Characteristics of wave reflection spectra

Experimental results of irregular wave reflection from impermeable walls and rubble mound breakwaters suggest that there is a characteristic form of wave reflection spectrum. The results indicate that the reflection coefficient at a particular frequency within a random wave spectrum is determined by an Iribarren number based on that frequency. An empirical relationship between reflection coefficient and local, frequency-dependent Iribarren number is provided for both structure types, although the range of parameters used in the rubble mound tests is limited. Therefore, the reflection coefficient spectrum can be determined from the structure slope, frequency, incident significant wave height, and two fitted coefficients that vary with structure type. Specification of the reflection coefficient spectrum becomes more critical as the width of the incident wave spectrum increases and as the Iribarren number decreases. Otherwise, random wave reflection can be adequately determined using the bulk reflection coefficient across the frequency range of the incident sea.