Author(s): Tin Tin Htwe; Yuji Hasegawa; Hiroshi Takebayashi; Masaharu Fujita
Linked Author(s): Hiroshi Takebayashi
Keywords: Narrow pass; Navigation; Braided channel; Erosion; Deposition
Abstract: This study presents experimental results on navigational braided streams with the same hydraulic condition for without narrow pass and with narrow pass cases. One of the typical features of the Ayeyarwady River near Mandalay City is the braided streams with narrow pass sections. Bed deformation is very active in braided channels and it is very difficult to control the bed geometry to keep the navigable flow depth. Therefore, it is very important for maintenance of fairway to clarify the effect of narrow pass to braided channel geometry. In this study, two 10 cm x 10 cm timber posts are set at both sides of the flume to make a narrow pass section. It is found that erosion is more predominant in without narrow pass case. But the erosion depth did not increase with time and some bars are reformed. On the other hand, the deposition occurred in the channel then it was gradually transferred to the upstream with time. The deposition depth increase with time. Hence, the water discharge over the deposition areas decrease because main flow shifted to the troughs. Sediment deposition around the deposition area increased and the crest of bars on the water surface was protruded. Therefore, the depth of the flow becomes deeper and the spatial change in thalweg become lesser. In this case, the deep water channel could keep for navigation and maintenance of the fairway after some years. The deposition repeated and increased was not only affected by narrow pass but also related to moving characteristics of bed material.
Year: 2018