TRANSPORTATION OF BED MATERIAL DUE TO WAVE ACTION 



by 



George Kalkanis , University of California 



ABSTRACT 



A practical method has been developed which can be used to 

 determine the rate of sediment transportation in a layer adjacent 

 to the ocean floor. The method is applicable only when the flow 

 in this layer caused by surface waves is unstable. The waves in 

 question should be of small amplitude and great length, permitting 

 the linearization of the equations of motion. The fundamental 

 principle of the supporting theory is that at equilibrium the sub- 

 merged weight of the solid particle resting on the ocean floor is 

 balanced by the vertical component of the resultant of all the 

 hydrodynamic forces exerted on the particle by the flow above. 

 Both effects of the unsteady mean flow velocity as well as of the 

 turbulent fluctuations are taken into account. The distribution 

 of the lift forces associated with the former was determined 

 experimentally while a statistical approach based on the experi- 

 ence with the same phase of the problem in a steady mean flow was 

 used to determine the latter. Proceeding on the premise that a 

 bed-load function exists for the type of flow we are dealing with 

 here the bed-load equation was developed. From this equation it 

 is possible to determine the rate at which sediment in the bed- 

 layer is shifted by the oscillatory flow across a section of unit 

 width. The concentration of bed material in the layer that at any 

 instance is at a state of oscillatory motion can be determined 

 from the above rate. Finally, this concentration in combination 

 with the velocity distribution in the bed-layer associated with 

 any incidental secondary flow is used to calculate the rate of 

 transportation of bed material in the direction of this flow. 



1. INTRODUCTION 



The purpose of this study is to develop a method by means of which 

 low rates of sediment transport due to the action of surface waves may be 

 predicted with sufficient accuracy. More specifically the waves considered 

 are long waves of small amplitudes in relatively deep water. The problem 

 is of great importance to engineers and scientists as can be witnessed 

 from the considerable amount of research devoted to it especially since 

 the beginning of the century. An extensive survey of the literature, how- 

 ever, revealed that so far the subject has been treated only qualitatively. 



