The Post-Forum Study Tour following the 4th World Landslide Forum 2017 in Ljubljana (Slovenia) focuses on the variety of landslide forms in Slovenia and its immediate NW surroundings, and the ...best-known examples of devastating landslides induced by rainfall or earthquakes. They differ in complexity of the both surrounding area and of the particular geological, structural and geotechnical features. Many of the landslides of the Study Tour are characterized by huge volumes and high velocity at the time of activation or development in the debris flow. In addition, to the damage to buildings, the lives of hundreds of people are also endangered; human casualties occur. On the first day, we will observe complex Pleistocene to recent landslides related to the Mesozoic carbonates thrust over folded and tectonically fractured Tertiary siliciclastic flysch in the Vipava Valley (SW Slovenia), serving as the main passage between the Friulian lowland and central Slovenia, and thus also an important corridor connecting Northern Italy to Central Europe. A combination of unfavourable geological conditions and intense short or prolonged rainfall periods leads to the formation of different types of complex landslides, from large-scale deep-seated rotational and translational slides to shallow landslides, slumps and sediment gravity flows in the form of debris or mudflows. The second day of the study tour will be held in the Soča River Valley located in NW Slovenia close to the border with Italy, where the most catastrophic Stože landslide in Slovenia recently caused the deaths of seven people, and the nearby Strug landslide, which is a combination of rockfall, landslide and debris flow. The final day of the Post-Forum Study Tour will start in the Valcanale Valley located across the border between Slovenia and Italy, severely affected by a debris flow in August 2003. The flow caused the deaths of two people, damaged 260 buildings; large amounts of deposits blocked the A23 Highway, covering both lanes. In Carinthia (Austria), about 25 km west of Villach, the Dobrač/Dobratsch multiple scarps of prehistoric and historic rockslides will be observed. Dobratsch is a massive mountain ridge with a length of 17 km and a width of 6 km, characterized by steep rocky walls. The 3-day study tour will conclude with a presentation of the Potoška planina landslide, a slide whose lower part may eventually generate a debris flow and therefore represents a hazard for the inhabitants and for the infrastructure within or near the village of Koroška Bela.
The Rebrnice area in the Upper Vipava Valley, SW Slovenia, is covered by Quaternary slope deposits that are very complex in their genesis and composition. Some of the sediments are deposited in the ...form of heterogeneously composed fossil landslides. One of these landslides in the Rebrnice area is the Lozice fossil landslide located above the village of Lozice. Analysis of this landslide includes geological mapping of the fossil landslide, classifiation of different sedimentary facies, 3-D modelling of the landslide, and transverse and longitudinal cross-sections. The geological mapping of the fossil landslide is based on fild work mapping and analysis of shaded digital terrain models (DTMs) with a resolution of 1 × 1 m obtained by airborne laser scanning. Lithological data from boreholes and excavation trenches have been classifid into eight specifi sediment facies that had been defied in previous studies. The 3-D model of the landslide was made using the ArcScene application in the program ESRI ArcGIS. For each sediment facies, a surface was made in the form of a Triangulated Irregular Network (TIN), which gave us a wireframe object. TIN nets were merged in Multipatch objects and exported to 3-D Analyst, where a 3-D model was created. In addition, a shaded DTM image was added for a better placement of the 3-D model in space. Previous fidings indicate that deposition of fossil landslides in the Rebrnice area was inflenced by palaeotopography. Based on borehole data, transverse and longitudinal cross-sections of the fossil landslide were made and indicate concave depressions under the Lozice fossil landslide. Analysis of the Lozice fossil landslide indicates its complex structure of intertwined heterogeneous sedimentary facies.
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