The Hydraulics and Morphodynamics of a Flooded Meandering Channel

Abstract

Meander dynamics has been the focus of river engineering for decades; however, it remains a challenge for researchers to precisely visualise natural evolution processes especially in alluvial plains. The evolution of meandering channels is a complex geomorphological process driven by the interactions between flow and alluvial channel beds and banks. The presence of vegetation along a riparian zone added the complexity of geomorphological process. Riparian vegetation is a major roughness element that influences channel morphology, decreases the average flow velocity and physically traps material that transported in alluvial rivers. A laboratory experimental investigation was carried out in Universiti Teknologi Malaysia in order to understand the flow behaviour and morphodynamics for a riparian vegetated flooded meandering channel. The morphological patterns visualisation and river channel profile changes estimation for pre and post flooding were obtained using digital close range photogrammetry technique. The findings prevailed that riparian vegetation had induced higher resistance to the flow and forced the flow to take place in main channel and right flood-plain while reduced the left floodplain flow velocity. The presence of riparian vegetation combined with the river bed morphology had increased the Manning’s n in left flood-plain. The influence of riparian vegetation on the sediment movement in the compound meandering channel was also identified. The sedimentation was 45% increased, while erosion decreased about 31% as the floodplain was roughened by vegetation.