Jiří Zvelebil

Reactivation of mass movements in Dessie graben, the example of an active landslide area in the Ethiopian Highlands

Dessie town is located in a tectonic depression along the western rift margin with a young, high energy relief. Study area is known for numerous landslides in the past. These landslides are of different types, from shallow soil creeping to huge deep-seated landslides with appreciable consequences. Landslides endanger the quickly growing regional centre of Dessie and its infrastructure. Four typical recent landslides have been selected and studied in detail using both remote sensing and field observations from 2013. The described reactivation and new landslide events have been caused by a combination of natural influences and anthropogenic activities. Since seasonal rainfall is the main external triggering factor, precipitation data from Dessie weather station were analysed. The degree of negative human impact on slope instability was also discussed. Endangered zones and the actual risk in the studied localities were identified, and adequate measures were proposed.

Geomorphological Investigations at Machu Picchu, Peru (C101-1)

The landslide hazards analysis was the principal motivation to start geomorphological investigations in the area of Machu Picchu Sanctuary. But very soon, the need of a broader research was revealed, because the landscape evolution of the Urubamba River meander, where the archaeological site is located, is rather complex. Besides slope movements, also deepwards erosion, and selective mass wasting by weathering, suffusion etc. has been active there. Majority of them have been following predisposition by tectonical structure. Large-scale slope deformations have seriously affected mountain morphology in the area. The actual activity of those deformations is not well known yet, inspite that systematic monitoring has provided information as about irreversible movements on open cracks of rock outcrops within the archaeological site up to 1 mmyr-1 (lengths of time series is mostly 3 years), as about movement across the Main Plaza up to 6 mmyr-1. There still are other possibilities to explain those movements by ground deformation due to underground erosion along tectonically shattered zones, or by settlements of heavy stone buildings on water more saturated grounds.

Tools for Rock Fall Risk Integrated Management in Sandstone Landscape of the Bohemian Switzerland National Park, Czech Republic (M121)

There are 327 monitored rock objects with more than 900 measuring sites on the territory of the Bohemian Switzerland NP and its nearest neighborhood, and the monitoring nets are ever growing. Therefore a high-tech, scientifically challenging Integrated System (IS) for effective, but nature-friendly management of rock fall risks on the Bohemian Switzerland NP territory has been under construction since 2002, there. Rapid processing and timely, on-line delivery of relevant, easy-to-understand information to an end-user through an information web portal and cellular phone emergency messages should be the highlights of IS. Other highlights are represented by the implementation of complex dynamical systems knowledge and methods to provide more realistic and mathematically more rigorous grasping of very complex dynamics of rock slope stability failure. Those methods also provide a basis for a qualitative step in implementation of computers for future highly automated run of data assessment, modeling and early warning modules of the system. Several successful case-histories have made those new tools very promising for the practical use. Nevertheless, there are some tasks still unfinished. Especially the one enabling to bridge the gap between science, civil protection and general public and by it to enhance effectiveness of utilization of delivered information by its end-users.

The application of non-destructive methods to assess the stability of the national nature monument of the Pravčická Brána Rock Arch, Czech Republic

The study contains the results of non-destructive research of the Pravcicka Brana Rock Arch which focuses on the structure and natural dynamics of this rock formation and its current level of stability. The main results include a description of the block fabric of the rock body and the nature of the contact zone between the arch beam and the southern pillar, discovery of relatively fresh secondary fissures and identification of zones with weakened strength within the sandstone massif. Also the local hydrodynamic regime was determined by a combination of geophysical methods. Long-term monitoring has demonstrated slow and irreversible body movements and reversible quasicyclical movements associated with changes in temperature on a scale of days up to years. The collected information was used to develop a structural deformation model of the arch body, including a description of the nature of the disintegration. The work was designed to fully respect the protective conditions of the site, to facilitate future follow-up activities and to monitor any possible negative changes in the rock massif.

COMBINED METHOD FOR RISK ASSESSMENT OF MASS MOVEMENT AND EROSION SUSCEPTIBILITY IN THE ETHIOPIAN HIGHLANDS

The Ethiopian Plateau and the Rift Valley typically display various symptoms of intensive erosion, mass movement and land degradation, which have arisen in response to rapid changes in land cover in an area of high dynamics of relief development. In order to assess the risk of these symptoms of intensive erosion and mass movement it is necessary to apply a method for the evaluation of non-linear systems. Therefore, our aim was to develop a combined method for evaluating the risk of landslides or erosion using complex system theory. This combined integrated method has been tested on two selected localities with landslide hazards on the border of the Ethiopian Highlands and the Main Ethiopian Rift. The method is suitable for a prompt risk evaluation and swift decision making.

Dilatometric and Extensometric Monitoring of Rock Blocks Displacements Within Machu Picchu Archaeological Site, Peru

The area of archaeological site of Machu Picchu was affected by large-scale slope movement in the past. This event in the paleogeomorphological evolution of the area, along with intensive fluvial erosion and tectonic disturbance of the rocks, has been significantly affecting the evolution of the landscape. Unknown triggering impulse for such huge slope deformation and presence of several younger generations of slope movements were reasons for complex geological – geomorphological investigation aimed to verify the potential recent activity of deep-slope movement. In order to understand the mechanism and recent activity of the mass movements the monitoring net of dilatometric and extensometric measurements was established during 2002, after preliminary field investigation in 2001 and aerial photo interpretations. The results of the monitoring supported by the field investigation suggest that large-scale slope movement is doubtful in close future. Nevertheless, continuation of monitoring will be useful and from point of view of the long-term landscape evolution the area is in unstable position. The recent detected movements can be explained by individual movements of rock blocks or several other mechanism including subsurface erosion and local sinking and deformation of archaeological structures.