Wave-current interaction off the Holderness coast

In the Holderness Experiment, waves were measured off the Holderness coast (NE England) by various moored instruments during the winters of 1994/95 and 1995/96. The instruments used were bottom-mounted pressure recorders, InterOcean S4DW wave-current meters and Directional and non-directional Waverider buoys. The wave data were examined for the effect of depth and current changes (particularly tidal) on the waves and the effect of waves on the tidal currents. These effects were seen to be significant. Tidal modulation of wave period is particularly noticeable, but effects on wave height and direction were also observed. The amplitude of the tidal current was found to be reduced in periods of high waves. Some of the related interaction mechanisms between waves, tides and surges are examined: in particular the Doppler shift, bottom friction and current refraction. The need to correct for currents in wave analysis in a regime of shallow water with relatively strong tidal currents is noted. It is found useful to look for semi-diurnal modulation of the wave parameters as a means of identifying interaction processes and it is important to use the intrinsic period rather than the absolute (or apparent) period in examining the interaction mechanisms.