K. Khalifehei - Department of Civil Engineering, University of Sistan and Baluchestan, Zahedan, Iran
G. Azizyan - Department of Civil Engineering, University of Sistan and Baluchestan, Zahedan, Iran
M. Shafai-Bajestan - Department of Hydraulic Structures, Faculty of Water Science Engineering, Shahid Chamran University of Ahvaz, Ahwaz, Iran
K. W. Chau - Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Yuk Choi Road, Hung Hom, Kowloon, Hong Kong

Flip buckets are a common configuration for side channel spillways. Similar to other spillways, the flip bucket or ski jump has its disadvantages, among which the scour hole downstream due to the flip bucket jet is the most important. The structure safety and stability may be influenced by the scour holes generated at the downstream side of bucket type energy dissipators. This study has employed an experimental model in order to examine the sediment scour created at the end of flip bucket energy dissipators at various flow rates and tail water depths. A total of ۴۵ experiments were performed under different conditions. The experimental invistigation was conducted at the hydraulic laboratory of Shahid Chamran University in Iran. The main objective of this research was to identify the maximum depth of sediment scour ( ) and the maximum distance of sediment scour hole ( ) from the structures. The results showed that the maximum depth of scour and its distance from the structure increased by increasing discharge. The results of experimental models show that, at the downstream depths ( ) of ۰.۲ and ۰.۳ m, the stack was formed by the scouring at the upstream side of the hole, and at a depth of ۰.۱ m, this stack was transferred to the area after the scour hole. This could be explained by the fact that at downstream depths of ۰.۲ and ۰.۳ m, the rolling flow moved from the bottom upwards in the opposite direction of the water flow and sequestrated the sediments upstream. According to Equation Mean Absolute Relative Error(MARE) proposed relation based on laboratory studies has MARE of about ۳۴.۲%.

Sediment Scour, Sediment transport, Hydraulic structures, Stilling basin, Large dam