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 Slano blato landslide is situated above the village of Lokavec, in the western part of Slovenia. This area is one of the seismically most active parts of the country. Considering just the last ...decade, movement of the landslide was observed in November 2000, when the displaced material reached a velocity of 60–100 m/day. Silty and clayey gravel above flysch layers of marl and sandstone formed the landslide mass.
Geotechnical investigations of the landslide were performed in 2003 and 2004, when the depth of the landslide was determined, as well as the geotechnical parameters and the sliding mechanism. Rheological tests were also carried out for further analysis. Based on the investigation results and the observed landslide velocity, the landslide was classified as an earth flow. Inclinometer measurements showed that the landslide has two shear surfaces, with different behaviour shown as each.
A stability analysis was carried out numerically by applying the Mohr–Coulomb and Burger elasto–plastic models. The Mohr–Coulomb model indicated that the high water level influences the landslide instability. In the case of the Burger elasto-plastic model, a higher velocity was calculated, at a water content of between 35 and 40%.
The Slano Blato landslide is more than 1290m long, 60 to 200m wide and 3 to 11m deep with a volume of about 700000m3. It is located in the Eocene flysch region of western Slovenia with a limestone ...overthrust in the direct vicinity, above the landslide. The landslide moves mainly as a viscous earth flow with occurrences of rapid mud flows. In dry periods or in freezing conditions it behaves as a group of several slow to moderate landslides. The landslide follows the course of the Grajšček stream and is presently only 220m away from Lokavec village. The landslide was first mentioned about 200 years ago. In 1887 it flowed as a liquid flow and reached and destroyed the main road in the valley 2 km away. The Austro-Hungarian monarchy sent one engineer to the site and 17 years later the slide was remediated with a series of torrential check dams. The monarchy prohibited any construction works in the influence area of the landslide. During the 20th century the region changed from Austrian, Italian, Yugoslav, and finally to Slovenian government in 1991. The relevant Austrian measures and decisions were forgotten during the course of the years, and building permits were issued after the World War II to local people who populated the part of the landslide influence area. Simultaneously, regular maintenance of the excellent past engineering works was neglected. In November 2000 a large landslide of mud and debris was triggered again and it still presents a danger to the relatively new residential houses today. At present, the village is protected against mudflows by a small rockfill dam and by the regulation of the stream bed. In rainy periods removal of mud is necessary to maintain safe conditions for the village. The paper discusses the geological, hydrogeological, hydrological and geotechnical conditions for the occurrence of the Slano Blato landslide. The primary reasons for the Slano blato landslide are the geological and hydrogeological conditions just beneath the overthrust of a Triassic limestone plateau over the Eocene flysch of Vipava valley. The direct reason for triggering the earth flow in 2000 was the intensive precipitation. During the course of years the precipitation threshold for earth flow movements has diminished. The landslide has to be remediated for two main reasons – (1) the village below the landslide is endangered, and (2) the landslide is still advancing retrogressively and laterally. The foreseen permanent remediation measures that are currently under construction are briefly presented.
Extended description:
Lokavec: napisna tabla, cesta, panorama vasi Lokavec, o zgodovini kraja pripoveduje Boris BLAŠKO, travniki v okolici, stare hiše, deklica Anja v šoli bere spis o nastanku vasi, ...potoki v okolici, deklica Polona bere spis Kovač pri delu, stare smuči, smučar na snegu, vaška gostilna in prireditev Lokavška furenga. Ročno sekanje lesa v gozdu, debla vlačijo s konji, star mlin, notranjost, nakovalo, Boris BLAŠKO pripoveduje o domačinu, izumitelju ladijskega vijaka Jožefu Resslu, opuščena cesta, kmetija Tatjane ŽIGON, konjski hlev, žrebiček, deklica Katarina bere zgodbo v narečju, hiše, portali cesta skozi vas, krajevna tabla Lokavec.
Our place: introducing the village of Lokavec in Vipavska dolina valley.
Original language summary:
Naš kraj: predstavitev naselja Lokavec v Vipavski dolini.
Extended description:
Lokavec: napisna tabla, cesta, panorama vasi Lokavec, o zgodovini kraja pripoveduje Boris BLAŠKO, travniki v okolici, stare hiše, deklica Anja v šoli bere spis o nastanku vasi, potoki v okolici, deklica Polona bere spis Kovač pri delu, stare smuči, smučar na snegu, vaška gostilna in prireditev Lokavška furenga. Ročno sekanje lesa v gozdu, debla vlačijo s konji, star mlin, notranjost, nakovalo, Boris BLAŠKO pripoveduje o domačinu, izumitelju ladijskega vijaka Jožefu Resslu, opuščena cesta, kmetija Tatjane ŽIGON, konjski hlev, žrebiček, deklica Katarina bere zgodbo v narečju, hiše, portali cesta skozi vas, krajevna tabla Lokavec.
Razglednica prikazuje novo župnijsko cerkev Sv. Lovrenca v Lokavcu. Fotografija na razglednici je nastala v 30. letih 20. stoletja, med zidavo cerkve po načrtih arhitekta Maksa Fabjanija.
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