Varied flow

From Glossary of Meteorology

varied flow

Used to describe nonuniform flow conditions in open channels and conduits, with changing cross section or slope with distance.

When discharge is constant, the velocity changes with changes in slope and cross section. Relatively slow changes are known as gradually varied flow and are strongly influenced by surface resistance. Dramatic changes in velocity and depth occurring over a very short distance are known as rapidly varied flow and surface resistance effects are small.