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 camera

摘要：潜没式导流板通过诱导二次环流改变泥沙输移过程，且不会显著降低河道过流能力。类似地，大型原木可应用于河道泥沙治理，同时兼具改善生物多样性的额外效益。本研究开展了一项室内试验，以探究大型原木（Large Wood, LW）对水流流态与河床形态的影响。研究对比了传统导流板布设区、由堆叠原木柱组成的筛状结构布设方案，以及单根大型原木阵列布设方案的治理效果。定床试验结果表明，所有布设构型均会降低纵向流速，其中单根大型原木阵列布设方案的流速降幅最为显著；该方案诱导二次环流的效果最差，且会产生更强的紊动与拖曳力。孔隙率提升对泥沙治理结构的治理效果无显著影响。动床试验中，三种试验布设方案均如预期般抬升了河床高程，但成因各不相同：单根大型原木阵列布设区因纵向流速大幅降低而起到泥沙截留作用，并未产生其他布设构型中占主导的强二次流。由大型原木构成的筛状结构可成功应用于河道治理，其治理效果仅略逊于传统导流板。结构下方发生管涌及伴随的冲刷发展风险是值得关注的问题。本数据集包含声学多普勒流速仪（Acoustic Doppler Velocimeter, ADV）采集的原始数据、预处理后ADV数据，以及通过线激光扫描仪与三维相机测得的河床高程数据。