previously described (Part VI), the optimvun K-value for the LWT calibration 

 was determined to be 1.6 10"^ m*/N. For the field data, a value of 0.7 10"^ 

 m^/N proved to give the best agreement. Three cases had a best fit for 0.9 

 10'^ m''/N, whereas the remaining case gave 0.4 10"^ m*/N. 



493. A smaller value of the transport coefficient is not unexpected 

 since the coefficient showed an inverse dependence on wave period for the LWT 

 experiments, and wave periods in the field data were somewhat longer than in 

 the LWT data set. Calibration of K using the LWT data set is somewhat 

 biased toward shorter period waves. Use of the K-value determined from the 

 LWT data caused the beach profile to respond too quickly and the bar to become 

 too pronounced, not having the smooth character of the field measurements. 

 Transport induced by irregular waves that exist in the field, i.e., wave 

 heights and periods varying above and below the representative monochromatic 

 (but time-varying) waves used in the model, is also expected to alter the 

 value of the transport coefficient, as both transport thresholds and mean 

 rates will be different (Mimura, Otsuka, and Watanabe 1987). From these 

 considerations, the amount of change in K between LWT and field calibrations 

 is surprisingly small . 



494. Values of other empirical coefficients appearing in the various 

 transport rate relationships were kept at the values given by the LWT calibra- 

 tions. In the breaker decay model, the stable wave height coefficient was set 

 to r = 0.4 as for the LWT calibration, whereas a wave decay coefficient of k = 

 0.13 gave better agreement between measured and simulated profile evolution. 



A smaller wave decay coefficient is expected for the FRF data compared to the 

 LWT data since this coefficient depends slightly on beach slope (Part V), and 

 the field profiles had more gentle slopes than the LWT profiles. The stable 

 wave height coefficient was also varied, but the simulation was insensitive to 

 changes in this parameter. 



495. The breaking criterion developed from the LWT data caused waves to 

 break too far offshore, creating a bar farther seaward than found in the 

 measurements. Instead, a constant value of the breaker ratio of 1.0 was 

 applied, which gave a better description of the bar location. In the breaker 

 criterion derived from the CRIEPI data set, the slope seaward of the break 

 point was used. At the seaward side of the bar the slope was normally 



207 



