Author(s): A. B. M. Faruquzzaman Bhuiyan; Richard D. Hey
Linked Author(s): A.B.M. Faruquzzaman Bhuiyan
Keywords: Hydraulic structure; J-vane; River restoration; Bank protection; Mobile bed; Scour; Deposition
Abstract: The effectiveness of instream J-vanes for river restoration and bank protection in meander bends have been investigated in a laboratory study. The experiments were carried out in a large scale meandering mobile bed channel with a bed composed of graded materials. Detailed data on three-dimensional velocities around the structures, bed load transport, erosion-deposition and corresponding cross-sectional shape changes have been collected. If a single or an array of such vanes are installed in the channel the scour hole at the outer bank was infilled and a deeper channel was formed with coarser substrate away from the outer bank. These influences extend further upstream and downstream of the location of the structures. The structures modify the flow pattern so that a counter rotating secondary flow cell is formed near the outer bank. In contrast to common spurs, no large scale horizontal vortices are generated behind the structures. The longitudinal slope of water surface does not change significantly due to the structure and lateral water levels show slight variations which are related to the generation of eddies. Structures which grade to the bed from bankful level at the bank show better performance than low level ones where multiple structures show positive effects through the bend as far as the next crossover. Following installation of the structure bed material is transported along the evolving thalweg but afterwards transport occurs mainly over the point bar. The flow structure, downstream vortex pattern and erosion-deposition characteristics induced by the vanes should be considered thoroughly before this type of structure is recommended for habitat improvement and bank stabilisation.
Year: 2001