Reach‐averaged sediment routing model of a canyon river

Wiele, Stephen M.; Wilcock, Peter Richard; Grams, Paul E.

doi:10.1029/2005wr004824

Cited by 17 publications

(7 citation statements)

References 23 publications

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“…Predicting initial sediment motion is one of the most fundamental and practical problems in sedimentology and geomorphology. Sediment transport predictions are needed to route sediment through river networks [ Cui and Parker , 2005; Cui et al , 2006; Wiele et al , 2007], model river incision into bedrock [ Sklar and Dietrich , 2004; Lamb et al , 2007], restore river functionality and habitat [ Rosgen , 1996; Buffington et al , 2004], and mitigate debris flows initiated from channel‐beds [ Papa et al , 2004]. Sediment transport predictions also are crucial for understanding surface processes on planets and satellites like Mars and Titan, as they provide a straightforward and quantitatively robust method for constraining the amount of fluid that is flowing or once flowed across these planetary surfaces [ Komar , 1979; Burr et al , 2006; Lamb et al , 2006; Perron et al , 2006].…”

Section: Introductionmentioning

confidence: 99%

Is the critical Shields stress for incipient sediment motion dependent on channel‐bed slope?

Lamb¹,

Dietrich²,

Venditti³

2008

J. Geophys. Res.

443

728

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[1] Data from laboratory flumes and natural streams show that the critical Shields stress for initial sediment motion increases with channel slope, which indicates that particles of the same size are more stable on steeper slopes. This observation is contrary to standard models that predict reduced stability with increasing slope due to the added downstream gravitational force. Processes that might explain this discrepancy are explored using a simple force-balance model, including increased drag from channel walls and bed morphology, variable friction angles, grain emergence, flow aeration, and changes to the local flow velocity and turbulent fluctuations. Surprisingly, increased drag due to changes in bed morphology does not appear to be the cause of the slope dependency because both the magnitude and trend of the critical Shields stress are similar for flume experiments and natural streams, and significant variations in bed morphology in flumes is unlikely. Instead, grain emergence and changes in local flow velocity and turbulent fluctuations seem to be responsible for the slope dependency due to the coincident increase in the ratio of bed-roughness scale to flow depth (i.e., relative roughness). A model for the local velocity within the grain-roughness layer is proposed based on a 1-D eddy viscosity with wake mixing. In addition, the magnitude of near-bed turbulent fluctuations is shown to depend on the depth-averaged flow velocity and the relative roughness. Extension of the model to mixed grain sizes indicates that the coarser fraction becomes increasingly difficult to transport on steeper slopes.

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Section: Introductionmentioning

confidence: 99%

Is the critical Shields stress for incipient sediment motion dependent on channel‐bed slope?

Lamb¹,

Dietrich²,

Venditti³

2008

J. Geophys. Res.

443

728

View full text Add to dashboard Cite

show abstract

“…Sediment‐transport dynamics and rates in steep streams are important for routing sediment from hillslopes to river networks [ Grant et al ., ; Montgomery and Buffington , ; Benda et al ., ; Cui and Parker , ; Wiele et al ., ], aquatic habitat quality [ Lisle , ; Buffington et al ., ; Montgomery , ], and landscape evolution modeling [ Dietrich et al ., ; Tucker and Hancock , ]. Nonetheless, the role of fluvial processes in conveying sediment through steep channels has received little study relative to lower gradient channels ( S < 1%, where S is channel bed slope) and may differ in important ways [ Comiti and Mao , ].…”

Section: Introductionmentioning

confidence: 99%

Influence of bed patchiness, slope, grain hiding, and form drag on gravel mobilization in very steep streams

et al. 2013

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[1] Steep streams are a major portion of channel networks and provide a link to transport sediment from hillslopes to lower gradient rivers. Despite their importance, key unknowns remain, perhaps foremost of which is evaluating in steep streams empirical laws for fluvial sediment transport developed for low-gradient rivers. To address this knowledge gap, we painted sediment in situ over 3 years to monitor incipient sediment motion and sediment-patch development in five small (drainage areas of 0.04-2 km 2 ) and steep (slopes of 5-37%) tributaries of Elder Creek, California, United States. We found that channel beds organized into size-sorted sediment patches which displayed active fluvial transport of gravel annually, consistent year-to-year patch median grain sizes, partial transport of bed material, and significantly higher values of critical Shields stress for incipient sediment motion compared to that observed for lower gradient rivers. The high critical Shields stresses (up to %0.5 for the median grain size) agree within a factor of~3 to theoretical predictions which account for slope-dependent hydraulics, grain hiding, and sediment patches. For grains of approximately the same size as the roughness length scale, slope-dependent hydraulics and bed patchiness are the dominant controls on critical Shields stress values, while grain hiding is important for grains larger or smaller than the roughness length scale. Form drag exists in our monitored tributaries but has a smaller influence than the above effects. Our field observations show fluvial processes contribute to sediment mobilization in steep channels which are often considered to be dominated by debris flows.

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Section: Study Sitementioning

confidence: 99%

“…In addition to the rating curve model of Randle and Pemberton [1987], a variety of more complex numerical models have been developed and applied as well, including multidimensional models of specific eddy sandbar sites [ Wiele et al , 1996, 1999, Wiele , 1998, Wiele and Torizzo , 2005] and a pseudo‐one‐dimensional, reach averaged, multiple particle size, sand‐routing model [ Wiele et al , 2007]. While the Wiele et al [2007] model has the potential for application to multi‐year time scales, its complexity in terms of initial and boundary conditions dictate that it is more suitable to event‐scale (e.g., weeks to months) applications. In contrast, the approach described herein was developed specifically to reduce the required input data and number of tunable parameters to facilitate multi‐year simulations of sand flux and thus help address the primary sediment‐related question identified by program scientists at a knowledge assessment workshop held in July 2005 [ Melis et al , 2006]: “Is there a ‘flow‐only’ (nonsediment augmentation) operation that will restore and maintain eddy sandbar habitats over decadal time scales?”…”

Section: Study Sitementioning

confidence: 99%

An approach for modeling sediment budgets in supply‐limited rivers

Wright

Topping

Rubin

et al. 2010

Water Resources Research

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1] Reliable predictions of sediment transport and river morphology in response to variations in natural and human-induced drivers are necessary for river engineering and management. Because engineering and management applications may span a wide range of space and time scales, a broad spectrum of modeling approaches has been developed, ranging from suspended-sediment "rating curves" to complex three-dimensional morphodynamic models. Suspended sediment rating curves are an attractive approach for evaluating changes in multi-year sediment budgets resulting from changes in flow regimes because they are simple to implement, computationally efficient, and the empirical parameters can be estimated from quantities that are commonly measured in the field (i.e., suspended sediment concentration and water discharge). However, the standard rating curve approach assumes a unique suspended sediment concentration for a given water discharge. This assumption is not valid in rivers where sediment supply varies enough to cause changes in particle size or changes in areal coverage of sediment on the bed; both of these changes cause variations in suspended sediment concentration for a given water discharge. More complex numerical models of hydraulics and morphodynamics have been developed to address such physical changes of the bed. This additional complexity comes at a cost in terms of computations as well as the type and amount of data required for model setup, calibration, and testing. Moreover, application of the resulting sedimenttransport models may require observations of bed-sediment boundary conditions that require extensive (and expensive) observations or, alternatively, require the use of an additional model (subject to its own errors) merely to predict the bed-sediment boundary conditions for use by the transport model. In this paper we present a hybrid approach that combines aspects of the rating curve method and the more complex morphodynamic models. Our primary objective was to develop an approach complex enough to capture the processes related to sediment supply limitation but simple enough to allow for rapid calculations of multi-year sediment budgets. The approach relies on empirical relations between suspended sediment concentration and discharge but on a particle size specific basis and also tracks and incorporates the particle size distribution of the bed sediment. We have applied this approach to the Colorado River below Glen Canyon Dam (GCD), a reach that is particularly suited to such an approach because it is substantially sediment supply limited such that transport rates are strongly dependent on both water discharge and sediment supply. The results confirm the ability of the approach to simulate the effects of supply limitation, including periods of accumulation and bed fining as well as erosion and bed coarsening, using a very simple formulation. Although more empirical in nature than standard one-dimensional morphodynamic models, this alternative approach is attractive because its simplicity allows for ...

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Reach‐averaged sediment routing model of a canyon river

Cited by 17 publications

References 23 publications

Is the critical Shields stress for incipient sediment motion dependent on channel‐bed slope?

Is the critical Shields stress for incipient sediment motion dependent on channel‐bed slope?

Influence of bed patchiness, slope, grain hiding, and form drag on gravel mobilization in very steep streams

An approach for modeling sediment budgets in supply‐limited rivers

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