Statistical accuracy for estimations of large wood blockage in a reservoir environment

Furlan, Paloma; Pfister, Michael; Matos, Jorge; Amado, Conceição; Schleiss, Anton

doi:10.1007/s10652-019-09708-7

Cited by 5 publications

(9 citation statements)

References 28 publications

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“…i. Overflowing structures such as dam spillways, PK weirs and our closed dam exhibit the smallest h/h 0 values ranging 0 %-50 % (Hartlieb, 2012(Hartlieb, , 2017Schmocker, 2017;Furlan, 2019;Pfister et al, 2013aPfister et al, , b, 2020, with lower values when a rack or protruding piles are set upstream of the spillway (Schmocker, 2017;Furlan, 2019;Pfister et al, 2020).…”

Section: Comparison With Existing Studiesmentioning

confidence: 93%

“…The first question has been addressed for reservoir dams: for ogee crest spillways with piles by Hartlieb (2012Hartlieb ( , 2017, Schmocker (2017) and Pfister et al (2020) and for piano-key weirs (PK weirs) by Pfister et al (2013b). It was also recently thoroughly covered by the hydraulic research team of ETH Zürich for rack structures made of poles (Schalko, 2020;Schalko et al, 2018Schalko et al, , 2019aSchmocker and Hager, 2013;Schmocker and Weitbrecht, 2013;Schmocker et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Open check dams and large wood: head losses and release conditions

Piton¹,

Horiguchi²,

Marchal³

et al. 2020

Nat. Hazards Earth Syst. Sci.

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Abstract. Open check dams are strategic structures to control sediment and large-wood transport during extreme flood events in steep streams and piedmont rivers. Large wood (LW) tends to accumulate at such structures, obstruct their openings and increase energy head losses, thus increasing flow levels. The extent and variability to which the stage–discharge relationship of a check dam is modified by LW presence has so far not been clear. In addition, sufficiently high flows may trigger a sudden release of the trapped LW with eventual dramatic consequences downstream. This paper provides experimental quantification of LW-related energy head loss and simple ways to compute the related increase in water depth at dams of various shapes: trapezoidal, slit, slot and sabo (i.e. made of piles), with consideration of the flow capacity through their open bodies and atop their spillways. In addition, it was observed that LW is often released over the structure when the overflowing depth, i.e. total depth minus spillway elevation, is about 3–5 times the mean log diameter. Two regimes of LW accumulations were observed. Dams with low permeability generate low velocity upstream, and LW then accumulates as floating carpets, i.e. as a single floating layer. Conversely, dams with high permeability maintain high velocities immediately upstream of the dams and LW tends to accumulate in dense complex 3D patterns. This is because the drag forces are stronger than the buoyancy, allowing the logs to be sucked below the flow surface. In such cases, LW releases occur for higher overflowing depth and the LW-related head losses are higher. A new dimensionless number, namely the buoyancy-to-drag-force ratio, can be used to compute whether (or not) flows stay in the floating-carpet domain where buoyancy prevails over drag force.

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Section: Comparison With Existing Studiesmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Open check dams and large wood: head losses and release conditions

Piton¹,

Horiguchi²,

Marchal³

et al. 2020

Nat. Hazards Earth Syst. Sci.

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“…Several studies proposed structures or countermeasures to avoid an interference of driftwood with the flow section fixing the undisturbed rating curve. Alternatively, the effect of driftwood on the rating curve or its trapping rate (or blocking probability) were described (Hartung and Knauss 1976;Perham 1986;Johansson and Cederström 1995;USACE 1987USACE , 1997Le Lay and Moulin 2007;Hartlieb 2012;Pfister et al 2013;Yang 2013;Schmocker 2017;STK 2017;Walker and Shinbein 2020;Schalko et al 2018;Lassus et al 2019;Furlan et al 2019Furlan et al , 2020Furlan et al , 2021Piton et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Partial Driftwood Rack at Gated Ogee Crest: Trapping Rate and Discharge Efficiency

2022

Self Cite

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Driftwood belongs to natural rivers just like water and sediment do. A sound ecosystem requires driftwood, although it might jam at civil structures, altering the flow section and rise the backwater. Safety considerations suggest removing wood from rivers, whereas ecological experience asks for its presence. The situation might become critical if spillways clog during floods, so that their discharge capacity reduces. For narrow bays, full racks mounted upstream of the weir or overhanging piers trap the driftwood distant from the flow control section. The hydraulic capacity is then maintained, but the driftwood has to be removed after the event. We thus investigated herein with a physical model a novel partial rack, motivating the driftwood for uncongested appearance to partially pivot and pass, but ensuring a high discharge capacity under hypercongested appearance. The partial rack configuration was specified, together with the related trapping rate and discharge efficiency.

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“…The topics dealt with in the papers range from the development and validation of numerical models to describe the interaction between flow and driftwood [11,17,21,23] to the experimental assessment of the Large Wood blocking at inline structures [14,20,27,31], to the evaluation of the stability of riparian vegetation during flood events and its consequent entrainment in the flow [12].…”

mentioning

confidence: 99%

“…In the second group of papers, Furlan et al [14] focus on the evaluation of the influence of experimental repetitions on the accuracy of LW blocking probability estimations from a statistical analysis derived by laboratory experiments. The results refer to the specific case of the blocking at an ogee crested weir with round nose, as a consequence of semicongested transport of logs (represented in the experiments by artificial plastic stems).…”

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confidence: 99%

Recent developments in the analysis of Large Wood dynamics in fluvial systems

Sibilla

Meninno²,

Canelas

2020

Environ Fluid Mech

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Wood in river plays a significant role in river geomorphology and ecology, by interacting with erosion and sedimentation processes, influencing the nutrients budget and providing physical habitats for a variety of species. However, Large Wood elements (LW, with a trunk diameter > 0.1 cm and a length > 1 m, as defined by Wohl et al. [38] transported during floods can aggravate the expected drawbacks and augment the overall risk at which the urban areas are exposed [7,8,28].LW may cause obstructions along the channel network, mostly in correspondence of bridges or weirs, where it accumulates, clogging the openings and causing a backwater rise upstream. Hydraulic structures can collapse as a result of the increased loads, and unexpected overflowing can occur at the jammed river cross-sections.The formation of LW accumulation is thus a key issue in the hydraulic risk assessment and its mechanism, as well its subsequent modelling, is still object of study [1,10,13,15,32,34]. It is highly affected by the interactions between water, sediments and structures, and it is also influenced by the physical features of LW element and river morphology [30].Due to the potential implications of LW during floods, different types of practical measures have been developed and employed [2, 5] to retain LW upstream of the critical sections (e.g. fins and racks, [26,33] or to reduce its presence in the river. These measures remain highly linked to the expertise of single practitioners, although recent works have proposed physically based designs of safety structures [25] both in mountain streams and low-land rivers.The need of giving a quantitative prediction of wood transport during floods throughout the river network has led researchers to investigate water-wood interactions both at a laboratory scale [3,4,6,9] and through numerical models [19,29]. The motion of floating wood on the water surface has been modelled with different strategies [22,28,35], mostly based on Eulerian-Lagrangian approaches able to trace wood motion and rotation.As an input, the aforementioned models require the volume and distribution of the wood that can be transported by the flood, and these data are affected by high uncertainty and derived through wood budget at basin scale [16,37]. In fact, wood entrained in a river can

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Statistical accuracy for estimations of large wood blockage in a reservoir environment

Cited by 5 publications

References 28 publications

Open check dams and large wood: head losses and release conditions

Open check dams and large wood: head losses and release conditions

Partial Driftwood Rack at Gated Ogee Crest: Trapping Rate and Discharge Efficiency

Recent developments in the analysis of Large Wood dynamics in fluvial systems

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