The abrupt increase in depth of rapidly flowing water is called hydraulic depth.Flow at the jump changes from a supercritical to a subcritical stage with an accompanying loss of kinetic energy. The change in depth occurs over a finite distance, known as the length of jump. The upstream surface of the jump, known as the roller, is a turbulent mass of water.
The depth before a jump is the initial depth, and the depth after a jump is the sequent depth. The specific energy for the sequent depth is less than that for the initial depth because of the energy dissipation within the jump.

F=[ d₂²- d₁²]w/2

where d₁ =depth before jump, ft (m)

d₂ =depth after jump, ft (m)

w=unit weight of water, lb/ft³ (kg/m³)