Abstract:

The purpose of the study is the determination of the shoreline changes and the sediment processes along the beach of Marathon Bay, which is located at northeast Attica. In the wider on shore area the Schinias National Park, at the northeast of the bay, the Olympic Rowing Centre, military bases, archeological sites, museums etc. are encountered. The area is also characterized by high touristic activity during summer. In the area there are specific locations and constructions endangered due to coastal retreat. A lagoon was established in the study area 3.500 years BP (Pavlopoulos et al., 2006) as it is characterized by low elevations, gentle slopes and fine sediments.
A survey of the coastal and marine geomorphology was carried out by acoustic scanning of the seafloor with an echo sounder and sonar side scan topographical sections perpendicular to the shoreline along with collection and analysis of surface sediments. The quantification of long-term shoreline displacements was carried out by comparing historical and contemporary aerial photographs (1945, 1960, 1969, 1988, 1996, 2001, 2010) along with very high resolution satellite imagery (2012, 2014, 2015, 2016, 2017, 2018), not to mention the tracing of the coastline (2013) with Real Time Kinematics equipment (RTK-GNSS). The quantification of long-term shoreline displacements was made with the use of the add-on application of Digital Shoreline Analysis System (DSAS) within the GIS platform ArcMap 10.6 (Thieler et al., 2009). This was accomplished by drawing 261 transects (every 50 meters), except those neighboring anthropogenic structures, perpendicularly to the historical shorelines from a stable baseline (Tsokos et al., 2018). At each transect the rate of displacement was measured.

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