Recently, Tuscaloosa received a sustained storm with significant rainfall. The video shows a hydraulic jump (shock) at Lake Tuscaloosa’s spillway (channel flow).

The depth ratio is relatively small. We can compute the Froude number (and the velocity) based on this ratio of depth before and after the jump.

$$\frac{y_2}{y_1} = \frac{-1}{2} + \frac{\sqrt{1+8 Fr_1^2}}{2}$$

For a 10 foot depth before the jump and a 11 foot depth after (generous), the Froude number \(Fr = \frac{v_1}{\sqrt{g y_1}} \) is approximately 1.1. This gives a pre-jump velocity of 20 ft/s. Reasonable based on my video.