The northeastern slope of the Sella group near Corvara was hit in year 2014 by a hill-slope debris flow (also called debris avalanche). Therefore with the present work a geological investigation of the slope has been carried out. The main lithologies in the area are the St. Cassian formation, the Wengen formation and the Cassian dolomite. A sediment-petrographical analysis was performed on thin sections of the St. Cassian formation resulting in a marine depositional setting, with its depth located between the platform slope and the deep shelf. Different genera of foraminifera belonging to the suborders Textulariina, Fusulinina, Involutinina, Miliolina, Lagenina and Robertinina, as well as some algae and microproblematica have been recognised. The biostratigraphical analysis showed salinity of normal marine marshes, with reduced biodiversity in the lower part of the section, probably due to scarce oxygenation of water. By analogy, the mudstone prevails in the lower part, while limestone layers prevail in the upper part of the profile. The hill-slope debris flow, with a surface of 70,000m2 and a depth up to 10m, moved for 250m downwards, mobilizing about 70,000m3 material within two days. The sediment of the landslide is very well graded and contains the whole range of grain sizes, whereas the high amount of fine particles confers to the mass high plasticity and viscous consistency. The rock of the St. Cassian formation is often weathered and narrowly jointed, matching small block dimensions. Laboratory tests on the mudstone have proved their high susceptibility to weathering. The monitoring of a crack on the slope shows a sudden widening in summer 2016. There are many springs by the foot of the slope, some of which are highly mineralised, suggesting the presence of an intergranular and probably fractured rock aquifere along the slope. The preparatory factors for the landslide are represented by the high joint count and the high affection by weathering of the St. Cassian formation, as well as the destabilisation due to tectonic deformation. The rapid snowmelt and the long rainy period before the event are involved as triggering factors of the landslide. For similar reasons during summer 2016 developed a new smaller hill-slope debris flow. Finally, a plan for the hazardous areas has been proposed.