Summary:
One result of the global rise of sea level as well as the uncontrolled
development of the coastal zone is considered to be coastal erosion; this
natural process is considered to be a serious global problem. Unlike other
natural disasters (such as earthquakes, hurricanes, tsunamis, etc) coastal
erosion is an ongoing process; fortunately, today it can be predicted and
mitigated early because of advanced technological development. In this thesis a
standard methodology for assessing the risk of erosion is developed, taking the
coastal zone of the island of Skyros as a case study. The aforementioned
methodology was applied to the entire coastline of the island. The distinctive
morphological characteristics of the coastal zone, affect (positively or
negatively) the evolution of the phenomenon of coastal erosion. On the island
of Skyros and found beachrocks, at length about of this of the island. So it
was necessary to examine in depth these landforms to determine whether and how
the impact negatively or positively to the phenomenon of coastal erosion. In
this frame, data was collected, which after being processed led to results
supporting the relationship of the coastal erosion with beackrocks, providing a
complete picture of the situation in the study area (island of Skyros). To
determine the risk we applied the Coastal Vulnerability Index (Coastal
Vulnerability Index - CVI), which includes bibliographic variables related to
geographical and morphological variables-characteristics of the area
(geomorphology, geology, tidal range, average wave height topography,
horizontal historical shoreline position changes etc.), however, does not take
account of the geology of each region, and socio-economic criteria. For these
reasons it was considered appropriate to modify the index adding two more
variables, the socioeconomic status of the area, such as land use, and the
lithology of the geological formations. Especially for the variable of the
geomorphology an exercise in the countryside using modern portable devices to
record rural maps. Some 1:5000 scale maps were also used in order to determine
the landforms developed along the shoreline. Cartographic material,
specifically 1:5.000 maps, 1:50.000 aerial photos and a detailed depiction of
terrain and landforms were used. The identification of the coastal landforms
and especially of the beachrocks formations played a key role in the study. A
quantitative estimate of the calibration process’ variables is achieved by
using Geographic Information Systems (ArcGIS 10). The results are depicted in
hazard maps and the findings were commented upon. Especially for the
classification of the geomorphological beachrocks formation took a value equal
to 3. This was based on the fact that in the iterative there is no clear
evidence if these formations protect from erosion or not. It must be mentioned
that in the areas of beachrocks (areas that also have low elevation) high
vulnerability was found. Moreover, the sea level rise scenarios based on the
IPCC (2007) were processed and vulnerability maps presented. By applying the
CVI models in the study area (Skyros Island) it is found that 12% of the coasts
have high to very high vulnerability. The areas that have very high
vulnerability are Moli, ancient mines, Achilli port, Palamari, Airport, Aspous,
Kalamitsa, Acherounes, Gyrismata and Almyri Lake. This fact is also verified by
the two applied models with small differences in the areas known as Aspous,
Palamari and in SE coast of Skyros.From all the aforementioned areas only in
Moli, Gyrismata and Palamari beachrocks are found. The variables that
eventually affect the geographical distribution of the final CVI vales are
geomorphology, geology and the slope of the coastal zone. Moreover tidal range,
average wave height topography, horizontal historical shoreline position
changes, land use and sea level affect much less the final results in specific
areas of the coastline. One of the most important conclusions is that the
variables that essentially determine the geographic diversification of the
final index value are geomorphology (including beachrocks), geology and the
morphological gradient of the coastal zone. In contrast, waves, tides and the
rising rate of sea level do not play a significant role in the diversification
of the index in different parts of the coastline.
It is worth noting that the beachrock areas most at risk from erosion, as
derived from the model applied, are largely identical to those expected to be
flooded with water due to future scenarios of the IPCC. In this area there are
Neogene formations and specifically marine formations, consisting of
sandstones, conglomerates and marls. By dating that it is expected that the age
of the samples will be recent (Late Holocene, 1000 – 2000BP), because the
amount of quartz is greater than the feldspars
Keywords:
Costal erosion, Costal Vulnerability Index, Skyros, GIS, Beachrocks
