Rozmieszczenie i geneza form osuwiskowych w przełomowej dolinie Bobru w okolicach Wlenia (Sudety Zachodnie)

The paper presents results of field mapping and geomorphometric LiDAR DEM-based analysis of the Bóbr river valley (Izerskie Foothills, Western Sudetes), between Wleń and Nielestno, where a number of individual landslides and their groups were recognized in 2015-2016. The area affected by mass-movements is located within the Wleń Graben - a regional geological unit that constitutes the south-eastern prolongation of the North-Sudetic Synclinorium. The Wleń Graben is a NW-SE trending, elongated morphological and structural depression composed of sedimentary and volcanic rocks of Late Carboniferous, Permian, Triassic and Cretaceous age. The specific geological structure of the graben is reflected in geomorphic features of the study area. Based on mass movement classifications, the forms are considered as: (i) deep-seated rotational landslides (Świerkowa Dolina and Czerwony Wąwóz landslides); (ii) shallow slides and flows of weathered material and rock blocks (headwater areas in the south-western slopes of Gniazdo Hill, "Izerskie Gołoborza” locality), and (iii) complex landslide forms (deep-seated and shallow landslides on the south-eastern slopes of Gniazdo Hill). The studies confirmed the usefulness of geomorphometric analysis based on LiDAR-derived DEMs combined with field investigations. The landslides are located mainly in heavily forested mountainous areas. It was probably the main reason they had not been identified in the past.