Impact of Establishment Distance of Permeable Protective Groyne on Local Scouring Depth Control of the Nose on a Series of Vertical Impermeable Groynes

One of the most important criteria for designing groynes is the stability of groynes during floods passing around them. To be able to protect the riverbank, the groynes should maintain their stability over the years. One of the main reasons for groynes instability is the local scouring around them. In this study, to protect and reduce the maximum local scouring depth of the nose of a series of impermeable groynes, a permeable protective groyne (PPG) is installed upstream. For this purpose, the maximum local erosion depth of the nose of series of impermeable groynes was determined under laboratory conditions and the scour depth in two cases without protective groyne and with protective groyne at five different distances i.e. L', 1.5L', 2L', 2.5L', 3L' (L': Protective groyne Length) at the upstream side of the first groyn was determined and evaluated. The results show that the establishment of permeable protective groyne at the upstream of a series of impermeable groynes with equal length at 3L' distance from the first groynes reduces the maximum local scouring depth of the first groyne by 34.3% at 3L' distance from the first groynes.