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Flow Characteristics of Compound Open Channel Flow with Discontinuous Flood Plain

Author(s): Md. Ashiqur Rahman; Md. Munsur Rahman; Shampa; Anisul Haque; Md. Maruf Dustegir; Nusrat Jahan Nishat; Hajime Nakagawa; Motaher Hossain

Linked Author(s): Hajime Nakagawa

Keywords: Bandal-like Structure; Sedimentation; Jamuna River; ADCP; Braided River

Abstract: In sand-bed braided Jamuna River, the performance of conventional structures have shown mixed experiences of failure/success to protect the erodible river bank. While, bandal-like structures (traditionally used for increasing navigation depth) might be an alternative measure of bank protection and stabilize the minor channels in a long term scale. Laboratory experiments confirmed the potentiality of bandal-like semi-permeable structures to accelerate the near bank sedimentation and mid channel bed degradation. Nevertheless, performance of bandal-like structures in real-world unsteady regime is not confirmed yet. Therefore, a set of prototype bandal-like structure was implemented along the right bank of 1500 m reach of the Jamuna River at Kazipur in Bangladesh to investigate spatial and temporal changes of flow field and sediment deposition around the structures during high and low flow period. Measurements were executed during high (July) and low flow (November) period over the river reach using ADCP and Echo-sounder to capture the changes of flow and sedimentation. It is found that during the period of monsoon (July, 2018), near bank bed was elevated by about 5~6 m behind the structure. However, as the water level goes higher during the monsoon, high velocity (2~3 m/s) impaired the structure due to excessive scouring (~7 m) and vortex from the toe of the structure. The structure was eventually washed away and subsequently the deposited sediment was also washed away partly. Confronting the real-world, bandal-like structure shows promising results on managing minor channels in sandbed braided Jamuna River.

DOI:

Year: 2020

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