Abstract. Rapid snow melting and intense precipitation triggered and reactivated tens of mostly shallow landslides in the eastern part of the Czech Republic at the turn of March and April 2006. This area is build up by highly fractured flysch rock units with variable content of sandstones and claystones. The landslide complex at Hluboče (Brumov-Bylnice town) is composed of shallow translational (up to 10 m thick) as well as deep-seated (up to 20 m thick) rotational landslides, which generated a catastrophic earthflow at their toe. This earthflow destroyed three buildings, the access road and caused total loss of about 350 000 EUR. Detailed field investigation, review of the archive sources and interviewing of local inhabitants allowed brief description of slope movement history prior the catastrophic event as well as detailed reconstruction of slope failure mechanisms during the main movement activity (3-4 April 2006). This information, along with the detailed description of the passive as well as active causative factors (structural and morphologic settings) can contribute towards better identification of potentially dangerous slope failures in the study region.
Abstract. The catastrophic landslide at Eisenberg in North Bohemia was reactivated during January 2011. This study integrates a range of geoscientific evidence in order to constrain the spatial and temporal development of this reactivation. It has investigated long-term geodetic measurements to assess the morphological development of the site over the last two decades. There is evidence to suggest that, over this period, the site had been subjected to progressive deformation caused by the collapse of an old mine gallery. However, climatic data show that the reactivation itself was triggered by a dramatic rise in the water table induced by rapid snowmelt during a period of winter warming. Furthermore, geomorphological mapping has been used to characterise the morphology of the reactivated landslide and geophysical profiling has been used to analyse its internal structure. The results show that fissures are continuing to develop above the reactivated landslide scarp while highly saturated stiff-fissured claystones provide an incipient slide plane. The application of laser scanning has shown minimal evidence for ongoing landslide activity. It is, however, clear that future landslide events will occur here due to the favourable lithological, structural, and geotechnical conditions. Finally, we propose that future landslide activity at the site may be predicted by the height of water table as this defines theoretical pore pressure at the depth of the shear plane.
Understanding the impact of data uncertainty is a fundamental part of ensuring safe design of manmade excavations. Although good levels of knowledge are achievable from field investigations and experience, a natural geological environment is subject to intrinsic variability that may compromise the correct prediction of the system response to the perturbations caused by mining, with direct consequences for the stability and safety of the operations. Different types of geoscientific evidence, including geological, geomorphic, geotechnical, geomatics, and geophysical data have been used to develop and perform two-dimensional Limit Equilibrium and Finite Element Method stability analyses of a lignite open-pit mine in North Bohemia (Czech Republic) affected by recent landslides. A deterministicprobabilistic approach was adopted to investigate the effect of uncertainty of the input parameters on model response. The key factors affecting the system response were identified by specific Limit Equilibrium sensitivity analyses and studied in further detail by Finite Element probabilistic analyses and the results were compared. The work highlights that complementary use of both approaches can be recommended for routine checks of model response and interpretation of the associated results. Such an approach allows a reduction of system uncertainty and provides an improved understanding of the landslides under study. Importantly, two separate failure mechanisms have been identified from the analyses performed and verified through comparisons with inclinometer data and field observations. The results confirm that the water table level and material input parameters have the greatest influence on the stability of the slope.
Vessel lumen area is influenced by both genetic and environmental forces. Its alterations balance hydraulic water transport efficiency and safety from cavitation or embolism. We tested the hypothesis that environmental stress inflicted by rockfall injury influences average vessel lumen area in newly formed tree rings of Betula pendula Roth, which would make it useful for retrospective detection of rockfall events. We took samples from 11 trees injured by a rockfall that occurred in the winter of 2010–2011, specifically from the stem area adjacent to the injury, parts of the stem located perpendicular to the injury, parts located opposite to the injury, and from four undisturbed trees. We measured the mean vessel lumen area of each tree ring in every sample, comprising up to 10 pre-event tree rings and generally 3 tree rings formed after rock injury. On average, 115 vessels were measured in each tree ring. We then compared the vessel lumen area in tree rings formed after the event with that of rings formed before it as well as with values predicted by an age-trend model inferred from vessel lumen area chronologies. Our results show a strong reduction in vessel lumen area in the first tree ring formed after the event regardless of the position around the stem circumference. This reduction is strongest in wood just next to the callus tissue zone, with decreasing significance in distal parts of the stem circumference. During the three years after the rockfall, the trees mostly recovered their pre-event vessel lumen area, even right next to the place of injury. Still, this value is significantly lower than the value predicted for growth without injury. Abrupt reductions of vessel lumen area turn out to be potentially useful for identifying former rockfall events and can improve on results obtained by traditional methods of dendrogeomorphological dating.
Abstract. Recent mass movements currently comprise one of the main morphogenetic processes in the extensive anthropogenic relief of the foreground of the Krušné Hory Mountains in the Czech Republic. These mass movements result in several types of deep-seated slope failures, depending on the type of movement and the water saturation of the landslide material. This paper presents the results of a detailed geomorphic survey and orthophotograph analysis combined with geodetic monitoring data in an area affected by openpit coal mining. An interdisciplinary approach has enabled an in-depth review of both the dynamics and development of recent slope failures. The article describes deep-seated landslide complex in this part of the foothills of the Krušné Hory Mountains. At the study site, mass movements occur in thick colluvial mantle and weathered Tertiary claystones. The main factors influencing their development include rainfall culminations, groundwater flowing from the valley of Sramnický Brook and former slope failures. All of the slope failures that have occurred here have originated at former slope failure sites.
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