BRAMATO, S.; ORTEGA-SÁNCHEZ, M.; MANS, C., and LOSADA, M.A., 2012. Natural recovery of a mixed sand and gravel beach after a sequence of a short duration storm and moderate sea states.
Using time-averaged images collected by a high-resolution camera, this paper examines the natural recovery of a mixed sand and gravel beach (Carchuna, Spain) after the passing of a westerly storm (significant wave height, H0 > 3 m; significant wave period, T0 = 7–9 s; 0.19% occurrence per year; duration 36 h), followed by mild to low-energy (H0 < 1 m, T0 = 4–6 s, 33.78%) and moderate-energy (H0 = 1–3 m, T0 = 6–9 s, 15.80%) sea conditions. The response of the beach after two storms approaching from the east (0.28%) is also examined. The analysis focuses on one of the beach horn-embayment cells characterized by a bimodal sediment distribution, which is representative of the beach coastline.
The most significant morphological changes occurred after the westerly storm episode and consisted of a shoreline erosion in the order of 5 m/d with a reduction in the beach slope and the cusp horn cross-shore dimension. In conditions of erosion, the sand on the coastline was rapidly transported cross-shore, exposing the underlying gravel sediments which were dragged a short distance seaward to create a longshore bar. The bar subsequently acted as a natural barrier, which helped to protect the beach from further erosion.
During the mild to low-energy and moderate sea states which followed, the beach rapidly recovered and the coastline morphology showed a visible seaward advancement of the horn with an increase in the width of the cross-shore section in comparison to the initial prestorm profile. Through conditions of accumulation, the sand was resuspended and mobilized onshore, creating a layer of sand along the shoreline and rapidly recuperating the beach to its original state.
Morphologic evolution of Carchuna is further investigated through several parameterizations on the forcing condition and in consideration of sediment distribution and beach bathymetry. The results provide insight into the interrelation between the sand and gravel of a mixed beach, showing that bimodal beaches respond differently to commonly accepted empirical sandy-beach relationships.