X(em) 



Figure 54. Comparison of wave setup for irregular waves and theory of 

 Battjes (after Battjes, 1974a). 



to measured data. A thorough investigation of possible reasons for the dis- 

 crepancy was made by Battjes (1974a). Air entrainment was ruled out after 

 separate tests proved this effect was not significant. Battjes concluded 

 that because of the uncertainty regarding the laboratory system to measure 

 the setup, it is not known whether the differences are real or apparent. 



166 



