Flow resistance in gravel-bed rivers: Progress in research

Powell, D. Mark

doi:10.1016/j.earscirev.2014.06.001

Cited by 152 publications

(154 citation statements)

References 127 publications

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“…This observation is consistent with the increased energy dissipation by macroturbulent eddies considered in spillway design (Hunt and Kadavy, 2010a). This observation is also consistent with the 15 fluvial geomorphology literature that indicates a significant proportion of total energy dissipation is caused by macroturbulent eddies in natural rivers (Leopold et al, 1960;Bathurst, 1980;Prestegaard, 1983;Powell, 2014). Therefore, seismic monitoring may be a tool to quantify macroturbulent eddies and associated flow resistance in complex natural channels.…”

Section: Resultssupporting

confidence: 76%

Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

Goodling¹,

Lekić²,

Prestegaard³

2018

Preprint

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Knowing the location of large-scale turbulent eddies during catastrophic flooding events improves predictions of erosive scour. The erosion damage to the Oroville Dam flood control spillway in early 2017 is an example of the erosive power of turbulent flow. During this event, a defect in the simple concrete channel quickly eroded into a chasm 47 meters deep.Erosion by turbulent flow is difficult to evaluate in real time, but near-channel seismic monitoring provides a tool to evaluate 10 flow dynamics from a safe distance. Previous studies have had limited ability to identify source location or the type of surface wave (i.e. Love or Rayleigh wave) excited by different river processes. Here we use a single three-component seismometer method (Frequency-Dependent Polarization Analysis) to characterize the dominant seismic source location and seismic surface waves produced by the Oroville dam flood control spillway, using the abrupt change in spillway geometry as a natural experiment. We find that the scaling exponent between seismic power and release discharge is greater following damage to 15 the spillway, suggesting larger turbulent eddies excite more seismic energy. The mean azimuth in the 5-10 Hz frequency band was used to resolve the location of spillway damage. Observed polarization attributes deviate from those expected for a Rayleigh wave, though numerical modelling indicates these deviations are explained by propagation up the hillside topography. Our results suggest Frequency-Dependent Polarization Analysis is a promising approach for locating areas of increased flow turbulence. This method could be applied to other erosion problems near engineered structures and to 20 understanding energy dissipation, erosion, and channel morphology development in natural rivers, particularly at high discharges.Earth Surf. Dynam. Discuss., https://doi

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Section: Resultssupporting

confidence: 76%

Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

Goodling¹,

Lekić²,

Prestegaard³

2018

Preprint

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“…According to Fig. 5, the channel roughness decreases with increasing discharge, which is in line with the literature (e.g., Chow 1959;Ferguson 2010;Powell 2014). Moreover, the Chézy coefficient increases slightly when bedload is supplied, which indicates an increase in the channel roughness.…”

Section: Roughness and Constriction Head Lossessupporting

confidence: 78%

Effects of Lateral and Vertical Constrictions on Flow in Rough Steep Channels with Bedload

2017

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Two-phase flows occurring at flow constrictions such as bridges or open sediment check dams are complex, especially for steep rivers with bedload transport. Dangerous bedload deposition and backwater effects may occur in steep mountain rivers at bridges. In contrast, sediment deposition is desirable at open check dams combined with sediment traps. For design purposes, the discharge and bedload capacity across these flow constrictions must be known. The energy losses, discharge capacity, and bedload transport capacity of vertical and lateral flow constrictions are experimentally studied in a rough, 2% inclined, trapezoidal channel. Both free surface and pressurized flow conditions, as caused by lateral and vertical flow constrictions, respectively, were analyzed because both may occur at bridges and check dams. The experiments demonstrate that the vertical flow constrictions cause a faster increase in the backwater depth, with increasing discharge, than lateral constrictions. The resulting upstream flow conditions can be described by the upstream Froude number, defined as a function of the constriction dimensions (height and width). The bedload transport capacity through the flow constriction decreases with the upstream Froude number. The practical relevance of the findings is illustrated by a design example of flow constrictions at open sediment check dams.

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“…Furthermore, estimates of roughness for Manning's equation were developed for open channel flow. The Darcy-Weisbach equation was derived in pipefull settings, but under conditions simplified to a straight circular pipe with uniform roughness and cross section (Powell, 2014). Applying these equations to a subglacial conduit with high and variable relative roughness and changing cross section and direction, may be outside of their empirically derived bounds (Gulley and others, 2014).…”

Section: Introductionmentioning

confidence: 99%

Roughness of a subglacial conduit under Hansbreen, Svalbard

et al. 2017

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ABSTRACT. Hydraulic roughness exerts an important but poorly understood control on water pressure in subglacial conduits. Where relative roughness values are <5%, hydraulic roughness can be related to relative roughness using empirically-derived equations such as the Colebrook-White equation. General relationships between hydraulic roughness and relative roughness do not exist for relative roughness >5%. Here we report the first quantitative assessment of roughness heights and hydraulic diameters in a subglacial conduit. We measured roughness heights in a 125 m long section of a subglacial conduit using structure-from-motion to produce a digital surface model, and hand-measurements of the b-axis of rocks. We found roughness heights from 0.07 to 0.22 m and cross-sectional areas of 1-2 m 2 , resulting in relative roughness of 3-12% and >5% for most locations. A simple geometric model of varying conduit diameter shows that when the conduit is small relative roughness is >30% and has large variability. Our results suggest that parameterizations of conduit hydraulic roughness in subglacial hydrological models will remain challenging until hydraulic diameters exceed roughness heights by a factor of 20, or the conduit radius is >1 m for the roughness elements observed here.

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Flow resistance in gravel-bed rivers: Progress in research

Cited by 152 publications

References 127 publications

Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis

Effects of Lateral and Vertical Constrictions on Flow in Rough Steep Channels with Bedload

Roughness of a subglacial conduit under Hansbreen, Svalbard

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