Open Channel Flow

In a channel reach, bed slope is $S_0 = 0.0012$, energy friction slope is $S_f = 0.0004$, and Froude number is $Fr = 0.5$ (so $Fr^2 = 0.25$, $1 - Fr^2 = 0.75$). The water surface slope $\frac{dy}{dx} = \frac{0.0012 - 0.0004}{0.75} = \frac{0.0008}{0.75}$ in dimensionless units (rounded off to four decimal places) is: