Fixed-Bed and Mobile-Bed Resistance of Channels with Steep Gradients in Mountainous Areas

Flood discharge and sediment transport are closely linked to channel resistance in steep mountain streams. Previous research has mainly focused on the resistance of fixed-bed channels with steep gradients and mobile-bed channels in alluvial rivers. The present study performs an experiment and establishes a calculation method for the fixed-bed resistance of mountain channels. The basic expression of the mobile-bed resistance of steep mountain channels is derived by determining the controlling factors of the bed load movement on the riverbed resistance. The proposed formula can accurately predict the variation of the bed load resistance. The results of the present research improve the understanding of fluid dynamics and sediment transport in steep mountain channels.

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Effect of bed load supply on sediment transport in mountain streams

International Journal of Sediment Research ◽

10.1016/j.ijsrc.2017.03.004 ◽

2017 ◽

Vol 32 (2) ◽

pp. 240-252 ◽

Cited By ~ 8

Author(s):

Johannes Kammerlander ◽

Bernhard Gems ◽

Daniel Kößler ◽

Markus Aufleger

Keyword(s):

Sediment Transport ◽

Mountain Streams ◽

Bed Load

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Experimental Study on Uniform and Mixed Bed-Load Sediment Transport under Unsteady Flow

Applied Sciences ◽

10.3390/app10062002 ◽

2020 ◽

Vol 10 (6) ◽

pp. 2002

Author(s):

Zihao Duan ◽

Jie Chen ◽

Changbo Jiang ◽

Xiaojian Liu ◽

Bingbing Zhao

Keyword(s):

Particle Size ◽

Sediment Transport ◽

Unsteady Flow ◽

Steady Flow ◽

Transport Rate ◽

Bed Load ◽

Sediment Transport Rate ◽

Particle Size Ratio ◽

Load Movement ◽

Sediment Particles

The scouring and deposition of sediment caused by unsteady flows (e.g., storm waves and floods) produces many secondary disasters. The resultant bed-load movement exhibits different transport laws compared with that by steady flow. In this study, the flume experiments were performed to study the bed-load movement under unsteady flow with different velocity skewness. The movement of uniform and non-uniform non-cohesive sediment under unsteady flow as well as the influence of the steady and unsteady flow on sediment transport rate are compared. Additionally, the non-uniform sediment transport formula of fine-to-coarse particle diameter ratio was investigated. The results showed that the sediment transport rate between uniform and non-uniform sand under the same median diameter is different. The non-uniform sediment transport rate is 1.27-, 3.19-, and 0.68-times as large as that in uniform sediment under d50 = 0.664, 1.333, and 2.639 mm under unsteady flow, respectively. For non-uniform sand, the transport rate of non-uniform sand with a larger adjacent particle size ratio (δ = 0.29) was 1.31-times greater than that of the non-uniform sand with a smaller adjacent particle size ratio (δ = 0.50). Moreover, theoretical deduction was carried out and the incipient sediment motion was analyzed from the force mechanism. A new unsteadiness parameter based on the acceleration concept was proposed. The relationship between the travel distance and velocity skewness of sediment particles was set up. The experimental results and theoretical analysis showed that sediment under unsteady flow were easier to start and transport than those under steady flow in the same flow effect. The travel distance of sediment particles was longer under unsteady flow than that under steady flow.

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Mathematical modelling of riverbed dynamics – a Canadian case study

Canadian Journal of Civil Engineering ◽

10.1139/l91-094 ◽

1991 ◽

Vol 18 (5) ◽

pp. 772-780 ◽

Cited By ~ 5

Author(s):

B. Morse ◽

R. D. Townsend ◽

M. Sydor

Keyword(s):

Mathematical Model ◽

Sediment Transport ◽

Model Simulation ◽

Fixed Bed ◽

Channel Network ◽

Bed Elevation ◽

Mobile Bed ◽

Cumulative Change ◽

Degradation Pattern ◽

River Training

A new mobile-bed mathematical model for simulating sediment transport in river networks under unsteady flow conditions is presented. The new model, ONE-D-SED, is an extended version of the extensively validated fixed-bed, one-dimensional hydrodynamic model ONE-D. This paper reports the results of an application of ONE-D-SED to simulate bed profile development along a 43-km-long tidal channel network of the Lower Fraser River in British Columbia. The sand-bed study reach has been undergoing degradation caused by navigational dredging and river training works in lower channel reaches and by borrow dredging within the study reach itself, ONE-D-SED was used to simulate bed degradation in the study reach during the 1979–1984 period. The simulated annual change in bed elevation at the downstream end of the study reach showed good agreement with that observed during 1968, the data year used to calibrate the model. The predicted cumulative change in bed profile from 1979 to 1984 also compared favourably with the overall degradation pattern observed during that same period. Key words: mathematical model, simulation, sediment transport, river network, finite difference, model validation.

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PRACTICAL SCALING OF COASTAL MODELS

Coastal Engineering Proceedings ◽

10.9753/icce.v14.121 ◽

1974 ◽

Vol 1 (14) ◽

pp. 121

Author(s):

J.W. Kamphuis

Keyword(s):

Sediment Transport ◽

Theoretical Approach ◽

Wave Motion ◽

Scale Effects ◽

Fixed Bed ◽

Mobile Bed ◽

Long Wave ◽

Motion Time ◽

Practical Design ◽

Basic Scale

In this paper the practical design of coastal mobile bed models is considered. The semi-theoretical approach expressed by the author in earlier publications (9,10,11,12) is extended and used to classify and design coastal models. Fixed bed coastal models are discussed first to form a basis for the argument. Subsequently, mobile bed models are classified according to criteria of dynamic similarity satisfied in their design and scale effects present in their operation. Basic scale laws are next derived for all classifications of coastal models. This is done for both inshore and offshore models, the distinction being brought about by adjusting the velocity scales for unidirectional (and long wave) motion. Time and sediment transport scales are next derived and some well known models are compared. The presence of bedform and model distortion is also treated. The work is compared with that of other authors.

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Rill flow resistance law under sediment transport

Journal of Soils and Sediments ◽

10.1007/s11368-021-03083-x ◽

2021 ◽

Author(s):

Costanza Di Stefano ◽

Alessio Nicosia ◽

Vincenzo Palmeri ◽

Vincenzo Pampalone ◽

Vito Ferro

Keyword(s):

Sediment Transport ◽

Flow Velocity ◽

Friction Factor ◽

Flow Resistance ◽

Fixed Bed ◽

Accurate Estimate ◽

Mean Flow ◽

Mobile Bed ◽

Resistance Equation ◽

Rill Flow

Abstract Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurements carried out on mobile bed rills (grain resistance and sediment transport) and the values estimated by flow resistance equation (grain resistance) for fixed bed rills in the same slope and hydraulic conditions; (iii) the Γ function relationship was calibrated using measurements carried out on mobile bed rills and the data of Jiang et al. (2018). Results This analysis demonstrated that the effect of sediment transport on rill flow resistance law is appreciable only for 7.7% of the examined cases and that the theoretical approach allows for an accurate estimate of the Darcy-Weisbach friction factor. Furthermore, for both fixed and mobile beds, the mean flow velocity was independent of channel slope, as suggested by Govers (1992) for mobile bed rills. Conclusions The investigation highlighted that the effect of sediment transport on rill flow resistance is almost negligible for most of the cases and that the experimental procedure for fixing rills caused the unexpected slope independence of flow velocity.

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Application of Bed Load Formulations for Dam Failure and Overtopping

Civil Engineering Journal ◽

10.28991/cej-030932 ◽

2017 ◽

Vol 3 (10) ◽

pp. 997 ◽

Cited By ~ 1

Author(s):

Seyed Alireza Hosseinzadeh-Tabrizi ◽

Mahnaz Ghaeini-Hessaroeyeh

Keyword(s):

Dam Failure ◽

Bed Load ◽

Test Cases ◽

Mobile Bed ◽

Boussinesq Hypothesis ◽

Turbulence Effects ◽

Load Movement ◽

Slope Condition ◽

Volume Method ◽

Dam Overtopping

The Enhanced HLLC scheme as a robust approximate Riemann solver is used for numerical modeling of three different test cases of mobile bed and stepped mobile bed in dam failure and dam overtopping conditions. The current research has been done in the frame of the finite volume method using shallow water equations along with the Exner equation for sediment continuity. The Ribberink, Wong and Parker formulations have been used for the modelling of bed load movement. A convenient approach based on the Boussinesq hypothesis is deployed for considering turbulence effects in the second case. The affections of stepped and slope condition for the flow bed are considered through a corrected version of the HLLC flux components. Finally, the model is applied for modelling overtopping in the third case. The results of the present model are relatively reasonable by comparing with the experimental data.

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theory of generalized diffusion on suspended sediment transport in the flows with mobile bed

Vietnam Journal of Mechanics ◽

10.15625/0866-7136/10273 ◽

1990 ◽

Vol 12 (1) ◽

pp. 7-13

Author(s):

Nguyen Van Diep ◽

Dang Huu Chung

Keyword(s):

Sediment Transport ◽

Suspended Sediment ◽

Suspended Sediment Transport ◽

Bed Load ◽

Two Dimensional ◽

Mobile Bed ◽

Dimensional Models ◽

The One

In this work the authors have used the theory of generalized diffusion to establish the one and two-dimensional models describing suspended sediment transport in the flows with mobile bed. Here the exchange between suspended sediment and bed-load is taken into account. The set of equations obtained is closed by using the known experiment formulas.

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Sediment transport over fixed deposited beds in sewers - An appraisal of existing models

Water Science & Technology ◽

10.2166/wst.1997.0654 ◽

1997 ◽

Vol 36 (8-9) ◽

pp. 123-128 ◽

Cited By ~ 9

Author(s):

C. Nalluri ◽

A. K. El-Zaemey ◽

H. L. Chan

Keyword(s):

Sediment Transport ◽

Fixed Bed ◽

Transport Equations ◽

Design Criterion ◽

Pipe Diameter ◽

Transport Velocity

An appraisal of the existing sediment transport equations was made using May et al (1989) and Ackers (1991) sediment transport equations for the limit of deposition design criterion and with a deposit depth of 1% of the pipe diameter allowed in the sewers. The applicability of those equations for sewers with larger fixed bed deposit depth was assessed, the equations generally over-estimated the transport velocity. Modifications were made to enable the equations to apply to sewers with large fixed bed deposits present.

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