Alongshore variations in morphology and incident wave energy on a human-impacted coast: Agadir, Morocco

Aouiche, I.; Daoudi, L., Anthony, J.A., Sedrati, M., and Dussouillez, P., 2016. Alongshore variations in morphology and incident wave energy on a human-impacted beach: Bay of Agadir, Morocco. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No.75, pp. 1027 - 1031. Coconut Creek (Florida), ISSN 0749-0208. Beaches in developing countries are increasingly affected by human impacts, notably the construction of harbors and tourist infrastructure. In Morocco, the city of Agadir is a fine example of this situation. Agadir was destroyed by an earthquake in 1960 (5.7 on the My scale and 60,000 dead). The Agadir city front corresponds to a semi-sheltered bay that has been strongly impacted by economic development and rapid (> 10% a year) demographic growth in the course of its recovery following this earthquake. The northern sector of the bay is sheltered by a commercial harbor constructed in 1988. In order to understand how this harbor has affected sediment circulation, the morphology and hydrodynamics of the beach have been monitored since 2012. This study discusses beach morphological variations between the harbor-sheltered northern sector and the exposed southern sector. The offshore and nearshore wave regime, analysed using the MIKE 21 coupled model Fm, is largely dominated by waves approaching from the north. The modeling results show that wave energy attenuation between the inner shelf and the shore in the northern sector ranges from 30% to 80% as a result of diffraction caused by the harbor breakwater, whereas the southern sector is exposed to much higher waves. Two digital elevation models obtained in March 2012 and April 2015, confirm these expected results from the alongshore wave-energy gradient, and show that the northern sector of the beach is largely dominated by accretion, whereas the southern sector is undergoing erosion.