G. Koukis

Landslide susceptibility zonation in Greece

The objective of this study is to perform a preliminary national-scale assessment of the landslide susceptibility in Greece using a landslide inventory derived from historical archives. The effects of controlling factors on landslide susceptibility combined with multivariate statistics have been evaluated using GIS aided mapping techniques. Thousand six hundred thirty-five landslide occurrences, mainly earth slides obtained from Public Authorities archives, covering a long time period were recorded and digitally stored using a spatial relational database management system. Ten landslide predisposing factors (predictors) were identified, while digital thematic maps on the spatial distribution of those factors were generated. The correlation between the landslide locations and predictor classes was analyzed by using the Landslide Relative Frequency. R-mode factor analysis was applied to study the interrelations between predictors (independent variables) while weighting coefficients were determined. Landslide susceptibility was derived from an algorithm which modeled the influence of predictors, and a susceptibility map was compiled. The landslide susceptibility map was verified using a data set of 375 new landslide locations. It is the first comprehensive attempt to illustrate the landslide susceptibility in the total country based on the interpretation of historical data only.

Landslide Hazard Zonation in Greece

Landslide occurrences in Greece, covering a long time period (1950–2004) were recorded and digitally stored using a relational database management system. The first evaluation of engineering geological data and the geographical distribution of the recorded cases led to the determination of most critical landslide prone geological formations, regarding lithology and structure and to a landslide hazard map compilation at a national scale.

Engineering-geological conditions of the formations in the Western Thessaly basin, Greece

An engineering-geological map of the Western Thessaly basin has been compiled, providing a valuable guide to both urban planning and industrial development of the wider area. This map contributes significantly to the optimization of land use and improved planning of technical work. Additionally, the engineering-geological conditions of the formations encountered in the Western Thessaly basin are examined. The formations are grouped into thirteen (13) engineering-geological entities, with regard to their geotechnical behaviour. This entire study was based on both in situ investigations and geotechnical information extracted from 1,039 boreholes.Furthermore, a landslide inventory map of the Western Thessaly basin has been compiled. In addition, the surface subsidence ruptures, due to ground-water overexploitation, have been examined in the eastern part of the study area.

The Acropolis Hill of Athens: Engineering Geological Investigations and Protective Measures for the Preservation of the Site and the Monuments

A detailed engineering geology study was conducted in the Acropolis hill aiming to the examination of the geological, tectonic, hydrogeological, geomechanical conditions and the seismicity in relation to the slope stability problems. The hill is covered by limestones of a thickness up to 35 m, underlain at the base of the steep slopes by the schist-sandstone-marl phase in a continuous sedimentation without unconformities. Οn the basis of the examined lithologic, tectonic and microtectonic conditions and those of natural processes of rock weakening, it is clear that οn the upper surface (where the monuments are found) not any anxiety would be justified. On the slopes certain places were indicated as attaining unfavourable stability conditions, without suggesting an immediate danger for the monuments. Some of these measures, such as anchoring of the loosened rock masses and filling of the cracks with mortar, have been applied in parts of the NE and E-SE mainly slopes.

Landslide Phenomena in Greece: Types of Movement Related to the Lithology and Structure of the Geological Formations

The problem of landslides in Greece has many aspects—technical, economic, social—the extent and severity of which is due to the serious consequences that are encountered in numerous engineering works and especially problems that are addressed on the road network and the inhabited areas. It can be mentioned that more than 500 villages have been relocated into geologically more stable areas within the past decades. The highest percentage of landslides is recorded in Cretaceous sediments to Quaternary deposits mainly in the Western-Central parts of the country. They are numerous incidences of instability recorded in tertiary sedimentary rocks such as flysch and neogene, transition zones to the flysch as well as in the quaternary screes. In flysch, neogene and loose quaternary formations one can found the 79 % of the total number of landslides. From other hard rock formations very unstable are the upthrusted limestones and schist-cherts on the more plastic flysch. Consequently, the only way to determine the high risk regions is to examine the territorial distribution in combination with classified characteristics of the numerous landslides occurred in the Greek territory. That way the several parameters combine and point out the main characteristics and the extension of these regions.