water Article A Shear Reynolds Number-Based Classification Method of the Nonuniform Bed Load Transport Gergely T. Török 1,2,* ,János Józsa 1,2 and Sándor Baranya 2 1 MTA-BME Water Management Research Group, Hungarian Academy of Science—Budapest University of Technology and Economics, M˝uegyetemrakpart 3, H-1111 Budapest, Hungary;
[email protected] 2 Department of Hydraulic and Water Resources Engineering, Faculty of Civil Engineering, Budapest University of Technology and Economics, M˝uegyetemrakpart 3, H-1111 Budapest, Hungary;
[email protected] * Correspondence:
[email protected]; Tel.: +36-1-463-2248 Received: 30 November 2018; Accepted: 24 December 2018; Published: 3 January 2019 Abstract: The aim of this study is to introduce a novel method which can separate sand- or gravel-dominated bed load transport in rivers with mixed-size bed material. When dealing with large rivers with complex hydrodynamics and morphodynamics, the bed load transport modes can indicate strong variation even locally, which requires a suitable approach to estimate the locally unique behavior of the sediment transport. However, the literature offers only few studies regarding this issue, and they are concerned with uniform bed load. In order to partly fill this gap, we suggest here a decision criteria which utilizes the shear Reynolds number. The method was verified with data from field and laboratory measurements, both performed at nonuniform bed material compositions. The comparative assessment of the results show that the shear Reynolds number-based method operates more reliably than the Shields–Parker diagram and it is expected to predict the sand or gravel transport domination with a <5% uncertainty.