Downstream change of velocity in rivers

Because river slope generally decreases in a downstream direction, it is generally supposed that velocity of flow also decreases downstream. Analysis of some of the large number of velocity measurements made at stream-gaging stations demonstrates that mean velocity generally tends to increase downstream. Although there are many reaches in nearly all rivers where mean velocity decreases downstream, the general tendency for conservation or for downstream increase was found in all data studied.

Computations of bed velocity indicate that this parameter also tends to increase downstream.

Near the streambed, shear in the vertical profile of velocity (rate of decrease of velocity with depth) tends to decrease downstream. This down-valley decrease of shear implies decreasing competence downstream.