Landslide Susceptibility Maps in Slovenia: landslides, rock falls & debris flows

Situated in the South-Eastern Alps, Slovenia belongs to the (high-)mountainous countries of Europe, with Mount Triglav marking the highest elevation at 2,864 masl. The country is crossed by several mountain ranges in the north and the Dinaric Alps stretching from the center towards the south-east; further south-west, a karst plateau elevates the topography of the country. Throughout all the lithologic and topographic diversity, mass movements are common and frequently associated with a variety of spatial factors favoring their formation.

Slovenia recognizes the need for comprehensive mapping of mass movements and analyzing the associated contribution factors to provide safe frameworks for land use planning, and the Slovenian Geological Survey (GeoZS) has been working regularly in accordance with these guidelines for several years. Initial works by Komac (2000–2009) set prominent contributing factors (e.g., lithology, elevation, slope aspect, slope inclination, terrain roughness, terrain curvature, distance to streams, distance to faults, and land cover) in relation to landslide formation by uni- and multivariate statistics. Here, the term “landslide” covers different types of mass movements without further differentiation.

Based on the relations of the univariate statistical analysis, further refined individual algorithms were developed for landslides, rock falls and debris flows, selecting and gradually adjusting contributing factors for each of the three phenomena.

Applying fuzzy logic and linear membership functions, weights are attributed to relevant factors for landslides, rock falls, and debris flows, respectively. This concept entails that the GeoZS’ approach to the national risk assessment of mass movements is based on susceptibility (i.e., not on probabilities) and, hence, the notion of return periods for events of specific characteristics does not apply.

We present the Slovenian Landslide Susceptibility Map at the scale of 1:250,000 as well as some of the 95 already processed municipality Landslide Susceptibility Maps at the scale of 1:25,000 reflecting the geomorphologic variability of the country resulting in different mass movement patterns with respect to magnitude, frequency, type, contributing factors, and associated risk.

The map at the scale of 1:250,000 is one of the components of the Slovenian Landslide Forecasting and Warning System MASPREM.