HOW MUCH DO WE KNOW ABOUT WAVE BREAKING IN THE NEARSHORE WATERS?

摘要

A review is made on the statistical features of breaking waves in the nearshore waters. Physical criteria of wave breaking are discussed with a table of theoretical breaking limit on a horizontal bed. The breaker index for regular waves is not a deterministic but a stochastic value with a certain range of variation. The coefficient of variation increases from 6% for 1/100 slope to 14% for 1/10 slope as the bed becomes steep. The breaker index for random waves is lower than the regular wave index by some 20%. Both indices should be expressed with the parameters of the bed slope and the relative depth h/L0. The wave height distribution becomes wider than the Rayleigh just outside the surf zone, narrower in the middle of the surf zone, and nearly the same near the shoreline. No truncation of the probability density at the breaking limit is observed in the field and laboratory data. The wave height ratios such as H1/10/H1/3 and Hrms/H1/3 vary gradually throughout the surf zone, as demonstrated by the field and laboratory data. Discussions are made on the method of incorporating wave breaking process in numerical models of wave transformation with demonstration of different prediction of wave height decay by various numerical models.