Resistance to flow in gravel-bed rivers

Bray, Dale I.; Davar, K. S.

doi:10.1139/l87-130

Cited by 36 publications

(53 citation statements)

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“…The model proposed by Lawrence [1997] to explain hydraulic behavior during marginal inundation is based on an extension of mixing length theory for turbulent flow and is comparable to roughness-based resistance models used for gravel bed rivers for this range of flows [e.g., Bray, 1982]. In contrast to the drag model considered in section 6, the mixing length model characterizes the bulk flow hydraulics, based on the contribution of boundary roughness to the overall flow disturbance, rather than the resistance introduced by individual elements.…”

Section: Modified Mixing Length Modelmentioning

confidence: 99%

Hydraulic resistance in overland flow during partial and marginal surface inundation: Experimental observations and modeling

Lawrence¹

2000

Water Resources Research

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Abstract. Hydraulic resistance as a function of surface roughness inundation was evaluated in a set of experiments designed to simulate overland flow on a rough, granular surface. The data are compared with an additive drag model based on the contribution of individual elements to flow resistance and a mixing length model for estimating bulk flow resistance. During partial inundation of the surface roughness the observed coefficient of drag per element is much higher than for an isolated element, and a model based on element form drag alone underestimates the observed friction. These high resistance values are strongly correlated with the hydrostatic wave drag estimated from the free surface deformation around elements. The mixing length model, incorporating a multiplier setting the hydraulically effective roughness height, reliably reproduces the trends in resistance during marginal inundation. This multiplier is shown to have a value similar to the root-mean-square of the surface height. IntroductionOverland flow is an important mechanism for the surface transport of particulate and dissolved nutrients and contaminants and contributes to surface erosion and, potentially, land degradation in environments where it is an active runoff process. Many physically based and quasi-empirical methods designed to assess transport and erosion processes assume that overland flow hydraulics are well understood and can be readily characterized in terms of simple resistance models. This is, however, not generally the case. During a single storm event, overland flow hydraulics are quite complex because of, in part, the varying contribution of boundary roughness to total flow resistance as a surface is progressively inundated. In many cases, the surface will only be partially or marginally inundated, so that the roughness disrupts the flow throughout its depth and classical boundary layer theory cannot be invoked to model the flow. The moderate Reynolds number of these flows (often of order 100-10, 000) introduces significant variability in the occurrence and interaction of wakes behind roughness elements and, for the case ofRe • 500, further invalidates the assumptions underlying boundary layer approximations. The pronounced distortion of the free surface around and over roughness elements is difficult to model hydrodynamically and also hinders the development of alternative approximate models based on the momentum balance equations. Each of these physical factors may have a significant effect on transport, mixing, and dispersion in the flow as well as on the most suitable form of a hydraulic approximation for characterizing mean flow behavior.Hydraulic approximations are used to estimate mean flow velocity and depth for a given specific discharge over a surface of known roughness. They are required when hydrodynamic modeling is either unfeasible or the data for it are not avail-

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Section: Modified Mixing Length Modelmentioning

confidence: 99%

Hydraulic resistance in overland flow during partial and marginal surface inundation: Experimental observations and modeling

Lawrence¹

2000

Water Resources Research

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“…[2] Grain size measurements of fluvial gravels are a fundamental descriptor for many fields of geomorphological research, including sediment transport [e.g., Middleton and Southard, 1984;Wiberg and Smith, 1987] and the study of flow resistance and the prediction of flow velocities in open channel flow [e.g., Bray, 1982;Clifford et al, 1992]. Furthermore, grain size has also been demonstrated to be an important variable for the habitat preferences of salmonids [e.g., Rimmer et al, 1983;Cunjak, 1988;Heggenes, 1996].…”

Section: Introductionmentioning

confidence: 99%

Catchment‐scale mapping of surface grain size in gravel bed rivers using airborne digital imagery

Carbonneau

Lane

Bergeron

2004

Water Resources Research

180

255

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[1] This study develops and assesses two methods for estimating median surface grain sizes using digital image processing from centimeter-resolution airborne imagery. Digital images with ground resolutions of 3 cm and 10 cm were combined with field calibration measurements to establish predictive relationships for grain size as a function of both local image texture and local image semivariance. Independently acquired grain size data were then used to assess the algorithm performance. Results showed that for the 3 cm imagery both local image semivariance and texture are highly sensitive to median grain size, with semivariance being a better predictor than image texture. However, in the case of 10 cm imagery, sensitivity of image semivariance and texture to grain size was poor, and this scale of imagery was found to be unsuitable for grain size estimation. This study therefore demonstrates that local image properties in very high resolution digital imagery allow for automated grain size measurement using image processing and remote sensing methods.

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“…Sin embargo, la validez de esta fórmula ha sido discutida en lechos con materiales gruesos, razón por la cual diferentes autores han propuesto modificaciones a la fórmula de MANNING o bien han sugerido otras nuevas (KEULEGAN, 1938;LIMERINOS, 1970;COWAN, 1954;LA.CEY, 1946). Investigaciones posteriores (HEY, 1979;BRAY, 1979BRAY, , 1982 han intentado mejorar los resultados modificando los coeficientes propuestos por aquellos. Su originalidad estriba en calibrar la rugosidad a partir del diámetro de los sedimentos del lecho, superando la dificultad de trabajar con coeficientes elegidos de manera arbitraria.…”

Section: Estimación De La Velocidad De Flujo En Canales No Aforadosunclassified

“…Para ello siguiendo la metodología propuesta por BRAY (1979BRAY ( , 1982 se han contrastado las fórmulas de MANNING-LIMERINOS, KEULEGAN, LACEY y también la de LEOPOLD et al ( 1964):…”

Section: Estimación De La Velocidad De Flujo En Canales No Aforadosunclassified

“…siendo, V= velocidad media (m/s); g= aceleración de la gravedad; d= profundidad; S= pendiente; Dn =Diámetro del porcentaje más fino que n. Conviene recordar que la aplicación de estas fórmulas sólo es válida para aquellos casos en que el valor de la rugosidad aparente (d/Dn) es superior a 3 (BRAY, 1982).…”

Section: Estimación De La Velocidad De Flujo En Canales No Aforadosunclassified

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Procesos fluviales en lechos con materiales gruesos

Beltrán

2013

CIG

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Resistance to flow in gravel-bed rivers

Cited by 36 publications

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Hydraulic resistance in overland flow during partial and marginal surface inundation: Experimental observations and modeling

Hydraulic resistance in overland flow during partial and marginal surface inundation: Experimental observations and modeling

Catchment‐scale mapping of surface grain size in gravel bed rivers using airborne digital imagery

Procesos fluviales en lechos con materiales gruesos

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