After detailed investigations cracks in the support of a 100 years old gallery were attributed to a postglacial landslide reactivated most probably by exceptional rainfalls as well as by works for the renewal of a weir in the valley bottom in 2009. Monitoring showed that landslides just some hundred meters a.s.l. move more rapidly during wintertime caused by reduced evapotranspiration as well as by surface freezing. Thus they behave completely different from landslides in higher altitudes, which are influenced predominantly by snowmelt causing larger displacements during late spring and summer.