Flow and bed morphology response to the introduction of large wood for sediment management

Abstract: Submerged vanes alter sediment transport by inducing a secondary circulation without significantly compromising the conveyance capacity of the river. Similarly, large trunks of wood may be implemented in rivers as a means of sediment management, with the additional benefit of improving bio-diversity. A laboratory study is conducted to investigate the effects of large wood (LW) on flow patterns and bed morphology. The effectivity of a traditional vane field is compared to a set-up with screens composed of a stacked pile of wooden cylinders, and a set-up with an array of large individual trunks. Results from experiments with a fixed bed indicate that a reduction of streamwise velocity occurs for all configurations, and is markedly larger for the set-up with an array individual trunks. The trunks are least effective in inducing a secondary circulation and cause higher turbulence and drag. Increased porosity does not significantly influence the effectivity of the sediment management structures. In experiments with a mobile sediment bed, all three experimental set-ups have increased bed elevation conform expectations, but for different reasons. A field of trunks acts as a sediment trap because of strong reduction of the streamwise velocity, without producing a strong secondary flow such as dominant in the other configurations. Screens of large wood may be successfully implemented in rivers, as they are only slightly less effective than traditional vanes. The risk of piping underneath structures and the associated development of scour are points of concern. This dataset contains the ADV data, processed ADV data and bed elevation data measured with a line laser scanner and 3D camer