PART X: CONCLUSION 



251. Guidance for engineering design of coastal structures which can 

 withstand or modify attacking wind waves must ultimately rely on a proper 

 description of sea state. In view of the paucity of complete, shallow-water, 

 sea state observations and the demonstrable importance of wave directionality 

 described by the experiments of Vincent and Briggs (1989) and Kaihatu and 

 Briggs (in preparation), a long-term series of detailed wave field observa- 

 tions has begun at the CERC FRF. A preliminary analysis of 1,046, high- 

 resolution, frequency- direction spectra from the first year of data collection 

 has been done . 



252. Directional distribution characteristics of the observed wave 

 fields have been defined in terms of integral properties of the angular 

 distributions of wave energy at three levels of detail: (a) total energy in 

 the form of the integrated direction spectriim, (b) energy at each frequency 

 from subdivision of the frequency-direction spectra, and (c) energy in 

 isolated modes from subdivision of distributions at each frequency. Distribu- 

 tion parameters have been defined in terms of the angles that bound the four 

 quarters of the directional energy distribution at any given level of detail. 

 In particular, a measure of directional spread is the arc bounding the central 

 half of total energy. A measure of the extent to which a distribution is 

 skewed (higher concentration of energy on one side of a distribution) is 

 determined from the ratio of the arc length bounding the second quarter of 

 total energy to the arc length bounding the third quarter. 



253. This study consists of basic correlation of parameters and 

 evaluation of information from the observed frequency- direction spectra alone, 

 primarily to isolate the geometric properties of spectral shape. Little 

 consideration was given to wave generation or transformation processes. 

 Working data are the set of observed directional distribution functions and an 

 extensive but obviously necessary set of parameters with which to characterize 

 the observed sea states. 



254. In terms of bulk conventional parameters, the observed ocean-wave 

 climate is in the normal ranges of behavior for a shallow, nearshore site 

 adjacent to a broad, shallow continental shelf and subject to forcing by high 

 winds from a preferred quadrant. Bulk peak direction tends to have wide 

 scatter at low energy, reflecting the effects of light, variable winds and 



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