Efthimios Karymbalis

Paleoenvironmental Evolution of the Coastal Plain of Marathon, Greece, during the Late Holocene: Depositional Environment, Climate, and Sea Level Changes

Abstract The Middle-Late Holocene infill of the coastal plain of Marathon, Greece, consists of lagoonal deposits related to the decrease of the sea level rise rate. Between a little earlier than 5800 and 3500 Cal BP, mesohaline-oligohaline lagoonal carbonate muds were uninterruptedly accumulating in the central and more seaward areas of the embayment. At the same time in the nearshore environment, oligohaline pelloidal charophytic muds were deposited during periods of a relatively increased rate of sea level rise, whereas during periods with lower rates of sea level rise, extensive marshes were forming in supratidal settings. The formation of framboidal pyrite and evaporitic minerals point to a periodic anoxic, sulfidic, and schizohaline environment. In addition, a warm, strongly seasonal climate under the influence of resurgent continental groundwater is suggested. After 3500 Cal BP, the lagoon witnessed a relatively abrupt change to palustrine mud deposition. The embayment was frequently exposed, and communication with the sea was not perennial. This period, terminated at about 2400 Cal BP, is most likely associated with a wetter and probably more temperate climate. The uppermost depositional unit is dominated mostly by fluvial sediments deposited in a wetland with no recorded communication with the sea. The sea level rise, indicated by several peat formations, is estimated to be lower than that predicted by the glacio-hydroisostatic model and the data from other Greek areas that are considered relatively stable. Hence, a tectonic uplift of the area is suggested at a rate of about 0.4–0.5 mm/y, which almost counterbalances the predicted rate of relative sea level rise of about 0.6–0.7 mm/y for the last 2000 years. This is a plausible explanation for the relative geomorphological stability, since at least Classical times, suggested by the historical documents.

Assessment of the sensitivity of the southern coast of the Gulf of Corinth (Peloponnese, Greece) to sea-level rise

The eustatic sea-level rise due to global warming is predicted to reach approximately 18–59 cm by the year 2100, which necessitates the identification and protection of sensitive sections of coastline. In this study, the classification of the southern coast of the Gulf of Corinth according to the sensitivity to the anticipated future sealevel rise is attempted by applying the Coastal Sensitivity Index (CSI), with variable ranges specifically modified for the coastal environment of Greece, utilizing GIS technology. The studied coastline has a length of 148 km and is oriented along the WNW-ESE direction. CSI calculation involves the relation of the following physical variables, associated with the sensitivity to long-term sea-level rise, in a quantifiable manner: geomorphology, coastal slope, relative sea-level rise rate, shoreline erosion or accretion rate, mean tidal range and mean wave height. For each variable, a relative risk value is assigned according to the potential magnitude of its contribution to physical changes on the coast as the sea-level rises. Every section of the coastline is assigned a risk ranking based on each variable, and the CSI is calculated as the square root of the product of the ranked variables divided by the total number of variables. Subsequently, a CSI map is produced for the studied coastline. This map showed that an extensive length of the coast (57.0 km, corresponding to 38.7% of the entire coastline) is characterized as highly and very highly sensitive primarily due to the low topography, the presence of erosionsusceptible geological formations and landforms and fast relative sea-level rise rates. Areas of high and very high CSI values host socio-economically important land uses and activities.

Time Series Synthetic Aperture Radar Interferometry for Ground Deformation Monitoring over a Small Scale Tectonically Active Deltaic Environment (Mornos, Central Greece)

ABSTRACT Parcharidis, I.; Kourkouli, P.; Karymbalis, E.; Foumelis, M., and Karathanassi, V., 2013, Time series synthetic aperture radar interferometry for ground deformation monitoring over a small scale tectonically active deltaic environment (Mornos, Central Greece). This study deals with the estimation of subtle ground deformation at millimetric accuracy over the broader area of the Mornos River delta in Central Greece and its spatio-temporal distribution for the period between 1992 and 2009 through Persistent Scatterers Interferometry (PSI). The results showed that the majority of the scatterers, which show subsidence, are located within the delta plain with mean subsidence rates throughout the delta varying between −7.2 and +0.7 mm/y. An attempt is made to highlight the geographic distribution, the amplitude, and the causes of the observed delta plain subsidence. The positive correlation between the thickness of the fine-grained Holocene deltaic deposits and the subsidence rates reveals that the main cause is the natural compaction of sediments. The highest subsidence is observed at Bouka Karahassani village, which corresponds to the area of the most recently abandoned river mouth, which is intensely eroded by marine processes. Apart from the dominance of fine sediments in the study area, subsidence may also be attributed to submarine gravitational mass movements along the steep slopes of the prodelta as well as to the reduction of sediment load after the dam construction in 1979. The NW part of the delta seems to have been affected by aseismic slip along a NE-SW trending normal fault buried beneath the alluvial deposits of the Skala torrent fan.

Geomorphological study of Cephalonia Island, Ionian Sea, Western Greece

In this paper a geomorphological map, at a scale of 1:50,000, of the Cephalonia Island located in the Ionian Sea (western Greece) is presented and discussed. The geology of the island is represented in an individual smaller inset map. The map was produced from field surveys based upon 1:50,000 scale topographic maps and 1:5000 topographic diagrams, differential global positioning system surveys, aerial photos and visual inspection and interpretation of Google Earth images, and analysis of a digital elevation model of the island derived from 1:50,000 scale topographic maps. Landforms were grouped on the basis of the main morphogenetic processes and include fluvial landforms, erosional landforms, gravitational landforms, karst landforms, and coastal features. The objective of this map is to provide information about the landscape evolution of the island during the Quaternary. The study of the landforms depicted on the geomorphological map showed that the recent evolution of the landscape is dependent mostly on neotectonic processes and eustatism.

Geomorphology of the Pinios River delta, Central Greece

ABSTRACT This paper presents the results of geomorphological investigations carried out on the Pinios River delta, which is a Late Holocene arcuate type delta, located in the southern Thermaikos Gulf (Central Greece). Digital elevation model (DEM) analysis and the study of maps of the last two centuries, accompanied by field survey and aerial photo interpretation have led to the production of a geomorphological map at 1:15,000 scale which outlines the features of the deltaic plain and coastal zone. The evolution and the associated morphology of the delta are the result of the complex interplay of fluvial sedimentation, wave activity and prevailing longshore currents. The dominant landforms of the delta are the numerous abandoned meandering channels, as the river has changed its course several times, and a series of sub-parallel linear sandy beach ridges (cheniers) occupy the lower delta plain. The shoreline of the delta is generally retreating due to marine processes, especially where former river mouths occur whereas the presently active mouth of the river and its immediate surrounds are prograding.

Maximum macroseismic intensity map of Greece for the time period 1953–2011

The aim of this paper is to present the spatial distribution of macroseismic intensities assigned in modified Mercalli (MM) scale, across the Greek territory. For this purpose, a digital database with more than 30,000 local seismic intensity recordings from 156 major earthquake events that affected Greece and adjacent areas during the period 1953–2011 was developed. These events have focal depths up to about 150 km and surface-wave magnitudes (Ms) greater than 4.4. Various GIS-based techniques for data analysis and map creation were applied. A number of seismic intensity maps have been produced taking into account different attributes like intensities for shallow or deep events, maximum intensities by administrative units, maximum intensity for significant earthquakes, etc. The main map produced is the national map of maximum seismic intensities for shallow earthquakes (scale 1:1.500.000). The final layout also contains the maximum seismic intensities for deep earthquakes, the tectonic lines of Greece, the earthquakes of the database as well as the seismic intensities for two significant earthquakes in the last six decades.

Applied Hydrological Modeling with the Use of Geoinformatics: Theory and Practice

Water resource management and catchment analysis are crucial aspects of the twentyfirst century in hydrological and environmental sciences. Linked directly with studies and research about climate change effects in global resources (e.g., diminution of rainfall dynamic), as well as continuously growing extreme natural phenomena with catastroph‐ ic results (e.g., floods and erosion), hydrological modeling has become a key priority in modern academic research goals. On a national or lower administrative level, the need for coping with natural disasters—affecting mainly human life, property, local econo‐ my, infrastructure, etc.—and the need to design management plans and projects for sustainable exploitation of natural resources set hydrological modeling in high demand by government organizations and local authorities. Thus, hazard assessment and risk evaluation modeling have become a strategic aim and an extremely useful tool for stakeholders, decision-makers, and scientific community.

Investigation of flash flood natural causes of Xirolaki Torrent, Northern Greece based on GIS modeling and geomorphological analysis

This paper presents an attempt to evaluate the flood discharge for a severe flood event, which took place on October 25th, 2009. Based on spatial and meteorological data, a simulation of the flood event was established, through hydrological modeling, in a GIS environment. Furthermore, the geomorphological characteristics of the drainage basin and the drainage network were analysed. The results of the modeling such as the peak discharge, hydrograph, and volume, derived from the analysis of measured hydrographs in a number of non-flood causing rainfall events with operating stage gauge, were used for calibration and verification of the simulated stage-discharge hydrographs. Drainage basin characteristics such as steepness of the relief combined with a relatively short main channel of the drainage network as well as abnormalities in the hierarchical drainage by stream order are the main natural flood causes amplified of course by the intense human interference at the lower part of the drainage network with a series of constructions such as roads inside the main channel. Geomorphological analysis combined with GIS techniques are fundamental components of flood risk management as they provide the basis for a broad understanding of the relationship between river processes and flood causes in a fast and effective way in the context of policy makers.

Use of morphometric variables and self-organizing maps to identify clusters of alluvial fans and catchments in the north Peloponnese, Greece

Abstract We applied a computational method to aid in clustering 41 alluvial fans along the southern coast of the Gulf of Corinth, Greece. The morphology of the fans and their catchments was quantitatively expressed through 12 morphometric parameters estimated using geographical information system techniques and the relationships among the geomorphometric features of the fans and their catchments were examined. Self-organizing maps were used to investigate the clustering tendency of fans based on morphometric variables describing both the fans and their corresponding catchments. The results of unsupervised classification through the self-organizing maps method revealed correlations among the morphometric parameters and five groups of alluvial fans were identified. These groups had a clear physical explanation, showed a preferred geographical distribution and reflected the processes related to the development of the fans. The geographical distribution of the fan catchment groups was partially controlled by variations in the relative tectonic uplift rate, which was the main control on the accommodation space for the development and accretion of the fans. The smaller fans were located in the central part of the study area, where the uplift rates were higher, whereas larger fluvial-dominated fan deltas formed to the east and west of the central group, where the uplift rates were lower.

Interactions between alluvial fans and axial rivers in Yukon, Canada and Alaska, USA

Abstract In contrast with the archetypal definition of an alluvial fan, this study shows that fans interacting with axial rivers in Yukon and Alaska commonly exhibit asymmetrical morphology in planform. Hypothesis tests relating to the geomorphological characteristics of these alluvial fans were conducted on a dataset of 63 fluvial-dominated fans. A significant relationship existed between fan asymmetry and the direction of axial river flow, which was attributed to two factors supported by examples: (1) axial rivers have a propensity to trim the toes on the up-valley sides of fans; and (2) axial river channels are deflected across the broad valley floors, which allows the profiles on the down-valley sides of fans to be longer than on the up-valley sides. However, an asymmetrical planform morphology does not lead to a significant bias in the spatial distribution of surface streams towards the up-valley sides of fans, which typically have shorter profiles from apex to boundary. If the asymmetry in fan morphology is preserved in the sedimentary record, then the interpretation of fan deposits that developed in broad valleys and that interacted with axial rivers would be improved by understanding this modern analogue.