I1.2, In using Figure 16, the mean wave height of a group of ugyes 

 should first be found hj use of equation 10, The diagonal line correspond- 

 ing to Hjn is followed to its intersection with the vertical line labeled 

 (say) 95 percent. The height which irill not be exceeded hj 95 percent of 

 the waves in a group whose inean height is Hj^ is read on the vertical scale. 

 In the exanple on the graph this height is 5 feet where B^ is 2,5 feet, 



[i3. Breaking IJaves . - At a certain point in its advance toward shore 

 a wave becomes unstable, peaks up, and breaks. The water motion changes 

 from a Isminai:' orbital flow to turbulent, iriiite-XT-ater conditions. The 

 determination of point of breaking and brealclng wave heights is of major 

 inportance in the plannj.ng and designing of shore protection measures, 



hh* Three different sets of curves are currently used to determine 

 breaking depths and wave heights on brealcLngj one theoretical, and two 

 erpirical. The theoretical curve is derived from the analysis of a so-called 

 solitary wave and results in the following equations? 



\ 1 



-^o' 3.3 ^H 'A„ (11) 





= 1.2P (12) 



1.28 



3.3 ¥ h' 'A (13) 



Graphs drawn from these relations as well as those from the two other 

 studies ax'e presented in Figure 17 and 18. All three cvxve sets relate 

 the breaker depths d, and the breaker i-xave height R to deep water wave 

 length L and deep water wave height, H ', which would exist if refraction 

 were ignored, (Khoxri.ng the deep water wave height H and the refraction 

 coefficient K, K ' maj be determined from H ' = K H 7« The solid line 

 curves include the additional pararaeter of Bottom slope , tlie effect of 

 which was adequately verified under controlled laboratory conditions, 



I1.5. To use the curves on Figures 17 and 18, H ' is determined as 

 above, L from the Icnown relationship L (in feet) = 5,12 T^, and the 

 beach slope from hydrographic charts. By conputing the ratio H '/L 



the ratios d /H and E /H • m^y be picked off the graph and, from these, 

 d, and H, determined by multipication by H ' . 



^■^* Diffrg-ction of V/aveS o - Diffraction in rater waves is that 



phenomenon whereby energy is trsiisf erred latera].ly along a wave crest. It 



is most noticeable where an otherwise regular train of waves is interrupted 

 by a barrier such as a brealwater. 



