Abstract
Abstract. The present contribution constitutes the first comprehensive attempt to (a) record the spatial characteristics of the beaches of the Aegean archipelago (Greece), a critical resource for both the local and national economy, and (b) provide a rapid assessment of the impacts of the long-term and episodic sea level rise (SLR) under different scenarios. Spatial information and other attributes (e.g., presence of coastal protection works and backshore development) of the beaches of the 58 largest islands of the archipelago were obtained on the basis of remote-sensed images available on the web. Ranges of SLR-induced beach retreats under different morphological, sedimentological and hydrodynamic forcing, and SLR scenarios were estimated using suitable ensembles of cross-shore (1-D) morphodynamic models. These ranges, combined with empirically derived estimations of wave run-up induced flooding, were then compared with the recorded maximum beach widths to provide ranges of retreat/erosion and flooding at the archipelago scale. The spatial information shows that the Aegean pocket beaches may be particularly vulnerable to mean sea level rise (MSLR) and episodic SLRs due to (i) their narrow widths (about 59 % of the beaches have maximum widths < 20 m), (ii) their limited terrestrial sediment supply, (iii) the substantial coastal development and (iv) the limited existing coastal protection. Modeling results indeed project severe impacts under mean and episodic SLRs, which by 2100 could be devastating. For example, under MSLR of 0.5 m – representative concentration pathway (RCP) 4.5 of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate change (IPCC) – a storm-induced sea level rise of 0.6 m is projected to result in a complete erosion of between 31 and 88 % of all beaches (29–87 % of beaches are currently fronting coastal infrastructure and assets), at least temporarily. Our results suggest a very considerable risk which will require significant effort, financial resources and policies/regulation in order to protect/maintain the critical economic resource of the Aegean archipelago.
Highlights
Beaches are critical components of the coastal zone; are they significant habitats in their own right (e.g., Defeo and McLachlan, 2013), but they provide protection from marine flooding to other transitional ecosystems and the coastal assets, infrastructure and activities they front (e.g., Neumann et al, 2015)
The spatial information shows that the Aegean “pocket” beaches may be vulnerable to mean sea level rise (MSLR) and episodic SLRs due to (i) their narrow widths, (ii) their limited terrestrial sediment supply, (iii) the substantial coastal development and (iv) the limited existing coastal protection
Under MSLR of 0.5 m – representative concentration pathway (RCP) 4.5 of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate change (IPCC) – a storm-induced sea level rise of 0.6 m is projected to result in a complete erosion of between 31 and 88 % of all beaches (29–87 % of beaches are currently fronting coastal infrastructure and assets), at least temporarily
Summary
Beaches are critical components of the coastal zone; are they significant habitats in their own right (e.g., Defeo and McLachlan, 2013), but they provide protection from marine flooding to other transitional ecosystems and the coastal assets, infrastructure and activities they front (e.g., Neumann et al, 2015). Beaches are very dynamic environments, controlled by complex forcing-response processes that operate at various spatiotemporal scales (Short and Jackson, 2013). They are generally under erosion (Eurosion, 2004; IPCC SREX, 2012; IPCC, 2013), which can be differentiated into (a) longterm erosion, i.e., irreversible retreat of the shoreline, due to mean sea level rise (MSLR) and/or negative coastal sedimentary budgets that force either beach landward migration or drowning (Nicholls and Cazenave, 2010), and (b) short-term erosion caused by storm surges and waves which, may or may not, result in permanent shoreline retreats but can be devastating (e.g., Smith and Katz, 2012; UNECE, 2013). The accelerating MSLR coupled with episodic storm events will aggravate the already significant beach erosion with severe impacts on coastal activities, infrastructure and assets (e.g., Jiménez et al, 2012), and the beach carrying capacity for recreation/tourism (Valdemoro and Jiménez, 2006; McArthur, 2015)
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