Spatio-temporal patterns of recurrent slope instabilities affecting undercut slopes in flysch: A dendrogeomorphic approach using broad-leaved trees

The undercut slope of the Skalická Strážnice/Vrchy hill situated in the piedmont of the Carpathian Mountains (Czech Republic) is a regional landslide “hotspot”, notorious for its repeated recent and historical sliding reactivations. We performed tree-ring analysis of a large number (n=274) of broad-leaved trees to reconstruct the spatio-temporal patterns of landslide reactivation for a period spanning more than one hundred years (1884–2011). Although tree rings of broad-leaved trees are less-reliable archives of landslide activity than those of conifers, the application of a methodology based on the weighting of disturbance signals within eccentricity series generated a usable dataset of sliding activity affecting anisotropic flysch bedrock. Although some known landslide years could not be found (or were expressed by only weak signals) in the reconstructed dataset, the majority of landslide events reconstructed from the tree-ring series coincide with hydrometeorological data, revealing a correlation with heavy summer rainfalls lasting from two to ten days. The spatial distribution of landslide recurrence derived from the tree-ring records together with electrical resistivity tomography and a kinematic analysis of slope failures suggest a close link between the concentration of landslide activity and the presence of faulted or fractured flysch bedrock. •Presentation of an active landslide undercutted by a river.•A new dendrogeomorphic method based on analysis of broad-leaved trees is presented.•Results of analysis correspond with morphological features of the landslide.•Analysis of triggering factors is presented.