Flow Resistance Equation in Sand-bed Rivers and Its Practical Application in the Yellow River

Abstract

To fully reflect the effect of the flow characteristics, sidewall conditions and sediment concentrations on the bed roughness of sand-bed rivers, this study established a new flow resistance equation by introducing a comprehensive influence coefficient presented via a combination of power-function forms of the relative flow velocity, von Karman constant of sediment-laden flows and the ratio of particle size to viscous sublayer thickness. The comprehensive influence coefficient accordingly acts as a synthesized factor representing the combined effects of the flow intensity, bed material movement, energy consumption condition, and relative friction condition in the near-wall region of sediment-laden flows. Based on the field data from sediment-laden flows under scenarios of both high and low sediment concentrations, the performance of the proposed equation was validated to achieve the best accuracy in the calculation of Manning’s roughness coefficient compared with that of several previously presented flow resistance equations. Furthermore, the proposed flow resistance equation was adopted to quantify the stable channel width of the Lower Yellow River (LYR), i.e., the optimum main channel width for sediment transportation in the typical wandering reach of the LYR. The calculated stable channel width is consistent with the current river training width of the LYR, indicating that the proposed equation has great potential as a theoretical tool that can be used to support the determination of the river training strategy for the LYR.

Flow resistance at lowland and mountainous rivers

“…The nondimensional hydraulic geometry approach could establish a connection between velocity distribution and the Darcy-Weisbach friction factor. This approach effectively captures the influence of bed features on flow resistance, particularly in the presence of bedforms in deep flows over sand-bed rivers in lowland areas (Cai et al, 2020;Champion and Tanner, 2000;Okhravi et al, 2022a) and moderately deep flows over gravel-bed rivers (Ferguson et al, 2017;Namaee et al, 2017;Rickenmann and Recking, 2011). The findings of this study align with this behavior, highlighting the lower accuracy of the flow resistance predictor in gravel-bed rivers (Eq.…”

“…It has been particularly successful in lowland rivers that feature low-gradient sand-sized channels, high relative submergence (with R d 84 ⁄ > 10 or even >100), relatively uniform and quasi-steady flow, low sediment transport, and seasonal changes in vegetation. Several studies, such as Song et al (2017), Cai et al (2020), and Okhravi et al (2022a) have validated the performance of the hydraulic geometry approach in these river types.…”

“…On the other hand, sand-bed rivers or low-gradient rivers are characterized by a river bed dominated by sand-size particles (Schügerl et al, 2020;Sulaiman et al, 2017). However, in lowland areas, the presence of aquatic vegetation becomes a significant factor, particularly during the summer season, and must be considered as a resistance source (Cai et al, 2020;Champion and Tanner, 2000;Mewis, 2021;Okhravi et al, 2022a;Song et al, 2014Song et al, , 2017. Among the physical and environmental factors influencing vegetation accumulation in lowland rivers (e.g., river management practices, bed texture, nutrient and light availability, and flow conditions), Franklin et al (2008) emphasized that flow velocity has the most significant impact.…”

Study on the Stable Water and Sediment Parameters in the Middle Reaches of Fenhe River

“…Flood disasters are often concerned by the state and people, but the natural evolution of rivers will also cause losses to the surrounding economy and security. For example, when the river type changes from straight type to open branch type, it will also rush out of the original river channel and cause damage to the surrounding area [3]. River evolution is often caused by changes in water and sediment conditions [4][5][6][7][8].…”

Flow Resistance in Lowland Rivers Impacted with Distributed Aquatic Vegetation

“…Several field studies have investigated the behavior of overgrown streams on roughness coefficient in terms of improving the developed flow resistance predictors (Champion and Tanner 2000;Green 2005;Cai et al 2020) or optimizing the model performance (Song et al 2017). The present study aims to explore the seasonal variation of roughness coefficients in lowland streams with distributed vegetation.…”