movement on the steeper beach may be in excess of that on the more 

 gentle (1 on 20) slope, depending somewhat on the deep water wave 

 characteristics. Measurements on the steeper slope also indicate 

 that the rate of movement may be increased by including in the 

 transported material a very small portion of silt or mud-sized 

 material; this indication is also in general agreement with results 

 of studies in turbulence tanks and of transport in some rivers. Tests 

 on this beach also involved a period of starving and then overfeeding 

 the beach to determine the rate of movement of the erosion hole and 

 slug of excess material along the beach. Results of the tests made so 

 far with groins indicate generally that considerably more must be kncwn 

 about the movement of material along the unencumbered beach before the 

 effects of the groins can be definitely separated quantitatively. 

 Accordingly, tests now underway are being directed primarily toward 

 studying the relation of rate of littoral movement to the incident wave 

 characteristics and to the beach characteristics. 



(e) Measurement of Suspended Material in Laboratory Wave Tanks 



A report "Suspended Sediment Sampling in Laboratory Wave Action" 

 was published as Technical Memorandum No. 115 of the Board. This 

 report tabulates and discusses measurements of suspended sediment 

 made under controlled conditions in the laboratory, both with waves 

 of small (several inches) and large (several feet) height. Measure- 

 ments made on the effect of water temperature on the amount and type 

 of material in suspension, and the rate at which beach deformation 

 takes place, are also discussed in the report. 



(f ) Wave Theory 



Work continued at the Board on basic wave theory with particular 

 emphasis on the determination of design wave criteria. A report 

 describing theoretical distribution functicms and comparing them with 

 observed wave conditions is in preparation. This report also indicates 

 analytical functions describing families of wave spectra based on the 

 distribution functions determined. These spectra are compared with 

 others proposed and with observed data. 



(g) Equilibrium Profile and Model Scale Effects Studies 



Crushed coal having a particle distribution size the same as the 

 0.2-mm. material previously tested in the large tank, and having a 

 specific gravity of 1.5, was obtained. The specific gravity is scaled 

 to that of the sand in the large tank by settling velocity ratio. A 

 single test has been performed with this coal at a 1 to 10 model of 

 large tank conditions. A preliminary look at the profile results of 

 this test seems to indicate that the coal beach reacted similarly to 

 the sand beach for the first hour or so, but then deteriorated much 

 more rapidly and to a much greater degree than the large-scale test. 



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