abruptly in one-minute intervals. An energy comparison shows that the 

 continuously changing wave delivers about 1.5% more energy than the waves 

 of the tests having a fixed time interval between wave period changes. 

 This result is therefore inconsistent with the two general findings of 

 more energy - more transport and decreasing time intervals - more transport, 

 and consequently cannot be explained in terms of the quantity of energy 

 delivered by the waves or the time interval of wave variability. Since 

 most laboratory tests have been run with a single constant wave period, 

 this general finding has considerable implication in the interpretation of 

 earlier results. This variation in wave period is, of course, more nearly 

 a modeling of actual wave conditions, although still greatly different from 

 the true wave spectrum generated in nature. 



(f) Measurement of Suspended Material in Laboratory Wave Tanks. 



Additional suspended sediment samples were obtained (under wave action) 

 utilizing a pump-type sampler in a wave flume testing lower specific gravity 

 coal rather than sand. It is hoped that these measurements may aid in de- 

 fining scale relations and prototype measurements. Comparison is being made 

 with measurements of sand in suspension under the same wave conditions, and 

 with waves scaled upward according to the settling velocity of the sediment. 

 A few suspended sediment samples were also taken in the large wave tank with 

 waves of 2 to 5 feet in height in conjunction with tests on beach deformation. 



(g) Equilibrium profile, beach deformation, and model scale effect 

 studies. 



Testing was continued in a small tank utilizing low specific gravity 

 material (crushed coal) to study the effect of scale on movable bed models 

 under wave, action. The specific gravity of the coal was chosen so as to 

 model the settling velocity of the sand used in earlier large scale tests. 

 Profiles derived from these tests appear to bear basic resemblance to the 

 profiles obtained with the large (5.5-foot) waves on a sand beach, partic- 

 ularly in the nearshore area shoreward of the breaker. Some of the dif- 

 ferences observed may be attributable to the variation in specific gravity 

 of individual coal grains , although the average specific gravity of the 

 coal is as desired. 



A series of beach deformation tests were initiated in the large wave 

 tank, using waves of 2 to 6 feet in height acting on a Ion 15 beach slope 

 of 0.4-mm median diameter sand. The profiles resulting from these tests 

 will be compared with tests made some years previously with 0.2-mm diameter 

 sand. The immediate purpose of the tests was to enable estimates of the 

 greater width of beach fill required for smaller grain sand sizes to pro- 

 vide protection equivalent to coarser sands, with application to require- 

 ments for emergency protection following the east coast storm of March 

 1962. However, the results should also serve the broader purpose of 

 advancing our knowledge of beach deformation under wave action in general, 

 and also of general scaling relationships. Because of the impracticability 



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