(1) Nonlinear wave theory (e.g., cnoidal waves) should be studied 

 further. Cnoidal theory fits the data best for wave setdown near breaking. 

 Its use for wave field specification and in radiation stress calculation 

 should be considered in a general higher order current theory. 



(2) Irregular wave theory (e.g., Battjes and Goda theory) should 

 be studied further. Surf zone probability models could be devised to in- 

 clude the wave harmonics observed in nature. Lateral mixing terms must also 

 be included. 



(3) Analytic theories require too many assumptions and thus limit 

 generality and accuracy. Computer solutions are now necessary for both 

 longshore current (one-dimensional) and nearshore circulation (two-dimensional) 

 computations. 



b . Mean Water Level Change . 



(1) First-order (linear) theory gives incorrect results for wave 

 setdown. Cnoidal (nonlinear) theory has been verified to near the breaking 

 limit. Use first-order cnoidal wave theory for normal incidence setdown cal- 

 culations. 



(2) First-order (linear) theory is only verified for wave setup 

 on steep plane beaches (tan 3 - 0.1) where constant y ratio is also observed. 

 Use of a constant y ratio across relatively flat (tan 3 == 0.01) and bar-trough 

 profiles in incorrect. New surf zone energy dissipation models (Battjes and 

 Janssen) used to compute wave setup show promise but need further research. 

 Use of wave setup theory based upon constant y ratio to modify longshore cur- 

 rent formulas gives incorrect emphasis on bottom profile. Nonlinear wave 

 theories for wave setup need further research. 



(3) Special formulas for setdown and setup under oblique wave 

 incidence should be avoided. Solution must be based on coupled two-dimensional 

 equations where wave-current interaction effects are included. 



c. Longshore Currents . 



(1) Use V fi K /gH, sin 2a (K = 0.3-0.6) to roughly estimate the 

 average longshore current. 



(2) The original model by Longuet-Higgins (1970), which gives 

 qualitative results, paved the way for all subsequent versions, but is now 

 relatively incorrect. 



(3) The analytic model of Kraus and Sasaki (1979) should be used 

 for plane beach computations on relatively steep beaches. 



(4) No verified analytical or numerical model exists to compute 

 currents on relatively flat (tan 6 = 0.01) or bar-trough profiles. 



(5) Existing nonlinear and irregular wave current theories require 

 some modification and extensive comparisons with laboratory or field data 

 sets in order to be useful. 



(6) The model of Kraus and Sasaki (1979) should be developed 

 further to include flat and bar-trough profiles plus more general bed-stress 

 formulations. Ntimerical solution methods will then be required. 



(7) Complete strong current large- angle bed-stress formulations 

 should be considered in future models where numerical methods are employed. 

 The model devised by Bijker and v.d. Graff is recommended for further study 

 since fundamental closure coefficient and boundary layer principles are ap- 

 plied. 



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