River regime

River regime can describe one of two characteristics of a reach of an alluvial river:

The latter is described by the fact that the discharge through a river of an approximate rectangular cross-section must, through conservation of mass, equal

where is the volumetric discharge, is the mean flow velocity, is the channel width (breadth) and is the channel depth.

Because of this relationship, as discharge increases, depth, width, and/or mean velocity must increase as well.

Empirically-derived relationships between depth, slope, and velocity are:

refers to a "dominant discharge" or "channel-forming discharge", which is typically the 1–2 year flood, though there is a large amount of scatter around this mean. This is the event that causes significant erosion and deposition and determines the channel morphology.