Publications by Year: 2017

2017
Mitsopoulos I, Chrysafi I, Mallinis G, Vassilakis E, Arianoutsou M, Lekkas E.

Fire severity estimation using very high spatial resolution satellite imagery: the case of Chios island

. In: 17th Congress of Hellenic Forestry Society. Edessa, Greece; 2017.Abstract
The aim of this study is to spatially assess fire severity and to explore the relationship between the Normalized Vegetation Index (NDVI) derived from WorldView- 2 imagery and the field-based fire severity index “Composite Burn Index” (CBI) on a recent large fire that occurred on the island of Chios, Greece, in 2016. The statistical analysis indicated a relatively strong linear relationship between the NDVI and the CBI (R2 = 0.71). Predictive local thresholds of NDVI values have been determined for accurate thematic classification and mapping of fire severity classes. The overall classification accuracy based on NDVI from WorldView-2 was relatively high (71%), pointing to the potential of using such data for mapping forest fires in the Mediterranean as well as for assessing their severity. The application of the classification thresholds calculated in this study over other forest fire events on similar ecosystem types, could support the rapid assessment of fire severity and hence could enable the decisions needed for proper post-fire management.
Diakakis M, Nikolopoulos E, Mavroulis S, Emm. V, Korakaki E. The effects of the 2007 Peloponnese forest fires in rainfall-triggered, flood and mass movement phenomena. A 10-years lasting impact. In: 11th International Hydrogeological Conference. Athens; 2017.Abstract
Apart from direct consequences, forest fires induce water related effects related to geomorphological and hydrological processes, triggering 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 country’s record. It examines the occurrence of flood and mass movement phenomena, before and after this 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 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 2 years 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.
Nastos PT, Vassilakis E, Nastos M-PP, Charalampopoulos I, Matzarakis A. Assessment of continuous sky view factor based on ultra-high resolution natural colour images acquired by remotely piloted airborne systems for applications in an urban area of Athens. International Journal of Remote Sensing [Internet]. 2017;38:5814-5829. https://doi.org/10.1080/01431161.2017.1346845Abstract
The thermal comfort conditions in a complex urban area is influenced by the surrounding structures and obstacles which modify the incoming radiation fluxes. A measure of this modification is the sky view factor (SVF), which could be estimated in each point of a selected area if a high resolution digital elevation model (DEM), or other urban morphological data including the manmade infrastructure, are available. The goal of this study is to model the continuous SVF for a complex building environment in the campus of National and Kapodistrian University of Athens, based on a high resolution DEM (0.09 m). For this purpose, we applied the structure-from-motion (SfM) technique, which takes advantage of the interpretation of ultra-high resolution colour images acquired by remotely piloted airborne systems, also known as drones or unmanned aerial vehicles. A quantitative analysis, by applying statistical metrics, yields perfect agreement between modelled and observed SVF values, over the examined area. The proposed methodology could be applied for human-biometeorology research in micro scale complex urban environments.
Diakakis M, Nikolopoulos EI, Mavroulis S, Vassilakis E, Korakaki E. The effect of large forest fires on floods and landslides. The case of the 2007 fires in Ileia, Greece. Safe Athens 2017. 2017.Abstract
Although forest fires are considered an integral part of Mediterranean forest ecosystems, they nevertheless constitute one of the most devastating natural hazards. Apart from the direct consequences, fires induce longer 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 burnt 1773 km2, causing 78 fatalities and very significant damages in property and infrastructure and went down as the largest fire in the country’s record. It examines the occurrence of flood and mass movement phenomena, before and after this mega-fire and studies 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 2 years 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 changes in hydrogeomorphic response of the fire affected basins.
Gouliotis L, Foumelis M, Vassilakis E, Papanikolaou D, Pavlopoulos K. Geologic, Geomorphic and Geodetic Constraints on Vertical Motion Trends of Itea-Amfissa Basin (Northern Corinth Rift, Central Greece). In: EGU2017-6766. Vol. 19. Vienna, Austria; 2017.Abstract
Combining geological and geomorphological data together with geodetic SAR interferometry (InSAR) measurements an attempt has been made to investigate the vertical deformation of the Itea-Amfissa basin at the northern part of the Corinth rift. The north–south trending basin has been developed normally to the east – west trending Corinth Rift and on the hanging wall of the Itea-Amfissa detachment. In the stratigraphy of the Itea–Amfissa supra-detachment basin, two sequences can be distinguished; the lower marine polymict conglomerate of Early–Middle Miocene age and the upper terrestrial monomict carbonate breccia of Late Miocene age. The unconformity between them has been uplifted to the north of the basin up to the elevation of 1100m and subsided below sea level at its southern part. Remnants of low-relief surfaces are retained on top of the upper terrestrial sequence, that permit to reconstruct the paleo-landscape of the basin and to measure the spatial distribution of its vertical deformation after compensating the erosional isostatic adjustment. The exact delineation of the paleo-landscape, involved detailed mapping as well as quantitative analysis of geomorphological features caused by river incision, based on measurements of several tectonic geomorphology indices. Geodetic InSAR estimates of vertical ground displacements, combining almost 10 years of ascending and descending ENVISAT data, were also utilized both for refinement of delineated surfaces as well as for validation of geology-based deformation trends. Interferometric results were constrained to the geologic time frame, considering the well-defined long-term deformation trend of a doline, proven to be sinking over the last 6000 years. It is shown that over the last 10 years the largest uplift rates are observed within the Itea-Amfissa basin, while the coastline regions follow a more complex spatial deformation pattern of successive submergences and uplifts. The synthesis of geological and geomorphological data indicates that the Itea-Amfissa extensional basin from its development in the Middle-Late Miocene and throughout Plio-Quaternary, has been tilted towards south, while contemporary geodetic measurements from InSAR confirm that the basin is still uplifting with regard to its surrounding mountains and coastal areas.  
Arianoutsou Μ, Mitsopoulos Ι, Vallatou Μ, Vassilakis Ε, Mallinis G. A spatial modeling approach to assess fire risk and exposure of biodiversity hotspots in Cephalonia island, Greece. In: XIV MEDECOS & XIII AEET meeting. Seville, Spain; 2017. pp. 16.Abstract
Recent global changes seem to have affected fire regimes by inducing more severe larger fires in the thermomediterranean vegetation zone but also more frequent incidents in territories of higher altitudes. Cephalonia island hosts Mt Ainos, one of the most important National Parks of Greece, focal geographical area of the non-fire adapted endemic fir Abies cephalonica. The island has suffered several fires in the past. The aim of this work is to introduce a framework for assessing spatial fire risk and exposure of biodiversity hot spot areas, using Cephalonia as a pilot case study. Fuel parameters in representative vegetation types were measured across the island for models development as well as for collecting training and validation points for satellite data classification. The Minimum Travel Time algorithm, as it is embedded in FlamMap spatial fire simulation software, was applied in order to assess critical fire behavior parameters and exposure of the island’s biodiversity hotspots under three different meteorological and fuel moisture scenarios simulating predicted climate changes. In addition, the risk of change in the island's ecological value due to biodiversity loss was studied under the same scenarios. According to the analysis, loss of all biodiversity values was found under the severe meteorological and fuel moisture scenario and was estimated to be higher in the endemic fir forests. The outputs of this study may be used as an application of quantitative and probabilistic risk assessment for biodiversity conservation planning, prioritization and management of high value natural and cultural resources.
Farangitakis G, Christopoulou A, Vassilakis Ε, Papanikolaou I, Arianoutsou Μ. Do landscape properties affect the process of post-fire vegetation recovery? A case study from the Taygetos Mountain, Greece. In: XIV MEDECOS & XIII AEET meeting. Seville, Spain; 2017. pp. 114. posterAbstract
Fires of 2007 have consumed large areas of Black pine and endemic fir forests in Greece. The current research aims at examining the role of geomorphology and lithology that govern the soil properties upon the post-fire vegetation recovery at the landscape level. A case study from Taygetos Mt, a large part of which was burned in 2007, is presented. Based on the interpretation of a high spatial and spectral resolution satellite image (WorldView-3, 4/2015), GIS thematic layers have been created showing unburned and regenerated patches over various lithological types. A network of sites was selected for field sampling representing various combinations of the above. Data on recovery of the main tree species as well as on total vegetation cover were collected. Results prove the relationship between regeneration ability and plant species traits as well as the existence of unburned patches near the burned ones. Black pine had regenerated from seeds dispersed from cones that have remained intact on unburned or scorched trees, close enough to the burned patches, while Greek fir presented remarkably low regeneration, lacking of any response mechanism. Plant species recovery seems to be controlled by the geology as it was found weaker in plots overlying carbonate, permeable, not easily erodible formations as compared to that observed over clastic, impermeable, erodible formations of schists, even for the same species. In conclusion, post-fire vegetation recovery at the landscape level seems to be a complex process controlled not only from species biology but also from the landscape features.
Diakakis M, Nikolopoulos E, Mavroulis S, Vassilakis E, Korakaki E. Observational evidence on the effects of mega-fires on the frequency of hydrogeomorphic hazards. The case of the Peloponnese fires of 2007 in Greece. Science of The Total Environment [Internet]. 2017;592:262-276. https://doi.org/10.1016/j.scitotenv.2017.03.070Abstract
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 country's record that burnt 1773 km2, 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 2 years 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.
Vassilakis E, Mallinis G, Christopoulou A, Farangitakis GP, Papanikolaou I, Arianoutsou M. Mapping Post-Fire Vegetaτion Recovery at Different Lithologies of Taygetos Mt (Greece) With Multi-Temporal Remote Sensing Data. In: EGU2017-7452. Vol. 19. Vienna, Austria; 2017. posterAbstract
Mt Taygetos (2407m), located at southern Peloponnese (Greece) suffered a large fire during the summer of 2007. The fire burned approximately 45% of the area covered by the endemic Greek fir (Abies cephalonica) and Black Pine (Pinus nigra) forest ecosystems. The aim of the current study is to examine the potential differences on post-fire vegetation recovery imposed by the lithology as well as the geomorphology of the given area over sites of the same climatic and landscape conditions (elevation, aspect, slope etc.). The main lithologies consist of carbonate, permeable, not easily erodible formations (limestones and marbles) and clastic, impermeable (schists, slate and flysch) erodible ones. A time-series of high spatial resolution satellite images were interpreted, analyzed and compared in order to detect changes in vegetation coverage which could prioritize areas of interest for fieldwork campaigns. The remote sensing datasets were acquired before (Ikonos-2), a few months after (Quickbird-2) and some years after (Worldview-3) the 2007 fire. High resolution Digital Elevation Model was used for the ortho-rectification and co-registration of the remote sensing data, but also for the extraction of the mountainous landscape characteristics. The multi-temporal image dataset was analyzed through GEographic-Object Based Image Analysis (GEOBIA). Objects corresponding to different vegetation types through time were identified through spectral and textural features. The classification results were combined with basic layers such as lithological outcrops, pre-fire vegetation, landscape morphology etc., supplementing a spatial geodatabase used for classifying burnt areas with varying post-fire plant community recovery. We validated the results of the classification during fieldwork and found that at a local scale, where the landscape features are quite similar, the bedrock type proves to be an important factor for vegetation recovery, as it clearly defines the soil generation along with its properties. Plant species recovery seems to be controlled by the local lithology as it was found weaker in plots overlying limestones and marbles, comparing to that observed over schists, even for the same species. In conclusion, post-fire vegetation recovery seems to be a complex process controlled not only from species biology, but also from the geological features.