Backwater Rise due to Large Wood Accumulations

Schalko, Isabella; Schmocker, Lukas; Weitbrecht, Volker; Boes, Robert M.

doi:10.1061/(asce)hy.1943-7900.0001501

Cited by 98 publications

(171 citation statements)

References 18 publications

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“…However, additional LW volume still increases flow resistance and compactness of the LW accumulation, thereby increasing backwater rise. Due to the smaller accumulated area for the natural setup, the resulting backwater rise for the same amount of wood is lower compared to the predefined, box‐shaped setup (Schalko et al, ).…”

Section: Resultsmentioning

confidence: 99%

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Laboratory Flume Experiments on the Formation of Spanwise Large Wood Accumulations: I. Effect on Backwater Rise

Schalko

Lageder

Schmocker

et al. 2019

Water Resources Research

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Transported large wood (LW) in rivers may lead to accumulations at natural or artificial obstructions. The hydraulic and geomorphic conditions change due to these accumulations. Backwater rise as well as scour can evolve in the vicinity of such an accumulation. In this first companion paper, results of hydraulic model tests are presented on backwater rise due to spanwise LW accumulations in combination with a movable bed. The findings are summarized in design equations and allow the estimation of (1) characteristic LW volume generating the primary backwater rise, (2) effect of LW accumulation shape and bed material on resulting backwater rise, and (3) effect of LW volume on backwater rise. Compared to a fixed bed, movable bed reduces backwater rise as the open cross-section area and thus discharge capacity increase. This work improves the understanding and predictability of the formation and impact of spanwise LW accumulations at natural or artificial obstructions (e.g., LW retention racks).

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Section: Resultsmentioning

confidence: 99%

“…(a) Predefined, box‐shaped LW accumulation (Schalko et al, ) versus (b) natural LW accumulation with a fixed bed and (c) natural LW accumulation with a movable bed. LW = large wood.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Flume Experiments on the Formation of Spanwise Large Wood Accumulations: I. Effect on Backwater Rise

Schalko

Lageder

Schmocker

et al. 2019

Water Resources Research

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“…Gippel et al () reported that adjacent pieces of debris in river flow have complex interactions that can result in counterintuitive hydraulic effects. Schalko et al () used flume experiments to study the backwater effect of LW jams, finding that backwater rise depends mainly on the approach flow and LW jam porosity, the latter of which was significantly influenced by the percentage of fine organic material. Hartlieb () reported similar findings, but noted that backwater effect can vary significantly between different test runs with identical test conditions, due to the randomness of debris jam development.…”

Section: Introductionmentioning

confidence: 99%

Integrating Large Wood Jams into Hydraulic Models: Evaluating a Porous Plate Modeling Method

Ventres‐Pake

Nahorniak²,

Kramer

et al. 2020

J American Water Resour Assoc

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Research Impact Statement: Hydraulic models are error-prone where rivers interact with large wood jams. Our method for representing wood jams improves hydraulic model accuracy and ecohydraulic analysis.ABSTRACT: Large wood (LW) jams are key riverine habitat features that affect hydraulic processes and aquatic habitat. The hydraulic influence of LW jams is poorly understood due to the complexity of fluid dynamics around irregular, porous structures. Here we validated a method for two-dimensional hydraulic modeling of porous LW jams using the open-source modeling software Delft3D-FLOW. We sampled 19 LW jams at three reaches across the Columbia River Basin in the United States. We used computer-generated porous plates to represent LW jams in the modeling software and calibrated our modeling method by comparing model outputs to measured depths and velocities at validation points. We found that modeling outputs are error-prone when LW jams are not represented. By representing LW jams as porous plates we reduced average velocity root mean square error (RMSE) values (i.e., improved model accuracy) by 42.8% and reduced average depth RMSE values by 5.2%. These differences impacted habitat suitability index modeling. We found a 15.1% increase in weighted useable area for juvenile steelhead at one test site when LW jams were simulated vs. when they were ignored. We investigated patterns in average RMSE improvements with varying jam size, bankfull obstruction, porosity, and structure type, and river complexity. We also identified research gaps related to field estimation of LW jam porosity and porous structure modeling methods.(KEYWORDS: rivers/streams; fluvial processes; 2D simulations; field measurements; large wood jam; hydraulic modeling; fish habitat suitability; river restoration.) Paper No. JAWRA-18-0166-P of the Journal of the American Water Resources Association (JAWRA).

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“…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.…”

mentioning

confidence: 99%

“…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].…”

mentioning

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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Backwater Rise due to Large Wood Accumulations

Cited by 98 publications

References 18 publications

Laboratory Flume Experiments on the Formation of Spanwise Large Wood Accumulations: I. Effect on Backwater Rise

Laboratory Flume Experiments on the Formation of Spanwise Large Wood Accumulations: I. Effect on Backwater Rise

Integrating Large Wood Jams into Hydraulic Models: Evaluating a Porous Plate Modeling Method

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

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