described secondary waves (called salitons by Galvin) and their effects. 

 Although secondary waves were observed on the wave records, these waves 

 were not analyzed in this study; wave height variations due to secondary 

 waves did not affect the wave height data presented here. 



2. Profile Eqmlibrium . 



The experiments were extended over several hundred hours in hopes of 

 defining the equilibrium profile for the given wave and sediment condi- 

 tions. At the end, there was no indication that either experiment was 

 close to equilibrium (see Figs. 7 to 14). In experiment 71Y-10 the 

 profile had great lateral variation, which seemed to be getting con- 

 tinually more complex. 



The decreasing water temperature at the end of the experiments, 

 increasing the viscosity and presumably the sediment-carrying capacity 

 (Chesnutt, 1975; Chesnutt and Stafford, 1977), may have contributed to 

 the continuing erosion and lack of equilibrium. However, the lack of 

 an increase in recession rate at the times of the sharpest temperature 

 drop seems to discount this explanation. The continually changing dis- 

 tances between the wave generator and parts of the profile (foreshore and 

 offshore) causing variations in re-reflection and secondary waves may 

 also have prevented the profile from reaching equilibrium. 



To further complicate the question of profile eqmlibrium, Collins 

 and Chesnutt (1975, 19 76) showed that, even with constant water tempera- 

 ture, the final, unchanging profile for the same wave and sediment condi- 

 tions was not always repeatable. 



A constant rate of volume erosion might be an acceptable alternative 

 to profile equilibrium for defining steady-state conditions in some 

 coastal engineering experiments, but that may also be affected by water 

 temperature and other variables. 



3. Other Laboratory Effects . 



The differences in test conditions (tank width, initial test length, 

 and the loncont rolled water temperature) provide possible explanations 

 for the differences in rate of profile development discussed in Section 

 III,l,c, but also prevent a rigorous proof of the effect of any one of 

 these differences as definite causes. Chesnutt (1975) discussed the 

 effects of initial test length and water temperature. 



a. Water Temperature . The water temperature varied from 29° to 1° 

 Celsius for the experiments which began in May and June and continued 

 into early December. The dynamic viscosity varied from 1.7 x 10"^ to 

 3.0 X 10-5 pounds-second per square foot (7.98 x 10-3 ^g 14. 30 x lO'^ 

 grams-second per square centimeter). The existence of a temperature 

 effect seems to be disproven by the data presented in this study. How- 

 ever, the possibility of a temperature effect prevents the drawing of 

 strong conclusions about, profile equilibrium and other laboratory effects, 



98 



