Emm. Vassilakis

Observational evidence on the effects of mega-fires on the frequency of hydrogeomorphic hazards. The case of the Peloponnese fires of 2007 in Greece

Even though rare, mega-fires raging during very dry and windy conditions, record catastrophic impacts on infrastructure, the environment and human life, as well as extremely high suppression and rehabilitation costs. Apart from the direct consequences, mega-fires induce long-term effects in the geomorphological and hydrological processes, influencing environmental factors that in turn can affect the occurrence of other natural hazards, such as floods and mass movement phenomena. This work focuses on the forest fire of 2007 in Peloponnese, Greece that to date corresponds to the largest fire in the countrys record that burnt 1773km2, causing 78 fatalities and very significant damages in property and infrastructure. Specifically, this work examines the occurrence of flood and mass movement phenomena, before and after this mega-fire and analyses different influencing factors to investigate the degree to which the 2007 fire and/or other parameters have affected their frequency. Observational evidence based on several data sources collected during the period 1989-2016 show that the 2007 fire has contributed to an increase of average flood and mass movement events frequency by approximately 3.3 and 5.6 times respectively. Fire affected areas record a substantial increase in the occurrence of both phenomena, presenting a noticeably stronger increase compared to neighbouring areas that have not been affected. Examination of the monthly occurrence of events showed an increase even in months of the year were rainfall intensity presented decreasing trends. Although no major land use changes has been identified and chlorophyll is shown to recover 2years after the fire incident, differences on the type of vegetation as tall forest has been substituted with lower vegetation are considered significant drivers for the observed increase in flood and mass movement frequency in the fire affected areas.

Climate Change Implications on Groundwater in Hellenic Region

There is a general consensus that climate change is an ongoing phe- nomenon. This will inevitably bring about numerous environmental problems, in- cluding alterations to the hydrological cycle, which is already heavily influenced by anthropogenic activity. The available climate scenarios indicate areas where rainfall may increase or diminish, but the final outcome with respect to man and environment will, generally, be detrimental. The research is focused on the climate change implications to the underground water tables of the mainland in Greece, excluding the island complex. It is based on regional climate models (RCMs) simulations under emission scenarios (SRES) A1B (3.5 ο C), A2 (4.5 ο C) and B2 (3.1 ο C), for specific climatic zones of the Greek area during the period 2011- 2100, which were estimated by the third report of IPCC.

Adumbration of Amvrakia’s spring water pathways, based on detailed geophysical data (Kastraki - Meteora)

The Amvrakia spring is located at the bottom of Meteora pillars and more specifically near the village of Kastraki (Kalambaka municipality). It is a seasonal spring since it functions only during the wet period. The Meteora conglomerates which dominate the area are characterized by large discontinuities creating a network of groundwater pathways above the impermeable strata of the underlying marls. The research targets was to define these water pathways in order to understand the mechanism of Amvrakia spring, by mapping the exposed discontinuity network and define their underground extension with the contribution of geophysical techniques. Electrical Resistivity Tomography (ERT) and Very Low Frequency (VLF) methodologies were applied. The VLF method is indicated for the detection of water-bearing fracture zones, but before the application of their filters they had to be processed for topographic corrections, as the area had not smooth relief. Five (5) VLF profiles were conducted with different directions around the spring’s area, in order to detect possible conductive zones in the conglomerates surrounding the study area. Moreover, two (2) ERT sections of a total length of 140m were carried out, parallel to existent VLF sections, for cross-checking the geophysical information. Both techniques revealed important conductive zones (<200 Ohm.m) from the south-eastern Meteora conglomerate pillars, possibly interpreted as discontinuities filled with water feeding the spring.

Earth observation data and geographical information system (GIS) techniques for earthquake risk assessment in the western Gulf of Corinth, Greece

This study attempts to demonstrate the utility of differential synthetic aperture radar (SAR) interferometry and very high resolution satellite optical data for the assessment of earthquake risk, using a geographical information system (GIS), in the western part of the Gulf of Corinth, a seismically active region of Greece that suffered the effects of the Eigion earthquake (magnitude M = 6.1) of 15 June 1995. During the project, both archive and newly acquired European remote sensing satellite (ERS) data were used to generate conventional differential interferograms and produce a deformation map over the area. An IKONOS-2 image was used to create and update information concerning urban structures like buildings, road networks, and facilities like hospitals, churches, and factories. A first attempt to evaluate the Earth observation (EO) contribution in the earthquake risk assessment system shows that the differential interferometric synthetic aperture radar (DInSAR) is suitable only for co-seismic deformation monitoring, and very high resolution data perform very well in the mapping of urban structures.

Fracture pattern analysis of hardrock hydrogeological environment, Kea Island, Greece

The geological and hydrogeological regime of Kea Island is presented, focusing on the fracture pattern analysis of the crystalline-schist mass outcrops the island. The combined use of field mapping and geological data digital analysis extracting lineament density maps and fracture intersection density maps reveals a high relationship between the fracture pattern and the groundwater occurrence. In order to obtain a complete description of the fracture network, the study area is mapped at various scales with the aid of GIS and remote sensing techniques were integrated along with the data gathered from field work. Remarkable correlations between the hydrochemical data of the main springs (located along the SE and NW part of the island), and the results of lineament analysis and the hydrolithological regime of Kea Island, contribute to extract an integrated conception for the relation of the groundwater potential with the structure of fissured rocks.

SIR-C/X space shuttle images contribution in assessment of flood risk. The case of Athens basin

This study describes the investigation conducted for flood risk assessment in urban areas using SIR-C data. The Athens basin is a densely populated area with approximately four million inhabitants, affected very often by destructive flash-floods. These flood phenomena occur mainly at the margins of the urban area very close to the surrounding mountains. The SIR-C image, acquired on October 2nd, 1994, has been processed for speckle reduction and additionally a non-linear stretching has been applied. After the first observations at every single image, a false colour composite image was created using L-band HV, C-band HH, and L-band HH as R,G,B. The captured information concerns morphology (topography, slopes, gullies), land use and land cover, drainage characteristics and building shell extension, density and block orientation.

A Geophysical Insight for the Occurrence of Mediterranean Temporary Ponds on Mts. Oiti and Kallidromo (Greece)

A geophysical survey was performed at selected locations of Mt. Oiti and Mt. Kallidromon characterized by the hosting of priority habits of Mediterranean temporary ponds and the threatened plant species of Veronica oetaea, in order to understand the geoenvironment and contribute to the conservation of biodiversity. Primarily, the formation of these seasonal ponds, where Veronica oetaea occurs, seems to depend exclusively on the local hydrogeological regime. Thus, we investigated the subsurface structure of “Livadies” and “Nevropolis” ponds with the application of Electrical Resistivity Tomography for high accuracy information and Vertical Electrical Sounding for deeper data acquisition. Four ERT sections and 15 geoelectrical soundings in total were carried out. The combined results of their processing revealed differences at the geological structure beneath the ponds locations. At “Livadies” pond (Mt. Oiti), two geoelectrical layers were distinguished both corresponding to a folded flysch succession, contributing to the formation of this pond. On the contrary, at “Nevropolis” pond two geoelectrical layers were identified and interpreted as a surficial soil deposit stratum covering the geomorphological karst structure of a polje, created on the underlying limestones. The combined geophysical research offered significant data for the formation and the hydrogeological status of the priority habitats.