Ivo Baroň

Slope movements in the Flysch Carpathians of Eastern Czech Republic triggered by extreme rainfalls in 1997: a case study

Abstract The severe rainfalls in Northern and Central Moravia and Eastern Bohemia in July 1997, triggered slope movements recorded particularly in the flysch-type rocks of Northern and Eastern Czech Republic. The basis of the diversified woodland and agricultural landscape of the Western Carpathians is the highland and mountain erosion–denudation and structure-denudation relief, which consists of flysch rock complexes. The geomorphological and geological setting is predisposed to extensive slope deformations––especially landslides. Slope movements play an important role in topography modelling and cause great direct and indirect damages in the countryside as well. Slope deformations of different intensity and aerial extent control the character of relief on the local or regional scale. Significant changes of land use may result from the slope movements, especially when the reclamation of the slope deformations are not undertaken. Landslides themselves have a great impact on the water regime of the landscape and consequently on the development of ecosystems. That is why they are often considered to be a significant biodiversity factor. It is also necessary to pay attention to the opposite effect since the land use (dispersed woody patches, landscape mosaic) is to a certain extent influencing the development and progress of the slope deformations. Based on the order we focused our geological investigations on the area in which the slope movements began to develop to such an extent that human lives and properties were considerably endangered. The total damages from activated landslides reached about 40 million USD. The landslide research differs in individual localities and their topical situations and is accompanied by a stability assessment of the locality and a proposal of rescue measures. An alternative solution should consist of an assessment of necessary changes in the area plans of affected villages, prospects of their future habitability, and displacements of engineering networks and roads.

Airborne geophysical mapping as an innovative methodology for landslide investigation: evaluation of results from the Gschliefgraben landslide, Austria

Abstract. In September 2009, a complex airborne geophysical survey was performed in the large landslide affected area of the Gschliefgraben valley, Upper Austria, in order to evaluate the applicability of this method for landslide detection and mapping. An evaluation of the results, including different remote-sensing and ground-based methods, proved that airborne geophysics, especially the airborne electromagnetic method, has a high potential for landslide investigation. This is due to its sensitivity to fluid and clay content and porosity, which are parameters showing characteristic values in landslide prone structures. Resistivity distributions in different depth levels as well as depth slices along selected profiles are presented and compared with ground geoelectrical profiles for the test area of Gschliefgraben. Further interesting results can be derived from the radiometric survey, whereas the naturally occurring radioisotopes 40K and 232Th, as well as the man-made nuclide 137Cs have been considered. While the content of potassium and thorium in the shallow subsurface layer is expressively related to the lithological composition, the distribution of caesium is mainly determined by mass wasting processes.

Monitoring Giant Landslide Detachment Planes in the Era of Big Data Analytics

Open image in new window A small mesh of sensors which monitor movements across detachment planes of the giant San Andres Landslide on the northeastern lobe of El Hierro in the Canary Islands was established in 2013. In this paper we present the results obtained over a two year period spanning from October 2013 to October 2015. Our results demonstrate that the detachment planes are affected by sinistral strike slip displacements and subsidence of the depleted mass of the landslide. While these general trends are consistent the movements recorded at particular monitoring points differ in detail as one site is characterised by progressive strike slip and dip slip trends while another is characterised by movement pulses and reversals in the sense of movement. These findings contrast markedly with suggestions that the giant landslide is inactive and demonstrate that its reactivation is a possibility which cannot be dismissed categorically. Big data analytics have been used to identify interdependence between the recorded movements and a range of climatic and geophysical variables such as seismic data, tidal data, and geomagnetic data. We have found that the recorded movements correlate only weakly or moderately with climatic and seismic parameters but strongly to the horizontal and vertical intensity of the magnetic field. These findings are rather unexpected and we emphasise that special care must be taken in pushing the conclusions of a purely numerical analysis. The advantages of adopting a big data mindset led us to make significant improvements to the instrumental infrastructure in early 2016. These incremental improvements to the small mesh of sensors are driven partly by our desire to understand the kinematic behaviour of landslide itself and partly by our desire to explore the potential of big data analytics in geoscientific research.

A contactless positioning system for monitoring discontinuities in three dimensions with geological and geotechnical applications

In this paper, a contactless positioning system is presented which has been designed to monitor the kinematic behavior of mechanical discontinuities in three dimensions. The positioning system comprises a neodymium magnet, fixed on one side of a discontinuity, and a magnetoresistive sensing array, fixed on the opposing side. Each of the anisotropic magnetoresistive sensors in the sensing array records the magnetic field along three orthogonal directions. The positioning system intrinsically generates compact data packages which are transmitted effectively using a range of standard wireless telecommunication technologies. These data are then modeled using a global least squares fitting procedure in which the adjustable parameters are represented by the position and orientation of the neodymium magnet. The instrumental resolution of the positioning system can be tuned depending on the strength of the magnetic field generated by the neodymium magnet and the distance between the neodymium magnet and the magnetoresistive sensing array. For a typical installation, the displacement resolution is shown to be circa 10 μm while the rotation resolution is circa 0.1°. The first permanently deployed positioning system was established in June 2016 to monitor the behavior of an N-S trending fault located at the contact between the eastern Alps and the Vienna Basin. The robust design of the positioning system is demonstrated by the fact that no interruptions in the broadcasted data streams have occurred since its installation. It has a range of potential applications in many areas of basic and applied research including geology, geotechnical engineering, and structural health monitoring.

Large landslide stress states calculated during extreme climatic and tectonic events on El Hierro, Canary Islands

Composed volcanic edifices are particularly prone to large-scale failures—these often result from the acceleration of preexisting deep-seated gravitational slope deformations. Consequently, a complete understanding of the kinematic behaviour of such slope deformations would represent an important step towards mitigating against human casualties or fatalities and damage to critical infrastructure. In this manuscript, a 9-month time series of three-dimensional fault displacement measurements has been used to determine the stress states of the San Andrés Landslide on El Hierro in the Canary Islands. These stress states have been calculated on the basis of single-displacement events using a novel approach which only requires information about the magnitude of the movement vector and its orientation. The analysis focused on four specific periods: a reference period in November 2013; an extreme rainfall event at the beginning of December 2013; and two endogenous impulses at the end of December 2013 and during the middle of March 2014. On the basis that the direction of principal stress represents a marker for the direction of landslide mass movement, it has been possible to define six landslide activity modes which correspond to specific stress states. The response of the landslide to the extreme rainfall event was immediate and reflected increasing saturation of the porous landslide mass. The response of the landslide to the endogenous impulses was more complicated as compressional pulses often alternated with gravitational relaxation. In this study, it is demonstrated that the landslide stress state can be determined on the basis of a single-displacement event whenever fault displacements are monitored in three dimensions. This innovative approach may represent a valuable step towards a complete understanding of the kinematic behaviour of potentially catastrophic slope deformations, particularly those which are in a critical stability state.

Open image in new windowAge and Reactivations of Catastrophic Complex Flow-Like Landslides in the Flysch Carpathians (Czech Republic/Slovakia)

Catastrophic complex flow-like landslides (CFLLs) are characterised by a deep-seated retrogressive landslide of structurally unfavourably oriented rocks and earthflows that occupy the lower slope positions and originate due to the liquefaction of material accumulated on the upper slopes. These landslides are locally important geomorphic agents of Late Quaternary mountain evolution in the Flysch Belt of the Outer Western Carpathians (Czech Republic/Slovakia). Most of the CFLLs dammed and steepened adjacent valleys. Radiocarbon dating suggests that a majority of them moved repeatedly throughout the Holocene, namely approx. every 1–2 ka. Dated events occurred during humid phases of the Younger Dryas/Holocene transition (11.5–9.4 cal ka BP), Atlantic chronozone (7.4–6.6 cal ka BP), the beginning of the Subboreal chronozone (ca. 4.6 cal ka BP) and, primarily, within the Subatlantic chronozone at ca. 2–0.8 cal ka BP (>50 % of all events). Our study suggests that slopes based on an unfavourable structural setting and affected by long-term deep-seated gravitational deformations may produce CFLLs, even if they are located in medium-high mountains. Although our chronological dataset is influenced by the erosion of older landforms, most of the dated reactivations correlate with regional increase in precipitation identified by previous palaeoenvironmetal studies.

Field Measurement of Natural Electromagnetic Emissions near the Active Tectonic and Mass-Movement Fractures in Caves

Laboratory tests on a wide range of solid materials shoved that the electromagnetic emission (EME) signals are generated during the samples mechanical stress. EME anomalies have been observed also under natural conditions in association to fracture processes, tectonic loading, stress redistribution and crack propagation prior to earthquake or in relation to deep-seated gravitational mass movements. This paper describes a first prototype of the Emission data logger, which was specially developed for the continual EME monitoring in field conditions. Our equipment has been installed and tested in Obir Caves (Austria) at an active tectonic fault. The pilot long-term EME measurement results from this location are also presented in this paper.

Results of Geoelectrical Monitoring of Landslides Collected by the SafeLand/TEMPEL Network

Based on the promising results from a pilot monitoring project the GEOMON4D geoelectrical monitoring system was applied to several landslide monitoring tests sites, where also permanent monitoring data of displacement and hydrology are available to investigate the correlation of electrical parameters with other data. This monitoring network was set up in frame of the FP7 project SafeLand and the project TEMPEL (Austrian Science Fund) starting from October 2009 on. Analysis of the first monitoring results confirmed the potential of geoelectrical parameters as additional indicators to be applied within future early warning systems of landslides.