Scale model of a training dam using lightweight granulates

¹ Marine and Fluvial Systems, Department of Water Engineering and Management, Faculty of Engineering Technology, University of Twente, The Netherlands
² HZ University of Applied Sciences, Delta Academy, Vlissingen, the Netherlands
³ Hydrology and Quantitative Water Management Group, Department of Environmental Sciences, Wageningen University and Research, The Netherlands
⁴ Rijkswaterstaat Center for Water Management, Ministry of Infrastructure and the Environment, The Netherlands
⁵ River Dynamics and Inland Shipping Department, Deltares, The Netherlands
⁶ Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands

^* e-mail: B.Vermeulen@utwente.nl ^** e-mail: Ton.Hoitink@wur.nl

Abstract

Longitudinal training dams (LTDs) are a promising alternative for river groynes. Here we summarize findings of a recent study focused on the along river transition from a series of river groynes to an LTD, where the flow divides between the fairway and the side channel between the LTD and the river bank. A scale model is setup using lightweight granulates made of polystyrene to create conditions that are dynamically similar to a prototype situation in the River Waal. The key advantage of using lightweight granulates is that both the Shields number and the Froude number are similar in the model and the prototype. A high flow and a low flow experiment were carried out. The bedforms in the physical model have dimensions that correspond to theoretical dune height predictions, and also the channel incision due to width reduction is in accordance with expectations. The scour holes that develop near the tip of the groynes, however, are too deep, which may relate to improper scaling of the local turbulent vortices, initiated at the groynes. The morphodynamic developments in the flow divergence zone are subtle, and are overwhelmed by the mobile bed response to the presence of groynes. Considering that the physical model over-predicts the erosion caused by groynes, this suggests that the LTD configuration subject to study results in a comparatively stable bed morphology.