Dendrogeomorphological analysis of landslide activity along the planned S-69 road in the Węgierska Górka municipality (Beskid Śląski Mountains, S Poland)

Abstract

Our dendrogeomorphological analysis was completed for 4 landslides, situated in the municipality of Węgierska Górka in the Beskid Śląski Mountains in Southern Poland. The local landslides pose a direct threat to the newly designed S-69 expressway running through the north-western part of the municipality. The research material consisted of 127 samples, collected with the use of a Pressler increment borer, from three species of coniferous trees (Norway spruce, Scots pine, and Silver fir). The landslide activity periods were identified on the basis of the splitting of the dendrochronological curves representing the upslope and downslope parts of the tree trunks. The largest number of the studied trees indicated reactions to substrate mass movements in 1964, 1971, 1972, 1984, 1994, 1997, 1998, and 2010. The detailed locations of the sampled trees allowed us to reconstruct the activities of particular landslide sections in time. We identified the fact that parts of the landslides located downslope of the planned road S-69 are more active than parts of the same landslides located above it on the slope. Geological conditions in the studied area favour landslide activity while precipitation is the main triggering factor of landslides.