Publications by Year: 2019

2019
Mavroulis, S., Diakakis, Μ., Kotsi, E., Vassilakis E, Lekkas E. Earthquake-induced landslide inventory and landslide susceptibility mapping for the Ionian Islands. 12th Intern. Conf. of the Hellenic Geographical Society. 2019.Abstract
The synergy of different methods was used for the creation of an earthquake-induced landslides (EIL) inventory for the Ionian Islands. More specifically, post-earthquake field surveys were conducted shortly after recent earthquakes (2003 and 2015 in Lefkada, 2014 in Cephalonia and 2018 in Zakynthos) in order to obtain detailed field information of the EIL among other earthquake effects. The available literature on historical earthquakes were reexamined with emphasis on their environmental effects and especially EIL. Remote sensing products including satellite imagery and orthophotos were interpreted. All qualitative and quantitative information related to EIL and derived from the aforementioned steps were inserted in a database especially designed and developed in GIS environment for the purpose of this study and the respective inventory map was produced. This landslide inventory map was used and combined with other thematic maps in order to test the earthquake-induced landslide susceptibility (LS) of the Ionian Islands. The Analytical Hierarchical Process was applied along with the Weighted Linear Combination method in the frame of a multi-criteria decision analysis for the calculation of the spatial distribution of the Landslide Susceptibility Index (LSI). Along with the inventory, morphological data were derived from a TanDEM-X elevation model of the Ionian Islands based on data produced by TanDEM-X and TerraSAR-X satellite pair. Lithological and geological data were digitized from previous already published geological and neotectonic maps updated with corrections from field mapping for the purpose of this study. Land use and soil thickness were derived from the 2018 version of Corine Land Cover. Road network was digitized from the topographic maps of the Hellenic Military Geographical Service, while rainfall data was collected from the database of the National Meteorological Service. Data classification of each factor according to their estimated LS followed, by using the reverse ranking method, where 1 is the least and 10 is the most susceptible. Each category was normalized to 100% and the final raster thematic maps of landslide controlling factors were produced. Finally, using numerical weight for each factor, which was assigned by the Analytic Hierarchy Process using Pairwise Comparison Method and according to the weighted linear combination, a map was generated where each cell has a certain LSI value. The higher the LSI value, the higher the LS, whereas lower LSI value means lower LS. The resulted map, classified with natural breaks method, constitutes the earthquake-induced LS map of the Ionian Islands with five LS categories: very low, low, moderate, high and very high LS. Comparison of the EIL inventory map and the LS map show that the EIL in the Ionian Islands are structurally controlled as the majority of them have been generated along morphological discontinuities formed by active faults or inactive thrusts and overthrusts.
Mavroulis, S., Diakakis, Μ., Kotsi, E., Vassilakis E, Lekkas, E. Susceptibility and Hazard Assessement in the Ionian Islands for Highlighting Sites of Significant Earthquake-Related Hazards. SafeCorfu 2019 - 6th Intern. Conf. on Civil Protection & New Technologies. 2019:Ι13-Ι16.Abstract
The identification of the earthquake environmental effects by using various methods has become significant in recent years due to the fact that among others it serves as a valuable tool for revealing and highlighting sites of significant earthquake-related hazards. In the frame of the project entitled "Tilemachos - Innovative Operational Seismic Risk Management System of the Ionian Islands" included in the Priority Axis "Environmental Protection and Sustainable Development" of the Operational Programme “Ionian Islands 2014-2020”, the landslide, liquefaction and tsunami hazards in the Ionian Islands are analyzed and assessed by combining different methods. Landslide, liquefaction and tsunami inventories for all Ionian Islands were initially created. Along with the inventories, different thematic maps were used and combined in order to test the earthquake-induced landslide and liquefaction susceptibility and the tsunami hazard of the Ionian Islands. The main result is the identification of sites of significant earthquake-related hazards in the Ionian Islands. This study and its results could constitute a basic guide for the future urban design and planning and the sustainable local development since all scientists and agencies competent to the prevention and management of natural disasters can be informed and guided.
Karantanellis, E., Marinos V, Vassilakis, Emm. Characterization of Landslide phenomena using UAV photogrammetry and Object-Based Image Analysis. 12th Asian Regional conference of IAEG [Internet]. 2019;2:163. http://www.iaegarc12.org/sub02/sub03_01.htmlAbstract
Late years, innovative close-range Remote Sensing (RS) technology such as Unmanned Aerial Vehicle (UAV) photogrammetry and Terrestrial Laser Scanning (TLS) are widely applied in the field of geoscience due to their efficiency in collecting surface data. Detection and mapping of landslide and rockfall events using RS products has been proved to be an effective approach to provide landslide inventories. However, most of the studies are lacking valuable semantic information about landslide elements and how they react with the surrounding environment. The proposed methodology was divided in five main working phases. The first phase includes designing and execution of an optimal UAV flight planning to collect accurate 3D data. During the second phase, the pre-processing and raw data preparation such as point cloud filtering and elimination of ambiguities is taking place, while at the next phase an image segmentation using the 3D point cloud RGB information is created. The main task was focused on identifying the specific landslide elements by using an object-based approach. A sequence of image-based processes was applied, including multi-scale object segmentation, spectral, morphometric and contextual information extraction aiming to detect the landslide among other features. The next phase was set up for object classification in meaningful and homogeneous landslide classes (e.g. scarp, depletion zone, accumulation zone) which are spatially connected by introducing contextual information. The proposed methodology presents the effectiveness and efficiency of UAV platforms to acquire accurate data from intense relief environments and complex surface topographies.
Alexopoulos J, Dilalos S, Mitsika G, Vassilakis E, Poulos S. A Geophysical Approach to the Phenomenon of Ground Fissures at the East Thessaly Basin (Greece). 25th European Meeting of Environmental and Engineering Geophysics [Internet]. 2019:Mo_25_P14. https://www.earthdoc.org/content/papers/10.3997/2214-4609.201902379Abstract
The disastrous phenomenon of aseismic ground fissures along the eastern Thessaly basin has deteriorated since 1989. The main reason for these fissures is the over-pumping, which leads to differential vertical compaction of the aquifer system and subsidence on the land surface. In this paper, we present the results of a combined geophysical survey applied in the area (VES and TEM soundings), in order to investigate the subsurface geological conditions. The geological regime of the area is comprised of the alpine basement, transgression formations and finally a package of post-alpine deposits with respectful thickness. A peudo-3D representation of resistivity maps for several depths of investigation was produced. Additionally, a dataset of deep boreholes was used for the calibration of the geophysical data. All the borehole and sounding interpreted data were grouped into three categories in order to produce the Lithology Model of the area. The alpine bedrock was adumbrated only at the southeast and central part of the basin, where we do not observe ground fissures. The absence of alpine bedrock for depths up to 300 meters, the thick and coarse-grained deposits and finally the over-pumping seem to contribute to the creation of the ground fissures.
Konsolaki A, Vassilakis E, Kontostavlos G. Morphological analysis of 3d subsurface structures with the use of a handheld laser scanning system.Case Study: The Koutouki Cave, Peania. In: 13th EuroSpeleo Forum. Sofia, Bulgaria; 2019.Abstract
In the presented case study, we combined re-mote sensing techniques and lidar technology by using a handheld laser scanner in order to generate a complete 3D model of the Koutouki Cave, at Peania, Greece. Using open – source software we made a quantification anal- ysis of the terrain and generate morphological features of the speleothems with high accuracy and detail in order to estimate the speleogenesis and monitor the evolution of the cave.
Konsolaki A, Vassilakis E, Giannopoulos V. Morphological analysis of karst features based on very high-density point clouds. Reg. Conf. on Geomorphology (IAG). 2019.Abstract
The generation of rock cavities and especially of those created under karstic procedures is a matter of research for the last decades. A high-resolution subsurface morphology could be produced after scanning the entire cave with state-of-the-art equipment based on Light Detection And Range technology. A handheld laser scanner was used for acquiring points with projected coordinate information (X,Y,Z) covering the entire show cave of Koutouki (Athens, Greece), including its hidden passages and dark corners. The point cloud covers the floor, the walls and the roof of the cave, as well as the stalactites, stalagmites and the connected columns that constitute the decoration of the cave. The absolute and exact placement of the point cloud within a geographic reference frame gives us the opportunity for three-dimensional measurements and detailed visualization of the subsurface structures.
Karantanellis E, Marinos V, Vassilakis E. Object-based characterization of landslide phenomena using UAV photogrammetry. Reg. Conf. on Geomorphology (IAG). 2019.Abstract
Detection and mapping of landslide and rockfall events using remote sensing products has been proved to be an effective approach to provide landslide inventories. However, most of the studies are lacking valuable semantic information about landslide elements and how they react with the surrounding environment; natural and man-made primitives. In addition, post classification object-based approaches have been proved to result in better accuracy compared with the pixel-based. Lately, innovative close-range remote sensing technology such as Unmanned Aerial Vehicle (UAV) photogrammetry and Terrestrial Laser Scanning (TLS) are widely applied in the field of geoscience due to their efficiency in collecting data about terrain morphology rapidly. This research aims to demonstrate the applicability of UAV technology for automated semantic labeling in managing landslide and rockfall hazard in mountainous environments during emergency situations. SfM photogrammetry in addition to high accuracy RTK-GNSS ground control point establishment, is used to provide detailed 3D point clouds describing the surface morphology of the landslide and rockfall elements. The proposed methodology was divided in five main working phases. The first phase includes designing and execution of an optimal UAV flight planning to collect accurate 3D data. During the second phase, the pre-processing and raw data preparation such as point cloud filtering and elimination of ambiguities is taking place, while at the next phase an image segmentation using the 3D point cloud RGB information is created. The main task was focused on identifying the specific landslide elements by using an object-based approach. Based on Object-Based Image Analysis (OBIA), a sequence of image-based processes was applied, including multi-scale object segmentation, spectral, morphometric and contextual information extraction aiming to detect the landslide among other features. The next phase was set up for object classification in meaningful and homogeneous landslide classes (e.g. scarp, depletion zone, accumulation zone) which are spatially connected by introducing contextual information in the ruleset. The proposed methodology presents the effectiveness and efficiency of UAV platforms to acquire accurate photogrammetric datasets from intense relief environments and complex surface topographies by providing a holistic assessment and characterization of the failure site based on semantic classification of the landslide and rockfall objects. Results have demonstrated the capabilities of combining UAV platforms with computer-based methods for rapid and accurate identification of valuable semantic information subjectively and even from inaccessible areas of the landslide and rockfall body.
Sakellaropoulos P, Vassilakis E, Tranos M, Lozios S. Differential Uplift of the Eastward Mountain Front of Olympus Mt (Greece) based on Tectonic Geomorphology Observations. Reg. Conf. on Geomorphology (IAG). 2019.Abstract
The study of the east dipping N-S mountain front of Olympus Mt that is presented in this work, was based on the interpretation of high-resolution digital elevation model (DEM), as the main dataset for calculating various tectonic geomorphology indices, through quantitative techniques. Since the fluvial network maintains its connection to the tectonic forcing and therefore contains potentially useful information about variations in rock uplift rates across the landscape, we used a highly detailed one generated from the DEM in order to calculate various indices and extract quantitate information. Calculations were made in a GIS platform by using the Ks index, the drainage basin asymmetry index and the geometry of the triangular facets on the front of the mountain, alongside the fault zone delineating the mountain. The results extracted by combining the previous methodologies are in agreement with the observations which were made during the fieldwork, that there is no uniform uplift along the main Olympus fault zone.
Christopoulou A, Mallinis G, Vassilakis E, Farangitakis G-P, Fyllas NM, Kokkoris GD, Arianoutsou M. Assessing the impact of different landscape features on post-fire forest recovery with multitemporal remote sensing data: the case of Mount Taygetos (southern Greece). International Journal of Wildland Fire [Internet]. 2019;28:521-532. https://doi.org/10.1071/WF18153Abstract
Fires affecting large areas usually create a mosaic of recovering plant communities reflecting their pre-fire composition and local conditions of burning. However, post-fire recovery patterns may also reveal the effects of landscape heterogeneity on the natural regeneration process of plant communities. This study combines field data and remote sensing image interpretation techniques to assess the role of various landscape characteristics in the post-fire recovery process in a mountainous region of Greece burned by a severe wildfire. Remote sensing techniques were used to accurately map secluded, large burned areas. By introducing a temporal component, we explored the correlation between post-fire regeneration and underlying topography, soils and basement rock. Pre-fire forest cover was reduced by more than half 8 years after fire. Regarding the dominant pre-fire forest trees, Abies cephalonica did not regenerate well after fire and most pre-fire stands were converted to grasslands and shrublands. In contrast, Pinus nigra regenerated sufficiently to return to its pre-fire cover, especially in areas underlain by softer basement rock. The use of different time series of high-resolution images improved the quality of the results obtained, justifying their use despite their high cost.
Alamanis Ν, Drimonas C, Milozis E, Lazogiannis Κ, Papageorgiou G, Vassilakis Ε, Alexopoulos J, Kotsopoulos S, Chouliaras Ι. Improvement measures and prospects for the development of “Glyfada Marina”, Attica, Greece. 1st International Scientific Conference on Design and Management of Port Coastal and Offshore Works [Internet]. 2019. Publisher's VersionAbstract
For several years, Greece has set as a priority the strengthening of maritime tourism, such as the tourism of yachts for which tourist marinas have been created. The most important marinas of the country include the “Glyfada Marina”, whose works began on the coastal front after 1960, thus changing the area’s shape and planning. The main objective of the present work is to investigate the improvement measures and prospects for the development of the “Glyfada Marina” consisting of four basins, being one of the most beautiful and developed marinas in the country since it is an important attraction for tourist yachts. For this reason, on-site visits to the port area were carried out, both on the sea and on the coastal part of the coastal zone, in order to record the current situation, so as to reach as accurately as possible the characteristics and the range of the internal port works and facilities of the aforementioned tourist port. Furthermore, any deficiencies or failures that need improvement are presented, labeled and classified in order to continue unhindered activities in the marina area. Finally, improvement and upgrading measures are proposed that can contribute positively to the tourist and economic development of the port and the municipality of Glyfada in general. 
Lazogiannis K, Vassilakis E, Poulos S, Kotsopoulos S, Alexopoulos J, Alamanis N, Papageorgiou G. UAS-SfM as a Cost-Effective Tool for Coastal Monitoring and Management. 1st International Scientific Conference on Design and Management of Port Coastal and Offshore Works [Internet]. 2019;1:135-139. pdfAbstract
Coastal zone monitoring is essential in order to understand their evolution and incorporate sustainable coastal management practices. Frequent data collection is essential but often surveys can be costly and time-consuming. Several costly and time-consuming tools and techniques have been developed during the last few years for change detection and monitoring, allowing for both qualitative and quantitative analysis. In this study we present the ability of an off-the-shelf Unmanned Aerial Systems (UAS) coupled with Structure-from-Motion (SfM) photogrammetry to map and measure coastal features (e.g. shorelines). The UAS surveys taken place over three campaigns during Autumn 2017 (November), Spring 2018 (March) and Autumn 2018 (October) in Pinios river deltaic coast. The demonstrated UAS-SfM methodology produced remote sensing data with great spatial resolution which could be used to visually identify important parameters for coastal research and management at a fraction of thecost of other available techniques and. Even an off-the-shelf UAS is suitable for repeat surveys to assess spatial and temporal changes at small spatial extents and to better comprehend how these may be related with site-specific natural processes along the coast.
Tsokos A, Tsoukala V, Petropoulos C, Sartampakos P, Vassilakis E. Combination of Very High Resolution satellite imagery and side scan data for low cost seagrass mapping. 1st International Scientific Conference on Design and Management of Port Coastal and Offshore Works [Internet]. 2019;1:157-161. pdfAbstract
The use of techniques of two different origin were compared and combined aiming to map the seagrass meadows at shallow waters of South Evoikos Gulf, in central Greece. The high spatial and spectral resolution of WorldView-2 satellite images and its ability of water penetration, offers a positive approach for sea bottom mapping, in a relatively high resolution. In addition, the ground truth fieldwork survey with side scan data acquisition revealed that it was in impressively high agreement with the outcomes from the remote sensing data interpretation.
Vassilakis E, Farangitakis G-P, Christopoulou A, Antoniou V, Arianoutsou M. Assessment of different methods for the quantification of soil erosion risk after fire: a case study from Geraneia Mt., central Greece. EGU General Assembly [Internet]. 2019;21:7561. pdfAbstract
The quantification of the amount of the expected eroded material that will migrate towards lower elevations after a forest fire is one of the most crucial and practical information needed from the local authorities, in order to design post-fire stabilization measures and actions. It is one of the greatest challenges in natural resources and environmental planning and computer simulation models are becoming increasingly popular in predicting soil loss for various land use and management practices. Quite a few models along with their modifications are being developed aiming to fulfil the need for accurate quantification of soil erosion risk. Depending on the availability and the quality of the spatial data, which have to be imported into the various models as parameters, different methodologies are followed. Geraneia Mt is an extended mountain range at the west outskirts of Attica, central Greece, reaching the altitude of 1351 m, part of which has been designated as Natura 2000 site and is characterized by almost vertical slopes of carbonate rocks. The mountain was almost completely burned by a wild fire in late July 2018, which consumed most of its Pinus halepensis forests. The ridge of the protected area, covered by endemic fir Abies cephalonica forest was also affected by the fire. The soil covers carbonate rocks which comprise the higher elevations and the vertical slopes of the mountain as debris and loose deposits crop out at the south-facing mountain front which was greatly affected by the fire. Several erosion risk spatial models were applied on the protected area of Geraneia Mt in order to compare the sensitivity of their results and evaluate the risk of the affected habitat to be deteriorated. For each model, the most sensitive model parameters were calibrated and predicted soil loss amounts were compared. A qualitative and quantitative estimation was achieved and the advantages and disadvantages of each model had been identified.
Andreadakis E, Diakakis M, Nikolopoulos E, Vassilakis E, Spyrou N-I. Estimation of flash flood peak discharge using Unmanned Aerial Vehicle (UAV)-derived imagery. The case of the 2017, Mandra flood in Greece. EGU General Assembly [Internet]. 2019;21:14573. pdfAbstract
The spatial and temporal scale of flash flood occurrence provides limited opportunities for measurements and observations using of conventional monitoring networks. These observational difficulties, often accompanied by a lack of instrumental data have turned the focus to event-based, post-disaster studies. Post-flood surveys are particularly useful, as they provide the opportunity to observe aspects of hydrological behaviour of catchments under rare runoff conditions and extreme meteorological forcing, by capitalizing on field evidence. Recently, unmanned aerial vehicles (UAVs) and the Structure for Motion (SfM) technique have been used to enhance field surveys and monitoring related to different aspects of disasters. The simple consumer-grade equipment required, its enhanced observation capabilities and certain conveniences they offer in field surveys indicate a strong potential of these technologies in many aspects of flash floods, especially given the opportunistic nature of their study. This work explores further this potential, aiming to demonstrate the application of UAVs in post-flood peak flow estimation. The research team surveyed two selected cross sections after the catastrophic 2017 flood of Mandra, developing a high resolution (2.7cm) digital surface model (DSM) using UAV imagery and the Structure from Motion technique (SfM). The detailed DSM was used to study channel geometry and flow obstructions, extract cross sections and calculate the cross sectional area and wetted perimeter. Water energy slope was defined with the use of high water marks that were placed on the DSM on the appropriate elevation. Peak discharge in the two ungauged sections were estimated at 170m3/s and 140m3/s (with a range to account for the uncertainty inherent in the dynamic nature of Manning coefficient), using the slope-conveyance method, indicating a unit peak discharge of approximately 9-10m3/s/km2. Following recommendations described in relevant literature on the integration of survey observations by means of hydrological modelling, we applied a spatially distributed hydrologic model to simulate discharge at the surveyed cross-sections (the Kinematic Local Excess Model (KLEM)) and other checks, all of which were in agreement, with the peak flow estimates provided by the UAV-aided survey analysis. The UAV allowed the collection of aerial imagery in a rapid way from an extensive area, despite that a large portion of it was inaccessible due to road closures and safety issues. In addition, detailed DSMs created using aerial imagery and the SfM technique was found to be particularly useful for studying channel geometry, obstructions and other characteristics of flow as well as for measuring cross sectional areas on demand, even at a later time, when the channel had changed due to human intervention (e.g. cleanup using heavy machinery) and water flow. These capabilities fit to the opportunistic context of studying flash flood events in the sense that UAVs can rapidly collect information within the short time frame that it is available. Nevertheless, it has to be noted that combination of ground with aerial observations is preferable.
Assimakopoulou P, Nastos P, Vassilakis E. Using Copernicus EO data and services in primary education. EGU General Assembly [Internet]. 2019;21:3549. posterAbstract
The Copernicus EO Programme offers information services based on vast amounts of satellite and in-situ data. This information content which is freely and openly available to all users, can directly impact teaching and learning systems by providing insights of our planet never available before. Specifically, the Copernicus ecosystem can enable students to develop a keen awareness of the intricate interrelationships that exist in the real world environment. The incorporation of Copernicus services and data in all levels of education is an ongoing effort which has been initiated with the establishment of the Copernicus Academy Network. Here, we present an application of Copernicus services into the Greek upper primary school curriculum, delivered in the form of “ready-to-use” hands-on activities. We use case studies from the latest natural disasters which have raised public awareness and are believed to be concrete examples of local events that are personally relevant to students, thus engaging them in an experiential learning process. The activity shown is related to the Athens’ devastating forest fires during the summer of 2018 (Mati, Kineta forest fires). We use the Sentinel-hub EO Browser tool to approach the issue of forest fires in urban compare to rural sites. Through simple concepts developed from these examples, the students are introduced to science subjects such as the interaction of light with matter, the reflection of light by different land surfaces, and the extinction of the radiation by atmospheric constituents. The interdisciplinary approach used in the suggested classroom activities promotes the UNESCO vision for education that helps students better understand the world in which they live by addressing the complexity and interconnectedness of environmental problems and thus promoting sustainable development concepts. Future work includes the use of additional natural phenomena and disasters or man-made emergency situations monitored by Copernicus in order to further promote a holistic approach in teaching and learning of Earth System Sciences. (e.g. floods, oil spills, algal blooms, desert dust outbreaks, volcanic eruptions etc.).
Karantanellis E, Marinos V, Vassilakis E. 3D Hazard Analysis and Characterization of Landslide Motion Mechanism using UAV Imagery. Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci. [Internet]. 2019;XLII-2/W13:425–430. https://www.int-arch-photogramm-remote-sens-spatial-inf-sci.net/XLII-2-W13/425/2019/Abstract
Late years, innovative close-range remote sensing technology such as Unmanned Aerial Vehicle (UAV) photogrammetry and Terrestrial Laser Scanning (TLS) are widely applied in the field of geoscience due to their efficiency in collecting data about surface morphology. Their main advantage stands on the fact that conventional methods are mainly collecting point measurements such as compass measurements of bedding and fracture orientation solely from accessible areas. The current research aims to demonstrate the applicability of UAVs in managing landslide and rockfall hazard in mountainous environments during emergency situations using object-based approach. Specifically, a detailed UAV survey took place in a test site namely as Proussos, one of the most visited and famous Monasteries in the territory of Evritania prefecture, in central Greece. An unstable steep slope across the sole road network results in continuous failures and road cuts after heavy rainfall events. Structure from Motion (SfM) photogrammetry is used to provide detailed 3D point clouds describing the surface morphology of landslide objects. The latter resulted from an object-based classification approach of the photogrammetric point cloud products into homogeneous and spatially connected elements. In specific, a knowledge-based ruleset has been developed in accordance with the local morphometric parameters. Orthomosaic and DSM were segmented in meaningful objects based on a number of geometrical and contextual properties and classified as a landslide object (scarp, depletion zone, accumulation zone). The resulted models were used to detect and characterize 3D landslide features and provide a hazard assessment in respect to the road network. Moreover, a detailed assessment of the identified failure mechanism has been provided. The proposed study presents the effectiveness and efficiency of UAV platforms to acquire accurate photogrammetric datasets from high-mountain environments and complex surface topographies and provide a holistic object-based framework to characterize the failure site based on semantic classification of the landslide objects.
Anifanti A, Sykioti O, Vassilakis E. Detection of chromite minerals using Spectral Linear Unmixing on Sentinel-2 imagery. Case study: Ingessana Hills, Blue Nile Province, Sudan. 15th International Congress of the Geological Society of Greece [Internet]. 2019. pdfAbstract
The Ingessana hills in the southern Blue Nile of Sudan consist of serpentinised and highly silicified dunites in contact with the intruding Bau granite. The observed chromite mineralization zones are associated with NE-SW trending shear-zones. The mineralization associated with ophiolitic belts includes podiform chromite, asbestos, talc, and base metal (Cu, Ni, Co) mineralization. We applied Linear Spectral Unmixing algorithm on a 10m spatial resolution Sentinel-2 images in order to detect and map the chromite mineralization and the associated mineralization of ophiolitic belts. The resulting abundance maps show the capability of Sentinel-2 for detailed mineral mapping and detection of potential chromite ore deposit locations.
Filis C, Karalemas N, Skourtsos E, Kranis H, Lozios S, Antoniou V, Diakakis M, Mavroulis S, Danamos G, Vassilakis E, et al. Geo-environmental impact on the aquifer systems of the wider fire-affected area (August 2017) on Kythira Island, Greece. 15th International Congress of the Geological Society of Greece [Internet]. 2019. pdfAbstract
Three main aquifer systems developed on Kythira Island include (Pagounis, 1981; Pagounis & Gertsos, 1984, Danamos, 1991; Koumantakis et al., 2006):
  • The porous aquifer system in Neogene and Quaternary formations.
  • The karstic aquifer system in the carbonate formations of the Pindos and Tripolis units.
  • The aquifer system (both shallow and deep) in the fractured hard rocks mainly of the Phyllites – Quartzites unit.
The main discharge of the aquifer systems takes place in coastal and submarine brackish springs around the island, except for its northern part where the Phyllites – Quartzites unit outcrops and its central part where springs of small capacity discharge the carbonate formations of the Pindos unit. The municipal water supply of Kythira has been reinforced by a series of projects and interventions, focusing on the summer touristic period, when water demand surpasses by far water availability, mainly consisting of new deep boreholes. Precipitation is the direct recharge of the three aforementioned aquifer systems while indirectly lateral discharge occurs in places between adjacent and tangential aquifer systems and from the streams runoff as well. On August 4, 2017 a shrub, rather a forest fire broke out close to the island hospital; it expanded rapidly due to strong winds blowing in the area and raged out of control for four days, inducing considerable damage. The size of the fire-affected area was about 20km2, 16km2 mainly of shrub and 4km2 of agriculture land. For the detailed evaluation of the geo-environmental impact of the aforementioned fire to the aquifer systems of the Kythira Island concerning the quantitative and qualitative degradation seventeen municipal water points were finally selected for further hydrogeological study. The water points monitoring network were used in September 2017, June 2018 and October 2018 for measurements of the water tables heads and springs discharges while water samples were collected and chemical, trace elements and microbiological analysis were carried out. The impact of the fire on the quantity of the aquifer systems of the wider fire-affected area could not be fully clarified and there was indirect evidence of their recharge (it remains unknown its rate compared to the recharge before the August 2017 fire) during the three field trips such as:
  • Fluctuation of the measurements of the water table heads.
  • Fluctuation of the measurements of springs discharges.
  • Fluctuation of the measurements of boreholes hydrometers.
  • Changes to the hydrochemical facies of the Piper’s, Durov’s and Stiff’s diagrams of the collected water samples.
The results and the evaluation of the chemical and trace elements showed that there was no impact of the fire on the quality of the wider fire-affected area aquifer systems. However, microbiological analysis from the Mylopotamos spring showed qualitative degradation, due to human activities in the wider area preexisting the August 2017 fire (Pagounis, 1981). For the sustainable water resources management of the wider fire-affected area new projects were proposed in order to prevent phenomena that favors the runoff instead of infiltration which lead to the restriction of the recharge of the three main aquifer systems, such as works of artificial recharge.
Assimakopoulou P, Nastos P, Vassilakis E, Antonarakou A. Earth Observation for Earth System Science Education: the MICE activity. 15th International Congress of the Geological Society of Greece [Internet]. 2019. pdfAbstract
Developing educational material based on satellite remote sensing technologies, information and methods, is a key trend in modern pedagogy of Earth System Sciences. Here, we present “MICE”, a classroom activity on Melting ICe Effects, that utilizes remote sensing information to demonstrate the value of Earth Observation (EO) as a context to teach the STEM (Science, Technology, Engineering and Mathematics) school curriculum. The activity focuses on the subject of polar ice melting as a main climate change effect and the different impact of land and sea ice melting on sea level rise. Students, have the opportunity to discover the above experimentally and subsequently, to observe the diachronic change on polar ice through sequences of satellite images and discover the positive climate feedback on global warming. The activity was translated and adapted to the Greek curriculum from the freely available classroom resources of the European Space Agency (ESA, “Teach with Space” collection). MICE, has been enriched with Greek scientific material, including up-to-date information on climate impacts, localized for the extended region. As part of an evolutionary process, the activity was pilot-tested with 6th grade primary school students and adjusted according to the trial findings. This work is considered as the first step towards the development of original Greek educational material that will utilize EO and climate change as the context to teach STEM school curriculum, capitalizing on the pedagogical role satellite remote sensing and inquiry-based teaching methods, can play.
Karantanellis E, Marinos V, Vassilakis E. Object-Based Characterization and Semantic Labeling of Landslide and Rockfall phenomena using UAV photogrammetry. 15th International Congress of the Geological Society of Greece [Internet]. 2019. pdfAbstract
A variety of remote sensing tools have been extensively used in the past years for landslide detection and mapping purposes. In addition, detection and mapping of landslide and rockfall events using remote sensing products has been proved to be an effective approach to provide landslide inventories (Scaioni et al., 2014). However, most of the studies are lacking valuable semantic information about landslide elements and how they react with the surrounding environment; natural and man-made primitives. In addition, post classification object-based approaches have been proved to result in better accuracies compared with the pixel-based (Martha et al., 2011). Lately, innovative close-range remote sensing technology such as Unmanned Aerial Vehicle (UAV) photogrammetry and Terrestrial Laser Scanning (TLS) are widely applied in the field of geoscience due to their efficiency in collecting data about terrain morphology rapidly. Their main advantage stands on the fact that conventional methods are mainly collecting point measurements such as compass measurements of bedding and fracture orientation only from areas that were accessible. Aerial platforms are capable to overcome technical issues such as potential occlusions and unfavorable incidence angles due to their ability to capture imagery from multiple positions and with different angles. Nowadays, UAVs tend to be more flexible and powerful tools for landslide and rockfall investigations compared to TLS, due to their low-cost and ease of transportability in harsh environments but also with technology advances such as maintaining of Real Time Kinematic (RTK) positioning. An important factor of their usefulness is their capability to offer unprecedented spatial resolution over wide inaccessible areas, maintain a variability of different sensors (optical, laser, thermal, multispectral) and great ability to reach remote areas and acquire data as close as the user defines. UAVs applications are widely used in post-disaster situations for emergency support, in infrastructure monitoring, in natural resources management, in geohazard monitoring etc. (Corominas et al., 2016; Vassilakis et al., 2019). The latter proves that UAV market has been rapidly growing over the last decade and in future more applications will be introduced in the public. Thus, rapidness and efficiency of Structure-from-Motion (SfM) technology in landslide management provides numerous advantages such as creating landslide inventory maps providing 3D information of large areas.
Kourliaftis G, Vassilakis E, Kapsimalis V, Poulos S, Vandarakis D. Evolution of the Coastal Environment of the Marathon Bay Based on the Shoreline Displacement Rate for the Last 80 Years. 15th International Congress of the Geological Society of Greece [Internet]. 2019. pdfAbstract
The purpose of the study is the determination of the shoreline changes and the sediment processes along the beach of Marathon Bay, which is located at northeast Attica. In the wider on shore area the Schinias National Park, at the northeast of the bay, the Olympic Rowing Centre, military bases, archeological sites, museums etc. are encountered. The area is also characterized by high touristic activity during summer. In the area there are specific locations and constructions endangered due to coastal retreat. A lagoon was established in the study area 3.500 years BP (Pavlopoulos et al., 2006) as it is characterized by low elevations, gentle slopes and fine sediments. A survey of the coastal and marine geomorphology was carried out by acoustic scanning of the seafloor with an echo sounder and sonar side scan topographical sections perpendicular to the shoreline along with collection and analysis of surface sediments. The quantification of long-term shoreline displacements was carried out by comparing historical and contemporary aerial photographs (1945, 1960, 1969, 1988, 1996, 2001, 2010) along with very high resolution satellite imagery (2012, 2014, 2015, 2016, 2017, 2018), not to mention the tracing of the coastline (2013) with Real Time Kinematics equipment (RTK-GNSS). The quantification of long-term shoreline displacements was made with the use of the add-on application of Digital Shoreline Analysis System (DSAS) within the GIS platform ArcMap 10.6 (Thieler et al., 2009). This was accomplished by drawing 261 transects (every 50 meters), except those neighboring anthropogenic structures, perpendicularly to the historical shorelines from a stable baseline (Tsokos et al., 2018). At each transect the rate of displacement was measured.
Konsolaki A, Vassilakis E, Giannopoulos V, Kontostavlos G, Psaltakis I. 3D rock thickness extraction by combining Point Clouds of different origin. Case Study: The roof of Koutouki Cave Peania, Greece. 15th International Congress of the Geological Society of Greece [Internet]. 2019. pdfAbstract
The purpose of this research is to combine two state-of-the-art technologies in surveying for extracting the rock thickness above a cavity. By combining Lidar technology for indoor surveying and photogrammetric processing of Unmanned Aerial Systems (UAS – drones) data, we managed to calculate and project with high accuracy the rock thickness of the roof of the underground environment of Koutouki Cave (Peania, Greece). Usually, cave systems are complex and unique because of their distinctive geometry and compound geomorphology along with natural harsh conditions such as constrained accessibility, limited light, high humidity and possible existence of water. Such environments make mapping difficult and further complicated (Kershaw, 2012). Nowadays, the state-of-the-art in surveying of open surface is based on LiDAR technology. Lately, similar technology has started to be used for indoor surveying and consequently in cave mapping, especially where the underground space allows it. Our research was based on the use of a recently released piece of equipment introducing a lightweight mobile handheld laser scanning system (GeoSLAM ZEB – REVO) that has the ability to produce a quite dense point cloud within an underground cavity. The x, y, z point cloud is generated while the operator walks through the cave (Zlot and Bosse, 2014). The specifications of this equipment include a 360o rotation, a (class 1 eye safe) 100Hz laser – making 100 rotations per second with the collection of 43,200 points per second. The maximum effective range is around 25-30m for indoor environment and data over 30m are usually excluded.
Vasilatos C, Anastasatou M, Pomonis P, Alexopoulos J, Vassilakis E, Stamatakis M. Hazard identification of the Mediterranean Temporary Mountain Pond ecosystems in Central Greece: Α Geo-environmental approach. 15th International Congress of the Geological Society of Greece [Internet]. 2019. pdfAbstract
Mediterranean Temporary Ponds (MTPs) are shallow water bodies which are characterized from a short wet period and their small size (Zacharias et al., 2007). MTPs of Europe have are under an effective protection status, as a result of their identification as a priority habitat (Annex I code 3170*) in the EU Directive 92/43/EEC (Habitats' Directive). These ponds are very delicate ecosystems regarding their hydrological and geochemical characteristics. Due to their small size, they are open to random destruction or other unpredictable dangers. Although small in size, MTPs are complex ecosystems where topography, soil, water and hydrological conditions and microorganisms are closely connected (Zacharias et al., 2007; Stamatakis et al., 2015). The conservation and restoration of such ecosystems is very difficult because of their unique characteristics. The most common threats for MTPs include destruction of the hosting area through human and animal pressures, hydrological disturbance, fire and generally changes in ecological conditions resulting in an increase of competitive plants, nutrition influx, toxic contaminants and wastes, sedimentary deposit filling, exotic-invasive fauna and flora and negative effects from domesticated or hunted fauna (Dimitriou et al., 2006).
Roufi A, Vassilakis E, Poulos S. Western Lefkada Shoreline Displacement Rates Based On Photogrammetric Processing Of Remote Sensing Datasets From Various Sources. 15th International Congress of the Geological Society of Greece [Internet]. 2019. posterAbstract
The aim of this study is to calculate the displacement rates of the coastline at the western part of the island, which is characterized of the escarpment coast. The shape of this coastal zone is caused mainly by tectonism which is very frequent in this wider area (Valkaniotis et al., 2018). The western coast of the island from Cape Agios Ioannis (NW) to the southernmost point of the peninsula, Cape Doukato is steep and precipitous, as a result of the high seismicity of the Ionian Sea area (Bornovas, 1964). Along this side of the island, several landslides and rock falls are observed. The situation changes only at the northern part of the island, with a distinctive coastal landform over the narrow zone called "Zostiras" (Leivaditis & Verikiou - Papaspyridakou, 1986). This work was conducted using two different types of data. Historical analogue panchromatic aerial images of high resolution (Zuidam and Van Zuidam-Cancelado, 1979) and contemporary digital high resolution multi-spectral satellite images were combined for extracting the coastline at the time period of acquisition. The acquisition of the aerial photographs took place during 1945 and 2010, while the satellite images where acquired during 2016, 2017 and 2018 (Figure 1). In all cases the images were digitally processed and optically optimized in order to produce a highly accurate representation of the shoreline at each time period. All the data were imported in a Geographic Information System platform, where they were subjected into comparison and geo-statistical analysis (Tsokos et al., 2018). Several transects were drawn normally to the coast and the distance between them was set at every 200 m as the relative displacement of the coastline was calculated for each one of them. In a way to achieve this, an extension of the ESRI ArcGIS v.10.6.1 software was employed as published by USGS and named Digital Shoreline Analysis System v.5 (DSAS). The DSAS extension (Thieler et al., 2009) lets the user define a constant straight line in a specific distance from the shoreline and take transects perpendicular to it among the evolving coastlines. The measurements give quantitative information on the change of the position of the shoreline, as well as more useful statistical data. Even if this seems to be an arbitrary value, it worked rather sufficiently at this almost 12 km long segment of the shoreline as it can be characterized as rather curvy and either a smaller value would result an oversampled area with transects intersect each other mixing the calculations or a larger value would result quite sparse transect locations without any representative outcome.
Tsokos Α, Tsoukala V, Petropoulos C, Sartabakos P, Vassilakis E. Combination of Very High Resolution satellite imagery and side scan data for low cost seagrass mapping. 1st International Scientific Conference on Design and Management of Port Coastal and Offshore Works [Internet]. 2019. pdfAbstract
The use of Very High Resolution (VHR) satellite imagery at various applications is gaining more and more popularity due to the growing number of offered data and the increasing spectral properties. WorldView-2 is the first commercial VHR multi-spectral satellite providing imagery in eight different sensors having bands that range from the visible to near-infrared (0.40-1.04 μm). The integration of the “Coastal” band (0.40-0.45 μm) in the 8-band WorldView series of satellite imagery data, which was followed by the addition of the similar wavelength band 1 (0.43 - 0.45 µm) in the Landsat-8 Operational Land Imager (OLI), gave a great boost to applications related to shallow water depths. The fundamental principle underlying the methods used to study the sea bottom from remotely sensed imagery is that different wavelengths of the solar light penetrate the water body to different depths (Phinn et al. 2008). The ability to accurately determine the seagrass at underwater regions is of great importance for the biodiversity of the submarine environment. The use of certain spectral wavelength data tends to be the most cost effective way of monitoring the marine habitats by mapping the sea bottom type along with several other jobs like modeling coastlines or even navigating through shallow aquatic areas by studying the bathymetry (Fornes et al. 2006).
Megremi I, Vasilatos C, Vassilakis E, Economou-Eliopoulos M. Spatial diversity of Cr distribution in soil and groundwater sites in relation with land use management in a Mediterranean region: The case of C. Evia and Assopos-Thiva Basins, Greece. Science of The Total Environment [Internet]. 2019;651:656-667. https://doi.org/10.1016/j.scitotenv.2018.09.186Abstract
The present study compiles new and literature data in a GIS platform aiming to (a) evaluate the extent and magnitude of Cr contamination in a Mediterranean region (Assopos-Thiva and Central Evia (Euboea) Basins, Greece); (b) combine spatial distribution of Cr in soil and groundwater with land use maps; (c) determine geochemical constraints on contamination by Cr; and (d) provide information that will be useful for better management of land use in a Mediterranean type ecosystem in order to prevent further degradation of natural resources. The spatial diversity of Cr distribution in soils and groundwater throughout the C. Evia and Assopos-Thiva Basins is considered. It is attributed to both natural Cr sources (Cr-bearing peridotites, affecting primarily soil) and human (industrial) activities (the dominant source of groundwater contamination). A combination of the spatial distribution of metals in soil and land use maps was used to define the specific areas of agricultural land use with elevated heavy metal contents. Furthermore, the combination of the spatial distribution of Cr in groundwater and land use maps allows for definition of specific areas of industrial land use with elevated Cr concentrations (Inofita, south Assopos-Thiva Basin). Despite the good correlation (r = 0.75) between Cr(VI) and the strong oxidant NO3− in C. Evia, the lower standard potential (E0) values for NO3− compared to those for Cr2O72− (the latter is a stronger oxidant than the former) suggest that NO3− is not an oxidant of Cr. This detailed assessment and presentation of the available analytical data for soil and groundwater in Assopos-Thiva and C. Evia Basins on a land use map provides information for land management decision makers.
Vasilatos C, Anastasatou M, Alexopoulos J, Vassilakis E, Dilalos S, Petrakis S, Delipetrou P, Georghiou K, Antonopoulou S, Stamatakis M. The geo-environmental status of the European Union Priority Habitat Type "Mediterranean Temporary Ponds" in Mt. Oiti, Greece. Water [Internet]. 2019;11(8):1627. https://doi.org/10.3390/w11081627Abstract
Mediterranean temporary ponds (MTPs) constitute priority habitats under the European Union Habitats Directive, inhabited by several rare endemic species and subjected to unstable environmental conditions. Lakes and pond act as early indicators of climate change, in which alpine ecosystems are especially vulnerable. The study area is located in a mountainous Natura 2000 site of Central Greece, designated as “National Forest Park of Mt Oiti” (Ethnikos Drymos Oitis), which hosts a number of MTPs. Field sampling of soil and water carried out in four MTPs during dry and wet periods between 2012 and 2014. Electrical Resistivity Tomography (ERT) technique was used for the delineation of the subsurface geological structure. This study aims to present the current ecological status of Mt Oiti MTPs with respect to their geo-environmental characteristics, emphasizing to their indirect correlation with plant species richness. Moreover, this paper aims to address the lack of basic ecological background on MPTs network of Mt Oiti concerning their characteristics along with the pressures received from various activities. MTPs of Mt Oiti were classified according to their ecological status, by identifying the habitats’ threats and defining their geological structure, mineralogy and physiochemical parameters of each pond.
Antoniou V, Vassilakis E. Diffusion of Geo-Environmental datasets through online interactive and real-time applications. Case study: the Natura GR2440006 protected area. Annals of Geographical Studies [Internet]. 2019;2(1):8-16. Publisher's VersionAbstract
A web - interactive application which spreads geo-environmental information over the internet and also accepts and manages real time rural data is described in this paper. Story Maps context has been chosen for this reason, since this is considered to be a new and innovative Web-based Geographic Information System application method for using it as a mean for organizing and presenting new digital geographic information by combining interactive maps with multimedia and other apps simultaneously in one platform. The protected area of Kallidromo Mt. (central Greece) was chosen as a case study, due to its environmental sensitivity since it is characterized as Natura protected area and also because of the availability of several kinds of geospatial data.
Vassilakis E, Foumelis M, Erkeki A, Kotsi E, Parcharidis I, Lekkas E. Multitemporal Surface Deformation Analysis of Amyntaio Slide (Greece) using Remotely Piloted Airborne System and Structure-from-Motion photogrammetry. 4th Joint International Symposium on Deformation Monitoring [Internet]. 2019. pdfAbstract
The results of Structure-from-Motion techniques in order to quantify the ground surface deformation due to the massive landslide that occurred at the lignite open pit in Amyntaio, Greece on June 10th 2017, are presented in this paper. This unexpected slide damaged the entire westernmost marginal area of the pit, significant number of buildings and infrastructures (incl. road network, powerlines, biological treatment, houses etc.) of the nearby village of Anargiri, as well as agricultural land at the head of the landslide. We generated a very high-resolution surface topography and corresponding co-registered ortho-rectified images covering a total area of 2 km2 by analyzing images acquired from Remotely Piloted Airborne Systems (RPASs). A high resolution (0.13 m) Digital Surface Model (DSM) was produced after photogrammetric processing, serving as a reference dataset for comparison with other surveys realized in December 2017 and September 2018. We compared the centimeter-resolution DSMs acquired during the post landslide periods, quantified the overall ground deformation and finally delineated regions of potential risk.