Author(s): Dehghani Amir Ahmad; Barzali Mohsen; Koichi Suzuki; Fazloula Ramin
Linked Author(s): Koichi Suzuki
Keywords: Series of groynes; Scouring; Temporal evolution; L-head
Abstract: The groynes are structures projected from the river bank into a stream to deflect the flow away from the bank. Groynes prevent erosion of the bank and establish a more desirable width and channel alignment. By deflecting the flow away from the bank and causing sediment deposits, a groyne or a series of groynes may protect the river bank more effectively than the other protecting structures. Due to the contraction of the flow area, the local velocity increases and the scouring around groynes will develope. The literature review reveals that most of the studies have been conducted on the straight groynes, and little information exists on local scouring around L-head groynes. In this study, the temporal evolution of scouring profile along the channel was investigated experimentally. The flow pattern around a series of groynes shows that there are 3 recirculation regions between groynes which pick up the sediment from the bed and suspended the sediment particles. The results also show that sediments deposit between groynes until 30 minutes after starting the experiments, and after 80 minutes scouring was observed between first and second groynes and sedimentation was observed between second and third groynes. After 200 minutes, the scouring was extending to the space between second and third groynes, and the process continued untills 23 hours. In an equilibrium condition, the maximum scour depth between first and second groynes is greater than the scour depth between second and third groynes.
Year: 2009