Swash, groundwater and sediment transport processes on a gravel beach

The morphodynamics of a steeply sloping gravel beach in the south western UK (tanβ = 0.15–0.2; d50 = 6 mm; ξb = 1–4) were measured during low energy wind-wave conditions (Hb < 0.5 m). Measurements of water depth, groundwater-level, waves and currents, concurrent with observations of morphological change and swash sediment loads, were successfully obtained over two spring-to-neap tidal cycles and used to investigate the short-term evolution of gravel beach morphology. Incident frequency motions dominated the hydrodynamics since wave transformation was concentrated at the base of the beach. Subharmonic energy was of secondary importance at most, never exceeding 15% of the total energy. Standing edge waves were generally absent since the lack of swell waves limited their forcing, and there was c. 50% reflection of the gravity-band energy. [Continues.]