Spatial and temporal variations in bed morphology at river contractions

Oliveto, Giuseppe; Marino, Maria Cristina

doi:10.1201/b17133-196

Cited by 2 publications

(6 citation statements)

References 5 publications

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“…Further details on the experimental work, main test conditions and results for each run included, are provided in Oliveto and Marino [13]- [15]. With reference to the run 21 characterised by sandy movable bed, contraction ratio  0.70, contraction length l 3.00 m, discharge Q 0.040 m 3 /s, and approach flow depth h o 0.100 m, Fig.…”

Section: Methodsmentioning

confidence: 99%

“…More important, most of the literature papers consider conditions of dynamic equilibrium, and hence concentrate on the maximum scour depth, overlooking the analysis of the channel bed morphology in its entirety, both in and outside the contracted zone. Based on experiments at laboratory scale and compared to previous papers by the author on the same topic (Oliveto and Marino [13]- [15]), new results are given in terms of empirical equations on the peculiar bed morphology characteristics also considering literature data, and predictive models on the temporal development of the bed degradation in and downstream of the contracted area.…”

Section: Introductionmentioning

confidence: 99%

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Sediment Transport at River Contractions

Oliveto

2019

WIT Transactions on Ecology and the Environment

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River contractions might occur because of either natural controls or hydraulic works. This paper aims to provide new insights on the temporal evolution of the morphological patterns at river contractions based on experiments at laboratory scale. Laboratory tests were performed in a 20 m long straight channel having a rectangular cross section, 1.0 m wide and 1.0 m deep. The erodible bed reach was made by almost uniform sediment consisting of either rough sand or medium gravel. The contraction model was 0.5, 1.0, 2.0, or 3.0 m long. Three contraction ratios = b/B = 0.9, 0.8, and 0.7 were considered, with b width of the contracted reach and B width of the approach channel. The experiments were performed in clear-water scour regime and steady flow conditions. Typically, they were of long duration (up to 15 days) to achieve conditions of dynamic equilibrium, but runs of short duration were also carried out to acquire suitable experimental data at the earlier stages of the bed forms development. Compared to previous studies by the author on the same topic, new results are provided on bed morphology characteristics, also considering literature data, and predictive models on the timedependent development of the bed degradation in and downstream of the contracted area.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sediment Transport at River Contractions

Oliveto

2019

WIT Transactions on Ecology and the Environment

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“…l/B≤1 according to [5]) and long contractions. More details on the experiments and main test conditions and observations are given [14][15][16][17]. In this study six new experiments were carried out under unsteady flow.…”

Section: Laboratory Experimentsmentioning

confidence: 99%

“…During each experiment from two to three surveys were carried out with special attention to the longitudinal bed profile around the channel centreline. The flow discharge was measured, with an accuracy of ±3%, by an orifice plate installed into the circuit pipeline; flow depths were measured by a point gage with an accuracy of ±0.1 mm, and bed levels were measured with a shoe-gage, of the type described by Oliveto et al [14], Oliveto and Marino [15,16], with an accuracy of the order of the grain size.…”

Section: Laboratory Experimentsmentioning

confidence: 99%

“…New special laboratory experiments are presented. They, along with previous ones carried out at University of Basilicata, Italy, Oliveto and Marino, and Oliveto [14][15][16][17] have allowed to develop predictive models on the temporal evolution of the bed profile, at and downstream of the contracted area, under both steady and unsteady flows.…”

Section: Introductionmentioning

confidence: 99%

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The Impact of River Contractions on the Bed Morphology under Unsteady Flows

Oliveto¹

2020

IJSDP

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Flow constrictions occur when canals or rivers are subjected to a reduction in width because of natural constraints (e.g. debris accumulations, longitudinal bars, confluences) or hydraulic works (e.g. bridge embankments, guide banks, spur dikes). This paper aims to provide new insights on the temporal evolution of the bed profiles at and downstream of river contractions based on special experiments at laboratory scale. In a previous experimental campaign at University of Basilicata, Italy, several runs were performed under steady flow and clear-water scour conditions. In this study new experiments are presented under unsteady flow conditions. Six experiments were carried out considering stepped hydrographs of different shapes. Laboratory tests were performed in a 20 m long straight channel having a rectangular cross section 1.0 m wide and 1.0 m deep. The working section was made by almost uniform coarse sand. The contraction model was 1.0 m long and the contraction ratio (i.e. the ratio of the width of the uniformly contracted area to the width of the undisturbed channel) equal to 0.80. The experiments were performed under clear-water scour regime also for the peak discharges. Starting from novel empirical formulas related to steady flow conditions, an approach is proposed for the prediction over time and along the channel centreline of the maximum (contraction) scour depth, the scour hole length, and the bed profile. Comparison between observed data and predicted values reveals a satisfactory agreement. The relationships here introduced appear to be suitable for practical purposes.

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Spatial and temporal variations in bed morphology at river contractions

Cited by 2 publications

References 5 publications

Sediment Transport at River Contractions

Sediment Transport at River Contractions

The Impact of River Contractions on the Bed Morphology under Unsteady Flows

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