**2. Study Area**

The study site is a failure-prone hillslope at the Dollendorfer Hardt located 16 km south-east of the city of Bonn in the Siebengebirge, Germany (Figure 1). This site has been investigated in several previous studies since the 1990s [39–41]. At least two major landslides occurred at the study site in the past 100 years (1958 and 1972), and minor movements have been observed since the last failure event [39,40]. There is anecdotal evidence that attributes the initiation of the first major landslide to the construction of a trail at the upper part of the current scarp area. However, intense rainfall is suspected to be the triggering factor of both major events [38].

**Figure 1.** Location of the study site near Bonn, Germany (source: Google Earth).
