The variation of water-surface slope and its significance for bedload transport during floods in gravel-bed streams

Meirovich, Lev; Laronne, Jonathan B.; Reid, Ian

doi:10.1080/00221689809498630

Cited by 37 publications

(36 citation statements)

References 13 publications

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“…The energy slope can significantly differ from the geometric slope during flooding [Meirovich et al, 1998;Smart, 1999], i.e., for incipient motion of the larger elements.…”

Section: Comparison With Nonuniform (Flume and Field) Sediment Datamentioning

confidence: 99%

“…Note that both the channel slope S b = tana and energy slope S are concerned in the calculation. This is not a problem for uniform flow conditions (which is the case for most flume experiments) for which S = S b , but in the field the energy slope can differ significantly from the geometric bed slope during flooding [Meirovich et al, 1998;Smart, 1999]. The model is compared with field and flume data in the following section.…”

Section: Theoretical Analysismentioning

confidence: 99%

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Theoretical development on the effects of changing flow hydraulics on incipient bed load motion

Recking¹

2009

Water Resources Research

174

247

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[1] Several decades of flume and field measurements have indicated that in rough turbulent flows the critical Shields stress increases with increasing slope and associated decreasing relative depth. This result contradicts the usual consideration of a decreased critical Shields value on very steep slopes because of increased gravitational effects. However, recent studies have demonstrated that these experimental results could be reproduced with a force balance model if the classical logarithmic velocity profile was replaced with a velocity profile that was more compatible with available velocity measurements over gravel beds. These measurements indicate the existence of a roughness layer that is a zone of almost constant velocity close to the bed, whose properties (mean velocity and turbulence) depended on the flow's relative depth. Unfortunately, velocity profile measurements for low relative depth associated with steep slopes are scarce, and it is still difficult to include such flow properties in a force balance model. Flow resistance data (on the basis of depth average velocity measurements) are very common and cover a wide range of slopes and relative depths. In this paper these data are used to fit a velocity profile including a roughness layer. When used in a force balance model for incipient motion, it adequately reproduced a data set composed of 270 critical Shields values measured in a flume with near-uniform sediments. The relevance of this research to field problems is discussed using a data set composed of 92 critical Shields stresses obtained from field measurements. Finally, a model is proposed for field applications taking into account the slope effect.

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“…The energy slope can significantly differ from the geometric slope during flooding [Meirovich et al, 1998;Smart, 1999], i.e., for incipient motion of the larger elements.…”

Section: Comparison With Nonuniform (Flume and Field) Sediment Datamentioning

confidence: 99%

Section: Theoretical Analysismentioning

confidence: 99%

Theoretical development on the effects of changing flow hydraulics on incipient bed load motion

Recking¹

2009

Water Resources Research

174

247

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“…Without backwater effect for the same water depths for incoming flood the average WSL slope is higher than when flood decreasing. That phenomena is typical for open channel flow and was observed previously by Meirovich et al [1998] who investigated influence of water slope on bedload transport intensity. With consideration of the backwater effect from the Vistula River the WSL slope is smaller when the flood is increasing than when it is decreasing.…”

Section: Modeling With Cche2d -Hydraulic Conditionsmentioning

confidence: 49%

The morphology and morphodynamics of sand-gravel subaquatic dunes: the Raba River estuary, Poland

Radecki‐Pawlik

Książek²

2012

GEOREVIEW

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ABSTRACT:In the outlet of the Raba River to the Vistula, the biggest river in Poland, the morphology and morphodynamics of sand and finegravel subaquatic dunes were investigated. The site is situated in highland region just about the entrance to Polish Carpathians. The dunes formed on the Raba River bed estuary are composed of sand and fine gravel (d 50 up to 11 mm). Systematic observation (within the [2000][2001][2002][2003][2004][2005] were made of geometry, sediment composition and hydraulic climate under which the dunes grew and decomposed. The investigation focuses here mostly on the geometrical parameters of these bed forms such as height, length, as well as granulometric characteristics of the sediment. Based on in-site measurements different hydraulic parameters were calculated such as shear stresses, resistant coefficient, Froude and Reynolds numbers and roughness coefficient. It was found that the relation between height (H) and length (L) of the Raba estuary dunes describes the formula: H = 0.05L0.35. Also these dunes are steeper and flatter then classical H/L index is: H/L = 0.0518L0.622. During the field campaign, when the foot access to the estuary was possible and dunes were spotted on the river bed the range of measured water velocity was from v = 0.39 m•s -1 to v = 0.81 m•s -1 with the highest velocity over the dune crest. At the same time the measured range of shear stresses within the dune field formation were from  = 0.115 Nm -2 to  = 1.59 Nm -2 . On the field investigations the CCHE2D -two-dimensional unsteady flow and sediment transport model for non-equilibrium transport of non-uniform sediment mixtures -was applied. The model was used to simulate the morphodynamic changes along the outlet of the Raba River basing on field observations of the 2005 summer flood as well as calculate hydraulics parameters. It was also used to test and confirm the range of morphodynamic changes, which take place along the research reach where the dunes are being developed. The maximum water flow velocity for and the shear stresses for the summer flood caused the hydrodynamic conditions when water velocity as well as shear stresses values reached respectively up to v = 1,93 ms -1 , and  = 19.74 Nm -2 which shows that critical conditions of bed load movement were exceeded for the Raba estuary.Morphology and morphodynamics of sand-gravel subaquatic dunes: Raba River estuary, Poland 9 GEOREVIEW, Vol. 21 (2012)

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“…For the TC events, the hydraulic radius includes an extensive zone of floodplain on the eastern side of the channel, and the values of slope, discharge, and boundary shear stress represent the peak stages of the events. Meirovich et al (1998) have shown that slope displays a hysteretic relation with stage as a flood wave passes, with maximum slope during the rising stage of the flood. The estimates of slope during TCs in Table I are therefore underestimates of the maximum slope attained during the rising stages of the floods.…”

Section: Sand Suspension Simulationsmentioning

confidence: 97%

Suspended sediment transport during tropical‐cyclone floods in Fiji

Kostaschuk

Terry

Raj³

2002

Hydrological Processes

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Abstract:Flow records, rising-stage sediment samplers, and a sand suspension model are used to examine suspended sediment concentrations during major floods caused by tropical cyclones TC Joni and TC Kina in the Rewa River, Fiji. The highest concentrations of total suspended solids were measured during the early stages of TC Kina. The suspension model predicts higher sand concentrations for TC Kina compared with TC Joni because of the larger slope and higher shear stresses during Kina. Extremely high wash load concentrations early in TC Kina are at least partly due to remobilization of fine sediment deposited during the earlier TC Joni flood. Samples from the TC Kina had volumetric concentrations larger than 5%, indicating hyperconcentrated streamflows. Mass-density shear stresses in the hyperconcentrated flows are up 1Ð6 times larger than clear-water shear stresses, but they occur early during low stages of the flood and probably do not result in severe bed erosion.

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The variation of water-surface slope and its significance for bedload transport during floods in gravel-bed streams

Cited by 37 publications

References 13 publications

Theoretical development on the effects of changing flow hydraulics on incipient bed load motion

Theoretical development on the effects of changing flow hydraulics on incipient bed load motion

The morphology and morphodynamics of sand-gravel subaquatic dunes: the Raba River estuary, Poland

Suspended sediment transport during tropical‐cyclone floods in Fiji

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