Longitudinal distribution of slope and sediment characteristics in headland -bay beaches in Cadiz, Spain

Headland-bay beaches are systems with an asymmetric curved planform that develop downdrift of a natural or artificial coastal headland. These beaches have some common features found along the coasts of the world, presenting a well differentiated zonation. The main objective of this work is to elucidate how parameters such as grain size, sorting and beachface slope in the different zones (shadow, central and distal sectors) determine the final morphology of the beach. For this purpose, twelve headland-bay systems in the coast of Cadiz (South Spain), with contrasting wave and tide regimes, were monitored in order to analyze the longitudinal gradient in slope and sediment distribution. Topographic surveys were conducted and sediment samples were collected and analyzed for grain size. Shore-normal transects were surveyed with a RTK-DGPS (Real Time Kinematics-Differential Global Positioning System) and beach slope was computed on each sector of the beaches. Three sediment samples were taken in each transect, corresponding to the dry beach, the high intertidal zone and the lower intertidal zone. A total of 152 topographic profiles and about 456 sediment samples were analyzed. All this information has allowed to gain insight into how the different parameters vary along the twelve headland-bays, as well as to establish common trends among them and to see how these parameters affect the final morphology of the beach. In a further step, future work will be focused on the detailed analysis of wave processes on each system, in order to more accurately determine the relations between the above parameters and the hydrodynamic regime.