considered for examining the decay of the transport rate distribution with 

 time. However, since the shape of the transport rate distribution also varies 

 with time, a peak transport rate may not be the best overall indicator. 

 Instead, the average absolute transport rate Q^^ along the profile was used 

 since it provided a better measure of all transport activity along the 

 profile. The average absolute transport rate was calculated as 



^1 



(19) 



where x^ is the seaward limit of profile change. 



323. Figure 38(a and b) shows the decay of Q^ with time for the CE 

 and CRIEPI experiments . The general trend was for rapid decay during the 

 first 10 hr , followed by a slower decrease with elapsed time. The approach to 

 zero transport was slow at longer elapsed time since small adjustments in the 

 profile occurred even if the profile had attained a near-equilibrium shape. 



324. In many of the CRIEPI cases, Q^^ was small from the beginning of 

 the run, since the initial beach profile was close to the equilibrium shape. 

 The maximum occurring for one of the CE cases (Case 700), just before 20 hr, 

 approximately coincided with a decrease in wave height that took place during 

 the experiment (Kraus and Larson 1988a) , forcing the profile toward another 

 equilibrium condition. The general conclusion made based on Figure 38(a and 

 b) is that the equilibrium concept is valid and that a numerical model 

 developed for simulating realistic beach profile change must include this 

 property. 



Peak offshore transport 



325. To quantify the time decay of the transport rate distribution as a 

 function of wave parameters and sand size, the peak onshore or offshore 

 transport rate is a good target quantity since the peak rate has a clear 

 physical meaning. Figure 39 plots the peak transport rate as a function of 

 time for 16 of the CE cases. For cases with strong erosion, decay with time 

 of the peak offshore transport rate was much more pronounced than for cases 

 with mainly accretion on the foreshore. If onshore transport prevailed, the 



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