Sediment Textural Distribution on Beach Profiles in a Rocky Coast. (Estremadura – Portugal)

The Portuguese coast of Estremadura is a cliff dominant coast with small beach systems revealing a lack of sediments. The beach systems' behavior is almost unknown. In this coastal stretch, three beach systems were selected (Sta. Rita, Azul and Foz do Lizandro) to understand sediment textural distribution over shore normal beach profiles. Collected data includes 143 superficial sand samples of the low tide terrace, base of the beach face, beach face and berm crest and 192 morphological beach profiles, between December 2005 and November 2006. The results show the importance of local sediment sources in beach textural distribution, namely cliff lithology and river discharge associated to a heavy rain event. This study reveals the absence of a longshore regional pattern. The textural distribution and maximum variability of the mean grain size along the intertidal morphologies was found to be well correlated between the selected systems. The base of the beach face recorded the greatest variation in sand mean size, contrasting with values observed in the beach face. The berm sediments prove to be considerable different from the grains of other morphologic elements and exhibit positive skewness linked to swash transport dominance over eolian deflation. Similar temporal trends of sediment textural distribution were found between the selected systems.