Turbulence and the Transportation of Rock Debris by Streams

Leighly, John

doi:10.2307/208917

Cited by 45 publications

(19 citation statements)

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“…Diffusive sedimentation would be driven by turbulent shearing between flowing water in the channel and the stagnant waters of the lake. The sharp velocity contrast between the channel and lake waters will result in lateral shear zones similar to those discussed by Leighly [1934], modeled experimentally by Sellin [1964] and numerically by James [1985], and described along the levees of the mainstem Middle Fly River by Day et al [2008]. Such diffusive mechanics are likely very similar to the shear driven turbulence occurring across the jet that develops as flow discharges into the lake at the channel terminus.…”

Section: Conceptual Modelmentioning

confidence: 74%

Formation and maintenance of single‐thread tie channels entering floodplain lakes: Observations from three diverse river systems

et al. 2009

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[1] Tie channels connect rivers to floodplain lakes on many lowland rivers and thereby play a central role in floodplain sedimentology and ecology; yet they are generally unrecognized and little studied. Here we report the results of field studies focused on tie channel origin and morphodynamics in the following three contrasting systems: the Middle Fly River (Papua New Guinea), the Lower Mississippi River, and Birch Creek in Alaska. Across these river systems, tie channels vary by an order of magnitude in size but exhibit the same characteristic morphology and appear to develop and evolve by a similar set of processes. In all three systems, the channels are characterized by a narrow, leveed, single-thread morphology with maximum width approximately one tenth the width of the mainstem river. The channels typically have a V-shaped cross section, unlike most fluvial channels. These channels develop as lakes become isolated from the river by sedimentation. Narrowing of the connection between river and lake causes a sedimentladen jet to develop. Levees develop along the margins of the jet leading to channel emergence and eventual levee aggradation to the height of the mainstem levees. Bidirectional flow in these channels is common. Outflows from the lake scour sediment and prevent channel blockage. We propose that channel geometry and size are then controlled by a dynamic balance between channel narrowing by suspended sediment deposition and incision and widening by mass failure of banks during outflows. Tie channels are laterally stable and may convey flow for hundreds to a few thousand of years.Citation: Rowland, J. C., W. E. Dietrich, G. Day, and G. Parker (2009), Formation and maintenance of single-thread tie channels entering floodplain lakes: Observations from three diverse river systems,

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Section: Conceptual Modelmentioning

confidence: 74%

Formation and maintenance of single‐thread tie channels entering floodplain lakes: Observations from three diverse river systems

et al. 2009

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“…In this shear zone, sediment laden waters will tend to rain loose sediment along a corridor that defines the levee. This is a mechanism similar to that described by Leighly [1934], modeled experimentally by Sellin [1964] and numerically by James [1985], and incorporated into Adams et al's [2004] conceptual model of levee formation. Levee formation during extended periods of flooding with limited to no hydraulic head out of the channel may explain why there were no crevasse splay deposits on the Fly.…”

Section: Discussionmentioning

confidence: 92%

The depositional web on the floodplain of the Fly River, Papua New Guinea

Day¹,

Dietrich²,

Rowland³

et al. 2008

J. Geophys. Res.

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[1] Floodplain deposition on lowland meandering rivers is usually interpreted as either lateral accretion during channel migration or overbank deposition. Previous studies on the Fly River in Papua New Guinea suggest, however, that floodplain channels (consisting of tie channel and tributary channels) play an important role in conveying sediment out across the floodplain. Here we report the results of an intensive field study conducted from 1990 to 1998 that documents the discharge of main stem water from the Fly River onto its floodplain and maps the spatial pattern of sediment deposition on the floodplain (using as a tracer elevated particulate copper introduced into the system by upstream mining). An extensive network of water level recorders demonstrates significant hydraulic heads from the main stem out the floodplain channels. For the monitoring period 1995-1998, net water discharge into the floodplain channels was about 20% of the flow. Another 20% is estimated to spill overbank from the main stem in wet years. Annual floodplain coring from 1990 to 1994 obtained over 800 samples across the 3500 km 2 Middle Fly floodplain for use in documenting temporal and spatial patterns of sediment deposition. Early samples record the rapid spread of sediment up to 10 km away from the main stem via floodplain channels. Later, more intensive coring samples documented a well-defined exponential decline in sediment deposition from the nearest channel (which differed little between floodplain and main stem channels). Deposition, averaging about 6-9 mm/a, occurred in a 1 km corridor either side of these channels and effectively ceased beyond that distance. About 40% of the total sediment load was deposited on the floodplain, with half of that being conveyed by the over 900 km of floodplain channels (equal to about 0.09% sediment deposition/km of main stem channel length). Levee topographies along the main stem and floodplain channels are similar but cannot be explained by the observed exponential functions. Channel margin shear flow during extended periods of flooding may give rise to the localized levee deposition. Our study demonstrates that tie and tributary floodplain channels can inject large volumes of sediment-laden main stem waters great distances across the floodplain where they spill overbank, forming a narrow band of deposition, thereby creating a depositional web.

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“…Maximum velocity is usually just below the surface of the water, and is attributable to turbulence with increased distance from the sides or bed of the stream. (Leighley, 1934). In some of these trials, the effect of skeletal parts protruding into higher velocities may have contributed to their higher transport potential.…”

Section: Discussionmentioning

confidence: 98%