Severe bank erosion is one of the most challenging problems in the management of large rivers in Bangladesh. This paper describes the detailed flow patterns around typical bank-protection works on the Brahmaputra/Jamuna River as well as their morphological implications. Based on field surveys at several locations along this large alluvial river that are highly susceptible to erosion, attempts are made to clarify the flow fields and mechanisms of bank erosion. The performance of existing measures such as revetments and spur dykes are evaluated, and possible solutions for further enhancements are proposed. It is found that existing conventional works are generally huge in both size and cost, potentially exerting great disturbances on the river's dynamism and ecosystem. That said, the Bandal -a historied and indigenous structure -is cost-effective and environmentally friendly. This study suggests the recurrent use of Bandallike structures for channel stabilisation and flood management of the braided Brahmaputra/Jamuna River.

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This paper presents the results obtained from the studies on turbulent flow and bed deformation around groins with experimental and numerical methods. Two impermeable or permeable groins were positioned on the left side of the model channel. The velocity distributions around the groins were measured under non-submerged conditions. In the case with impermeable groins, the local scour hole around the upstream groin resulted deeper than that of the case with permeable ones. A 3D numerical model based on unstructured meshes was developed. The numerical results for velocity distributions have been compared with those of the experimental measurements and show good agreement with the experimental data.

In this paper, the applicability of bandal-like structures as an alternative method for traditional river training structures like groins is investigated. This structure is usually used in Indian Sub-Continents for riverbank protection and improvement of navigation conditions in alluvial rivers. The mechanism behind the utilization of this type of structure which affects the flow patterns and sediment transport process was studied through experimental measurements and numerical simulations. During the calculations, the water flow is computed by solving the Reynolds-averaged Navier-Stokes equations in 3D domain. The k−ε model is used for the turbulence closure and the numerical simulation is conducted on the unstructured meshes with the finite volume method. The main characteristics of the sediment erosion/deposition process around the bandal-like structures are clarified. The promising use of bandal-like structures is demonstrated through the comparisons with conventional structures as impermeable groins.

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