fe, will be transmitted through the breakwater, the transmitted energy is esti- 
mated from an incident spectrum by summing all energy at frequencies lower than 
fe, regardless of where the spectral peaks are located. 
The assumption of independent spectral components seems adequate most of the 
time for such applications. However, for very steep waves or waves in very shal- 
low water the assumption is often incorrect. Cases have been documented in which 
all major spectral components at frequencies higher than the main peak frequency 
are closely tied to the main peak and do not represent independent energy con- 
centrations. The steepness and relative depth criteria in equations (5) and (6) 
can be used to indicate cases where the assumption of independent spectral com- 
ponents may be poor. 
VI. SUMMARY 
This report has presented guidelines for interpreting nondirectional wave 
energy spectra, including a simple method for identifying major spectral peaks 
and for estimating significant wave height, period, and energy for each major 
peak. Each major spectral peak is generally assumed to represent an independent 
wave train. Coarse guidelines are presented for identifying cases where major 
peaks do not represent independent trains. Spectral analysis and display tech- 
niques, and the natural variation of spectra in space and time, are discussed 
to show that the above method for interpreting spectra provides a relatively 
consistent description of general spectral characteristics. The method allows 
a more detailed and accurate description of ocean surface waves than that given 
by a single significant height and period, yet it eliminates much of the formi- 
dable detail of a full spectrum. 
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