Bragg reflection of ocean waves from sandbars

[1] Resonant Bragg reflection of ocean surface waves by a field of natural shore-parallel sandbars was observed in Cape Cod Bay, MA. Waves transmitted through the bars were reflected strongly from the steep shoreline, and the observed cross-shore variations in the onshore- and offshore-directed energy fluxes are consistent with theory for resonant Bragg reflection, including a 20% decay of the incident wave energy flux that is an order of magnitude greater than expected for wave-orbital velocity induced bottom friction. Bragg reflection was observed for a range of incident wave conditions, including storms when sediment transported toward and away from nodes and antinodes caused by the reflecting waves might result in growth and maintenance of the sandbars.