determine within broad limits, the effectiveness of a wall in repelling 

 these waves. 



The theoretical attack (by Munk)^°^ on the problem of breakers 

 has concentrated on the analogies between an oscillatory wave near 

 breaking and a so-called solitary wave . "The application of the solitary 

 wave theory was su^ested. . ,by an obvious resemblence between the 

 theoretically derived wave profile and the observed profile in the region 

 just outside the breaker zone." Actually, a solitary wave is a single 

 plus whose length is infinite o However, most of its energy is concentra- 

 ed about the crest, and in this manner resembles an oscillatory wave 

 about to break. The assumption here, is that a breaking oscillatory wave 

 is independent of following or preceding waves. Its wave length in the 

 breaker zone is not a determining parameter for the wave's character- 

 istics. There are two relations of importance derived from the applica- 

 tion of solitary wave theory to oscillatory waves of finite lengthy 

 that the relative height of a breaker is dependent only on the initial 

 steepness of the incident wave. 



(1) ^ 



= 1 



and that the ratio of depth of breaking to breaker height is constant. 



(2) db/Hb = I'^SS 

 therefore 



(3) db/Ho = db/Hb X Hb/Ho = lo28 1 



3.3 fHo/Lo 



Graphs drawn from relationships (1) and (3) are shown on Figures 

 1 and 2. Their most noteworthy aspect is the dependence of breaker 

 parameters on the initial steepness of the waves . The ratios between 

 breaker height and deep water wave height and between breaker depth and 

 deep water wave height increase with decrease in initial steepness. 

 This may be interpreted to mean that on a given beach, a steep wave will 

 break at a point before one less steep, and, before breaking, will have 

 a smaller growth in proportion to its original height. 



All observations, though with a large amount of scatter, have con- 

 firmed the existence of these general tendencies. 



Two compilations of empirical data should be noted which have a 

 bearing on this discussion of breakers. The first (7) is s. plot of a 

 great number of breaker obser-vations made both in the laboratory and in 

 the field. Through these points (which show a great deal of scatter) 

 is drawn an average curve for db/Ho vs. Hq/Lo and Hb/Lo vs. Ho/Lq. 

 (See Figures 1 and 2. Both curves lie fairly close to those developed 



