Spatial and temporal patterns of sediment activation depth on a high-energy microtidal beach

Sediment activation depth, by means of continuous temporal high-resolution sampling and tide-to-tide (DOD rods) field data were collected during six low tide conditions on a high-energy microtidal sandy beach. A large swell event also occurred during the experiment where offshore wave heights of 6m were measured. Waves at the intertidal zone reached heights of 0.30 m and periods 5 s during the pre- and post-storm scenarios; whereas waves achieved height values of 0.60 m and periods of 6 s during the swell event. The sediment activation previous to the swell event reached values of 0.035 m, whilst during the storm increased to 0.24 m, and finally once the beach had recovered and the tidal range increased, the sediment moving layer was 0.062 m in depth. The use of DOD rod data reveals a spatial gradient in sediment activation depth where the maximum activation depths are recorded at mean high water position at each high tide giving Gaussian-like distribution of activity across the beach width. As the daily tidal range increased during the experiment, the location of the highest activation depth also advanced landward with this increase.