(b) Model Materials Evaluation . 



(1) Pulverized PVC sieved to provide a desired size distribution 

 proved to be totally unsuccessful as a model material because o£ surface- 

 tension effects. 



(2] Pumice, although better than PVC, was not a satisfactory 

 model material; pumice abrades and its density varies when submerged. 



(3) Rocklite appears to be a potentially useful model material; 

 however, more comprehensive tests are required to determine its usefulness. 



(c) Equilibrium Profiles . 



(1) The initial beach slope influences the final stable profile 

 shape . 



(2) The position of the longshore bar on stable profiles produced 

 by identical wave conditions was not repeatable. 



(3) The validity of the concept of profile equilibrium (as usu- 

 ally understood) and of model laws based upon assumed equilibrium, are 

 doubtful . 



(d) Noda's (1972) Model Law . 



(1) The model law failed the verification tests. The shape of 

 the offshore and inshore zones was not reproduced and the movement of the 

 shoreline was not correctly predicted. 



(2) The slope of the foreshore zone (from the SWL intercept to 

 the toe of the foreshore) was correctly predicted in three of the four 

 verification tests. 



(3) Noda's empirical approach may be useful in establishing scale 

 relationships for other well-defined reference lengths of the nearshore 

 profile. 



2. Recommendations . 



(a) The use of model materials which have strongly bimodal or very 

 narrow unimodal size distributions should be avoided. 



(b) The use of model materials which have smooth spherical grain 

 shapes should be avoided. 



(c) The concept of the equilibrium profile needs further investigation. 



(d) Rocklite needs further evaluation as a potential model material. 



(e) Noda's (1972) model law apparently predicts only the slope of the 

 foreshore; its general use is not recommended. 



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