Sediment-level oscillations in the swash zone of a mixed sand and gravel beach

This paper reports on measurements of bed level changes in the swash zone on a mixed sand and gravel beach. Cooden Beach is a macrotidal beach with a spring tidal range of approximately 6 m. The beach is composed of mixed sand and gravel, with mean sizes varying between a minimum of 0.18 mm for the sand fraction and a maximum of 27 mm for the gravel. Bed levels were measured every 10-25 seconds for three hours on both the rising and falling tide. Waves were measured with a co-located pressure transducer. In general, the bed elevation increased on the rising tide and decreased on the falling tide. The high-frequency variation in bed level (3-4 cm in one time step) was nearly as much as the overall amount of bed level change (1.5-9 cm).