"dx~ 



0. 



0.05 



0.02 



0.01 



0.002 



0.001 



T 1 1 I I I I 



Gourlay 



Smith 



0.005 - ^^" \^"' 



Bowen et al. 



Putnam 



■ I I I I I I 



0.01 0.02 0.05 0.1 0.2 



tan /5 BED SLOPE 



Figure 48. Wave setup versus bed slope: all experiments versus theory of 

 van Dorn (1977) (after Gourlay, 1978). 



Because of these observed differences between theory and observation, 

 the assumptions for the theory are now being studied further. Wind (1978) 

 used 23 MWL readings on a 1:40 slope in the 'laboratory to compute S^^^^ by 

 direct integration of equation (28) from the shoreline toward deep water. 

 In the horizontal (deepwater) section, linear wave theory gives radiation 

 stress levels about 10 to 20 percent greater than found from the data. On 

 the slope, in the surf zone, the linear wave theory was found to give 

 estimates for S^^^ + S^.^^ (i.e., the orbital velocity components) about 

 three times smaller than measured values, found by subtracting the observed 

 potential energy density, S^^^ from the total radiation stress, S • 



160 



