Pocket beaches of Elba Island (Italy) – Planview geometry, depth of closure and sediment dispersal

The significance of geometry in natural embayments has been at the center of attention in only a few coastal studies and needs to be analyzed in detail. The present paper focuses on 1) the significance of planform geometry and orientation of embayed beaches and headlands relative to incident wave energy; 2) Depth of closure, whether located inside or outside bays; 3) cross-shore sediment size variation in embayments. Studies were performed in 23 pocket beaches of Elba Island (Italy). The results indicate that exposure to incident wave energy does not determine the orientation of pocket beaches. Regardless of the angle of wave incidence, there is a strong correlation between the orientation of pocket beaches and the alignment of headlands, indicating a static equilibrium. The location of Depth of closure in the embayments shows that bed activity is fully captured inside seven bays, while nine bays are partially closed and seven are completely open. Sediment size data, available for five embayments, suggest an offshore-coarsening trend starting where the depth increase is counteracted by higher exposure to waves. A conceptual model is proposed for this process.