Comparison of Static and Dynamic Young’s Modulus of Prasinites

This study aimed to investigate the statistical correlation between the static and dynamic Young’s modulus of prasinites, a metabasic rock type that outcrops at various localities in the southern part of the Attica peninsula. A total of 39 cylindrical specimens was prepared and an extensive experimental program was carried out to determine the static and dynamic deformational properties for each specimen. Using ordinary least squares regression techniques, a new empirical linear equation was established between the aforementioned properties that can be used in the study region, or elsewhere where metabasic rocks with similar characteristics are investigated

Ground subsidence phenomena in the Delta municipality region (Northern Greece): Geotechnical modeling and validation with Persistent Scatterer Interferometry

Land subsidence is a common phenomenon occurring in several regions worldwide. Persistent subsidencecauses strong consequences on the affected areas and related problems include environmental, economicand social aspects.A set of forty-two Synthetic Aperture Radar (SAR) images, acquired in 1995–2001 by the EuropeanSpace Agency (ESA) satellites ERS1 and ERS2, were processed with Persistent Scatterer Interferometry(PSI) technique to investigate spatial and temporal patterns of deformation in the Delta municipality(Thessaloniki plain, Northern Greece), a deltaic area with a long history of land subsidence related toaquifer system compaction.Exploitation of output products of a PSI analysis, both average LOS (Line of Sight) deformation ratesand displacement time series, revealed a large subsidence area due to intense groundwater withdrawal.Higher displacement velocities have been observed south-west of Kalochori and south of Sindos, fromboth sides of the Gallikos River. In those areas deformation rates of roughly 4.5 cm/yr have been recorded,during the period from 1995 to 2001.Increasing subsidence rates are measured moving toward the mouth of the Gallikos River, where thethickest sequence of compressible Quaternary sediments is observed. Displacement time series retrievedby PSI technique has been compared with the temporal evolution of the deformation as measured bypre-existing leveling surveys, showing a great agreement.A 2-D finite element model has been run along two representative cross sections in the Kalochori area,in order to simulate the observed temporal evolution of subsidence, coupling the geotechnical behaviorof the formations and the piezometric surface level. Finally, results obtained by the subsidence modelhave been positively compared with the PSI-based information on displacement, providing accurate andperfectly verified results.Outcomes of this work demonstrated the potential of repeat-pass satellite SAR interferometry (InSAR)as suitable technique for increasing knowledge about the extent and the rate of the deformations in caseof subsidence events. Moreover, InSAR turned out to be a valuable tool to validate subsidence modelsand represents a cost-efficiency method, alternative to ground-based measurements for investigatingsurface deformation phenomena

Physical and Anthropogenic Factors Related to Landslide Activity in the Northern Peloponnese, Greece

The geological, geomorphic conditions of a mountainous environment along with precipitation and human activities influence landslide occurrences. In many cases, their relation to landslide events is not well defined. The scope of the present study is to identify the influence of physical and anthropogenic factors in landslide activity. The study area is a mountainous part of the northern Peloponnesus in southern Greece. The existing landslides, lithology, slope angle, rainfall, two types of road network (highway-provincial roads and rural roads) along with land use of the study area are taken into consideration. Each physical and anthropogenic factor is further divided into sub-categories. Statistical analysis of landslide frequency and density, as well as frequency and density ratios, are applied and combined with a geographic information system (GIS) to evaluate the collected data and determine the relationship between physical and anthropogenic factors and landslide activity. The results prove that Plio-Pleistocene fine-grained sediments and flysch, relatively steep slopes (15°–30°) and a rise in the amount of rainfall increase landslide frequency and density. Additionally, Plio-Pleistocene fine-grained sediments and flysch, as well as schist chert formations, moderate (5°–15°) and relatively steep slopes (15°–30°), along with the amount of rainfall of >700 mm are strongly associated with landslide occurrences. The frequency and magnitude of landslides increase in close proximity to roads. Their maximum values are observed within the 50 m buffer zone. This corresponds to a 100 m wide zone along with any type of road corridors, increasing landslide occurrences. In addition, a buffer zone of 75 m or 150 m wide zone along highway and provincial roads, as well as a buffer zone of 100 m or 200 m wide zones along rural roads, are strongly correlated with landslide events. The extensive cultivated land of the study area is strongly related to landslide activity. By contrast, urban areas are poorly related to landslides, because most of them are located in the northern coastal part of the study area where landslides are limited. The results provide information on physical and anthropogenic factors characterizing landslide events in the study area. The applied methodology rapidly estimates areas prone to landslides and it may be utilized for landslide hazard assessment mapping as well as for new and existing land use planning projects

Establishing and Operating (Pilot Phase) a Telemetric Streamflow Monitoring Network in Greece

This paper describes HYDRONET, a telemetry-based prototype of a streamflow monitoring network in the Greek territory, where such data are sparse. HYDRONET provides free and near-real-time online access to data. Instead of commercially available stations, in-house-designed and -built telemetric stations were installed, which reduced the equipment cost by approximately 50%. The labour of hydrometric campaigns was reduced by applying a new maximum-entropy method to estimate the discharge from surface velocity observations. Here, we describe these novelty elements succinctly. The potential of HYDRONET to provide civil protection services is exemplified by a flood warning demonstrator for Kalamata’s City Centre. The network’s operation, including the hydraulic criteria for monitoring site selection, the characteristics of the telemetric equipment, the operational monitoring and hydrometric procedures, and the specifics of data transmission, quality control, and storage are described in detail, along with experiences with problems encountered during this pilot phase