The present study investigates alterations in the coastal area of the Acheloos deltaic complex (W. Greece) during the period 1945 – 2020 and the shoreline response to anticipated sea-level rise under various RCP scenarios. The authors used two methods of analysis: area measurement in non-linear sections of the coast, and longitudinal displacement of the coastline using DSAS. The future state of the coastal area analyzed by considering IPCC predictions, adjusted for local conditions. The results reveal severe erosion in the entire study area, reaching 250 m (~3.4 m/yr) in places, mostly due to the diversion of the main Acheloos River channel, whereas coastal protection works constructed in the 90s have partially mitigated the erosional rate. The IPCC predictions for 2100 show a continuous shrinking of the delta by 10% to 20% of the present area, while under the most extreme climate scenario, deltaic area loss could reach 60%. Regardless of the prevailing scenario, it was estimated that for each 0.1 m of sea-level rise, the average land loss at the deltaic area is approximately 2.8 km2.

Karst caves preserve complex morphologies that reflect long-term landscape evolution while also presenting significant challenges for documentation and stability assessment. This study develops and applies an integrated workflow that combines multi-sensor close-range remote sensing equipment and techniques, to produce high-resolution 3D models of two of the most popular show caves in Greece. The combined datasets enabled the construction of detailed geomorphological maps and a quantitative description of the cave interiors, including the spatial distribution of speleothems. Because manual counting and measurement of speleothems is often impractical, a semi-automatic procedure was implemented based on geometric feature extraction, morphometric filtering and connected-component segmentation. The method reproduced manual counts accurately in areas where speleothems are well separated, and it also captured dense clusters that are difficult to document visually. The structural configuration of both caves was examined through fracture analysis performed directly on the 3D models, and these structural data were incorporated into three-dimensional distinct element simulations to evaluate potential instability mechanisms. The combined geomorphological and mechanical results demonstrate how multi-sensor 3D mapping can support cave management by providing a basis for hazard assessment and establishing a framework suitable for future multi-temporal monitoring.

Geomorphological transformations represent one of the most significant outcomes of high-magnitude flood events, as intense hydraulic forces have the capacity to rapidly reshape river channels, redistribute sediments, and modify the connectivity and functionality of adjacent floodplains. Understanding these processes is crucial for both hazard assessment and sustainable river management. In this context, the present study employs a multi-temporal approach using Unmanned Aerial Systems (UAS) combined with Structure-from-Motion (SfM) photogrammetry to detect, visualize and quantify geomorphological changes induced by flooding along selected sections of the Lilas River, located on Evia Island in Central Greece. These particular river reaches were strongly affected by the extreme flash flood that occurred in August 2020, an event that caused significant geomorphic disruption.High-resolution aerial surveys were carried out both before the flood event, and shortly thereafter, in June 2018 and in September 2020 respectively. These surveys enabled the generation of highly detailed Digital Surface Models (DSMs) and orthomosaics, with a ground sampling resolution of approximately 2.5 cm. By performing differential analyses of the DSMs, the study was able to capture detailed patterns of erosion and deposition along the river corridor. The results indicate a pronounced spatial variability, with areas of intense erosion exhibiting local vertical lowering exceeding 7 meters, while zones of sediment accumulation showed depositional aggradation of up to approximately 5 meters after corrections for vegetation cover. Such extreme geomorphic changes highlight the uneven distribution of flood-induced forces along the river channel.One of the most striking findings of the study is the substantial channel widening that occurred in response to the flood. At specific locations, cross-sectional widths expanded by factors ranging from three to nine, primarily as a result of lateral bank erosion. These findings underscore the complex interactions between natural geomorphic processes, extreme hydrological forcing, and anthropogenic landscape modifications, demonstrating that flood impacts cannot be understood without considering the coupled effects of these factors.Overall, the study illustrates the capability of repeatable UAS–SfM workflows to provide high-resolution, quantitative evidence of flood-driven geomorphic change. Such data are invaluable for supporting post-event assessments, informing river restoration planning, and guiding the design of infrastructure adaptation strategies. Moreover, the results contribute to broader efforts in flood risk management, particularly in Mediterranean catchments that are highly susceptible to extreme weather events. By integrating detailed topographic measurements with hydrological and ecological considerations, the methodology presented here represents a powerful tool for anticipating and mitigating the consequences of future floods.

The Red Beach in Santorini, Greece, is a dynamic landscape formed by the rapid erosion of unstable volcaniclastic cliffs. This study presents a comprehensive, decadal analysis of cliff instability activity using a Multi-Temporal Object-Based Image Analysis (MT-OBIA) framework. Driven by a systematic collection of Unmanned Aerial System (UAS) high-resolution imagery, we developed a time series of high-resolution Digital Surface Models (DSMs) and orthomosaics. Our OBIA workflow was specifically designed to segment and classify features unique to this environment, including scarps/sources, deposits, and cracks. The results quantify a mean annual cliff retreat rate of 0.45 m/year, with significant spatial and temporal variability, including a major collapse event in the winter of 2019 that resulted in over 1 meter of instantaneous retreat. The OBIA-derived inventory, comprising over 1,200 individual objects, reveals a strong seasonal pattern linked to intense storm surges and coastal erosion. This research establishes a robust and transferable methodology for high-frequency geohazard monitoring in coastal environments, providing critical data for the safety management of one of Greece's most visited tourist destinations.

The hydrogeological regime and the persistent moisture intrusion phenomena at the Holy Monastery of Kleiston are fundamentally dictated by a complex tectonic framework within the Sub-Pelagonian Unit of Mount Parnitha, NW of Athens, Greece. This study identifies the monastery’s location as a site of intense structural deformation, where the stratigraphic sequence is governed by a series of successive tectonic nappes. The structural architecture is defined by two primary thrust faults: an upper thrust (No 1) that positions carbonate rocks over volcanosedimentary formations, and a lower, sub-parallel thrust (No 2) that repositions the volcanosedimentary sequence atop an underlying lower carbonate series. Central to the water intrusion mechanism is the identification of two low-angle fault surfaces, designated as No 3 and No 4, which act as primary hydraulic discontinuities. Crucially, both of these tectonic surfaces are situated within the mass of the lower carbonate rocks and are oriented sub-parallel to the lower thrust, effectively mirroring its geometry. These intra-lithic discontinuities serve as the primary structural controls for groundwater movement, with the upper surface (No 3) coinciding with the main foundation level and the roof of the Catholicon, while the lower surface (No 4) dictates the base of the local epikarst hydrogeological system.The interaction between this tectonic fabric and the carbonate lithology has facilitated the development of an extensive epikarst zone, exceeding 10 meters in thickness, characterized by high secondary porosity. This zone is defined by two principal discontinuity systems -striking NNW-SSE and NE-SW- alongside secondary fractures that have undergone significant karstification. The mechanical widening of these joints is further enhanced by the deep penetration of root systems, which extend up to seven meters into the rock mass, creating vertical conduits. Hydrogeologically, the epikarst functions as a perched aquifer, recharged through a combination of direct autogenic precipitation and lateral allogenic contribution from upstream debris and weathered volcanosedimentary mantles.The manifestation of water and humidity within the monastery's functional spaces is the direct result of epikarst spring fronts emerging at the intersections of these specific tectonic surfaces with the building infrastructure. The upper fault surface (No 3) directs groundwater discharge into the Catholicon and the adjacent storage caverns, a process exacerbated by the thin carbonate cover which offers minimal lag time between precipitation events and intrusion. Simultaneously, the lower fault surface (No 4) facilitates discharge into minor caves and areas beneath the monastery’s retaining walls and communal spaces. This structural control explains the persistence of moisture even during arid periods, as the complex network of tectonic voids and karstified joints within the epikarst serves as a shallow reservoir. Consequently, the study concludes that the water intrusion at the Holy Monastery of Kleiston is a structurally driven phenomenon, where sub-parallel tectonic discontinuities within the lower carbonates serve as the primary conduits for the localized hydrogeodynamic discharge of the epikarst aquifer.

Geomorphological change is a fundamental consequence of high-magnitude flood events, as extreme hydraulic forcing can rapidly reshape river channels, redistribute sediment, and alter floodplain connectivity. This study applies multi-temporal UAS-based Structure-from-Motion (SfM) photogrammetry to quantify flood-induced geomorphological changes along two representative reaches of the Lilas River (Evia Island, Central Greece) affected by the extreme August 2020 flash flood. High-resolution aerial surveys were conducted prior to the event (June 2018) and shortly after the flood (September 2020), producing Digital Surface Models (DSMs) and orthomosaics with a ground sampling distance of ~2.5 cm. Differential DSM analysis reveals pronounced spatial heterogeneity in erosion and deposition, with net erosional lowering locally exceeding 7 m and depositional aggradation reaching up to ~5 m after accounting for vegetation effects. Channel widening was the dominant response, with cross-sectional widths increasing by a factor of three to nine at selected locations, driven primarily by lateral bank erosion. The results highlight the strong interaction between extreme hydrological forcing, loose alluvial sediments, vegetation removal, and human interventions such as roads and engineered terraces. The study demonstrates how repeatable UAS–SfM workflows can provide quantitative evidence to support post-flood assessment, guide infrastructure adaptation, and inform river restoration and flood risk management in Mediterranean catchments prone to extreme events.

As the frequency and severity of extreme weather events may increase due to climate change, understanding their impacts on water systems, resources, and infrastructure becomes very important. This study contributes to the growing body of knowledge on how extreme storms and floods disrupt interrelated elements comprising water systems by examining the case of Storm Daniel, which struck the Thessaly region of Greece in September 2023. Using a multi-source approach, including field data, institutional reports, scientific assessments, and publications, the study systematically identifies and categorizes the impacts of the storm and the ensuing flood across surface waters, drinking water supply, and wastewater infrastructure and other water-related systems through various mechanisms. The findings provide an overview of how such extreme storms may affect such systems and reveal widespread, interconnected disruptions that highlight systemic vulnerabilities in both natural and engineered systems, synthesizing these impact pathways. The study presents evidence of poor resilience against extreme events and climate change hazards in water-related infrastructure.

The Amynteo mega-landslide in northern Greece represents one of the most significant mass-wasting events in southeastern Europe in recent decades, with substantial geomorphological, geotechnical, and socio-economic impacts, causing the relocation of an entire village (Anargiri). Understanding such large-scale slope failure requires a multi-scale and multitemporal approach that captures both the surface dynamics and underlying controlling processes. This study investigates pre- and post-failure surface motion associated with the event by integrating Earth Observation (EO) data and Unmanned Aerial System (UAS) surveys. Surface motion gradients extending from the mine toward the nearby village of Anargyri were assessed using multi-temporal SAR interferometry (MT-InSAR) and offset tracking techniques, together with high-resolution UAS-derived Digital Surface Models (DSMs) and orthophotos. We examined the limits of each technique in measuring surface motion and exploited their complementarities across multiple spatial and temporal scales. Multi-sensor SAR datasets, including Copernicus Sentinel-1 and TerraSAR-X, were processed using MT-InSAR, supported by Copernicus EGMS products and the SNAPPING online service. Offset tracking contributed insights in areas with high displacement gradients where phase decorrelation limited interferometric methods. Repeated UAS campaigns further enhanced spatial interpretation and deformation quantification. Our analysis indicated persistent ground deformation in the pre-failure phase, spatial variability in displacement rates, and post-failure reactivation zones. The integration of InSAR and UAS photogrammetry links geomorphic process domains, such as headscarp retreat, lateral spreading, and toe bulging, with slope kinematics. We also investigate how hydrological forcing, mining-related disturbances, and lithological controls contribute to the triggering of the landslide. The study highlights the spatial and temporal dynamics of the Amynteo landslide and demonstrates the value of integrating diverse EO and UAS techniques for advancing landslide geomorphology and hazard assessment in complex slope systems. This multi-scale, multitemporal monitoring approach enhances the early detection of instability and supports the development of early warning strategies in mining environments.

The Komolithoi badlands, located in the Kissamos providence of Chania, Crete (Greece), are dunes consisting of soft clay that form conic shapes and represent a visually striking and geomorphologically active landscape, shaped by intense erosional processes characteristic of Mediterranean semi-arid environments. Their study can offer insights into the processes and mechanisms of erosion since due to their unique rock properties, including their high clay content, low organic matter, and low infiltration capacity, they are exceptionally vulnerable to erosion. Capturing the complexity and evolution of such landforms requires high-resolution, georeferenced data and a flexible methodological framework adapted to this challenging terrain.In this study, we combine Unmanned Aerial Systems (UAS) and Terrestrial Laser Scanning (TLS) data to generate ultra-detailed 3D models of the Komolithoi formations. Two full surveys were conducted in 2023 and 2024, enabling the construction of multitemporal point clouds. The integration of aerial and terrestrial methods enables dense, accurate surface coverage, overcoming limitations posed by occlusions, steep gradients, and fine-scale roughness. The resulting point clouds achieve high spatial resolution and geolocation precision, offering valuable insights into both surface morphology and potential erosion pathways. In addition to forming a baseline for future monitoring, the datasets allow for preliminary assessment of geomorphic dynamics and sediment redistribution.This contribution emphasizes the methodological potential of combining UAS and TLS technologies for badland research. It highlights how modern geomatics can advance the study of erosional landscapes where traditional surveying methods may fall short. Ultimately, this work contributes to the development of standardized, high-accuracy protocols for mapping and modeling badlands, aligning with broader efforts to monitor landscape change and aid land management in sensitive geomorphic environments.

The present study investigates the alterations of the coastal area of the Acheloos’ deltaic complex (E. Greece) for the last 20 ka and the shoreline response to the anticipated sea level rise, according to various sea-level rise prediction scenarios. The distant and near past were reconstructed through the interpretation of seismic data, sediment cores and historical aerial imagery, while the future state was evaluated considering the IPCC sea-level rise projections, adapted to the specific geomorphological and sedimentological characteristics of the study area. The results indicate a significant alteration of the area throughout the Holocene, primarily driven by the constant sea level fluctuation, while for the recent past, severe erosion has been observed in the entire study area, in places reaching 250 m (~3.4 m/yr) for the past 75 years. The IPCC predictions for 2100 suggest a continuous reduction of the delta, by 10% to 20% of the present area, while considering the most extreme climatic scenario, the percentage of the lost area could reach up to 60% of the total deltaic plain. Regardless of the prevailing scenario, it was estimated that for each 0.1 m of sea-level rise, the average land loss at the deltaic area is approximately 2.8 km2.