Use of a LiDAR-derived landslide inventory map in assessing Influencing factors for landslide susceptibility of geological units in the Petrinja area (Croatia)

A landslide inventory was created for an area of 22.6 km2 near Petrinja city in northern Croatia, based on the high-resolution LiDAR data complemented by orthophoto maps. A total of 216 landslides were identified, covering 2.91 % of that area. Landslide polygons were overlain on geological units based on the Basic map of SFRY at a scale of 1:100,000 that is the largest scale geological map available for the whole of Croatia. The relationship between landslides and geological units was expressed as a landslide index. Three geological units displayed increased landslide susceptibility. A Pliocene unit clearly had the largest susceptibility, followed by a Palaeocene-Eocene unit, and finally a Badenian unit. Landslide density was analyzed within these geological units to identify influencing factors for landslide initiation. Each geological unit revealed different influencing factors. The Pliocene unit is mostly influenced by bedding plane orientation and local relief. Heterogeneousness lithology is the dominant factor in the Paleocene-Eocene unit, while the Badenian unit demonstrated the least certain interpretation as there are multiple factors involved. The forest road is presumed to be crucial, followed by spring occurrences and proximity to the tectonic boundary. The basic geological map of SFRY proved to be a viable source of geological information for the creation of landslide susceptibility maps at a scale of up to 1:100,000, but with limitations in the case of lithologically heterogeneous geological units. Larger scale maps require more detailed research as landslide susceptibility factors vary in each geological unit.