At Kerschbaumsiedlung which is located within the municipality of Navis in Tirol, Austria, massive damage to buildings has occurred as a result of slope instabilities which are being mainly expressed into two discrete forms: a deep sited landslide and an earth flow. The reason for these land movements is, on the one hand, a deep sited rock slide, and on the other hand, an earth flow with a thickness of up to 40 m. Movement rates on the surface of the earth flow were determined by means of a total station and reached velocities of 1-3 cm / a. The difference in altimeter between the ridge region and the foot of the slope (Navisbach) is about 1000 m. The average slope is about 22 The aim and challenge of this Masters Thesis was to investigate to what extend the long-range (overall) slope movement is influenced or controlled by seasonal fluctuations of the mountain water-table level.^ ^In order to answer these questions, a numerical model was developed using the Distinct Element Code UDEC (Itasca Consulting Group). The effect of minor changes in the mountain water-table on the factor of safety has been modeled, based on hydrological data of the Torrent and Avalanche Control, Austria, and data reported in the Masters Theses of Pichler (2015) and Rieder (2016) In the numerical investigations, the stability of the slope was systematically assessed for different mountain water-table levels, by calculating the global safety factor according to ÖNORM B4433. The safety factor was derived by means of the strength reduction method, which was applied both to the strength parameters of the intact rock as well as to the strength parameters of the discontinuities.^ ^With the help of UDEC and the calculations carried out according to the balance equilibrium approach, it has been possible to quantify the effects of mountain water-table level fluctuations on mass movement rates, as well as, to recognize their basic mechanical relationships and interaction. It could also be shown that sliding surfaces, calculated in this Thesis compared with those reported in the work of Pichler (PICHLER, 2015), can occur at the same depth but a different failure mechanism, other than sliding on polygonal surfaces could be in effect.