X = T H, = (4.0 -9.25 m)H, 

 p p b ^ ' b 



(7-4) 



where m is the nearshore slope (ratio of vertical to horizontal distance) 

 and T = (4.0 - 9.25 m) is the dimensionless plunge distance (see Fig. 7-1). 



Region where Breaking Storts 



Xp = Breaker Travel 



Wave Profile ot Start 

 of Breaking 



SWL 



Wave Profile when Breoking 

 s Nearly Complete 



Figure 7-1. Definition of breaker geometry. 



Analysis of experimental data shows that the relationship between depth at 

 breaking dj, and breaker height Hj, is more complex than indicated by the 

 equation dj, = 1.3 Hj, . Consequently, the expression dj, = 1.3 h.-, should not 

 be used for design purposes. The dimensionless ratio d^/Hj, varies with 

 nearshore slope m and incident wave steepness Hj,/gT as indicated in 

 Figure 7-2. Since experimental measurements of d^p/Hj, exhibit scatter, even 

 when made in laboratory flumes, two sets of curves are presented in Figure 

 7-2. The curve of a versus Hj|/gT represents an upper limit of 

 experimentally observed values of ^h^^b ' hence a = (d^/Hi )^i2jj. . 

 Similarly, 3 is an approximate lower limit of measurements of dj,/Hj, ; 

 therefore, 3 = (di /H, ) . . Figure 7-2 can be used with Figure 7-3 to 

 determine the water depth in which an incident wave of known period and 

 unrefracted deepwater height will break. 



**************** * EXAMPLE PROBLEM 1************** 



GIVEN : A Wave with period T = 10 s , and an unrefracted deep-water height of 

 H^ = 1.5 meters (4.9 ft) advancing shoreward over a nearshore slope of m = 

 0.050 (1:20) . 



7-5 



