Mapping the Shoreline Evolution in Response to Sea Level Rise Along Agadir Bay, Morocco: Geospatial and Empirical Approach

Global warming resulting from meteorological and oceanic perturbations manifests itself, among other things, in the rise of sea level and the increase in the energy of marine storms, as well as their frequency. The IPCC predictions put forward the probability of sea level rise (SLR), which could even exceed 1m by 2100 for the most pessimistic scenarios (i.e., RCP8.5). As a result, coastal erosion events will increase. Sandy coasts are generally considered to be sensitive to erosion and SLR. They become more vulnerable when they are heavily occupied by socio-economic activities and marine structures. To predict Agadir's bay shoreline movement due to erosion and sea level rise in the long term (2100), we used multi-date aerial photographs to initially deduct the historical rates of shoreline movement (1969–2016) and spatially delimit eroding areas and accreting areas, using Digital Shoreline Analysis System (DSAS). The calculated and geospatialised rates were then used to predict the displacement of the shoreline by 2100, using the empirical models of (Bruun in J Waterways Harbors Div 88:117–130, 1962) adjusted by Ferreira (2006) as well as the IPCC projections. The results show a considerable impact of marine structures on the erosion, balance and accretion processes along Agadir Bay (7 km), which reach 38%, 20%, and 42%, respectively. The shoreline prograde in the northern zone (1.35 m/year), and retreated in the south (− 1.54 m/year). Predictions of shoreline displacement by 2100 under RCP8.5 reveal a potential risk for tourist infrastructures bordering the sea (hotels, cornices, etc.) and call on coastal managers to develop protection and adaptation strategies. The predicted average setback rates of the shoreline are between − 16.8 m and − 33.7 m for 2050 and 2100, respectively, exceeding the width of the beach in several localities.