17 research outputs found
Flash Flood Susceptibility Evaluation in Human-Affected Areas Using Geomorphological Methods—The Case of 9 August 2020, Euboea, Greece. A GIS-Based Approach.
Flash floods occur almost exclusively in small basins, and they are common in small Mediterranean catchments. They pose one of the most common natural disasters, as well as one of the most devastating. Such was the case of the recent flood in Euboea island, in Greece, in August 2020. A field survey was accomplished after the 2020 flash floods in order to record the main impacts of the event and identify the geomorphological and man-made causes. The flash flood susceptibility in the urbanized alluvial fans was further assessed using a Geographic Information System (GIS)-based approach. Our findings suggest that a large portion of the alluvial fans of Politika, Poros and Mantania streams are mainly characterized by high and very high hazard. In fact, ~27% of the alluvial fans of Politika and Poros streams are characterized with very high susceptibility, and ~54% of Psachna area. GIS results have been confirmed by field observations after the 2020 flash flood, with significant damages noted, such as debris flows and infrastructure damages, in buildings, bridges and the road networks. In addition, even though the adopted approach may be more time-consuming in comparison to purely computational methods, it has the potential of being more accurate as it combines field observations and the effect of past flooding events
Layer-by-Layer Assembly of Clay-Carbon Nanotube Hybrid Superstructures
Much of the research effort concerning layered materials is directed toward their use as building blocks for the development of hybrid nanostructures with well-defined dimensions and behavior. Here, we report the fabrication through layer-by-layer deposition and intercalation chemistry of a new type of clay-based hybrid film, where functionalized carbon nanotubes are sandwiched between nanometer-sized smectite clay platelets. Single-walled carbon nanotubes (SWCNTs) were covalently functionalized in a single step with phenol groups, via 1,3-dipolar cycloaddition, to allow for stable dispersion in polar solvents. For the production of hybrid thin films, a bottom-up approach combining self-assembly with Langmuir-Schaefer deposition was applied. Smectite clay nanoplatelets act as a structure-directing interface and reaction media for grafting functionalized carbon nanotubes in a bidimensional array, allowing for a controllable layer-by-layer growth at a nanoscale. Hybrid clay/SWCNT multilayer films deposited on various substrates were characterized by X-ray reflectivity, Raman, and X-ray photoelectron spectroscopies, as well as atomic force microscopy
Improved Genotyping Vaccine and Wild-Type Poliovirus Strains by Restriction Fragment Length Polymorphism Analysis: Clinical Diagnostic Implications
The combination of preventive vaccination and diagnostic typing of viral isolates from patients with clinical poliomyelitis constitutes our main protective shield against polioviruses. The restriction fragment length polymorphism (RFLP) adaptation of the reverse transcriptase (RT)-PCR methodology has advanced diagnostic genotyping of polioviruses, although further improvements are definitely needed. We report here on an improved RFLP procedure for the genotyping of polioviruses. A highly conserved segment within the 5′ noncoding region of polioviruses was selected for RT-PCR amplification by the UC(53)-UG(52) primer pair with the hope that it would be most resistant to the inescapable genetic alteration-drift experienced by the other segments of the viral genome. Complete inter- and intratypic genotyping of polioviruses by the present RFLP method was accomplished with a minimum set of four restriction endonucleases (HaeIII, DdeI, NcoI, and AvaI). To compensate for potential genetic drift within the recognition sites of HaeIII, DdeI, or NcoI in atypical clinical samples, the RFLP patterns generated with HpaII and StyI as replacements were analyzed. The specificity of the method was also successfully assessed by RFLP analysis of 55 reference nonpoliovirus enterovirus controls. The concerted implementation of these conditional protocols for diagnostic inter- and intratypic genotyping of polioviruses was evaluated with 21 clinical samples with absolute success
Inventory and Assessment of the Geomorphosites in Central Cyclades, Greece: The Case of Paros and Naxos Islands
The Cycladic landscape is characterized by landforms of natural beauty and rarity. Landforms resulting from differential erosion, weathering, tectonics, drainage network, sea level changes, and depositional processes can contribute to the development of geotourism in the area. This can be achieved by supporting conservation, protection and promotion of the geo-environment and nature, educating students, residents, and visitors. The aim of this work is to develop an inventory of the main geomorphosites of Paros and Naxos islands by assessing their scientific and additional values, using qualitative and quantitative criteria. Our results show that, besides the high scientific interest of the 75 geomorphosites, most are also characterized by a high ecological value and can potentially lead to a significant increase in the islands’ tourism. The results of this work aim at raise awareness on the geomorphological heritage of central Cyclades and provide a basis for their promotion, protection, and management
A GIS-Based Assessment of Flood Hazard through Track Records over the 1886–2022 Period in Greece
This paper addresses the riverine flood events that have occurred in Greece over the last 136 years (i.e., during the 1886–2022 period), focusing, amongst others, on the case of urban floods. The flood record of various sites of the country has been collected and analyzed to determine their spatial and temporal distribution. Greece is a country where flood data and records are very scarce. Therefore, as there is not an integrated catalog of Greek floods spanning from the 19th century to recently, this is the first attempt to create an integrated catalog for Greece. The sources used include published papers, local and regional newspapers and public bodies (mainly the Ministry of Environment and Energy and the official websites of Greek municipalities). Additionally, the main factors responsible for their occurrence have been issued, regarding the country’s climatic, geological and geomorphological setting, as well as human interventions. In addition, the atmospheric circulation driving factors of floods are assessed via an unsupervised neural network approach (i.e., Self-Organizing Maps). Based on the results of this research, an online GIS-based database has been created, depicting the areas that have been struck by riverine floods in Greece. By clicking a flood event in the online database, one can view several characteristics, depending on data availability, such as duration and height of the rainfall that caused them and number of fatalities. Long-term trends of mean and extremes seasonal precipitation also linked to the spatial distribution of floods. Our analysis shows that urban floods are a very large portion of the overall flood record, and they mainly occur in the two large urban centers, Athens and Thessaloniki, as well as near large rivers such as Pineios. Autumn months and mainly November are the periods with higher flood hazards, based on past records and cyclonic atmospheric circulation constitutes the principal driving factor. Our results indicate that a flood catalog at national level is of fundamental importance, as it can provide valuable statistical insights regarding seasonality, spatial distribution of floods, etc., while it can also be used by stakeholders and researchers for flood management and flood risk analysis and modelling
Inventory and Assessment of the Geomorphosites in Central Cyclades, Greece: The Case of Paros and Naxos Islands
The Cycladic landscape is characterized by landforms of natural beauty and rarity. Landforms resulting from differential erosion, weathering, tectonics, drainage network, sea level changes, and depositional processes can contribute to the development of geotourism in the area. This can be achieved by supporting conservation, protection and promotion of the geo-environment and nature, educating students, residents, and visitors. The aim of this work is to develop an inventory of the main geomorphosites of Paros and Naxos islands by assessing their scientific and additional values, using qualitative and quantitative criteria. Our results show that, besides the high scientific interest of the 75 geomorphosites, most are also characterized by a high ecological value and can potentially lead to a significant increase in the islands’ tourism. The results of this work aim at raise awareness on the geomorphological heritage of central Cyclades and provide a basis for their promotion, protection, and management
Inventory and Assessment of the Geomorphosites in Central Cyclades, Greece: The Case of Paros and Naxos Islands
The Cycladic landscape is characterized by landforms of natural beauty
and rarity. Landforms resulting from differential erosion, weathering,
tectonics, drainage network, sea level changes, and depositional
processes can contribute to the development of geotourism in the area.
This can be achieved by supporting conservation, protection and
promotion of the geo-environment and nature, educating students,
residents, and visitors. The aim of this work is to develop an inventory
of the main geomorphosites of Paros and Naxos islands by assessing their
scientific and additional values, using qualitative and quantitative
criteria. Our results show that, besides the high scientific interest of
the 75 geomorphosites, most are also characterized by a high ecological
value and can potentially lead to a significant increase in the islands'
tourism. The results of this work aim at raise awareness on the
geomorphological heritage of central Cyclades and provide a basis for
their promotion, protection, and management
GIS-Based Assessment of Fire Effects on Flash Flood Hazard: The Case of the Summer 2021 Forest Fires in Greece
Greece, like the rest of the Mediterranean countries, faces wildland fires every year. Besides their short-term socioeconomic impacts, ecological destruction, and loss of human lives, forest fires also increase the burnt areas’ risk of flash flood phenomena, as the vegetation, which acted in a protective way against runoff and soil erosion, is massively removed. Among the most severe wildland fire events in Greece were those of summer 2021, which were synchronous to the very severe heat waves that hit the broader area of the Balkan Peninsula. More than 3600 km2 of land was burnt and a significant amount of natural vegetation removed. Three of the burnt areas are examined in this work, namely, Attica, Northern Euboea, and the Peloponnese, in order to assess their risk of future flash flood events. The burnt areas were mapped, and their geological and geomorphological features studied. Flash flood hazard assessment was accomplished through a Boolean logic-based model applied through Geographic Information Systems (GIS) software, which allowed the prioritization of the requirement for protection by identifying which locations were most prone to flooding. The largest part of our study areas is characterized by geomorphological and geological conditions that facilitate flash flood events. According to our findings, in almost all study areas, the regions downstream of the burnt areas present high to very high flash flood hazard, due to their geomorphological and geological features (slope, drainage density, and hydrolithology). The only areas that were found to be less prone to flood events were Vilia and Varimpompi (Attica), due to their gentler slope inclinations and overall geomorphological characteristics. It is known that vegetation cover acts protectively against flash floods. However, in this case, large areas were severely burnt and vegetation is absent, resulting in the appearance of flash floods. Moreover, imminent flooding events are expected to be even more intense in the areas downstream of the burnt regions, possibly bearing even worse impacts on the local population, infrastructure, etc
Assessment of Fire Effects on Surface Runoff Erosion Susceptibility: The Case of the Summer 2021 Forest Fires in Greece
The wildfires of summer 2021 in Greece were among the most severe forest
fire events that have occurred in the country over the past decade. The
conflagration period lasted for 20 days (i.e., from 27 July to 16 August
2021) and resulted in the devastation of an area of more than 3600
Km(2). Forest fire events of similar severity also struck other
Mediterranean countries during this period. Apart from their direct
impacts, forest fires also render an area more susceptible to runoff
erosion by massively removing its vegetation, among other factors. It is
clear that immediately after a forest fire, most areas are much more
susceptible to erosion. In this paper, we evaluate the erosion hazard of
Attica, Northern Euboea, and the Peloponnese that were devastated by
forest fires during the summer of 2021 in Greece, in comparison with
their geological and geomorphological structures, as well as land cover
and management. Given that a very significant part of these areas were
burnt during the major conflagrations of this summer, erosion risk, as
well as flood risk, are expected to be very high, especially for the
coming autumn and winter. For the evaluation of erosion risk, the burnt
areas were mapped, and the final erosion-risk maps were constructed
through GIS software. The final maps suggest that most of the burnt
areas are highly susceptible to future surface runoff erosion events