hydraulic gradient

(fluid mechanics) With regard to an aquifer, the rate of change of pressure head per unit of distance of flow at a given point and in a given direction.
(hydrology) The slope of the hydraulic grade line of a stream.

The rate of change in hydraulic head with distance.

1. The loss of head per unit distance of flow.
2. In a drainage system, the slope of a drainage line between the trap outlet and vent connection.