Abstract: Energy dissipation ratio of stepped spillways could not reflect the energy dissipation status in detail. In order to reflect the energy dissipation function of steps, the total energy dissipation is divided into two parts energy dissipation of traditional spillways and energy dissipation purely created by steps. The unit height energy dissipation ratio of steps and the proportion of energy dissipation created by steps are calculated. Results demonstrate that the unit height energy dissipation ratio of step is about 0.80%/m- 0.83%/m, uncorrelated with unit discharge and step amount, and has a slight increase of 4.5% with the increment of step height; the proportion of energy dissipation created by steps increases with unit discharge and decreases with the increase of step amount. The decrease in energy dissipation ratio with the increase of unit discharge is because that the energy dissipation of smooth spillway reduces while the energy dissipation of stepped spillway remains unchanged.

Key words: stepped spillway, skimming flow, discharge per unit width, step height, energy dissipation ratio