After a long rainy season in February 2014, a large landslide was launched on the slope along the river Rječina, not far from the city of Rijeka. After the landslide activation, studies were conducted that revealed the existence of two sliding surfaces, one by which the sliding took place in 2014 and one much larger, which shows that the slid of the observed slope happened a lot prior then 2014., and which activity has not been recorded. Therefore, the 2014 landslide is a reactive landslide whose sliding surface is entirely situated in the sliding body of that historic landslide. At the bottom of the landslide is the reservoir and dam Valici, which is why there is a danger of material slipping into the reservoir, overflowing the dam and creating a water wave that would cause the water level in Rijeka to rise. The slope on which the Valici landslide lies is formed in a flysch lying on limestone, and the peaks of the slope are composed of limestone rocks forming cliffs. Unlike limestone, flysch is sensitive to weather conditions, so where flysch is exposed to them, rock mass is consumed and clay deposits form above the fresh flysch base. At the contact of the two geological units, the clay deposits with different proportions of unbound to weakly bound fragments of limestone origin that arrived from the tops of the slopes and the base rock, flysch, a surface of fracture developed. A reverse 3D analysis of the historic Valici landslide was performed using the Hungra (1987) method to determine soil parameters at the time of collapsing. In addition, an analysis for different groundwater levels was conducted in order to determine the effect of groundwater level on the slope safety factor.