Field Observation of the Wave-Induced Water Particle Velocity in the Surf Zone

Field experiments were conducted in the surf zone of bar-type bottom profile. Surface elevation, wave angle and vertical distribution of horizontal water particle velocity were measured simultaneously. The results show that the horizontal velocity fluctuation has different characteristics according to the vertical position. Therefore in this paper a three layer (surface, middle and bottom) model is proposed to explain the observed fluctuation characteristics.The on-offshore average velocity shows a vertical distribution similar to the two-dimensional net flow pattern observed by Horikawa et al. (1972) in a laboratory experiment, in contrast to a uniform distribution in the longshore component.It is also shown that the wave angle (the direction of the wave crest line) is rather well calculated by using records of the velocity near the bottom in the surf zone.