Gradenbach Landslide

The landslide Gradenbach is situated at the junction of the Graden-Valley and the Möll-Valley in Carinthia (Austria). The hamlet Putschall (see Figure 1) is threatened by this landslide. Its active deformation zone involves the entire slope with widths ranging between 600 m and 1.000 m, and extends over approximately 1.000 m in height below the head scarp. The moving mass was estimated with 15·107 m3. The clearly developed main head scarp lies slightly lower than the mountain ridge (2.270 m), see Figure 1. For the past 30 years, the landslide Gradenbach has been investigated using geodetic, geotechnical and seismic surveys. For a summary of these investigations and an interpretation of the kinematics of this landslide reference is made to [3]. During the years 1965 and 1966 a very high acceleration of the movements was observed. However, the catastrophic mass movement came to a halt. This pattern occurred again during the summer months of the years 1972, 1975, 1977, 1980, 1991 and 1992, however, with motions which were not as large as those of 1966.