Sediment Grain Size Distribution under Quasi-Unsteady Flows through River Reaches

Document Type : Original Article

Author

Associate Professor of Hydraulic Structures, Civil Engineering Department, University of Maragheh, Maragheh, Iran.

10.22044/jhwe.2025.15462.1047

Abstract

This study explores the temporal and spatial dynamics of sediment transport and bed morphology under quasi-unsteady flow conditions, with an emphasis on the mean sediment grain size (d50). The experiments were conducted in an 18-meter-long, 1-meter-wide, and 1-meter-deep laboratory flume with a mixed sediment supply. Four sediment feeding scenarios were tested: no feed, constant feed, rising limb feed, and falling limb feed, under a symmetric hydrograph comprising seven flow stages. Each stage lasted one hour, with discharges ranging from 50 to 100 L/s. Data were collected to analyze temporal variations in d50 and the influence of discharge on sediment sorting. Comparative analyses of sediment transport during rising and falling limbs revealed distinct behavioral patterns, with flow deceleration promoting deposition. Hysteresis loops highlighted temporal asymmetries between accelerating and decelerating flows, emphasizing the critical role of flow history in shaping bed composition. Bed stability assessments indicated that rapid discharge changes induce transient instability, evidenced by increased d50 variability during abrupt transitions. However, the bed exhibited resilience as flow conditions stabilized. A linear regression model demonstrated the ability to estimate d50 as a function of discharge and time, offering preliminary insights into sediment dynamics. However, limitations inherent to linear models- such as their inability to capture nonlinear interactions- suggest that advanced machine learning approaches could improve predictive accuracy. By integrating empirical analysis and predictive modeling, this study advances sediment forecasting capabilities under variable hydraulic conditions, providing valuable insights for river management and sediment transport processes.

Keywords


Almedeij, J., & Diplas, P. (2005). Bed load sediment transport in ephemeral and perennial gravel bed streams. EOS, Transactions American Geophysical Union, 86(44), 429-434.
An, C., Hassan, M. A., Ferrer-Boix, C., & Fu, X. (2021). Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers. Earth Surface Dynamics, 9(2), 333-350.
Beltrán, F. S. (2013). Fluvial processes in gravel-bed rivers. Cuadernos de Investigación Geográfica, 16, 123-140.
Brewer, P. A., & Passmore, D. (2002). Sediment budgeting techniques in gravel-bed rivers. Geological Society, London, Special Publications, 191(1), 97-113.
Buscombe, D., & Masselink, G. (2006). Concepts in gravel beach dynamics. Earth-Science Reviews, 79(1-2), 33-52.
Chabokpour, J., & Samadi, A. (2020). Analytical solution of reactive hybrid cells in series (HCIS) model for pollution transport through the rivers. Hydrological sciences journal, 65(14), 2499-2507.
Chabokpour, J., Shojaei, B., & Azamathulla, H. (2024). Numerical investigation of river bed forms on pollution dispersion. LARHYSS Journal P-ISSN 1112-3680/E-ISSN 2521-9782(59), 211-228.
Church, M. (2006). Bed material transport and the morphology of alluvial river channels. Annu. Rev. Earth Planet. Sci., 34(1), 325-354.
Church, M. (2010). Gravel‐bed rivers. Sediment cascades: An integrated approach, 241-269.
Cienciala, P., & Hassan, M. A. (2013). Linking spatial patterns of bed surface texture, bed mobility, and channel hydraulics in a mountain stream to potential spawning substrate for small resident trout. Geomorphology, 197, 96-107.
Dingle, E. H., Sinclair, H. D., Venditti, J. G., Attal, M., Kinnaird, T. C., Creed, M., Quick, L., Nittrouer, J. A., & Gautam, D. (2020). Sediment dynamics across gravel-sand transitions: Implications for river stability and floodplain recycling. Geology, 48(5), 468-472.
Garcia, C., Cohen, H., Reid, I., Rovira, A., Ubeda, X., & Laronne, J. B. (2007). Processes of initiation of motion leading to bedload transport in gravel‐bed rivers. Geophysical Research Letters, 34(6).
Gomez, B., & Church, M. (1989). An assessment of bed load sediment transport formulae for gravel bed rivers. Water Resources Research, 25(6), 1161-1186.
Gray, J. R., Laronne, J. B., & Marr, J. D. (2010). Bedload-surrogate monitoring technologies (2328-0328).
Hassan, M. A., Li, W., Viparelli, E., An, C., & Mitchell, A. J. (2023). Influence of sediment supply timing on bedload transport and bed surface texture during a single experimental hydrograph in gravel bed rivers. Water Resources Research, 59(12), e2023WR035406.
Kadota, A., Suzuki, K., & Mori, K. (2001). Study on Flow Resistance Over Steep-Slope Gravel-Bed. PROCEEDINGS OF HYDRAULIC ENGINEERING, 45, 619-624.
Konsoer, K. M., Rhoads, B. L., Langendoen, E. J., Best, J. L., Ursic, M. E., Abad, J. D., & Garcia, M. H. (2016). Spatial variability in bank resistance to erosion on a large meandering, mixed bedrock-alluvial river. Geomorphology, 252, 80-97.
Lamarre, H., MacVicar, B., & Roy, A. G. (2005). Using passive integrated transponder (PIT) tags to investigate sediment transport in gravel-bed rivers. Journal of Sedimentary Research, 75(4), 736-741.
Laronne, J. B., & Reid, L. (1993). Very high rates of bedload sediment transport by ephemeral desert rivers. Nature, 366(6451), 148-150.
Marquis, G. A., & Roy, A. G. (2013). From macroturbulent flow structures to large‐scale flow pulsations in gravel‐bed rivers. Coherent flow structures at Earth's surface, 261-274.
Mosselman, E. (2012). Modelling sediment transport and morphodynamics of gravel‐bed rivers. Gravel‐bed rivers: processes, tools, environments, 101-115.
Mrokowska, M. M., & Rowiński, P. M. (2019). Impact of unsteady flow events on bedload transport: A review of laboratory experiments. Water, 11(5), 907.
Palucis, M. C., Ulizio, T. P., Fuller, B., & Lamb, M. P. (2018). Flow resistance, sediment transport, and bedform development in a steep gravel-bedded river flume. Geomorphology, 320, 111-126.
Papangelakis, E., & Hassan, M. A. (2016). The role of channel morphology on the mobility and dispersion of bed sediment in a small gravel‐bed stream. Earth Surface Processes and Landforms, 41(15), 2191-2206.
Parker, G., Fu, X., Lamb, M., & Venditti, J. (2020). Morphodynamics of downstream fining in rivers with unimodal sand-gravel feed.
Pfeiffer, A. M., Finnegan, N. J., & Willenbring, J. K. (2017). Sediment supply controls equilibrium channel geometry in gravel rivers. Proceedings of the National Academy of Sciences, 114(13), 3346-3351.
Redolfi, M., Bertoldi, W., Tubino, M., & Welber, M. (2018). Bed load variability and morphology of gravel bed rivers subject to unsteady flow: A laboratory investigation. Water Resources Research, 54(2), 842-862.
Robert, A. (2014). River processes: an introduction to fluvial dynamics. Routledge.
Roushangar, K., & Shahnazi, S. (2020). Prediction of sediment transport rates in gravel-bed rivers using Gaussian process regression. Journal of hydroinformatics, 22(2), 249-262.
Singh, M., Singh, I. B., & Müller, G. (2007). Sediment characteristics and transportation dynamics of the Ganga River. Geomorphology, 86(1-2), 144-175.
Wickert, A. D., & Schildgen, T. F. (2019). Long-profile evolution of transport-limited gravel-bed rivers. Earth Surface Dynamics, 7(1), 17-43.
Wlodarczyk, K., Hassan, M. A., & Church, M. (2023). Annual and decadal net morphological displacement of a small gravel‐bed channel. Earth Surface Processes and Landforms, 48(8), 1630-1645.
Zhu, L. L., & Ge, H. (2014). Balance Adjustment of the gravel-sand river downstream reservoir. Applied Mechanics and Materials, 444, 1218-1221.