ESTIMATING WAVE-INDUCED BOTTOM VELOCITIES AT VERTICAL WALL

A linear theory equation is presented for estimating water velocity parameters beneath reflected, two-dimensional, irregular, nonbreaking waves as a function of the incident wave spectrum, water depth, and spatial location. The estimation procedure requires specification of wave reflection and phase shift as a function of frequency. For the special case of normally incident, unidirectional, nonbreaking irregular waves being perfectly reflected by a vertical wall, the equation provides estimates of near-bottom (above boundary layer) fluid particle velocity parameters as a function of only the incident wave spectrum, water depth, and distance from the wall. Comparisons between laboratory fluid velocity measurements and velocity estimates based on the measured incident spectrum are good for this special case. Furthermore, the distribution of peak horizontal velocities compares well with estimates based on the Rayleigh distribution. For two cases of a TMA spectrum wherein the significant height and peak period vary but other shape parameters are held constant, explicit formulas are given to estimate maximum bottom velocity parameters as a function of water depth, peak period, and significant height.