reasonably complete year of data. It seems doubtful that more extensive 

 summaries would be worth the requisite cost and effort until techniques 

 for interpreting and applying spectra are better established. 



This report is intended to provide coastal engineers a better quali- 

 tative understanding of shallow-water waves and spectra as well as pro- 

 viding quantitative information for engineering use. Qualitatively, it 

 provides: 



(a) Perspective on how to interpret shallow-water wave 

 energy spectra; 



(b) numerous examples of high-energy, shallow-water field 

 wave spectra from the U.S. Atlantic, Pacific, gulf, and Great 

 Lakes coasts; 



(c) evidence that the ratio of significant wave height to 

 water depth never approaches the commonly used limit of 0.78 

 in the water depths considered; and 



(d) perspective on the likelihood of relatively high 

 individual waves occurring in succession in a sea state. 



Quantitatively, the report provides the following information helpful to 

 coastal engineers: 



(a) Average spectra corresponding to the more common sig- 

 nificant height and period combinations at each site; 



(b) frequency of occurrence of sea states with major sec- 

 ondary wave trains; 



(c) probability statistics for moments of the sea-surface 

 elevation distribution function, which can be related to prob- 

 abilities associated with instantaneous surface elevations 

 above and below the local mean; and 



(d) a computer program for identifying major peaks and 

 valleys in an irregular signal; it has many potential appli- 

 cations including identification of major peaks in a spectrum 

 and identification of meaningful crests and troughs in a time 

 series of sea-surface elevation. 



A brief discussion of the physical characteristics of shallow-water 

 ocean waves is presented in Section II. Wave gage data collection, 

 analysis, and summarization techniques are described in Section III 

 which includes a discussion of the motivation for grouping spectra by 

 both significant height and dominant period and computing average spec- 

 tra. Spectra computed for several theoretical cases of cnoidal wave 

 profiles are presented for perspective in interpreting field spectra. 

 The choice, computation, and interpretation of spectral parameters and 

 sea-surface elevation distribution function parameters are also dis- 

 cussed in Section III. 



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