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

MODELING COASTAL EROSION IN WESTERN PART OF NAXOS ISLAND

Σκοπός της παρούσας πτυχιακής εργασίας είναι η ταξινόμηση των ακτών της δυτικής Νάξου ως προς την τρωτότητά τους στην αναμενόμενη (μελλοντική) άνοδο της θαλάσσιας στάθμης εφαρμόζοντας τον Δείκτη Παράκτιας Τρωτότητας (ΔΠΤ) με τη χρήση Γεωγραφικών Συστημάτων Πληροφοριών (ΓΣΠ). Ο δείκτης αυτός επιτρέπει τη συνεκτίμηση έξι παραμέτρων με ημι-ποσοτικό τρόπο, με σκοπό την αναγνώριση περιοχών που είναι συγκριτικά περισσότερο ευάλωτες στις μεταβολές της θαλάσσιας στάθμης. Οι ημι-ποσοτικές παράμετροι είναι η παράκτια γεωμορφολογία, η παράκτια μορφολογική κλίση, ο ρυθμός μεταβολής της σχετικής στάθμης της θάλασσας, ο ρυθμός προέλασης ή υποχώρησης της ακτογραμμής, το μέσο εύρος παλίρροιας και το μέσο ύψος κύματος. Η παράμετρος της γεωμορφολογίας σχετίζεται με την ανθεκτικότητα στη διάβρωση των παράκτιων γεωμορφών που οροθετήθηκαν με την χρήση διαφορικού DGPS-RTK Spectra Precision. Οι ρυθμοί προέλασης ή υποχώρησης της ακτογραμμής προέκυψαν από επιτόπια έρευνα και μελέτη τοπογραφικών διαγραμμάτων. Η μορφολογική κλίση υπολογίστηκε χρησιμοποιώντας το Ψηφιακό Μοντέλο Εδάφους. Για τις υπόλοιπες παραμέτρους χρησιμοποιήθηκαν βιβλιογραφικά δεδομένα. Η ακτογραμμή της περιοχής μελέτης διαιρέθηκε σε τμήματα μήκους 20 m και για κάθε τμήμα εκτιμήθηκε η τιμή του Δείκτη Παράκτιας Τρωτότητας ως η τετραγωνική ρίζα του γινομένου των τιμών των έξι μεταβλητών προς τον αριθμό 6 που είναι το σύνολο των παραμέτρων που ελήφθησαν υπόψη. Οι τιμές του δείκτη που εκτιμήθηκαν για την περιοχή κυμαίνονται από 5.0 έως 32.0 με τις περισσότερο τρωτές περιοχές (πολύ υψηλή και υψηλή τρωτότητα) να εντοπίζονται στην περιοχή του Αγίου Γεωργίου, Αγίου Προκοπίου, Αγίας Άννας, Πλάκα, Μικρή Βίγλα, Καστράκι, Πυργάκη και Αγιασσός. Αντίθετα, συμπεραίνεται ότι οι ακτές που καταλαμβάνονται από παράκτιους βραχώδεις κρημνούς, είναι λιγότερο ευάλωτες χωρίς κάποια εξαίρεση.This thesis is specifically concerned with the classification of the coast of the western Naxos Island according to its vulnerability to an anticipated future sea-level rise, using the Coastal Vulnerability Index (CVI) and utilizing Geographic Information Systems (GIS) technology. This index relates in a semi-quantitative manner the following six physical variables, geomorphology, coastal slope, relative sea-level rise rate, shoreline erosion or accretion rate, mean tidal range and mean wave height, aiming to identify areas that are comparatively more vulnerable to sea level change. The variable of geomorphology expresses the relative erodibility of various coastal landforms and was derived from detailed field geomorphological mapping. Shoreline erosion or accretion rates were obtained from interpretation of field survey and topographic maps. The slope of the coastal zone was estimated using the Digital Elevation Model (DEM) of the area derived from topographic maps at the scale of 1:5,000. Bibliographic data were used for the mean tidal range, mean wave height and relative sea level change The shoreline of the study area was divided into sections, with a length of 20.0 m. The Coastal Vulnerability Index (CVI) was estimated for each section, as the square root of the values of the ranked variables divided by their total number involved. According to the produced CVI values (ranking between 5.0 and 32.0), the most vulnerable coastal regions (of high and very high vulnerability) were found along the coastal area of Agios Georgios, Agios Prokopios, Agia Anna, Plaka, Mikri Vigla, Kastraki, Pirgaki and Agiassos. However, it was concluded that steepy rocky coast areas are the least vulnerable sections of understudy shoreline

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

Tsunamis in the Greek Region: An Overview of Geological and Geomorphological Evidence

The Greek region is known as one of the most seismically and tectonically active areas and it has been struck by some devastating tsunamis, with the most prominent one being the 365 AD event. During the past decade significant research efforts have been made in search of geological and geomorphological evidence of palaeotsunamis along the Greek coasts, primarily through the examination of sediment corings (72% of studies) and secondarily through boulders (i.e., 18%). The published data show that some deposits have been correlated with well-known events such as 365 AD, 1303 AD, the Minoan Santorini Eruption and the 1956 Amorgos earthquake and tsunami, while coastal studies from western Greece have also reported up to five tsunami events, dating as far back as the 6th millennium BC. Although the Ionian Islands, Peloponnese and Crete has been significantly studied, in the Aegean region research efforts are still scarce. Recent events such as the 1956 earthquake and tsunami and the 2020 Samos earthquake and tsunami highlight the need for further studies in this region, to better assess the impact of past events and for improving our knowledge of tsunami history. As Greece is amongst the most seismically active regions globally and has suffered from devastating tsunamis in the past, the identification of tsunami prone areas is essential not only for the scientific community but also for public authorities to design appropriate mitigation measures and prevent tsunami losses in the future

Tsunamis in the Greek Region: An Overview of Geological and Geomorphological Evidence

The Greek region is known as one of the most seismically and tectonically active areas and it has been struck by some devastating tsunamis, with the most prominent one being the 365 AD event. During the past decade significant research efforts have been made in search of geological and geomorphological evidence of palaeotsunamis along the Greek coasts, primarily through the examination of sediment corings (72% of studies) and secondarily through boulders (i.e., 18%). The published data show that some deposits have been correlated with well-known events such as 365 AD, 1303 AD, the Minoan Santorini Eruption and the 1956 Amorgos earthquake and tsunami, while coastal studies from western Greece have also reported up to five tsunami events, dating as far back as the 6th millennium BC. Although the Ionian Islands, Peloponnese and Crete has been significantly studied, in the Aegean region research efforts are still scarce. Recent events such as the 1956 earthquake and tsunami and the 2020 Samos earthquake and tsunami highlight the need for further studies in this region, to better assess the impact of past events and for improving our knowledge of tsunami history. As Greece is amongst the most seismically active regions globally and has suffered from devastating tsunamis in the past, the identification of tsunami prone areas is essential not only for the scientific community but also for public authorities to design appropriate mitigation measures and prevent tsunami losses in the future

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 Virtual Field Trip as a Tool for Remote Education

Geoscience courses, such as geology and geomorphology, require not only classroom lessons and laboratory exercises, but field trips as well. However, the COVID-19 restrictions did not allow the execution of most planned field trips, and an alternative needed to be developed. The use of virtual field trips is one such alternative. Through this research, we evaluate the usefulness of virtual field trips as tools for preparatory activities before an actual field trip takes place in the same area, and their contribution in providing a better understanding of geomorphological processes and landscape evolution. We performed a virtual navigation on the island of Naxos, Cyclades (Aegean Sea, Greece) for a series of virtual field trips, which took place during webinars in the framework of Erasmus+ CIVIS. The virtual field trip was also presented to the third-year students of the Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, in the framework of the obligatory course of Geomorphology. Upon completion, all participating students were asked to fill in a questionnaire in order to evaluate the contribution of virtual field trips to their education regarding geomorphology and state their opinion as to whether they can supplement and/or substitute actual field trips. According to the results, virtual field trips can aid, but not substitute, the actual field trip. Most students mentioned that they would attend another virtual field trip in the future, both as an alternative to classroom lessons and as a means of preparation for an actual field trip, but not in order replace the actual one. Virtual field trips can significantly support the realization of actual ones, by introducing the necessary tectonic, geological and geomorphological background of a particular study area and offering more time for practical activities or field methodologies during the actual field trip

Tsunamis in the Greek Region: An Overview of Geological and Geomorphological Evidence

The Greek region is known as one of the most seismically and tectonically active areas and it has been struck by some devastating tsunamis, with the most prominent one being the 365 AD event. During the past decade significant research efforts have been made in search of geological and geomorphological evidence of palaeotsunamis along the Greek coasts, primarily through the examination of sediment corings (72% of studies) and secondarily through boulders (i.e., 18%). The published data show that some deposits have been correlated with well-known events such as 365 AD, 1303 AD, the Minoan Santorini Eruption and the 1956 Amorgos earthquake and tsunami, while coastal studies from western Greece have also reported up to five tsunami events, dating as far back as the 6th millennium BC. Although the Ionian Islands, Peloponnese and Crete has been significantly studied, in the Aegean region research efforts are still scarce. Recent events such as the 1956 earthquake and tsunami and the 2020 Samos earthquake and tsunami highlight the need for further studies in this region, to better assess the impact of past events and for improving our knowledge of tsunami history. As Greece is amongst the most seismically active regions globally and has suffered from devastating tsunamis in the past, the identification of tsunami prone areas is essential not only for the scientific community but also for public authorities to design appropriate mitigation measures and prevent tsunami losses in the future

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