Scale Modeling of Wooden Debris Accumulation at a Debris Rack

Schmocker, Lukas; Hager, Willi H.

doi:10.1061/(asce)hy.1943-7900.0000714

Cited by 76 publications

(88 citation statements)

References 18 publications

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“…If the linear correlation of Schmocker und Hager [6] is extrapolated on higher Froude numbers, the relative backwater effect would be significantly larger than for the test series of Knauss [4]. However, this in fact corresponds with the fundamental finding of Knauss [4], debris jams at V-shaped racks cause smaller backwater effects than at 90˚-racks.…”

Section: Debris Jams At Retention Racksmentioning

confidence: 98%

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Decisive Parameters for Backwater Effects Caused by Floating Debris Jams

Hartlieb¹

2017

OJFD

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The dimensional analysis of the backwater effect caused by debris jams results in the Froude number of the approach flow in the initial situation prior to debris jam formation and the debris density as decisive parameters. For the more precise detection of the influence of both parameters the results of different hydraulic model test series at the Laboratory of Hydraulic and Water Resources Engineering of the Technical University of Munich concerning debris jams at spillways as well as at racks for the retention of wooden debris were uniformly evaluated. On the one hand a significant increase of the backwater effect with a rising Froude number of the approach flow could be shown. This is in good correlation to recent test results for debris jams at retention racks at the Laboratory of Hydraulics, Hydrology and Glaciology of the Swiss Federal Institute of Technology Zurich. On the other hand a significant increase of the backwater effect could also be shown for a rising debris density. However, the test results also show that significantly different backwater effects can occur in different test runs with identical test conditions. These differences are a result of the randomness of debris jam development, and therefore, a more exact quantification of the dependence of the backwater effect on the Froude number of the approach flow and on the debris density is not considered useful for the present results.

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Section: Debris Jams At Retention Racksmentioning

confidence: 98%

“…Hager [6] are included in Figure 6. These two studies tested retention racks with a layout of the pillars vertical to the flow direction (90˚) and lower Froude numbers of the approach flow.…”

Section: Debris Jams At Retention Racksmentioning

confidence: 99%

Decisive Parameters for Backwater Effects Caused by Floating Debris Jams

Hartlieb¹

2017

OJFD

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“…This amount of shear may be non-negligible, as the persistence of the inflection of the water surface profile demonstrates a constant gravitational acceleration of flow and significant drag on the logjam. Large wood effects on channel hydraulics are well-known from field measurements [Abbe and Montgomery, 1996] and the geometry of our water surface profile is similar to backwater effects studied in flume studies of debris accumulation [Schmocker and Hager, 2013;Schalko et al, 2019a,b]. Drag coefficients for single wood pieces have been measured in field experiments [Shields and Alonso, 2012;Alonso, 2013], proposed in numerical models [Hygelund and Manga, 2003;Manga and Kirchner, 2000] and measured for stable, engineered structures [Bennett et al, 2015;Gallisdorfer et al, 2014], but our measurement of the hydrodynamics are not sufficient to make a full connection with these models.…”

Section: C Backwater Persistence and Dragmentioning

confidence: 71%

Logjams are not jammed: measurements of log motions in Big Creek, Idaho

Deshpande

Crosby²

2019

Preprint

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Colloquially, a "logjam" indicates a kinematic arrest of movement. Taken literally, it refers to a type of dense accumulation of wood in rivers widely recognized as bestowing numerous biological and physical benefits to the system but also present serious hazards to infrastructure. Despite this, no in-situ field measurements have assessed the degree of arrest in a naturally-formed logjam. Using time-lapse photography, repeat total station surveys and water level loggers, we provide an unprecedented perspective on the evolution of a logjam in central Idaho. Despite the namesake, we find that the logjam is not jammed. The ensemble of logs progressively deforms in response to shear and buoyant lift of flowing water, modulated by the rising limb, peak and falling limb of the snowmelt hydrograph. As water rises and log drag against the bed and banks decreases, they collectively translate downstream, generating a heterogeneous pattern of deformation.As streamflow recedes and the logs reconnect with the bed and banks, the coherent deformation pattern degrades as logs settle opportunistically amongst their neighbors.Field observations of continuous movement at a low rate are qualitatively similar to creep and clogging, behaviors that are common to a wide class of disordered materials. These similarities open the possibility to inform future studies of environmental clogging, woodladen flows, logjams, hazard mitigation and the design of engineered logjams by bridging these practices with frontier research efforts in soft matter physics and granular rheology.

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“…Physical scale model tests are generally applied in hydraulic engineering (e.g. Armanini et al, 2010;Schmocker and Hager, 2013;Schmocker and Weitbrecht, 2013;Gems et al, 2014aGems et al, , 2014bSchmocker et al, 2015). The obtained insights into process dynamics are particularly valuable (1) for the development, calibration, and validation of computational models and (2) for analyses of complex flow processes and its mutual influences, which cannot be accurately simulated by numerical models or for which no physical-mathematical formulation has been proposed so far (Bocchiola et al, 2006;Gems et al, 2014aGems et al, , 2014bDe Cicco et al, 2015;Gems et al, 2016;Kammerlander et al, 2016).…”

Section: Physical Modelling Lw Dynamics and Related Hazardsmentioning

confidence: 99%

Assessing and mitigating large wood‐related hazards in mountain streams: recent approaches

Mazzorana

Ruíz-Villanueva

Marchi

et al. 2017

J Flood Risk Management

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The assessment and mitigation of floods in mountain streams, when large wood (LW) is transported, pose several challenges. The process chain consisting of flood propagation, LW recruitment, entrainment, transport, and entrapment triggers, at critical sections such as bridges, unexpected and exacerbated impacts to the exposed built environment. We provide a review on the recent advances in modelling LW dynamics during extreme river floods through computational approaches. Moreover, we describe how scaled flume experiments can enhance process understanding at critical flow sections such as bridges to address risk mitigation problems. Additionally, we present a framework based on Formative Scenario Analysis (FSA) to allow for expert knowledge integration and to subsequently derive consistent hazard process scenarios in steep mountain streams where the application of computational approaches is less reliable. Finally, we discuss how the application of the presented set of assessment methods can support integral flood risk management by explicitly considering LW dynamics since the effectiveness of mitigation critically depends on the acquired process understanding.

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Scale Modeling of Wooden Debris Accumulation at a Debris Rack

Cited by 76 publications

References 18 publications

Decisive Parameters for Backwater Effects Caused by Floating Debris Jams

Decisive Parameters for Backwater Effects Caused by Floating Debris Jams

Logjams are not jammed: measurements of log motions in Big Creek, Idaho

Assessing and mitigating large wood‐related hazards in mountain streams: recent approaches

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