Upper-Regime Plane Bed

The analysis of a laboratory and field data set for sand-bed channels defines the characteristics of upper-regime plane bed with sediment transport. The occurrence of upper-regime plane bed relates to the laminar sublayer thickness and depends on shear velocity u*, median grain size d50, and grain shear Reynolds number R*. Two different boundary conditions are recognized: (1) Transition to hydraulically smooth when R* < 11.6; and (2) transition to hydraulically rough when R* > 11.6. In the first case, upper-regime plane bed is obtained when u*2≅g , where g is the gravitational acceleration. In the second case, upper-regime plane bed is observed when d50≅ 2 . Temperature effects are possible when R* approaches 11.6, which explains the observations on the Missouri River. Resistance to flow for plane bed with sediment transport increases with the Shields parameter.