The effect of bedform on increasing the flow depth

Articles in Press

Document Type : Research Article

Authors

1 Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran

2 Water Engineering Department, Agriculture Faculty, University of Tabriz, Tabriz-Iran

3 Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Tabriz-Iran

Abstract

With transferring sediments in alluvial channels, regular and alternating triangular shapes are created in the river bed, which are called bedforms. According to the characteristics and regime of flow, the geometrical dimensions of the bedform are changed and its mutual effect in changing the roughness of the bed and increasing the flow depth (especially for ripple and dune forms) is significant. In this way, predicting the flow resistance and its corresponding depth in channels with movable bed is one of the design and modeling challenges in these channels due to the uncertainty related to the formation and change of bedforms. For this purpose, it will be very important and necessary to provide an accurate, simple and practical relationship for estimating the highest flow level in the presence of bed form. In this study, a practical linear relationship is presented to predict the flow level in the conditions of the lower flow regime using 292 recorded test cases. Based on the mentioned relationship, the coefficient of 1.25 is provided as a specific coefficient of University of Tabriz, which greatly simplifies the calculations related to the estimation of flow depth in the presence of ripple and dune bed forms. Based on the described special coefficient, a method for determining Manning's coefficient in natural channels is presented, and the accuracy evaluation of the proposed relationship for the Manning roughness coefficient in the laboratory flume was evaluated as appropriate.

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Amirkabir Journal of Civil Engineering

Articles in Press, Accepted Manuscript
Available Online from 17 October 2025

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