How Large Immobile Sediments in Gravel Bed Rivers Impact Sediment Transport and Bed Morphology

McKie, C. W.; Juez, Carmelo; Plumb, Benjamin; Annable, W. K.; Franca, Mário J.

doi:10.1061/(asce)hy.1943-7900.0001842

Cited by 10 publications

(6 citation statements)

References 39 publications

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“…However, with increasing boulder concentration, we expect channel slope to decrease as the channel self-organizes a new bed largely composed of boulders such that boulders are no longer significant roughness elements on the bed. This situation is equivalent to the role of boulder spacing, shown by flume experiments, to strongly influence grade conditions (McKie et al, 2021). Each boulder generates a unique zone susceptible to flow reversals and enhanced turbulence (Papanicolaou & Tsakiris, 2017).…”

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confidence: 94%

Influence of Rarely Mobile Boulders on Channel Width and Slope: Theory and Field Application

et al. 2022

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confidence: 94%

Influence of Rarely Mobile Boulders on Channel Width and Slope: Theory and Field Application

et al. 2022

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“…In a series of experiments by McKie et al, the various distance effects of stabilized large sediment particles on the bed and transported sediment sizes in gravel-bed rivers were investigated. The results reflected that reducing the spaces between the particles made the transported and bed sediment sizes coarser [12]. White and Nelson used a sinusoidal flume with constant flow rates to study the mechanisms influencing sediment sorting patterns in a channel bed.…”

Section: Introductionmentioning

confidence: 99%

An Empirical Relation for Estimating Sediment Particle Size in Meandering Gravel-Bed Rivers

Dehkordi,

Sharafati,

Mehraein

et al. 2024

Water

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This paper aims to obtain a relation for estimating the median size of bed sediment, , at the bends of meandering rivers based on real data. To achieve such a purpose, field data, including topographic, sediment sampling, and flow measurements, were collected from various rivers in Iran at different times of the year. Then, the Buckingham Π-theorem was applied to identify the effective dimensionless numbers such as the Shields function, Reynolds particle number, Froude number, submerged specific gravity of sediment, and aspect and curvature ratios. A correlation analysis was conducted between such factors to eliminate those dependent on others. In the following, three regression techniques, containing the power function approach, the general additive model (GAM), and the multivariate adaptive regression spline (MARS), were chosen to achieve the best relation. The obtained results indicated that the developed MARS model produced a better result than the others and was much more satisfactory, with a coefficient of determination (R2) of 0.96 and 0.95 and root-mean-square error (RMSE) of 140.64 and 140.47 for the training and testing phases, respectively. Furthermore, the MARS outputs were validated with an analytical method, which showed that MARS fitted with the field data much better. Consequently, the distinguished merit of this study is the development of a relation for determining that shows which geometric and hydraulic parameters have the most effect on sediment size in the river bend.

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“…The significant disparity between the predicted f values obtained from the two predictors (Fig. 4a) can be attributed to surface water variations influenced by abrupt changes in bed slope (see S in Table 1), the distribution of gravel, cobbles, and boulders elements (Okhravi and Gohari, 2020), the shape and position of large cobbles and boulders (Hodge et al, 2020;McKie et al, 2021;Nicosia et al, 2023), and their protrusion from the channel bed (Hodge et al, 2020). The study by Ferro (2018a) on the potential application of the self-similarity hypothesis to flowresistance laws demonstrated that flow resistance depends on the Reynolds, Froude, and Shields (1936) numbers.…”

Section: Discussionmentioning

confidence: 99%

Flow resistance at lowland and mountainous rivers

Okhravi,

Alemi,

Afzalimehr

et al. 2023

Journal of Hydrology and Hydromechanics

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This study initially examines the various sources of flow resistance in sand-bed (lowland) and gravel-bed (mountainous) rivers along with the limitations of traditional estimation methods. The nondimensional hydraulic geometry approach, relating dimensionless flow discharge (q *) to the Darcy-Weisbach friction factor (f), has demonstrated good performance for both river types, covering shallow to moderately deep flows. However, accuracy in estimating f is affected by simplifications like assuming uniform and deep flow, neglecting bed load transport and vegetation effects, which require further evaluation. To address these issues, the proposed method is evaluated using data from four sand-bed rivers in Slovakia (with vegetation), and three gravel-bed rivers in Iran (dominated by cobbles and boulders). Bedforms prove to be significant resistance sources in all studied rivers. The approach yields separate predictors for each river type, showing a satisfactory agreement between observed and calculated values within a maximum deviation of ±20% error bands. These predictors are further validated using field data and established equations from rivers with similar physiographic characteristics. Results indicate the method performs well in predicting flow resistance in sand-bed rivers, slightly overestimating overall (+40%). It effectively captures riverbed features and vegetation influence under small-scale roughness conditions. However, the predictor’s validity for gravel-bed rivers is somewhat limited due to high variability in water-surface profiles, making it challenging to accurately capture flow dynamics under large-scale roughness conditions. Addressing complex characteristics of gravel-bed riverbeds, including boulders and local energy extraction, is crucial for improving the estimation of water-surface profile variations and flow resistance using the hydraulic geometry approach.

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How Large Immobile Sediments in Gravel Bed Rivers Impact Sediment Transport and Bed Morphology

Abstract: A common approach used to mitigate riverbank erosion and maintain watercourse alignments has been through the application of riprap or larger, more stable particles, to channel boundaries along reaches of interest. Very often, however, these large particles become dislodged from their 1

Cited by 10 publications

References 39 publications

Influence of Rarely Mobile Boulders on Channel Width and Slope: Theory and Field Application

Influence of Rarely Mobile Boulders on Channel Width and Slope: Theory and Field Application

An Empirical Relation for Estimating Sediment Particle Size in Meandering Gravel-Bed Rivers

Flow resistance at lowland and mountainous rivers

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