Author(s): Chang-Lae Jang, Ellis Penning, Gi Jung Kim, Hyo Hwang, Yonguk Ryu
Linked Author(s): Chang-Lae Jang
Keywords: Vegetation, Morphodynamics, numerical modelling, suspended sediment concentration.
Abstract: This study investigated the effects of vegetation on flow, sediment distribution and morphodynamics via the outdoor laboratory experiments and 2-D numerical simulation. At the dense vegetation zone, flow velocity decreased severely and diverted toward unvegetated channel due to the high drag by vegetation. Flow is accelerated along the patch after diverging flow between the patch and the open channel. Maximum velocity pattern along the channel was meandering. At the sparse vegetation zone, however, the alternated flow pattern was not clear due to the low drag in the vegetation zone. The thalweg of the bed is meandering shape, and was relatively agreed with the maximum velocity pattern. Suspended sediment concentration was high in front of vegetation reach. However, the concentration was low at the outlet of vegetation reach because of the low velocity in the vegetation zone. The bed aggraded in the lee of vegetation patch. At the lee of dense and sparse vegetation regions, bed material size was fine at the aggradations region and coarse at the degradation region. The riparian vegetation reduced the suspended sediment transport capacity and changed the sediment profile according to the water depth. The suspended sediment concentration is 50 mg/L at 50 m from upstream. However, the concentration is reduced to 29. 5 mg/L at 86 m of dense vegetation patch. The vertical profiles of suspended sediment concentration from the bed are that the concentration is higher at 0. 4 m than at 0. 2 m in the dense vegetation patch. However, the concentration is lower at 0. 4 m than at 0. 2 m in the sparse vegetation patch. The numerical results are in reasonable agreement with the experimental results, capturing the most important characteristics of the alternate bar
Year: 2017