The movement of sediment which rolls and creeps along the bed of a river, and is known as bed load, is analyzed using basic physical principles of fluid dynamics. The conditions for the start of sand‐grain movement are set down and form an important part of the analysis. The turbulence mechanism in the flow above the bed plays a most significant role in the analysis of rate of bed‐load movement. The final equation developed for the rate of sediment transport is not empirical; all the numerical constants in it are definite physical measures either of the sediment or of the hydraulic and turbulence characteristics of the river. The equation fits laboratory and field data obtained for a wide variety of conditions by various experimenters.

The general theory of the vertical distribution of suspended sediment in a turbulent water stream has been sufficiently well established to permit its use in making calculations of the suspended material transportation in connection with engineering problems. It is the purpose of this paper to present simplified methods for making the necessary calculations of the total amount of sediment transported in suspension in a river or canal. Field‐data is presented for purposes of checking the validity of the various approximations made, and to indicate the accuracy of the proposed calculations.

It has been known for some time that if the average concentration of suspended sediment at any point in a wide straight stream was known, the average concentration at any other point could be determined. This was first demonstrated by O'Brien ]see 1 of ”Bibliography“ at end of paper] using the methods developed by Schmidt in a study of turbulence in the atmosphere. That the results obtained with this method agree with actual observations in streams and channels was demonstrated by Christiansen ]2[ and Richardsen ]3[. For artificial turbulence it has been checked by Hurst ]4[ and Rouse ]5[.

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