Discharge that occurs in a natural stream channel. Streamflow velocity varies with distance from bed; with distance from banks, downstream, and over time. Channel geometry affects turbulence, and thus velocity, and hydraulic jumps and drops affect velocity and depth. Variations in streamflow affect the amount and type of geomorphic work a river can do. The driving force is gravity, which varies with channel gradient; the resisting forces are the viscosity of the water; the Reynolds number; Manning’s roughness coefficient; and the Froude number.

See Rantz et al. (1982) US Geol. Surv. Water-Supply Paper 2175, 631 on the measurement and computation of streamflow.