8. There is evidence that wave breaking limits the ratio Hg/d at 

 the shallow-water gage locations considered to less than 0.55 rather 

 than the commonly used limit of 0.78. 



9. Individual shallow-water ocean spectra with comparable signifi- 

 cant heights and peak periods are highly variable in shape. 



10. Mean spectra for the same significant height-peak period group 

 show a surprising similarity between locations; however, there is a nota- 

 ble lack of low-frequency energy in gulf and Great Lakes spectra and a 

 lack of high-frequency energy in most southern Pacific coast spectra. 



11. The distribution of individual energy values about the mean 

 energy for each spectral band tends to be nearly Gaussian in the vicinity 

 of the dominant peak but non-Gaussian for low-energy bands away from the 

 peak. 



12. For most exposed ocean locations, a spectrum is more likely to 

 contain major secondary peaks when the period of the dominant peak is 

 long or short than when it has intermediate values. 



13. High values of the spectral-peakedness parameter, Qp, indicate 

 that high waves may be occurring in groups; however, high Qp values in 

 shallow water are usually associated with low-energy wave conditions. 



14. Low values of Q generally indicate that high waves are poorly 

 grouped. However, if the spectrum has secondary peaks which do not repre- 

 sent independent wave trains, Q is not a direct indicator of the extent 

 of wave grouping. 



15. Qp values tend to be higher in the Great Lakes than along the 

 ocean and gulf coasts. 



16. The distribution function for sea-surface elevations in shallow 

 water tends to have more high than low values far from the mean and tends 

 to show less variability than the normalized Gaussian distribution. 

 These features are consistent with cnoidal-type, shallow-water wave 

 profiles. 



VI . SUMMARY 



Digital wave records were obtained from 11 gages at 9 shallow-water 

 sites along the U.S. Atlantic, Pacific, gulf, and Great Lakes coasts. 

 The records were analyzed with a fast Fourier transform procedure to 

 produce energy spectra. Selected spectral parameters, including the 

 number of major spectral peaks and Goda's (1970) spectral-peakedness 

 parameter, and parameters of the distribution function of sea-surface 

 elevations were also computed. The physical meaning of the shallow- 

 water spectrum and computed parameters was discussed and illustrated 

 with three cases of cnoidal wave profiles. 



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