BREAKWATER ARMOR DAMAGE DUE TO WAVE GROUPS

The effects of wave groups on damage to the armor layer for non-overto pped, rubble mound breakwaters were analyzed by a large-scale experime nt. Two independent wave grouping parameters were evaluated in the exp eriment: (1) The mean run length correlated with the spectral peakedne ss parameter gamma; and (2) an envelope exceedance coefficient alpha c orrelated with a wave height function H(x, t). The observed damage lev els of the armor layer were found to be correlated with alpha; on the contrary, no significant correlation was found between armor damage an d spectral peakedness parameter gamma, or mean run length. Because onl y 224 damage observations were obtained, the experiment did not allow for a complete and reliable modeling of the armor response under wave group attack. The positive correlation between the envelope exceedance coefficient alpha with armor damage may be of the same order of magni tude as the storm duration, and should be considered in both prelimina ry designs and in analyses of experimental data for armor damage from random waves.