Jet Flow on Stepped Spillways

This technical note presents a method to estimate the energy loss on stepped spillways for the jet‐flow regime, which occurs when the ratio of the critical depth $y_c$ to the height of the step $h$ is less than approximately 0.8. It introduces the concept of $\alpha$, the proportional energy loss per step, and using the extensive experimental results of Horner, $\alpha$; was evaluated. It was found that $\alpha$ is a function of $y_c/h$ and $h/l$, where $l$ is the length of the step; and an equation has been developed that describes this variation. It was also found that the energy loss on a stepped spillway with a large number of steps can be very significant in the jet‐flow regime. It also appears that for skimming flow, which occurs for $y_c/h$ larger than about 0.8, the average energy loss per step would be less than that for jet flow.