possible to establish the existing materials and geological structures, allowing the development of a series of analysis which results provide conclusions about the behavior of the slope to changes producing variations of the reservoir as well as the forecast of the effects for quick emptying and an unfavorable impact of earthquake in the area. In order to show the procedure followed and the results obtained in this evaluation, this paper validate the response of the numerical model through a comparison with traditional limit equilibrium analysis is presented, allowing to define the likely behavior of rock mass located in a geologically extensional region in which there is a change in the stress state due to anthropogenic activities such as the construction of a hydroelectric project