T.M. No. 75 - June 1955 



Mechanics of Bottom Sediment Movement Due to Wave Action 

 by Madfiav Manohar 



Results are presented from an analytical and experimental (labor- 

 atory) investigation of the motion of sediment induced by action of 

 surface waves of large length and small amplitude in relatively deep 

 water. It is found that there are initial and general movements of 

 sediments; and initiation, various stages of development and complete 

 disappearance, of bed ripples. The initial and general motion of 

 small sizes of sediment that occur in the laminar boundary layer 

 are caused by laminar shear, while similar motions of large sizes 

 of sediment are caused by lift forces in a turbulent boundary layer. 

 Ripples in general are not formed unless the flow is turbulent in the 

 boundary layer. All motion in turbulent flow and the various stages 

 of ripple development are found to be functions of a d imension less 

 function representing Intensity of the flow near the bottom. The 

 phenomena of initiation of turbulence and motion of sediment in the 

 boundary layer at the bottom are expressed in terms of surface-wave 

 character i sties. 



T.M. No. 76 - June 1955 



Movement of Sand Around Southern California Promontories 

 by Parker D. Trask 



A series of 19 profiles and 175 bottom samples off three rocky 

 promontories - Points Arguel lo. Conception and Dume - show clearly 

 that sand moves around these promontories. The sand moves in three 

 distinct ways; along the beach and surf zone, in the water from sea 

 level to a depth of 30 feet, and between depths of 30 and 60 feet. 

 Beyond a depth of 60 feet relatively little sand moves. Underwater 

 diving operations at Point Dume indicate that 60 feet is the outer 

 limit of ripple formation and disturbance of the bottom by waves. 



T.M. No. 77 - February 1956 



Behavior of Beach Fill at Ocean City, New Jersey 

 by George M. Watts 



Field survey data taken in connection with a beach fill opera- 

 tion completed in 1952 at Ocean City, New Jersey are presented and 

 analyzed to evaluate the movement and effectiveness of the fill. 

 The rate of loss of the fill substantially exceeded the estimated 

 rate. Conclusions are drawn regarding the reasons for this loss 

 and the need for future work. 



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