Temperature Effects in Low-Transport, Flat-Bed Flows

Experimental data show that a dimensionless bed-load discharge q*b = qb/U*b Dg can be expressed as a function of a boundary Reynolds number R*b = U*bDg/ν and a dimensionless shear stress τ*b = τob/(γs-γ)Dg in which qb = bedload discharge in volume per unit-width and time; U*b = (τob/ρ)1/2 = shear velocity; τob = bed shear stress; ρ = density of the water; Dg = geometric mean size of sediment, ν = kinematic viscosity in the water, and γ and γs are, respectively, the specific weight of water and sediment. Contours of Q*b plotted on a Shields graph (i.e., τ* vs R*b) have the same shape as the Shields curve and the contour, q*b = 10-2, follows it closely. The effect of temperature on τo and qsb is shown by the data. For R*b < 20 increase in the temperature of a flow results in a decrease in τo and τ*b and an increase in R*b, qsg and q*b. For 20 < R*b < 200 an increase in water temperature results in an increase in τob, τ*b and R*b and a decrease in qsb and q*b > 200 there is no temperature effect.