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Unmeasured sediment discharges were computed by subtracting the measured suspended‐sediment discharges at alluvial sections from total sediment discharges that had been either measured at nearby contracted sections or computed from the modified Einstein procedure. Average curves show a general increase of unmeasured sediment discharge per foot of stream width as a function of about the third power of the mean velocity. At constant mean velocity the unmeasured sediment discharge per foot of width generally increases with concentration, especially with suspended sands concentration adjusted for depth of stream Such adjusted concentrations of suspended sands seems t o be reasonably good measures of the availability of sands. This availability is the relative rate of transport of sands for a given condition of flow and is related to particle sizes and cohesiveness of sediments of the stream bed and banks. Relationships of unmeasured sediment discharge to mean velocity and to concentration can be applied successfully in several kinds of sediment computations.

Introduction _______________________________________ Concept of sediment transportation ___________________ Complexity of sediment and streamflow relation-ships__ ______________________________________ Simplifying assumptions.________________________ Bedload discharge ______________________________ Meyer-Peter and Miiller equation___________ Einstein equations __________________________ Bagnold equation.__________________________ Major variables__--____--__-___-_____._____ Suspended-sediment discharge.___________________ Concentration immediately above the bed layer _ Vertical distribution of sediment concentration. _ The classical equation for sediment of one fall velocity._________________________ Theoretical and observed distributions. Equation for flow over dune beds _________ Total sediment discharge..______________________ General methods of computation___________ Fine sediment._____________________________

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PLATE 1. Nomograph for computing .VCRS)m and P. 2. Nomograph for computing iBQn. 3. Nomograph for computing z 2 from Q.'/iBQB=(lt"/J 1 ")(PJ.'+J:/). 4. Vertical distribution of streamflow. 5. Graphfor computing z's for each size fraction from the reference z. 6. Nomograph for computing Qa'(PJ 1 "+J 2 ")/(PJ•'+J2'). 7. Function 1 1 " in terms of A" and z.