water

Article Mapping of Coastline Changes in Riviera over the Past 76 Year’s Measurements

Hariklia D. Skilodimou 1, Vasileios Antoniou 2, George D. Bathrellos 1,* and Eleni Tsami 3

1 Department of Geology, University of Patras, 26504 Patras, ; [email protected] 2 UK Centre for Ecology & Hydrology, Wallingford OX10 8BB, UK; [email protected] 3 Faculty of Finance and Statistics, University of , Lampraki 126 Str., 18534 Piraeus, Greece; [email protected] * Correspondence: [email protected]

Abstract: Mapping of coastline changes assists in coastal development and monitoring. , located in the southwestern coastal zone in in central Greece, has undergone major and radical changes generated by human interference during the last decades. The aim of this paper is to map record and measure the coastline changes in Athens Riviera over the past 76 years. Aerial photographs and satellite images from 1945 to 2021 as well as geographic information system (GIS) techniques were used to depict the spatial and temporal variations of the coastline. The results show that 60% of the total length of the coastline is artificial coast, while 29% is rocky coast and 12% beach. The study of seven subareas showed that human interventions caused significant coastline changes in Faliro Bay, and . The adjacent coastal regions to Athens metropolitan area illustrate the highest modifications in the coastline. The main changes in the coastlines are recorded from 1960 to 1987, while the rate of changes in coastline slowed down from 1987 to 2021. The total changes in  the coastline of Athens Riviera demonstrate that, during the past 76 years, the coastline was enhanced  by 40% while land reclaimed to the sea area approaches 2.67 km2. The applied method is effective Citation: Skilodimou, H.D.; and rapid and may utilize in the coastal monitoring and management. Antoniou, V.; Bathrellos, G.D.; Tsami, E. Mapping of Coastline Changes in Keywords: remote sensing; GIS; spatial and temporal coastline changes; artificial coast; central Greece Athens Riviera over the Past 76 Year’s Measurements. Water 2021, 13, 2135. https://doi.org/10.3390/w13152135 1. Introduction Academic Editor: Thomas Meixner Coastlines are areas of utmost importance because they host multiple activities world- wide [1]. Today, numerous countries hold a large amount of population along their Received: 10 July 2021 coastlines. More than 600 million people, approximately 10% of the world’s population, Accepted: 31 July 2021 Published: 3 August 2021 live in coastal areas that are less than 10 m above sea level (m.a.s.l.). Additionally, 2.4 billion people, around 40% of the world’s population live within 100 km of the coastline [2]. The features of a coastline form through the continuous interaction of the geosphere, Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in the hydrosphere and the atmosphere. Dolan et al. [3] defined that coastline is the physical published maps and institutional affil- interface of land and water. Moreover, the position of the coastline changes frequently iations. throughout time, because of several morphodynamic parameters such as sediment move- ment in the littoral zone and the dynamic nature of water levels at the coastal boundary (e.g., currents, tides, waves, etc.) [4]. The coastline locations, as well as its boundary changes are of essential significance to coastal studies [5]. Thus, analysis of coastline information is needed in several scientific Copyright: © 2021 by the authors. works, such as to assess sea-level changes [6–9], for coastal zone protection [10], to esti- Licensee MDPI, Basel, Switzerland. This article is an open access article mate coastal development [11], to assist in coastal monitoring [12], as well as in coastal distributed under the terms and evolution [13–15], and to assess coastal hazards [16–19]. conditions of the Creative Commons Coastline changes are phenomena, which vary in magnitude, speed and duration. In Attribution (CC BY) license (https:// the last decades, earth observation (EO) data such as aerial photography, satellite imagery, creativecommons.org/licenses/by/ and GPS data have become integral means for the evaluation of shoreline changes over 4.0/). a long period of time. They have availability of temporal data at the same locations

Water 2021, 13, 2135. https://doi.org/10.3390/w13152135 https://www.mdpi.com/journal/water Water 2021, 13, 2135 2 of 19

and are cost effective [20,21]. Moreover, geographical information systems (GIS) are excellent tools in the spatial analysis of various natural phenomena [22–30]. These current geospatial technologies have been proved to be a unique tool for environmental research because the mapping of the coastline is accurate and provides with multiple and up-to- date information. More than 40% of the population of Greece lives in the metropolitan urban area of Athens, the capital. The plain of Athens has been extremely urbanized during the last seventy-five years and the environment has changed dramatically [31,32]. Apart from this, Athens’ southern coastal area, referred to as the Athens Riviera, has been subject to constant changes due to human interference during the same period of time. Its vicinity to the city of Athens is the cause of being affected by human activities. Human interventions caused the destruction of natural beaches and dunes as well as the drying up of wetlands and lagoons. These coastline changes affected the natural environment, caused significant ecological damage and increased the risk of flooding in several areas of the coastal zone of Athens Riviera [33,34]. On the other hand, climate changes and their impacts, such as sea level rise and the resulting coastal inundation, are potential hazards for coastal areas and communities. Coastline changes increase the vulnerability of the coastal population and ecosystems [19]. Thus the spatial monitoring of the coastline changes is a significant issue for the reduction of these vulnerabilities and the integrated coastal zone management. In this work, an effort has been made to identify, justify and calculate the changes in the coastline of Athens Riviera from 1945 to 2021, as well as to recognize vulnerable coastal areas and to provide information for coastal management practices. Aerial photographs and satellite images have been used to measure the coastline changes due to human interference. While being extremely efficient, this methodology is rapid, reliable and economical. In one word, it is a useful tool for the recording and monitoring of the coastline changes.

2. Materials and Methods 2.1. Study Area Athens Riviera is the coastal area in the southern suburbs of Athens metropolitan area, in central Greece (Figure1A). It is located about 16 km from downtown Athens stretching from the city of Piraeus to the southernmost point of Attica, Cape Sounio. The study area is a part of Athens Riviera and is extended from the Faliro Bay up to the Bay (Figure1B). The coastal zone from Faliro Bay to Anavyssos Bay, during the last decades and especially after 1960, has undergone major and radical changes. The intense and anarchic construction, as well as the lack of planning in infrastructure projects led to the alteration of the natural environment and the degradation of the life of the inhabitants of the area [33]. The development of facilities for commercial and mainly tourist exploitation, along the coasts, have affected the southern areas, where there is more intense residential devel- opment of summer houses [31]. Natural changes have also been observed in the coastal zone, such as significant movements of sediments towards the shores, which are corrosive materials. Between 1971 and 1992, Attica was the most fire-stricken region of Greece in terms of surface. Thus, in some areas, the movement of sediments is due to the effects of fires in recent decades, both on forests and on lower and sparser vegetation [35]. The study area consists of hills and valleys, which create a complex but low relief with gentle slopes. The lowlands of the wider area are relatively limited with the exception of the plain of Athens. The study area includes the southwestern part of the Athens Basin and the bay of Faliro, in which Kifissos and Ilissos rivers flow. The main wide plains, included in the area, are , Anavyssos, which are developed with general direction NE-SW. The drainage network is consisted of parallel streams of temporary flow; with general direction NE-SW. Artificial beaches characterize the coastal morphology of the area, similarly to other coastal areas of Attica. The substrate of area is formed mainly of Neocene and Quaternary deposits [34]. Water 2021Water, 132021, x FOR, 13, 2135PEER REVIEW 3 of3 19 of 19

Figure 1. A B Figure 1. (A) Location( ) Location map mapof the of study the study area; area; (B) ( the) the elevations elevations of of the the study study area,area, the the road road network network and and the the main main towns. towns. Athens Riviera has a Mediterranean climate. The mean annual temperature is of 18.5The◦ C,study while area the averageconsists annual of hills precipitation and valleys, reached which about create 368 mm a complex for the years but 1955 low to relief with2015 gentle [31]. slopes. The lowlands of the wider area are relatively limited with the excep- tion of the plain of Athens. The study area includes the southwestern part of the Athens Basin2.2. and Data the bay of Faliro, in which Kifissos and Ilissos rivers flow. The main wide plains, includedThe in the aerial area, photographs are Vari, Anavyssos, employed were which taken are from developed 1945 and with onwards general because direction there NE- SW.were The nodrainage available network data before is consisted that year. of Specifically, parallel streams the aerial of photographs temporary dated flow; from with 1945 general (scale 1:42,000), 1960 (scale 1:30,000), 1972 (scale 1:40,000), and 1987 (scale 1:35,000). The direction NE-SW. Artificial beaches characterize the coastal morphology of the area, sim- aerial photographs with variable spatial resolution were derived from Hellenic Geographic ilarlyMilitary to other Service. coastal areas of Attica. The substrate of area is formed mainly of Neocene and QuaternaryTwo Landsat deposits 7 TM [34]. satellite images have been used and its characteristics are: sensor: thematicAthens mapperRiviera ETM+,has a Mediterranean spectral bands (µ climate.m): B1: 0.45–0.515 The mean B2: annual 0.525–0.605 temperature B3: 0.63–0.690 is of 18.5 °C, B4:while 0.75–0.90 the average B5: 1.55–1.75 annual B6:precipitation 10.40–12.5 reached B7: 2.09–2.35 about B8: 368 0.52–0.90 mm for (panchromatic), the years 1955 to 2015spatial [31]. resolution: 30 m/(60 m for Band 6) (15 m for Band 8), radiometric resolution: 8 BIT PATH/ROW: 183/034, acquisition date: 16/05/2010 and 05/09/2010. Additionally a 2.2. Sentinel-2AData with a single multispectral instrument (MSI) sensor was used for the year 2021. The spectrum characteristics (central wavelength/bandwidth) are B1: 442.7/21, B2: 492.4/66,The aerial B3: photographs 559.8 B4: 664.6/31, employed B5: 704.1/15, were taken B6: 740.5/15,from 1945 B7: and 782.8/20, onwards B8: because 832.8, B8a there were864.7/21, no available B9: 945.1/20, data before B10: 1373.5/31,that year. B11:Specifically, 1613.7/91, the B12: aerial 2204.4/175, photographs Tile: T34SGG, dated from 1945radiometric (scale 1:42,000), resolution: 1960 12 (scale BIT, acquisition 1:30,000), date: 1972 25/05/2021, (scale 1:40,000), spatial and resolution, 1987 (scale 10 m. These1:35,000). The satelliteaerial photographs images do not with have variable video data. spatial resolution were derived from Hellenic Geo- graphic FieldworkMilitary Service. for this study was carried out during 2020–2021. Fieldwork data were collectedTwo Landsat for the 7 geological TM satellite and geomorphologicimages have been mapping used ofand coastline its characteristics forms, as well are: as thesensor: thematicrecognition mapper of theETM+, coastline spectral changes bands using (μm): a standard B1: 0.45–0.515 GPS receiver B2: 0.525–0.605 with 3 m accuracy. B3: 0.63–0.690 B4: 0.75–0.902.3. Methodology B5: 1.55–1.75 B6: 10.40–12.5 B7: 2.09–2.35 B8: 0.52–0.90 (panchromatic), spa- tial resolution:Image-processing 30 m/(60 coupledm for Band with GIS6) (15 techniques m for Band were 8), used radiometric to accomplish resolution: the present 8 BIT PATH/ROW:work. As a 183/034, first step acquisition aerial photos date: were 16/05/2010 used. They and are common 05/09/2010. data Additionally used for coastline a Senti- nel-2A with a single multispectral instrument (MSI) sensor was used for the year 2021. The spectrum characteristics (central wavelength/bandwidth) are B1: 442.7/21, B2: 492.4/66, B3: 559.8 B4: 664.6/31, B5: 704.1/15, B6: 740.5/15, B7: 782.8/20, B8: 832.8, B8a

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mapping and to determine shoreline changes (Dolan, 1980). Shorelines are identified by grey scale tonal variations. Nevertheless, they have several geometric distortions, which in many cases associated with errors [36,37]. The aerial photos belonged to different periods of time, between 1945 and 1987, and at different scales. They were scanned and converted to tiff format. Hence, they were adjusted into the projective system EGSA of the two topographic maps. Thus, each aerial photograph is characterized by a georeference adjusting their common points with the ones of the topographic maps. Furthermore, the coastline was digitized in each aerial photograph for all the four different data, and then they were compared. The further processing of the images occurred by the software ArcMap (Version 10.8). The final shorelines were manually digitized within GIS capabilities. The quality of black and white copies of aerial photos was not good due to their low contrast to a medium gray tone. For this reason field work was done to verify the results of their processing. The identification and mapping of both man-made and natural changes on the shoreline of the Athens Riviera was done with precision of 1 m, as it shown by the necessary control of the results in the fieldwork. A data fusion georeferenced image has been produced using bands 4, 4, 7 fold Landsat 7 and bands 1, 3, 4 for Sentinel 2 and the panchromatic one, in order to map the coastline on a recent date. Overlaying techniques have been used to identify the changes and measure the land expansion from 1945 to 2021. The studied coast includes a varied geomorphology marked by the presence of both natural and artificial coastal forms. Natural coastal areas with beaches and smooth slopes, rocky cliffs of considerable heights and artificial coastal areas by the implementation of structures and buildings were observed though aerial photo interpretations, satellite imagery and field work. Thus, the shoreline of the Athens Riviera was mapped and divided in beaches, rocky coasts and artificial coasts. The studied coastline corresponds to the coastline of the year 2021. The lengths of each type of coast were measured. Moreover from the coastal areas with beaches and smooth slopes, seven sub-areas were selected and studied. They cover the entire length of Athenian Riviera and they are: Faliro Bay, Alimos, Glyfada, , Bay, Barkiza Bay and Anavyssos Bay (Figure2). The identification and selection of these subareas was done after the identification of specific environmental problems, through aerial interpretations, satellite imagery, as well as from oral information of residents during field work. The coastline changes in these areas from 1945 to 2021 were studied. The length of the coastline and the surfaces of the earth filled area in each studied period were measured for each subarea using ArcGiS capabilities. Finally, the total changes in length and area for the Athenian Riviera were calculated. Water 2021, 13, x FOR PEER REVIEW 5 of 19 Water 2021, 13, 2135 5 of 19

Figure 2. Spatial distribution of subareas in which the shoreline changes were measured. Figure 2. Spatial distribution of subareas in which the shoreline changes were measured. 3. Results 3. Results3.1. Classification of Coastlines 3.1. ClassificationThe coastline of Coastlines of the year 2021 was classified in three different types. The spatial Thedistribution coastline of of the the coastline year 2021 types was of Athenianclassified Riviera in three is illustrateddifferent types. in Figure The3. spatial The dis- artificial coasts are mainly observed in the northern part of the study area. The beaches tributionwith of smooth the coastline slopes are types located of mainlyAthenian in bays Rivi whileera is rocky illustrated coasts arein Figure observed 3. mainlyThe artificial coastswhere are themainly geological observed stratum in consists the northern of carbonate part formations. of the study Table 1area. shows The the lengthsbeaches with smoothand slopes their percentages are located of mainly each type in of bays coast. while The total rocky length coasts of the are coastline observed of the mainly study where the geologicalarea was found stratum to be 122.1consists km. of The carbonat artificial coastse formations. are very extensive Table 1 representingshows the 60%lengths of and their thepercentages total length of of each the coastline. type of Artificialcoast. The structures total length such asof ports, the coastline marinas, etc.of the increase study area was foundthe length to be of 122.1 the coastline. km. The The artificial length of coasts the rocky are coasts very reachesextensive about representing 36 km, while 60% the of the most limited in length are the beaches which constitute 12% of the total coastline. total length of the coastline. Artificial structures such as ports, marinas, etc. increase the lengthTable of the 1. The coastline. type of coasts, The theirlength length of andthe percentage.rocky coasts reaches about 36 km, while the most limited in length are the beaches which constitute 12% of the total coastline. Type of Coast Length (in km) Percentage (%) Beaches 14.8 12 Rocky 35.6 29 Artificial 71.8 59 Total 122.1 100

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FigureFigure 3. Classification 3. Classification of the ofcoastline the coastline based based on 2021 on 2021imagery imagery and fieldwork. and fieldwork. The nort Theh north part partof the of study the study area area is charac- is terizedcharacterized as mainly artificial. as mainly artificial.

Table3.2. 1. FaliroThe type Bay of coasts, their length and percentage. The changes that occurred in the Faliro Bay were recorded by comparing aerial photographsType of andCoast satellite images and Length were examined (in km) in six periods of Percentage time: the first (%) from 1945 toBeaches 1960, the second from 1960 to 1972, 14.8 the third from1972 to 1987, the 12 fourth from 1987 to 2010Rocky the fifth from 2010 to 2021 and35.6 the sixth from 1945 to 2021. Moreover, 29 the lengthsArtificial of the coastline as well as the extended71.8 areas of each subarea are presented59 in Tables2 and3 respectively. Total 122.1 100 Table 2. The lengths of the coastline in each year, the changes in length (in km) and their percentage (%) between different years for each subarea. 3.2. Faliro Bay

The changes that occurred in the Faliro Bay wereVouliagmeni recorded by comparingAnavyssos aerial pho- Subarea Faliro Bay Alimos Glyfada Voula Vari Bay tographs and satellite images and were examined in six periodsBay of time: the firstBay from 1945 to 1960, the second from 1960 to 1972, theLength third in from1972 meters to 1987, the fourth from 1987 to 20101945 the fifth 5279 from 2010 2895to 2021 and 4543 the sixth 1137from 1945 4330to 2021. Moreover, 5900 the 3803 lengths of the1960 coastline 5316as well as the 2911 extended 4543 areas of each 1477 subarea 4330 are presented 5900 in Tables 4061 2 and 3 respectively.1972 9569 4339 no data 1459 5171 6452 4192 Year 1987The examination 10,480 of 10,171 the 1945 13,368to 1960 aerial 1486 photos reveals 5504 that 6452 minor changes 4192 of the coastline2010 occurred 19,267 in Faliro 10,300 Bay during 13,368 this pe 1486riod. Figure 5513 4 depicts 6452 the coastlines 4192 of the two2020 different 20,407 dates. According 10,300 to Table 13,368 2 the length 1486 of the 5513 coastline increased 6452 by 4192 1%, while the coastline extended to the sea covering an area of 0.07 km2 (Table 3). The change in the middle of the coastline stems from the natural deposits of Kifisos and Ilissos rivers. Con- sequently, the bay is not yet affected by human activities. Between the years 1960 and 1972 human interventions are significant leading to the first hints of alterations in the coastline (Figure 4). The length of coastline grew from 5.3 km in 1960 to 9.5 km in 1972 (Table 2). The alteration observed at the western part of the bay is originated from the earth filling in favor of the technical works. The same works take place between the rivers Kifisos and Ilissos aiming at the management of their beds. As for the eastern part of the bay, it has been banked up to construct new marinas.

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Table 2. Cont.

Vouliagmeni Anavyssos Subarea Faliro Bay Alimos Glyfada Voula Vari Bay Bay Bay m 1945–1960 37 16 0 340 0 0 258 % 1 1 0 30 0 0 7 m 1960–1972 4253 1428 no data −18 841 552 51 % 80 49 no data −1 19 9 1 m 1972–1987 911 5832 no data 27 333 844 0 Changes in % 10 134 no data 2 6 13 0 length m 1987–2010 8787 129 0 0 9 0 0 % 84 1 0 0 0.2 0 0 m 2010–2021 1140 0 0 0 0 0 0 % 6 0 0 0 0 0 m 1945–2021 15,128 7405 8825 349 1183 552 389 % 287 256 194 31 27 9 10

Table 3. The extended areas in each year, the changes in area (in km2) and their percentage (%) between different years for each subarea.

Faliro Vouliagmeni Anavyssos Subarea Alimos Glyfada Voula Vari Bay Bay Bay Bay Area in km2 1960 0.07 0.00 0.00 −0.02 0.00 0.00 0.00 1972 0.07 0.00 no data 0.02 0.02 0.00 0.00 Year 1987 1.06 0.29 0.85 0.02 0.05 0.09 0.07 2010 1.26 0.33 0.85 0.02 0.05 0.09 0.07 2020 1.27 0.33 0.85 0.02 0.05 0.09 0.07 km2 1945–1960 0.07 0.00 0.00 −0.02 0.00 0.00 0.00 km2 0.00 0.00 no data 0.02 0.02 0.00 0.00 1960–1972 % 0 0 0 200 0 0 km2 1.00 0.29 0.85 0.02 0.05 0.09 0.07 1972–1987 % 1510 0 112 Changes km2 0.19 0.33 0.00 0.00 0.00 0.00 0.00 in area 1987–2010 % 18 113 0 0 0 0 0 km2 0.09 0.00 0.00 0.00 0.00 0.00 0.00 2010–2021 % 1 0 0 0 0 0 0 km2 1.27 0.33 0.85 0.02 0.05 0.09 0.07 1945–2021 % 1922 113 200 112

The examination of the 1945 to 1960 aerial photos reveals that minor changes of the coastline occurred in Faliro Bay during this period. Figure4 depicts the coastlines of the two different dates. According to Table2 the length of the coastline increased by 1%, while the coastline extended to the sea covering an area of 0.07 km2 (Table3). The change in the middle of the coastline stems from the natural deposits of Kifisos and Ilissos rivers. Consequently, the bay is not yet affected by human activities. Between the years 1960 and 1972 human interventions are significant leading to the first hints of alterations in the coastline (Figure4). The length of coastline grew from 5.3 km in 1960 to 9.5 km in 1972 (Table2). The alteration observed at the western part of the bay is originated from the earth filling in favor of the technical works. The same works take place between the rivers Kifisos and Ilissos aiming at the management of their beds. As for the eastern part of the bay, it has been banked up to construct new marinas. Water 2021, 13, x FOR PEER REVIEW 7 of 19 Water 2021, 13, 2135 8 of 19

Figure 4. Classification of the coastlineFigure based 4. Changes on 2021 of theimagery Faliro coastlineand fieldwork. from 1945 The to nort 2021.h part of the study area is charac- terized as mainly artificial. Changes of the coastline occurred between 1972 and 1987 are depicted in Figure4 as well as Tables2 and3. The coastline extended to the sea covering an area of 1 km 2 and Changes of the coastline occurred between 1972 and 1987 are depicted in Figure 4 as increased about 1500% (Table3). The present Irinis–Filias stadium and secondary marinas 2 wellwere as Tables constructed 2 and at 3. the The western coastline part of extended the Bay (Figure to the4 ).sea The covering bed of the an Kifisos area riverof 1 km has and increasedbeen rearranged about 1500% and, thus,(Table flows 3). The into present the bay through Irinis–Filias an artificial stadium channel. and secondary In addition, marinas the weregovernment constructed constructed at the western central part roads of onto the theBay earth-filled (Figure 4). locations. The bed At of the the eastern Kifisos side river of has beenthe rearranged bay, a modified and, entrance thus, flows in the into marina the isbay constructed through andan artificial a second marinachannel. is added.In addition, the governmentThe changes constructed during 1987–2010 central (Figureroads 4onto) are detectedthe earth-filled between locations. the Kifisos At and the Ilisos eastern siderivers of the mouth bay, duea modified the continuous entrance filling in inthe the marina area. The is lengthconstructed of the coastline and a second increased marina by is added.84% and the area of the constructions rose by 18% (Tables2 and3). The Kifisos discharges throughThe changes an artificial during channel, 1987–2010 and, consequently (Figure 4) are has detected increased between its length; the a breakwater Kifisos and has Ilisos been constructed face to the channel to protect it from the wave activity. An additional riverschange mouth of the due coastline the continuous occurred with filling the expansionin the area. of theThe beach length in frontof the of coastline the Irinis–Filias increased by 84%stadium and that the was area produced of the constructions by the construction rose of by another 18% (Tables breakwater 2 and to protect 3). The the Kifisos beach dis- chargesfrom through sea-erosion. an Theartificial expansion channel, is, however, and, consequently the result of a has sediment increased deposit its fromlength; the a sea. break- waterMoreover, has been the constructed jetty of the marinas face to locatedthe channe at thel easternto protect part it of from the bay,the waswave artificially activity. An additionalextended change further of in the the coastline years between occurred 1987 andwith 2021. the expansion of the beach in front of the Irinis–FiliasThe changesstadium from that 2010 was to produced 2021 are shown by th ine construction Figure4. During of theanother last examined breakwater period to pro- tectthe the coastline beach from length sea-erosion. increased by The 6% and expansio the artificialn is, however, constructions the increased result of their a sediment area by de- posit1% from (Tables the2 sea.and3 Moreover,). the jetty of the marinas located at the eastern part of the bay, Between the years 1945 and 2021, the coastline of the Faliro Bay was artificially was artificially extended further in the years between 1987 and 2021. expanded (Figure4). Its length grew from 5.2 km in 1945 to 20.4 km in 2021 and it increased byThe 287%. changes All technical from 2010 works to such 2021 as are the shown Irinis–Filias in Figure stadium, 4. During the crossroads, the last the examined marinas pe- riodare the constructed coastline ontolength locations increased that by were 6% covered and the by artificial sea in the constructions past years, specifically increased in their area1945. by 1% Moreover (Tables the 2 and surface 3). of the earth-filled area now approaches 1.27 km2, an increase ofBetween 1922%. the years 1945 and 2021, the coastline of the Faliro Bay was artificially ex- panded (Figure 4). Its length grew from 5.2 km in 1945 to 20.4 km in 2021 and it increased by 287%. All technical works such as the Irinis–Filias stadium , the crossroads, the marinas are constructed onto locations that were covered by sea in the past years, specifically in 1945. Moreover the surface of the earth-filled area now approaches 1.27 km2, an increase of 1922%.

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which is probably due to coastal erosion. During the period from 1960 and 1972, human Water 13 2021, , 2135 interventions in the area began to be felt (Figure 5). The length of the coastline9 of in 19 1972 increased by 49% (Table 2). The first facilities of the marina were built and the first earth fillings were carried out, while concrete construction was created in the southern part of the 3.3.coast Alimos as a protection measure against coastal erosion. By 1987, the public works in the area areIn completed, Alimos, the with coastlines the final of 1945 construction and 1960 seem of the to marina, coincide (Figurewhich 5still, Tables exists2 and today.3 ). The surroundingThe only technical area is transformed work observed into in a the recreation area is the area. addition The riverbed of a small and jetty. the On estuary the of the contraryKalamaki a small stream retreat in its of northern the coastline part was are observed settled inand the the southern artificial part beach of the of coastal Alimos is formedarea, with which earth is probably fillings. due Anto earth coastal jetty erosion. is also Duringbeing constructed, the period from the 1960aim andof which 1972, is to human interventions in the area began to be felt (Figure5). The length of the coastline in protect the coast from erosion (Figure 5). In 1987 the length of the coastline more than 1972 increased by 49% (Table2). The first facilities of the marina were built and the first doubledearth fillingscompared were carriedto the out,coastline while concreteof 1972 constructionincreasing wasby 134%. created The in the coastline southern partthat was extendedof the coast covered as a protectionan area of measure 0.29 km against2. coastal erosion. By 1987, the public works in theComparing area are completed, the coastlines with the of final1987 construction and 2010, we of theobserve marina, that which the stillinterventions exists today. in the areaThe continued surrounding (Figure area is5). transformed The length into of coastline a recreation in area.2010 The increased riverbed by and 129 the m, estuary while the artificialof the interventions Kalamaki stream covered in its northern an area partof 0.33 are km settled2 (Tables and the 2 and artificial 3). As beach it is ofshown Alimos in Fig- ureis 5 formedas well with as Tables earth fillings.2 and 3, An from earth 2010 jetty to is 2021 also beingno changes constructed, were theobserved aim of whichin the is coast- line.to The protect interventions the coast from from erosion 1945 to (Figure 20215 caus). Ined 1987 a 287% the length increase of the in coastline the length more of thanthe coast- doubled compared to the coastline of 1972 increasing by 134%. The coastline that was line. They cover an area of 0.33 km2 (Tables 2 and 3). extended covered an area of 0.29 km2.

FigureFigure 5. Changes 5. Changes of of the the Alimos Alimos co coastlineastline fromfrom 1945 1945 to to 2021. 2021. Comparing the coastlines of 1987 and 2010, we observe that the interventions in the 3.4.area Glyfada continued (Figure5). The length of coastline in 2010 increased by 129 m, while the artificialIn the area interventions of Glyfada, covered from an 1945 area to of 1960 0.33 the km 2changes(Tables2 of and the3). coastal As it is zone shown were in mini- mal.Figure Comparing5 as well the as coastlines Tables2 and of3, 1960 from and 2010 1987 to 2021 we noobserve changes that were human observed interventions in the in the coastline.area were The extensive. interventions from 1945 to 2021 caused a 287% increase in the length of the 2 coastline.Marinas They and coveran artificial an area ofpeninsula 0.33 km were(Tables built2 and in3). the area. In the northern part of the peninsula,3.4. Glyfada an artificial beach was created through the earthworks (Figure 6). The length of coastlineIn the grew area offrom Glyfada, 4.5 km from in 1960 1945 toto 1960 13.5 the km changes in 1987, of and the coastalthe artificial zone were extension minimal. of the landComparing covered an the area coastlines of 0.85 of km 19602 (Tables and 1987 2 and we 3). observe During that the human period interventions 1987–2021 there in the were no changesarea were in extensive. the coastal zone of Glyfada.

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Marinas and an artificial peninsula were built in the area. In the northern part of the peninsula, an artificial beach was created through the earthworks (Figure6). The length of Water 2021, 13, x FOR PEER REVIEW coastline grew from 4.5 km in 1960 to 13.5 km in 1987, and the artificial extension of the 10 of 19 land covered an area of 0.85 km2 (Tables2 and3). During the period 1987–2021 there were no changes in the coastal zone of Glyfada.

Figure 6. The coastlines of Glyfada from 1945 to 2021. Figure 6. The coastlines of Glyfada from 1945 to 2021. The length of the coastline from 1945 to 2021 increased by 194%, while the area excavatedThe length was of 0.85 the km coastline2 (Tables from2 and3 1945). to 2021 increased by 194%, while the area exca- vated was 0.85 km2 (Tables 2 and 3). 3.5. Voula Figure7 shows the coastlines of 1945 and 1960. The coastline of 1960 illustrates 3.5. Voula very little difference from that of 1945, except for the area that appears to be retreating (FigureTables2 and7 shows3 ). This the change coastlines is probably of 1945 due and to the 1960. retreating The ofcoastline waters and of the1960 appearance illustrates very littleof difference land behind from the beachthat of rocks 1945, which except existed for inthe the area area that during appears the aerial to photographybe retreating of (Tables 2 and1945. 3). ThisThis phenomenon change is probably is often observed due to in the the coastsretreating of Attica of withwaters a similar and the morphology appearance of during the winter. Coastal zone changes between 1960 and 1972 include land expansion in land behind the beach rocks which existed in the area during the aerial photography of the northern part of the study area. The beach of Voula was created, with the simultaneous 1945.construction This phenomenon of three concrete is often platformsobserved parallel in the coasts to the coastline. of Attica The with beach a similar rocks morphology of the duringarea the were winter. removed Coastal and boxed zone under changes the platforms.between During1960 and the 1972 period include 1972 to land 1987, expansion the in thechanges northern in the part coastline of the of study the area area. were The limited beach (Figure of Voula7, Tables was2 and created,3). There with was the an simulta- neousextension construction of the coast of three to the concrete artificial concrete platform platforms.s parallel There to wasthe acoastline. sandy zone The added beach to rocks of thethe area central were platform, removed connecting and boxed it with under the opposite the platforms. land. In fact, During a coast the form period of tombolo 1972 to 1987, was created which is preserved to this day. The coastline has remained unchanged from the changes in the coastline of the area were limited (Figure 7, Tables 2 and 3). There was 1987 onwards. an extension of the coast to the artificial concrete platforms. There was a sandy zone added to the central platform, connecting it with the opposite land. In fact, a coast form of tom- bolo was created which is preserved to this day. The coastline has remained unchanged from 1987 onwards.

Water 2021, 13, x FOR PEER REVIEW 11 of 19 Water 2021, 13, 2135 11 of 19

Figure 7. The locations of the coastline from 1945 to 2021 in the coastal zone of Voula. Figure 7. The locations of the coastline from 1945 to 2021 in the coastal zone of Voula. From 1945 to 2021 the length of the coastline increased by 31%. The extension of the 2 artificialFrom 1945 land to covers 2021 an the area length of 0.02 of km the(Tables coastline2 and increased3). by 31%. The extension of the 2 artificial3.6. Vouliagmeniland covers Bay an area of 0.02 km (Tables 2 and 3). Figure8 shows all the coastlines of each year and their temporal changes can be seen. 3.6. VouliagmeniOn the coastline Bay of 1945 there were two in the western part of the area and on theFigure coast 8 ofshows 1960 the all firstthe operationcoastlines was of madeeach year with theand construction their temporal of the changes marina, which can be seen. On thedoes coastline not extend of to1945 the there height were of the two islands. islands On thein the other western hand, on part the coastlineof the area of 1972,and on the the extension of the works is clearly visible and the islets are connected on land with the coast of 1960 the first operation was made with the construction of the marina, which does concrete construction of the marina. The coast of 1987 was slightly different from that of not extend1972 in thisto the area height (Tables 2of and the3). islands. On the other hand, on the coastline of 1972, the extensionAnother of the works change is observedclearly visible further and north th one islets the beach are ofconnected Vouliagmeni. on Theland coasts with of the con- crete1945 construction and 1960 remained of the marina. unchanged The at coast this location. of 1987 Thewas coastline slightly of different 1972 showed from the that first of 1972 in thischanges, area (Tables with the 2 constructionand 3). of a jetty. The final changes of the coastline were made by 1987,Another following change the is extension observed of thefurther pre-existing north on jetty the and beach the extension of Vouliagmeni. of the beach The with coasts of the artificial deposition of sediments (Figure8). 1945 and 1960 remained unchanged at this location. The coastline of 1972 showed the first During the period 1987–2010, the length of the shoreline slightly increased 0.2%, while changes,no changes with the of the construction coastline were of recordeda jetty. The from final 2010 tochanges 2021 (Tables of the2 and coastline3). were made by 1987, followingThe artificial the extension extensions of caused the pre-existing a 27% increase jetty of the and coastline the extension in 2021 compared of the beach to with the artificialthat of 1945. deposition They are of observed sediments in a zone (Figure whose 8). the area is 0.05 km2 (Tables2 and3).

Water 2021, 13, x FOR PEER REVIEW 12 of 19 Water 2021, 13, 2135 12 of 19

Figure 8. The coastlines and their temporal changes from 1945 to 2021 in Vouliagmeni Bay. Figure 8. The coastlines and their temporal changes from 1945 to 2021 in Vouliagmeni Bay. 3.7. Vari Bay During the period 1987–2010, the length of the shoreline slightly increased 0.2%, The consecutive changes of the coastline from 1945 to 1987 are shown in Figure9. The whilegreatest no changes alterations of the in thecoastline coastline were were recorded between from the years 2010 1960to 2021 and (Tables 1972. Particularly, 2 and 3). theThe coasts artificial of 1945 extensions and 1960 were caused approximately a 27% increa similarse of withoutthe coastline important in 2021 changes. compared On to thatthe of contrary,1945. They in 1972 are observed there were in the a firstzone hints whose of human the area interventions is 0.05 km (Tables2 (Tables2 and 2 and3). In 3). 1987, the final interventions came when new marine works in took place as well as 3.7.coastal Vari Bay management for a beach, which is currently used as recreation area. No temporal changes of the coastline from 1987 to 2021 were recorded (Figure9, Tables2 and3). The consecutive changes of the coastline from 1945 to 1987 are shown in Figure 9. The coastline in 1945 was 5.9 km long, while in 2021 it was 6.4 km long, marking an Theincrease greatest of alterations 9%. The area in of the extended coastline land were is 0.09 between km2 (Tables the2 yearsand3). 1960 and 1972. Particu- larly, the coasts of 1945 and 1960 were approximately similar without important changes. On 3.8.the Anavyssoscontrary, Bay in 1972 there were the first hints of human interventions (Tables 2 and 3). In 1987,In the the coastal final interventions zone of the Anavyssos came when Bay, new anthropogenic marine works interventions in Varkiza during took theplace as wellperiod as coastal from 1945management to 1972 were for not a particularlybeach, which noticeable is currently (Figure used 10). as recreation area. No temporalComparing changes of the the coastline coastline of 1987 from with 1987 those to 2021 of previous were recorded years, we (F noticeigure the 9, Tables obvious 2 and 3). differences (Tables2 and3). The northwestern part of the bay was expanded by small port projects, which were done with the aim of launching small boats. Also, the beach was expanded due to the technical works that were done in the wider area, in order to conduct summer water sports (wind-surfing, etc.). The coastline has remained unchanged from 1987 to 2021 (Figure 10, Tables2 and3). The extension of the coast is estimated at a length of 0.3 km (10%) from 1946 to 2021. The total area of the earth fillings is estimated at 0.07 km2 (Tables2 and3).

Water 2021, 13, x FOR PEER REVIEW 13 of 19

Water 2021Water, 132021, x ,FOR13, 2135 PEER REVIEW 13 of13 19 of 19

Figure 9. The coastlines of Vari Bay from 1945 to 2021.

The coastline in 1945 was 5.9 km long, while in 2021 it was 6.4 km long, marking an increase of 9%. The area of extended land is 0.09 km2 (Tables 2 and 3).

3.8. Anavyssos Bay In the coastal zone of the Anavyssos Bay, anthropogenic interventions during the

period fromFigure 1945 9. The to coastlines 1972 were of Vari not Bay particularly from 1945 to noticeable 2021. (Figure 10). Figure 9. The coastlines of Vari Bay from 1945 to 2021.

The coastline in 1945 was 5.9 km long, while in 2021 it was 6.4 km long, marking an increase of 9%. The area of extended land is 0.09 km2 (Tables 2 and 3).

3.8. Anavyssos Bay In the coastal zone of the Anavyssos Bay, anthropogenic interventions during the period from 1945 to 1972 were not particularly noticeable (Figure 10).

Figure 10. The coastline changes from 1945 to 2021 in Anavyssos Bay.

Water 2021, 13, x FOR PEER REVIEW 14 of 19

Figure 10. The coastline changes from 1945 to 2021 in Anavyssos Bay.

Comparing the coastline of 1987 with those of previous years, we notice the obvious differences (Tables 2 and 3). The northwestern part of the bay was expanded by small port projects, which were done with the aim of launching small boats. Also, the beach was expanded due to the technical works that were done in the wider area, in order to conduct summer water sports (wind-surfing, etc.). The coastline has remained unchanged from 1987 to 2021 (Figure 10, Tables 2 and 3). The extension of the coast is estimated at a length of 0.3 km (10%) from 1946 to 2021. Water 2021, 13, 2135 14 of 19 The total area of the earth fillings is estimated at 0.07 km2 (Tables 2 and 3).

3.9. Total Coastline Changes in Athens Riviera 3.9.Figure Total 11 Coastline illustrates Changes the in changes Athens Riviera between 1945 and 2021 in Athens Riviera. High changes Figureare observed 11 illustrates in the the bay changes of Faliro, between in Alimos 1945 and 2021Glyfada. in Athens The artificial Riviera. interven- High tionschanges on the arecoastline observed are in more the bay intense of Faliro, in inthe Alimos areas and that Glyfada. are very The close artificial to Athens interventions metropol- on the coastline are more intense in the areas that are very close to Athens metropolitan itan area. Small changes are recorded in the southern part of the study area and specifi- area. Small changes are recorded in the southern part of the study area and specifically in callythe in baysthe bays of Vouliagmeni, of Vouliagmeni, Vari and Vari Anavyssos. and Anavyssos.

FigureFigure 11. The 11. coastlinesThe coastlines of 1945 of 1945 and and 2021 2021 as as well well as as their their temporal temporal changeschanges in in Athens Athens Riviera. Riviera.

As alreadyAs already mentioned mentioned before, before, the the length length of thethe coastlinecoastline in in the the study study area area was was esti- esti- mated to be 122.1 km. The coastline of 1945 was 87.4 km long. Thus, the length of coastline mated to be 122.1 km. The coastline of 1945 was 87.4 km long. Thus, the length of coastline increased by 39% from 1945 to 2021. increasedAs by it 39% is shown from in 1945 Table to3, 2021. between 1945 and 2021 the expanded surface approaches theAs 2.67it is km shown2. This in extension Table 3, caused between to the1945 earth and filling 2021 of the the expanded study area surface and the artificialapproaches the 2.67structures km2. This thattook extension place. Thecaused area to of the artificial earth land filling varies of fromthe study 1.27 km area2 in and Faliro the Bay artificial to structures0.07 km that2 in Anavyssostook place. Bay. The area of artificial land varies from 1.27 km2 in Faliro Bay to 0.07 km2 in Anavyssos Bay. 4. Discussion 4. DiscussionIn the present study, the changes in the coastline of Athenian Riviera were identified during the time interval of 1945–2021. Aerial photos and satellite images were compared inIn a the GIS present environment study, to the record changes and compare in the coas thetline coastlines of Athenian of the years Riviera 1945, were 1960, identified 1972, during1987, the 2010 time and interval 2021. of 1945–2021. Aerial photos and satellite images were compared As a first step the artificial coast of the current coastline of the year 2021 were measured. This type of coast corresponds to 60% of the total length of the coastline (Table1). According to Sengupta et al. [38] the coastal reclamation and the construction of buildings beyond land increase the length of artificial coast line. Therefore the long length of the artificial shoreline in the study area is justified. Moreover, 10% of the European Union’s coastlines are artificial, while more than 8% of the European Mediterranean coastline has been converted into artificial coast [39]. Although, the percentage of artificial coastline of the study area is Water 2021, 13, 2135 15 of 19

Water 2021, 13, x FOR PEER REVIEW higher than the average of Europe, it is probably due to the proximity of the study area16 to of 19 the Athens metropolitan area. In a second step, seven subareas in which human intervention is intense were ex- amined. These areas are: Faliro Bay, Alimos, Glyfada, Voula, Vouliagmeni Bay, Barkiza BayFinally, and Anavyssos the total Bay.changes The in area the in coastlin which thee of highest Athenian changes Riviera in thewere coastline examined. were The lengthobserved of coastline because was of human 87.4 km interventions in 1945 and is 122.1 Faliro km Bay. in 2021. According During to Tablethe past2 the 76 length years, the coastlineof the coastline was enhanced increased by by 40% 287% while from the 1945 land to reclaimed 2021, because to the of thesea artificial area now expansion approaches 2.67of thekm2 land because to the of sea. human The increasedinterventions. rate of The coastline growth was of 3.8,urban more fronts specifically in the coastal because area resultedthe effects this of artificial anthropogenic increase activities of coastline the length length. of the For coastline example increased in Asia, 1% fromYasir 1945 et al. to [41] found1960, from 80% from2000 1960to 2019 to 1972, a rise 10% of 68% from in 1972 the tolength 1987, of 84% artificial from 1987 coastline to 2021 of and Qingdao 22% from in East China,2010 tocompared 2021. The to rates the of total increase length were of 0.06about (1945–1960), 500 km. Chee 6.6 (1960–1972), et al. [42] found 0.06 (1972–1987), 21 km of arti- ficial3.6 (1987–2010),coast in a coastline 2.2 (2010–2020), 106 km-long with ain trend Penang of reduction Island, in growth. Malaysia. Additionally, In the Mediterranean the exten- sion of the land to the sea nowadays occupies an area of 1.27 km2 (Figure 12, Table3). The Sea, Llorens et al. [43] registered changes in southeastern coastline of Spain due to human increase in the length of the artificial coastline as well as the decrease in its growth trend landhas reclaimed been observed to the and sea in otherfrom coastaldifferent urban times areas. (1956–1957 Li et al. [40 and] compared 2014–2016). the coastlines Anthony in [44], reportsXiangshan that Baythe ofMediterranean China and Tampa coastline Bay of ha USAs been from drastically 1985 to 2015 modified and they by resulted human that inter- ventionsthe length over of artificialthe last coastlinetwo centuries. increased These first modifications and then maintained have been stable. notably Additionally, associated withFaliro the bay construction has undergone of marinas, extensive leisure coastline ha modificationsrbours and artificial and is probably beaches, a vulnerableand have re- sultedarea toin athe future emergence sea level of rise. artificial shorelines.

FigureFigure 12. 12. GraphicalGraphical presentation presentation of of land land increase increase inin eacheach examined examined year year for for the the seven seven subareas. subareas.

RegardingMoreover the in the applied other methodol two subareas,ogy, Alimos aerial photos and Glyfada and remote the artificial sensing surfaces data are took often up the coastal area. In Alimos, the length of the coastline increased by 256%, while the used to map and estimate the coastline changes worldwide [33,37,43,45]. Aerial photos artificial interventions covered an area of 0.33 km2 from 1945 to 2021 (Tables2 and3, supply high-resolution images, but they are an expensive and time-consuming process when covering a large area. On the other hand, medium spatial resolution satellite images such as Landsat can be very helpful in the case of provincial, national or global scale tem- poral mapping processes and are available for free of charge [20]. Another advantage of the method is that aerial photos and remote sensing data can easily and quickly combined and processed in a GIS environment. Thus, it can provide fast and reliable results to the estimation of coastline changes.

Water 2021, 13, 2135 16 of 19

Figure 12). It should be mentioned that, after the year 2010, no changes in the coastal zone of Alimos were observed. In Glyfada, from 1945 to 2021 the human interventions caused a 194% increase in the length of the coastline and they cover an area of 0.85 km2 (Figure 12). After the year 2010 no changes in the coastline of Glyfada were recorded. These three subareas are suburbs of Athens and are located close to the city Centre. Thus, they are impacted extent of human activities. As it is shown in Table2, the closer an area is to the capital, the greater the results of artificial interventions in the coastal zone. According to Skilodimou et al. [34] Alimos and Glyfada are locations with high vulnerability to flooding. The elimination of the vegetation cover, the urbanization of the streams and coastal zone, are causes of flooding generation in the study area. Voula is the subarea with important changes in coastline compared to the other rest subareas. In Voula the length of coastline increased by 31%, while the extended area was 0.02 km2 (Tables2 and3, Figure 12). On the other hand Anavyssos Bay recorded the lowest changes in relation to the other subareas. In this region, the length of the coastline increased by 31%, and the artificial extension of the land towards the sea has an area of 0.09 km2 (Tables2 and3, Figure 12). The main changes in the coastlines of the seven subareas were from 1960 to 1987. Exceptions are Faliro Bay where changes in coastline were observed until the present, as well as Alimos where the changes were recognized until 2010. According to [33,34], this is because the coastal reclamation project of the study area started in 1970 and was completed before 1987. Thus, although the intensity of human activities was enhanced in Athens Riviera, the degree of changes in coastlines slowed down from 1987 to 2021. Finally, the total changes in the coastline of Athenian Riviera were examined. The length of coastline was 87.4 km in 1945 and 122.1 km in 2021. During the past 76 years, the coastline was enhanced by 40% while the land reclaimed to the sea area now approaches 2.67 km2 because of human interventions. The growth of urban fronts in the coastal area resulted this artificial increase of coastline length. For example in Asia, Yasir et al. [41] found from 2000 to 2019 a rise of 68% in the length of artificial coastline of Qingdao in East China, compared to the total length of about 500 km. Chee et al. [42] found 21 km of artificial coast in a coastline 106 km-long in Penang Island, in Malaysia. In the Mediterranean Sea, Llorens et al. [43] registered changes in southeastern coastline of Spain due to human land reclaimed to the sea from different times (1956–1957 and 2014–2016). Anthony [44], reports that the Mediterranean coastline has been drastically modified by human interventions over the last two centuries. These modifications have been notably associated with the construction of marinas, leisure harbours and artificial beaches, and have resulted in the emergence of artificial shorelines. Regarding the applied methodology, aerial photos and remote sensing data are often used to map and estimate the coastline changes worldwide [33,37,43,45]. Aerial photos supply high-resolution images, but they are an expensive and time-consuming process when covering a large area. On the other hand, medium spatial resolution satellite images such as Landsat can be very helpful in the case of provincial, national or global scale temporal mapping processes and are available for free of charge [20]. Another advantage of the method is that aerial photos and remote sensing data can easily and quickly combined and processed in a GIS environment. Thus, it can provide fast and reliable results to the estimation of coastline changes. Therefore, engineers, planners and environmental managers may utilize the proposed procedure in the recording and monitoring of the coastline changes. Additionally, it may be used by the local authorities to guide the adoption of policies and strategies aiming towards coastal management.

5. Conclusions The total length of the coastline in Athens Riviera was found to be 122.1 km. Sixty percent of the total length of the coastline are artificial coasts, while rocky coasts and beaches represent 29% and 12% respectively of the total length. Water 2021, 13, 2135 17 of 19

The examination of seven subareas showed that human interventions caused the highest coastline modifications in Faliro Bay. The length of the coastline increased by 287% from 1945 to 2021 and surface of the technically filled area now approaches 1.27 km2. High coastline changes were found in Alimos and Glyfada, while the lowest coastline modification was recognized in Anavyssos Bay. The nearest coastal regions to Athens metropolitan area show the highest modifications in the coastline. The main changes in the coastlines were recorded from 1960 to 1987, with the exception of the coastal area of Faliro Bay and Alimos. The degree of changes in coastline slowed down from 1987 to 2021. The study of the total changes in the coastline of Athenian Riviera shows that during the past 76 years, the coastline was enhanced by 40% while land reclaimed to the sea area approached 2.67 km2 because of human interventions. Engineers, planners and environmental managers may utilize the proposed method in the recording and monitoring of the coastline changes.

Author Contributions: Conceptualization, H.D.S. and V.A.; methodology, H.D.S., V.A. and G.D.B.; software, V.A. and G.D.B.; validation, G.D.B. and E.T.; formal analysis, E.T.; investigation, H.D.S., V.A. and G.D.B.; resources, H.D.S., V.A., G.D.B. and E.T.; data curation, H.D.S.; writing—original draft preparation, H.D.S.; writing—review and editing, V.A., G.D.B. and E.T.; visualization H.D.S., V.A. and G.D.B.; supervision, H.D.S. and G.D.B. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Data Availability Statement: Data that support the findings of this study are available from the corresponding author upon reasonable request. Acknowledgments: The constructive and thorough reviews of anonymous reviewers are warmly ac- knowledged. Conflicts of Interest: The authors declare no conflict of interest.

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