Experiments on the effect of hydrograph characteristics on vertical grain sorting in gravel bed rivers

Hassan, Marwan A.; Egozi, Roey; Parker, Gary

doi:10.1029/2005wr004707

Cited by 162 publications

(209 citation statements)

References 33 publications

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“…Also, the grain size distribution of the bed material and, in particular, the increase in sand content plays a role in the armoring process by reducing vertical sorting (Marion and Fraccarollo, 1997) or by reducing surface roughness and facilitating the rearrangement of the bed particles (Curran and Waters, 2014). Another aspect is the influence of different flow rates on the development of the armor (Hassan et al, 2006;Guney et al, 2013). Hassan et al (2006) indicated a general increase in the armoring degree with an increase in the flow rate.…”

Section: Introductionmentioning

confidence: 99%

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Armor breakup and reformation in a degradational laboratory experiment

2016

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Abstract. Armor breakup and reformation was studied in a laboratory experiment using a trimodal mixture composed of a 1 mm sand fraction and two gravel fractions (6 and 10 mm). The initial bed was characterized by a stepwise downstream fining pattern (trimodal reach) and a downstream sand reach, and the experiment was conducted under conditions without sediment supply. In the initial stage of the experiment an armor formed over the trimodal reach. The formation of the armor under partial transport conditions led to an abrupt spatial transition in the bed slope and in the mean grain size of the bed surface, as such showing similar results to a previous laboratory experiment conducted with a bimodal mixture. The focus of the current analysis is to study the mechanisms of armor breakup. After an increase in flow rate the armor broke up and a new coarser armor quickly formed. The breakup initially induced a bed surface fining due to the exposure of the finer substrate, which was accompanied by a sudden increase in the sediment transport rate, followed by the formation of an armor that was coarser than the initial one. The reformation of the armor was enabled by the supply of coarse material from the upstream degrading reach and the presence of gravel in the original substrate sediment. Here armor breakup and reformation enabled slope adjustment such that the new steady state was closer to normal flow conditions.

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Section: Introductionmentioning

confidence: 99%

“…Another aspect is the influence of different flow rates on the development of the armor (Hassan et al, 2006;Guney et al, 2013). Hassan et al (2006) indicated a general increase in the armoring degree with an increase in the flow rate. They also showed that temporally varying flows lead to stronger armoring than steady flows.…”

Section: Introductionmentioning

confidence: 99%

Armor breakup and reformation in a degradational laboratory experiment

2016

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“…This term has an order of magnitude 10 -5 while the S0 or Se has an order of 10 -3 (Graf and Altınakar, 1998). It was assumed that the spatial variation of velocity in the channel is negligible (Powell et al 2001, Hassan et al 2006. Therefore the term…”

Section: The Slope Method Saint-venant Equations (U*un and U*sv)mentioning

confidence: 99%

“…Under unsteady flow conditions, some researchers prefer to estimate the shear stress using the depth-slope product rule corresponding to normal (steady, uniform) flow especially when the purpose of their study is to focus on overall parameters rather than local parameters (Hassan et al 2006, Güney et al 2013 or prefer to neglect the contribution of velocity gradient to energy slope (Powell et al 2001). Qu (2002), Song and Graf (1996) and Afzalimehr et al (2007) used some of these methods in unsteady flows, but the comparison of these methods is limited.…”

Section: Introductionmentioning

confidence: 99%

The Hysteresis and Shear Velocity in Unsteady Flows

Bombar

2016

JAFM

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The shear velocity is an important parameter in characterizing the shear at the boundary in open channels and there exist methods to estimate the shear velocity in steady flows, but the application and comparison of these methods to non-uniform unsteady flows is limited. In this study, three artificial triangular-shaped hydrographs were generated where the base flow is non-uniform with fine sand bed and the shear velocity was obtained by the methods, u*SV by using the Saint-Venant equations, u*L by using the procedure given by Clauser Method, u*P by using the parabolic law, u*UN by using the momentum equation assuming the slope of energy grade line is equal to bed slope and u*avg by using the average velocity equation are used in this study. The stream-wise components of velocity time series and the velocity profiles were obtained by means of an acoustic Doppler velocity meter. The variation of the shear velocity and the constant for the parabolic law with time is discussed. It is concluded that the shear velocities found by the parabolic law and the average velocity equation can be used interchangeably. Furthermore a hysteresis intensity parameter is proposed in order to examine the depth variation of hysteretic behavior of depth variation both with point velocity and average velocity. It is revealed that the more the unsteady the hydrograph the more the hysteresis both in terms of point velocity and cross-sectional mean velocity.

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“…Since turbidity current occurring due to sediment laden reduces dam storage capacity, turbidity current and carrying sediment laden also can be an important parameter. Numerous researches related to density current were carried out both experimentally and theoretically by Stefan (1973), Garcia (1993Garcia ( , 1994, Bradford et al (1997), Lee and Yu (1997), Yu et al (2000), Parker (2003, 2006), Wright and Parker (2004), Violet et al (2005), Lamb et al (2004), De Cesare et al (2006, Hassan et al (2006) and Toniolo et al (2006). However, at present, new master projects include many consecutive dam constructions.…”

Section: Introductionmentioning

confidence: 99%

Investigation of seasonal thermal flow in a real dam reservoir using 3-D numerical modeling

Üneş

Varçin

2015

Journal of Hydrology and Hydromechanics

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Abstract:Investigations indicate that correct estimation of seasonal thermal stratification in a dam reservoir is very important for the dam reservoir water quality modeling and water management problems. The main aim of this study is to develop a hydrodynamics model of an actual dam reservoir in three dimensions for simulating a real dam reservoir flows for different seasons. The model is developed using nonlinear and unsteady continuity, momentum, energy and k-ε turbulence model equations. In order to include the Coriolis force effect on the flow in a dam reservoir, Coriolis force parameter is also added the model equations. Those equations are constructed using actual dimensions, shape, boundary and initial conditions of the dam and reservoir. Temperature profiles and flow visualizations are used to evaluate flow conditions in the reservoir. Reservoir flow's process and parameters are determined all over the reservoir. The mathematical model developed is capable of simulating the flow and thermal characteristics of the reservoir system for seasonal heat exchanges. Model simulations results obtained are compared with field measurements obtained from gauging stations for flows in different seasons. The results show a good agreement with the field measurements.

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Experiments on the effect of hydrograph characteristics on vertical grain sorting in gravel bed rivers

Cited by 162 publications

References 33 publications

Armor breakup and reformation in a degradational laboratory experiment

Armor breakup and reformation in a degradational laboratory experiment

The Hysteresis and Shear Velocity in Unsteady Flows

Investigation of seasonal thermal flow in a real dam reservoir using 3-D numerical modeling

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