ABSTRACT

Alexandrakis, G.; Ghionis, G., and Poulos, S. 2013. The effect of beach rock formation on the morphological evolution of a beach. The case study of an eastern Mediterranean beach: Ammoudara, Greece.

The present work investigates the decadal morphological evolution of a microtidal, perched beach and the effect that beach rock formations can have on coastal morphology. Using historical and recent morphological observations from Ammoudara Beach on the island of Crete, Greece, and numerical modeling, the interaction of beach rock formation and retreating coastline are investigated. The principal feature of the morphological evolution of the coastal zone under investigation has been the transformation of a beach rock formation, initially attached to the shoreface (1950s), to a submerged reef that is aligned subparallel to the present-day shoreline. At present, the beach rock is attached to the shoreface at sea level at the western part of the beach, but it has evolved to a submerged reef toward the east, being approximately 40 m off the shoreline at the central part and ∼70 m off the coastline at the eastern part of the beach. This kind of beach evolution is attributed to the interplay of natural hydrodynamic and sediment transport processes (that have been changing as the beach rock formation evolved to an offshore submerged reef) and to human intervention. The latter is exhibited mainly as changes in the sediment supply to the coastal zone (e.g., reduction in terrestrial freshwater/sediment influx, deterioration of sand dune field, and arbitrary abstraction of beach material). After a period of readjustment of the nearshore hydrodynamics to the changing morphology and vice versa, it seems that, at present, Ammoudara Beach has attained a new morphodynamic equilibrium where the shore-parallel reef acts as a submerged breakwater.

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