iONCun>HisoiNS 



"M) 



Figure 70. 



Comparison of irregular theory of Collins (1972) with unsteady 

 field data (after Meadows, 1977). 



to fit the data set employed, whereas Kraus and Sasaki (1979) matched 

 Vjjj so that Cf and V could be computed. Some previous efforts to summarize 

 values have appeared in the literature. Table 8 lists the major formu- 

 lations and results. 



a. Bed Friction Coefficients . The coefficients found for bed shear- 

 stress models must be approached with caution. No satisfactory formulation 

 exists and the user must apply coefficients consistent with the model type, 

 beach slope, laboratory or field situation, etc. under consideration. In 

 any event, values ranging from 0.001 to 0.06 have been applied. For the 

 weak current small- angle (linear) model used in early investigations, it 

 is generally true that C^ decreased with flatter beach slopes as found 

 in the field. In fact, Komar (1975b, 1976b) argued that the ratio tan 3/C^ 

 is approximately constant. This argument has been attacked on physical 

 grounds by Longuet-Higgins (1972b) and also experimentally by Huntley (1976) 

 and Kraus and Sasaki (1979). 



185 



