Optimum configuration of groynes for stabilization of alluvial rivers with fine sediments

Severe bank erosion at lowland rivers in Bangladesh devours vast tract of lands and renders thousands of people homeless at high flood; also, rapid deposition changes bed topographies and seriously reduces navigability at low flow time. Conventional groynes and revetments are used to mitigate these problems, but the targeted goal is not achieved as expected. This study investigates the optimum configuration of a groyne to improve groyne performances at both high flow and low flow. RIC-Nays, a two-dimensional model for flow and morphology, is utilized in this study upon confirmation through the detailed experimental data. The channel and flow parameters are taken conforming to a typical river of Bangladesh. Three different configurations are compared to obtain the optimum one. The performance of a groyne is evaluated through three key features - erosion in channel bed (thalweg), deposition in groyne field, and scour near groynes. The computation reveals that the modified groynes function better than the conventional ones in respect of maintenance of navigation channel at low flow and bank protection at high flood as well.