The flow specific energy exceeds the critical

energy

Flow energy is dominant over the energy associated with the structure in the channel

There is a sudden change in channel geometry (e.g.

slope, width etc) over a short length of channel

Roughness

exceeds a critical value causing flow to suddenly change depth

Elevation head, hydrostatic head and velocity head

hydrostatic head and velocity head

Elevation head and velocity head

Velocity head only

“X” – Decelerate “Y” - Increase

“X” – accelerate “Y” – Decrease

“X” – Decelerate “Y” – Decrease

“X” – accelerate “Y” – Increase

Always the normal energy

Always the critical energy of the flow

The larger energy value when an energy analysis is performed between two points in the channel flow

Rapidly varied flow (RVF): the flow depth (y), as well as the other parameters change abruptly over a large, near infinite, distance.

Rapidly varied flow (RVF): the flow depth (y), as well as the other parameters change instantly.

Rapidly varied flow (RVF): the flow depth (y), as well as the other parameters change abruptly over a short distance.