Observations and model simulations of wave‐current interaction on the inner shelf

Wave directions and mean currents observed for two 1 month long periods in 7 and 2 m water depths along 11 km of the southern shoreline of Martha's Vineyard, MA, have strong tidal modulations. Wave directions are modulated by as much as 70 ° over a tidal cycle. The magnitude of the tidal modulations in the wavefield decreases alongshore to the west, consistent with the observed decrease in tidal currents from 2.1 to 0.2 m/s along the shoreline. A numerical model (SWAN and Deflt3D‐FLOW) simulating waves and currents reproduces the observations accurately. Model simulations with and without wave‐current interaction and tidal depth changes demonstrate that the observed tidal modulations of the wavefield primarily are caused by wave‐current interaction and not by tidal changes to water depths over the nearby complex shoals.