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Fig. 1 Location map showing also the observed maximum width and the sediment texture classification (percentages in relation to the total) of the (71) beaches with increased touristic potential at the northern, eastern and southern coast of E. Crete under great pressure. In 2011, there were more than 2.8 million direct foreign tourist arrivals at the island airports with 2.16 million tourists landing at the eastern Cretan Heraklion airport (SETE 2012); these tourists form only a part of the annual, highly seasonal tourist influx that has to be accommodated and use the eastern Cretan beaches as environments of leisure. Cretan geology is dominated by pre-alpine and alpine formations that constitute a complex nappe and Neogene sediments that fill the basins forming between the moun- tains (Fytrolakis 1980). The island forms the central (and largest) island of the Cretan Arc, an island chain bounded by deep basins both to the north (Cretan Sea) and the south (Ionian and Levantine Basins); the Cretan Arc straits control the water exchanges between the Aegean Sea and the Eastern Mediterranean (Tsimplis et al. 1999; Velaoras et al.2014). The climate is of ‘Mediterranean type’, ie., cool and wet in the November—March period, and hot and dry in the May—September period. The annual wind field is dominated by a prevalence of northerly winds, which show a double maximum: the first during winter (December— February) and the second (known as the ‘Etesians’) during summer (July and August); recent studies project increases in the mean wind speeds of the area in the following decades (Weisse et al. 2014). Astronomical tides are small (few tens of cm on springs) and offshore wind waves are associated with average and extreme storm wave heights of less than 1.5 m and more than 6 m, respectively. With regard to storm surges, these are generally moderate in the Eastern Mediterranean, having heights that rarely exceed 0.4 m (Tsimplis and Shaw 2010).

Figure 1 Location map showing also the observed maximum width and the sediment texture classification (percentages in relation to the total) of the (71) beaches with increased touristic potential at the northern, eastern and southern coast of E. Crete under great pressure. In 2011, there were more than 2.8 million direct foreign tourist arrivals at the island airports with 2.16 million tourists landing at the eastern Cretan Heraklion airport (SETE 2012); these tourists form only a part of the annual, highly seasonal tourist influx that has to be accommodated and use the eastern Cretan beaches as environments of leisure. Cretan geology is dominated by pre-alpine and alpine formations that constitute a complex nappe and Neogene sediments that fill the basins forming between the moun- tains (Fytrolakis 1980). The island forms the central (and largest) island of the Cretan Arc, an island chain bounded by deep basins both to the north (Cretan Sea) and the south (Ionian and Levantine Basins); the Cretan Arc straits control the water exchanges between the Aegean Sea and the Eastern Mediterranean (Tsimplis et al. 1999; Velaoras et al.2014). The climate is of ‘Mediterranean type’, ie., cool and wet in the November—March period, and hot and dry in the May—September period. The annual wind field is dominated by a prevalence of northerly winds, which show a double maximum: the first during winter (December— February) and the second (known as the ‘Etesians’) during summer (July and August); recent studies project increases in the mean wind speeds of the area in the following decades (Weisse et al. 2014). Astronomical tides are small (few tens of cm on springs) and offshore wind waves are associated with average and extreme storm wave heights of less than 1.5 m and more than 6 m, respectively. With regard to storm surges, these are generally moderate in the Eastern Mediterranean, having heights that rarely exceed 0.4 m (Tsimplis and Shaw 2010).

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ensemble (combined s appears to give tighter particularly for the two 0.82 m). Therefore, and hort- and long-term ensembles) predictions (see Fig. 3c and 3d) lower SLR estimates (0.26 and as the analytical (mostly long- term) and the numerical (short-term) morphodynamic models are equally represented in the ensemble, the unified ensemble was preferred for providing a rapid assessment of the beach retreat risk in the study area. The mean projections (by all six models) were used to provide estimates of the beach retreat/erosion risk for the
ensemble (combined s appears to give tighter particularly for the two 0.82 m). Therefore, and hort- and long-term ensembles) predictions (see Fig. 3c and 3d) lower SLR estimates (0.26 and as the analytical (mostly long- term) and the numerical (short-term) morphodynamic models are equally represented in the ensemble, the unified ensemble was preferred for providing a rapid assessment of the beach retreat risk in the study area. The mean projections (by all six models) were used to provide estimates of the beach retreat/erosion risk for the
Fig. 4 Predictions of beach retreat due to 0.26 and 0.82 m SLRs for the Analipsi beach on the basis of the means of the analytical and numerical model ensembles
Fig. 4 Predictions of beach retreat due to 0.26 and 0.82 m SLRs for the Analipsi beach on the basis of the means of the analytical and numerical model ensembles
‘ig. 5 Retreats of E. Cretan yeaches for SLRs of, a 0.26 m, » 0.82 m and, c 1.86 m rojected by the model nsemble. Final width values ess than zero indicate beaches hat will retreat by more than heir entire dry beach width. 3each ID progresses clockwise
‘ig. 5 Retreats of E. Cretan yeaches for SLRs of, a 0.26 m, » 0.82 m and, c 1.86 m rojected by the model nsemble. Final width values ess than zero indicate beaches hat will retreat by more than heir entire dry beach width. 3each ID progresses clockwise
Table 1 Projections of the cross-shore beach retreats on the basis of mean predictions from all six models of the unified ensemble an comparisons between the estimated retreats with the observed maximum beach widths of the investigated 71 E. Cretan beaches hydrodynamic information and validated by appropriate synoptic field observations. Thirdly, the analysis has not considered other beach erosion factors, such as geological controls, coastal sedimentary budgets and extreme event duration and sequencing (Revell et al. 2011), as we presence of beach defenses and beach protecting ne l as the arshore ecosystems (Peduzzi et al. 2013). Fourth, the models used predict beach retreat, but not inundation; althoug run up is dealt within the numerical models h wave of the ensemble, its effects are reflected in the results only if it induces sediment transport and morphological c hanges. Nevertheless, wave run up-induced inundation that does not necessarily result in beach erosion may also pre cipitate significant damages and should be an important manage- ment consideration (Jiménez et al. 2012; Hoeke et al. However, there are c onstraints. First, the collected topographic information was ‘instantaneous’ and not syn- optic; it was collected in and May 2012 and during tions. Therefore, although small due to the microtid terranean, they could still different times in October 2011 different tidal and wave condi- tidal effects can be regarded as al regime of the Eastern Medi- be uncertainties regarding the E. Cretan beach spatial characteristics; these, however, cannot be avoided when working at large spatial scales (Allenbach et al. 2014). Secondly, a assumption that beaches with no lateral and/or of: 1 predictions are based on the comprise a sediment reservoir, fshore sediment losses; this is, however, an issue that can be studied only using detailed 2D and/or 3D morphodynamic modeling that will be based on detailed morp hological, sedimentological
Table 1 Projections of the cross-shore beach retreats on the basis of mean predictions from all six models of the unified ensemble an comparisons between the estimated retreats with the observed maximum beach widths of the investigated 71 E. Cretan beaches hydrodynamic information and validated by appropriate synoptic field observations. Thirdly, the analysis has not considered other beach erosion factors, such as geological controls, coastal sedimentary budgets and extreme event duration and sequencing (Revell et al. 2011), as we presence of beach defenses and beach protecting ne l as the arshore ecosystems (Peduzzi et al. 2013). Fourth, the models used predict beach retreat, but not inundation; althoug run up is dealt within the numerical models h wave of the ensemble, its effects are reflected in the results only if it induces sediment transport and morphological c hanges. Nevertheless, wave run up-induced inundation that does not necessarily result in beach erosion may also pre cipitate significant damages and should be an important manage- ment consideration (Jiménez et al. 2012; Hoeke et al. However, there are c onstraints. First, the collected topographic information was ‘instantaneous’ and not syn- optic; it was collected in and May 2012 and during tions. Therefore, although small due to the microtid terranean, they could still different times in October 2011 different tidal and wave condi- tidal effects can be regarded as al regime of the Eastern Medi- be uncertainties regarding the E. Cretan beach spatial characteristics; these, however, cannot be avoided when working at large spatial scales (Allenbach et al. 2014). Secondly, a assumption that beaches with no lateral and/or of: 1 predictions are based on the comprise a sediment reservoir, fshore sediment losses; this is, however, an issue that can be studied only using detailed 2D and/or 3D morphodynamic modeling that will be based on detailed morp hological, sedimentological
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