Chapter 3 

 THE LAWS OF SEDIMENT TRANSPORTATION 



H. A. Einstein 



and 

 J. W. Johnson 



Division of Mechanical Engineering 



University of California 



Berkeley, California 



It appears basically impossible to separate the description of sedi- 

 ment transport from that of erosion and deposition of the same par- 

 ticles, since erosion represents the initiation, and deposition the termi- 

 nation, of any sediment motion. However, if the term sediment trans- 

 portation laws is used in the specific sense, that is, restricting the de- 

 scription of the relationships which link the rate of sediment motion at 

 any flow section to the parameters of the flow and its boundaries, this 

 separation is fully justified. It is in this sense that the transportation 

 laws may be defined for the purpose of this chapter. 



It has been shown in Chapter 1 in this symposium that sediment 

 particles may differ in many respects, such as size, shape, specific grav- 

 ity, roundness, mineralogical composition, to mention only a few. For 

 the purpose of transportation studies, a knowledge of the size, settling- 

 velocity, and specific gravity of a grain is sufficient. Even at that, 

 this may represent grain types which behave in three different man- 

 ners.* The realization that each sediment mixture may contain all 

 these different grains at any possible frequency makes it clear that a 

 sediment mixture may be a very complex unit. It is not surprising 

 that under these conditions sediment mixtures cannot always be 

 treated as a unit, but that some part of a mixture may be moved in 

 the same flow according to entirely different laws than is some other 

 part. 



* The terminology proposed by the American Geophysical Union (see Transac- 

 tions, Vol. 28, Dec. 1947, p. 936) has been adopted in this chapter. 



62 



