The laboratory data of Saville (1961) give somewhat larger values than those 

 obtained by use of equation (3-72). The net wave setup at the shore is 



Sj^ = AS - S^ (3-75) 



Equations (2-92), (2-93), and (2-94) define dj, in terms of the breaker 

 height Hij , period T , and beach slope m . 



where a and b are (approximately) 



a = 43.75 (l - e-19mj 



1.56 



b = 



(l+e-19-5-) 



Longuet-Higgins and Stewart (1963) have shown from an analysis of 

 Saville 's data (1961) that 



AS = 0.15 d^ (approximately) (3-76) 



Combining equations (2-92), (2-93) , and (2-94) with equations (3-72), (3-73), 

 and (3-74) gives 



1/2 /,„\2 



s"^ {%Y ' 



where 



^W= Q-^^^b- ,, \3/2 ^^-''^ 



64 irdi 



d^ = ~ -nerv (3-78) 



1.56 43.75 (l - e"^^") H^ 



l+e-19-5- gT^ 



Figure 3-50 is a plot of equation (3-75) in terms of ^D^^b versus 



H^/gT^ for slopes of m = 0.02, 0.033, 0.05, and 0.10 and is limited to 

 values of 0.0006 < Hj^/gT^ < 0.027 . 



Wave setup is a phenomenon involving the action of a train of many waves 

 over a sufficient period of time to establish an equilibrium water level 

 condition. The exact amount of time for equilibrium to be established is un- 

 known, but a duration of 1 hour is considered an appropriate minimum value. 

 The very high waves in the spectrum are too infrequent to make a significant 

 contribution in establishing wave setup. For this reason, the significant 

 wave height Hg represents the condition most suitable for design purposes. 



3-102 



