wave height variations are all automatically produced as part of the calcu- 

 lation procedure. The unsteady asymetrical currents and instantaneous water 

 surface variations as solutions to the governing equations are only obtain- 

 able with the aid of large high-speed computers. Solution techniques and 

 applications are in their infancy. Wave breaking and surf zone simulations 

 have yet to be implemented. Nonbreaking solutions have indicated signifi- 

 cant differences with linear theories of wave height variation (Snell's 

 Law, diffraction) to require additional experimental data for analysis. 



The state-of-the-art summary of all the theories and experiments is 

 presented below, 



a. Mean Water Level Changes . Generally, the results are for normal 

 wave incidence which in itself greatly limits their practicality. The 

 original theory for wave setdown on plane beaches, based upon linear theory 

 radiation stress, sometimes referred to as first-order theory, cannot be 

 substantiated by the experiments. Consequently, equation (3) and its 

 variations (eqs. 31 and 32) are incorrect. The nonlinear theory (Svendsen 

 and Hansen, 1976) using first-order cnoidal wave theory and given by 

 equation (155), has been verified right up to the breaking limit. It is 

 repeated here 



n = - 



2g 



--0.35J--1.9- 



A computer-based solution would facilitate and should be no deterrent to 

 Its use. The irregular wave models of Battjes (1974a) or Goda (1975) also 

 derived setdown values close to measured data. 



The original theory for wave setup as given by equation (35) can only 

 be verified for relatively steep plane beach slopes (tan 3-0.1). It 

 makes use of a constant breaker height-to-depth ratio y i'^ the surf zone 

 which also has only been verified under steep beach conditions. Wave 

 steepness is also a factor. Consequently, use of equation (35) and varia- 

 tions therefrom (eqs. 68 and 69) should not be generally applied to long- 

 shore current theory as a correction for wave setup effects. This result 

 is contrary to the popular belief that the theory applies to spilling 

 breakers on dissipative-type (relatively flat) beaches. In fact, it has 

 only been verified on steep laboratory beaches with plunging-type breakers. 



The nonlinear setup theory of James (1973, 1974a) requires further 

 experimental verification. No cnoidal theory in the surf zone has been 

 attempted. 



The irregular wave setup theory of Battjes (1974a) could not be con- 

 firmed by laboratory experiments although it gave reasonable agreement with 

 limited field data. However, later efforts of a similar nature by Battjes 

 and Janssen (1976) in which a more sophisticated, hydraulic jump model of 

 surf zone dissipation was employed (eqs. 44 and 124) resulted in good to 



223 



