FIND : The range of depths where breaking may start. 



SOLU TION ; The breaker height can be found in Figure 7-3. Calculate 



^o 1.5 



— - = ii^ = 0.00153 



gT^ (9.8) (10)^ 



and enter the figure to the curve for an m = 0.05 or 1:20 slope. Hr/H' 

 is read from the figure 



Hi 



h:= '•" 



Therefore 



H^, = 1.65(h^)= 1.65 (1.5) = 2.5 m (8.2 ft) 



2 

 Hj,/gT may now be computed 



^b 2.5 



gT^ (9.8) (10)^ 



= 0.00255 



2 

 Entering Figure 7-2 with the computed value of Hr/gT the value of a is 



found to be 1.51 and the value of g for a beach slope of 0.050 is 0.93. 



Then 



^^b W = " % = ^-^^ ^2.5) = 3.8 m (12.5 ft) 



(^b)rnin = ^ "b = °-^^ ^^-^^ = 2. 3 m (7.5 ft) 



Where wave characteristics are not significantly modified by the presence of 

 structures, incident waves generally will break when the depth is slightly 

 greater than ^'^}^^rm'n ' ^ wave-reflection effects of shore structures 

 begin to influence breaking, depth of breaking increases and the region of 

 breaking moves farther seaward. As illustrated by the example, a structure 

 sited on a 1 on 20 slope under action of the given incident wave 

 (H' = 1.5 m (4.9 ft); T = 10 s) could be subjected to waves breaking 

 directly on it, if the depth at the structure toe were between (di ) . = 

 2.3 m (7.5 ft) and (d^),,,^^ = 3.8 m (12.5 ft) . '^^ 



NOTE: Final answers should be rounded to reflect the accuracy of the original 

 given data and assumptions. 



*************************************** 



b. Design Breaker Height . When designing for a breaking wave condition, it 

 is desirable to determine the maximum breaker height to which the structure 

 might reasonably be subjected. The design breaker height F^ depends on the 

 depth of water some distance seaward from the structure toe where the wave 

 first begins to break. This depth varies with tidal stage. The design 



7-8 



