Sediment transport partitioning in the swash zone of a large-scale laboratory beach

• Sheet flow flux estimates exceed suspended sediment flux.
• Depth-integrated sediment transport is dominated by suspended load during uprush.
• Sediment transport rates could not be estimated during the latter stages of backwash due to shallow water.

Swash zone sheet flow and suspended sediment transport rates are estimated on a coarse sand beach constructed in a large-scale laboratory wave flume. Three test cases under monochromatic waves with wave heights of 0.74 m and wave periods of 8 and 12.2 s were analyzed. Sediment flux in the sheet flow layer exceeds several hundred kg m− 2 s− 1 during both uprush and backwash. Suspended sediment flux is large during uprush and can exceed 200 kg m− 2 s− 1. Instantaneous sediment flux magnitudes in the sheet layer are nearly always larger than those for suspended sediment flux. However, sediment transport rates, those integrated over depth, indicate that suspended load transport is dominant during uprush for all cases and during the early stages of backwash except in the case for the 12.2 s wave case when the foreshore was steeper. Results could not be obtained for an entire swash event and were particularly truncated during backwash when water depths fell below the elevation of the lowest current meter.