Morfodinámica de una playa mesomareal expuesta con terraza de bajamar (Faro, Sur de Portugal)

Resumo

A field assessment of microtopographic changes and disturbance depth was carried out during a tidal cycle at Faro beach, southern Portugal. This mesotidal beach presents a well developed low tide terrace, wide and flat (tan β = 0.02), and an important (tan β = 0.11) foreshore slope. Erosive processes, related to sea waves, produced a beach profile rotation around mean sea level. Disturbance depth presented great variations according to beach morphology and sedimentology as well as wave characteristics, factors that controlled breaking wave type. Plunging breakers prevailed in the upper and middle foreshore, greatly affecting bottom sediments that recorded disturbance values of 25% of significant breaking wave height. Spilling breakers prevailed in the low tide terrace, with average disturbance values of about 4%. Lastly, values of disturbance depth obtained with two different methods, rods and plugs or rods with loose-fitting washers, were compared. The second method gave higher values of disturbance with coarser sediments.