Time evolution of scouring downstream of bed sills

Gaudio, Roberto; Marion, Andrea

doi:10.1080/00221680309499972

Cited by 67 publications

(56 citation statements)

References 4 publications

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“…From the analysis of measured bed level data it was determined that the channel reach affected by scouring phenomena has a total length, L TOT , of 50 cm. Two scour holes were located almost symmetrically with respect to the channel axis and the maximum scour depth occurred at a distance X from the initial section ranging from 0.3L TOT and 0.4 L TOT , in agreement with other experimental studies (Gaudio and Marion 2003). Figure 5 shows that a vortex structure develops inside the scour hole near the bed.…”

Section: Resultssupporting

confidence: 78%

River-bed erosion due to changing boundary conditions: performance of a protective measure

Termini

2014

Proc. IAHS

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Due to the introduction of man-made sediment barriers along a river, the amount of sediment load entering the downstream river reach is different to that leaving the reach, and erosion processes occur downstream of the barrier itself. Designers are often required to take into account the scouring process and to include adequate protective measures against the local scour. This paper addresses the performance of bio-engineering protective measures against the erosion process. In particular, a green carpet, realized with real flexible vegetation, has been used as the protective measure against erosion processes downstream of a rigid bed. Analyses are based on experimental work carried out in a straight channel constructed at the laboratory of the Dipartimento di Ingegneria Civile, Ambientale, Aereospaziale, dei Materiali, Palermo University (Italy).Key words rivers; local scouring; flow characteristics; protective measure; vegetation INTRODUCTIONDesigners are often required to take into account the scouring process around structural interventions and to include adequate protective measures against the local scour. The design of the protective measures, in turn, needs knowledge of the flow velocity field and of geometric characteristics of scour transient profiles.Most studies have been devoted to formulation of empirical equations to estimate the maximum (or equilibrium) scour depth and length (among others Breusers et al. 1977, Lenzi et al. 2002, Marion et al. 2006) for a specific scour problem. This information is important to identify adequate protective measures against scouring processes. However, to evaluate the advantages of a specific protective technique, it is important to investigate the effects of the technique itself on the flow velocity field and sediment transport processes.Vegetation has recently been used as a bioengineering technique against erosion. In an attempt to respond to the aforementioned question, an experimental programme has been conducted, at the Dipartimento di Ingegneria Civile, Ambientale, Aereospaziale, dei Materiali (DICAM) -Palermo University (Italy), to analyse scour caused by a horizontal jet downstream of a rigid bed. The experiments were conducted to examine the flow velocity field, including turbulent characteristics, within the scour hole. This analysis is fundamental to correctly simulate the bed-load transport and the temporal evolution of the scour hole and to define protective measures to reduce scouring. Some of the results on flow velocity and turbulence fields inside the scour hole were discussed in detail in previous work (Termini and Sammartano 2012). In this paper, attention is paid to the effects caused by vegetation used as a protective measure against the development of the scour hole downstream of the rigid bed.Analyses are based on experimental work carried out in a straight channel, with and/without the protective vegetated bed, constructed at the laboratory of the DICAM. Detailed measures of flow velocity field inside the scour hole have been obta...

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Section: Resultssupporting

confidence: 78%

River-bed erosion due to changing boundary conditions: performance of a protective measure

Termini

2014

Proc. IAHS

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“…Unless the toe of the structure is protected, the plunging jet has the potential to erode the bed locally, generating a scourhole. The predictive formulae for the depth of scour that can be found in the literature are all based on experimental tests based on scale models (Mason and Arumugam, 1985;Bormann and Julien, 1991;D'Agostino, 1994;Martin Vide and Del Agua Razquin, 1995;Rice and Kadavy, 1998;Gaudio et al, 2000;Chen and Hong, 2001;Ghodsian and Faradonbeh, 2001;Gaudio and Marion, 2003;Lenzi et al, 2002). Many approaches are fully empirical, being based on curve fitting of experimental data.…”

Section: Introductionmentioning

confidence: 99%

Effect of sill spacing and sediment size grading on scouring at grade‐control structures

Marion

Lenzi

Comiti

2004

Earth Surf Processes Landf

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Sequences of artificial steps are sometimes used to reproduce the natural step-pool morphology of high-gradient streams. The depth, length and shape of the scour holes in gravel-bed rivers can be predicted reasonably using recently developed formulae. However, the properties of the scour holes can sometimes be affected by the distance between structures. This effect is called 'geometrical interference' and leads to a reduction of the scour hole compared to its potential size. Geometrical interference may occur in sequences of artificial steps in high-gradient torrents, where structures are sometimes built at distances of a few tens of metres apart, but may also apply to natural step-pool systems. In this paper, a series of tests have been conducted to determine the effect of bed sill spacing and sediment grading on the potential erosion by jets forming over the sills. A new formula is derived, applicable to high-gradient streams (slope > 0·04), which can be applied to the special case of scour holes developed by interfering sills. Sediment size gradation, not accounted for in previous formulae, is found to have a significant effect on the scour dimensions and is included in the new predictive formula.

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“…Hence the question arises: Does the relation of MPM in fact fit the data used in its derivation? Answering this is of significance not only because the MPM bedload transport predictor is commonly used for comparative purposes in basic research (see e.g., Abdel-Fattah et al 2004;Barry et al 2004;Bettess and Frangipane 2003;Bolla Pittaluga et al 2003;Bravo-Espinosa et al 2003;Defina 2003;Gaudio and Marion 2003;Knappen and Hulscher 2003;Martin 2003;Mikoš et al 2003;Nielsen and Callaghan 2003;Ota and Nalluri 2003;Singh et al 2004;Yang 2005), but also because it is frequently used in engineering applications (it is one of the relationships available in HEC-6, a computer software used for sediment transport calculations that is very popular in the USA).…”

Section: Introductionmentioning

confidence: 99%

Reanalysis and Correction of Bed-Load Relation of Meyer-Peter and Müller Using Their Own Database

2006

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ABSTRACT:The pioneering predictor of fluvial bedload transport rate proposed by Meyer-Peter and Müller in 1948 is still extensively used in basic research and engineering applications. A review of the basis for its formulation reveals, however, that an unnecessary bed roughness correction was applied to cases of plane-bed morphodynamic equilibrium. Its inclusion followed a flow resistance parameterization in terms of the Nikuradse roughness height, which has been shown (well after the publication of their work) to be inappropriate for the characterization of

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Time evolution of scouring downstream of bed sills

Cited by 67 publications

References 4 publications

River-bed erosion due to changing boundary conditions: performance of a protective measure

River-bed erosion due to changing boundary conditions: performance of a protective measure

Effect of sill spacing and sediment size grading on scouring at grade‐control structures

Reanalysis and Correction of Bed-Load Relation of Meyer-Peter and Müller Using Their Own Database

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