ABSTRACT
Now, — AHjAL is the energy or friction slope St (negative because energy is decreasing in the direction of flow), —AzjAL is the bed slope S 0, and Ad/AL is the surface slope relative to the bed. Then —AzjAL — Ad/AL is the surface slope relative to the horizontal datum plane, denoted by Sw; it is of course more commonly referred to as the hydraulic gradient.
