GEOLOGICAL CHARACTERISTICS OF THE STOŽE LANDSLIDE

Abstract

The engineering geological background of the Stože landslide is the main topic of this contribution. The event is, in fact, a combination of two processes: – the sliding of soil in the upper part, and – debris flow in the lower part. Geological mapping of the site proved the existence of very good geological reasons for the triggering of a huge landslide (300 m in size, 1.5 km long and up to 50 m thick). The event occurred at an altitude of 1525 m, in glacial moraine and slope debris, covering tectonically highly-fractured dolomite lying on impermeable layers of marly limestone. Dolomite is an excellent aquifer and, during heavy precipitation, the water level in the rock rises substantially, saturating the overlying soils, rich in clay, with water. Precipitation data for November 2000 reveal that very intensive rainfall was registered in this region. In the lower part of the slope, at the bottom of a small valley, runs a torrent named Mangartski potok. The first landslide movement dammed up the torrent, resulting in a huge debris flow which flooded the village of Log pod Mangartom some 4 km downstream at an altitude of about 600 m. A part of the slope debris above the landslide (approx. 1 million m3 ) remained in place, but its stability was reduced to the limit state of equilibrium and continues to pose a threat... This paper presents the engineering geological work done by the Geotechnical Expert Group, describes the causes of the landslide and gives an overview of the initial measures proposed to ensure the safety of inhabitants in the threatened village.