Initial Profile 



151. Test TOG was conducted to examine the importance of initial profile on the equilibrium profile and 

 the attempt to reproduce the prototype event. During the base test, T03, a substantial erosional difference 

 was noted between the prototype and model profiles after 40 waves (see Figure 10). Because the difference 

 in profiles is quite significant after a relatively short time into the test, it was thought that part of the 

 prototype profile possibly had evolved as a result of massive slumping during the early portion of the 

 experiment. If this was the case, this type of behavior would not be in similitude in the scaled model 

 because it occurs in a regime controlled more by pore pressure than the fall speed parameter. 



152. The prototype profile measured after 40 waves was molded into the wave tank to serve as the 

 initial profile for test T06. The test was then conducted in the same manner as test T03. Figure 22 

 presents representative prototype-to-model comparisons of the temporal profile development. A complete 

 set of profile comparisons is given in Figure E5 in Appendix E. Other relevant data pertaining to test T06 

 can be found in the appropriate appendices. 



153. After 170 waves (the test was initiated at the 40-wave point) the prototype-to-model comparison 

 seems to be quite good; however, after 370 waves, not as much sediment was being deposited in the 

 offshore region as was observed in the prototype. This is more apparent after 1,650 waves, where a distinct 

 difference is seen between the model and prototype profiles. 



154. Figure 23 shows comparisons between tests T03 and TOG at selected surveying stops. Appendix E 

 (Figure E12) contains the complete set of comparisons. Initially, the two profiles are quite dissimilar due to 

 the different starting condition at 40 waves. Note in particular the difference in berm erosion. However, the 

 two profiles soon started to match more closely as equilibrium was approached, and at the 1,650-wave 

 profile, very little difference was observed. 



155. Placing the 40-wave prototype profile in the wave tank as the initial profile improved the 

 model-to-prototype comparisons for the short-term profile development (several hundred waves), but the 

 resulting profile at the near equilibrium condition was very similar to that of test T03, indicating that this 

 variation had little effect on the ultimate outcome of the experiment. 



156. Uliczka and Dette (1988) discuss prototype-scale movable-bed tests where the only difference was 

 a significantly different initial profile. Comparisons between tests indicated substantial differences in profile 

 development due to the different profile slopes. Gourlay (1980) discusses the differences arising from 

 varying the initial profile and also provides several references that give differing opinions. 



157. In designing movable-bed models, it is wise to approximate the initial condition profile, 

 particularly in the offshore portions, which may affect wave shoaling. However, the results from this test 

 indicate that a certain degree of profile variation in the nearshore portion of the initial profile is permissible 

 without unduly impacting the final outcome of the experiment. 



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