Energy Loss Promotion of Stepped Spillways Based On Step-Pool Formation In High Gradient Mountain Streams

The most important characteristic of a stepped spillway compared to other kinds of spillways is the high energy dissipation. The understanding of head loss, evaluation and promotion of energy dissipation are the basis of more research. In this study, a new step-pool formation is designed in stepped spillway based on natural high gradient mountain stream bed formation. Residual energy downstream of both the step-pool stepped spillway and the normal stepped spillway are measured in the hydraulic laboratory of the School of Engineering of Shiraz University. For new design, the experiments were made at two slopes, under six discharges and six step-pool configurations. Therefore, a total of 72 tests were performed. Based on this laboratory results, it was concluded that the step-pool (compound) stepped spillway caused an extra 30% reduction in energy dissipation compared to the simple stepped spillway. This result confirms the optimization of natural steppool formation for stepped spillways.