Formation of riffle—pool sequences: field evidence for an autogenetic process

Clifford, Nicholas J.

doi:10.1016/0037-0738(93)90074-f

Cited by 75 publications

(90 citation statements)

References 31 publications

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“…A study by Lisle [1986] found that 85% of pools were next to large obstructions or bends and that, conversely, 92% of large obstructions or bends had pools. Similarly, Clifford [1993b] suggested that pool-riffle units are initiated with the generation of eddies at a major flow obstacle. Further, Clifford [1993b] describes an autogenic process whereby the deposition downstream of a pool formed by an obstruction generates the next downstream flow irregularity.…”

Section: Flow Convergence Routingmentioning

confidence: 99%

“…Similarly, Clifford [1993b] suggested that pool-riffle units are initiated with the generation of eddies at a major flow obstacle. Further, Clifford [1993b] describes an autogenic process whereby the deposition downstream of a pool formed by an obstruction generates the next downstream flow irregularity. This process is consistent with the converging and diverging flow patterns fundamental to the flow convergence routing hypothesis.…”

Section: Flow Convergence Routingmentioning

confidence: 99%

“…For example, Clifford and Richards [1992] found that a reversal or its absence could be demonstrated simultaneously for a given pool riffle sequence depending on the parameter evaluated, and the location of the measurement or cross section. Keller [1970Keller [ , 1971 field near-bed velocity stated support implied support Keller [1972] theoretical N/A not discussed assumed support Richards [1978] 1-d model section average velocity and shear inconclusive not discussed Lisle [1979] field mean shear stress stated support not discussed Bhowmik and Demissie [1982] field N/A negative not discussed Jackson and Beschta [1982] field near-bed velocity stated support assumed support Lisle [1986] field N/A not discussed assumed support Petit [1987Petit [ , 1990 field point shear stress and velocity inconclusive assumed support Carling [1991] field velocity, shear velocity negative implied support Clifford and Richards [1992] field point and section-averaged velocity and shear stress negative implied support Keller and Florsheim [1993] 1-D model section average velocity stated support not discussed Clifford [1993aClifford [ , 1993b field N/A negative assumed support Carling and Wood [1994] 1-D model section average velocity and shear velocity conditional support not discussed Miller [1994] 2-D model N/A not discussed assumed support Sear [1996] field, review N/A negative not discussed Thompson et al [1996Thompson et al [ , 1998Thompson et al [ , 1999 For the velocity reversal hypothesis, stated support indicates that the study supports the velocity reversal hypothesis for the case(s) analyzed; conditional support indicates that the study supported the velocity reversal under some conditions; inconclusive indicates that no...…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Flow convergence routing hypothesis for pool‐riffle maintenance in alluvial rivers

MacWilliams

Wheaton

Pasternack

et al. 2006

Water Resources Research

155

238

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[1] The velocity reversal hypothesis is commonly cited as a mechanism for the maintenance of pool-riffle morphology. Although this hypothesis is based on the magnitude of mean flow parameters, recent studies have suggested that mean parameters are not sufficient to explain the dominant processes in many pool-riffle sequences. In this study, two-and three-dimensional models are applied to simulate flow in the pool-riffle sequence on Dry Creek, California, where the velocity reversal hypothesis was first proposed. These simulations provide an opportunity to evaluate the hydrodynamics underlying the observed reversals in near-bed and section-averaged velocity and are used to investigate the influence of secondary currents, the advection of momentum, and cross-stream flow variability. The simulation results support the occurrence of a reversal in mean velocity and mean shear stress with increasing discharge. However, the results indicate that the effects of flow convergence due to an upstream constriction and the routing of flow through the system are more significant in influencing pool-riffle morphology than the occurrence of a mean velocity reversal. The hypothesis of flow convergence routing is introduced as a more meaningful explanation of the mechanisms acting to maintain pool-riffle morphology.

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Section: Flow Convergence Routingmentioning

confidence: 99%

Section: Flow Convergence Routingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Flow convergence routing hypothesis for pool‐riffle maintenance in alluvial rivers

MacWilliams

Wheaton

Pasternack

et al. 2006

Water Resources Research

155

238

View full text Add to dashboard Cite

show abstract

“…summarized in Wohl, 1998), it is likely that the initial generation of a sequence of pools, adjusted to high flow erosivity but low bed erodibility (cf. Clifford, 1993), feeds-back into hydrology by influencing spatial variability in stream power, through variation in bed slope and roughness.…”

Section: Glaciofluvial and Baselevel Context Of Palaeodischarge Variamentioning

confidence: 99%

Eskers in a complete, wet-based glacial system in the Phlegra Montes region, Mars

Gallagher

Balme

2015

Earth and Planetary Science Letters

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This paper investigates the influences of palaeohydrology and geologicaltopographic inheritance in shaping the channel of the lower River Suir, southeast Ireland. Results of acoustic surveys of the lower River Suir and Waterford Harbour reveal two scales of pseudo-cyclic river bedforms. Longitudinal elevation profiles of the geological topography (undulating bedrock and till-mantled bedrock) bounding the present floodplain swath reveal pseudo-cyclicity in that terrain too. Spectral and statistical analyses are used to quantify the cyclicity of the long profile and geological-topographic series. These methods show that the dominant cyclicity of the long profile reflects autocorrelation more than inheritance of cyclicity from the bounding geological topography. The cyclicity of the long profile mainly reflects a hydraulic control on pool-spacing, although some cyclicity probably has been inherited from the geological-topography. Channel-forming palaeodischarge is estimated based on the dominant pool-spacing revealed by spectral analysis, validated using relationships between meander wavelength, channel cross-sectional geometry and hydraulically-informed discharge reconstruction. The palaeodischarge estimates are in close agreement and are two orders of magnitude greater than present flood maxima. Significantly, these palaeodischarge estimates also agree closely with palaeodischarge calculated for the submerged Pleistocene palaeochannel that extends across the near-shore continental shelf from Waterford Harbour. The pool-sequence of the lower Suir and the submerged palaeochannel represent a former land-system that was active during a period of low relative sea level during the last glacial. More broadly, the paper offers insights into the landscape evolution of formerly glaciated regions that experienced very wide This article is protected by copyright. All rights reserved. discharge variability during and after the transition from glacial to interglacial regimes, in a context of complex relative sea level change.

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“…Spatial variation of water velocity, with high and low current areas, controls the necessary alternation of erosion and deposition (Yalin 1971). Changes in near-bed turbulence induced at the beginning of shallow-depth sequences create differences in sediment entrainment (shear stress); these enhance and maintain the sequence through a form of feedback process (Clifford 1993a(Clifford , 1993b. Thus, the longitudinal succession of different geomorphologic units is related to the longitudinal oscillations in the velocity field of turbulent flow (Knighton 1998).…”

Section: Hydrological Processes In Geomorphologic Unitsmentioning

confidence: 99%

Nitrogen dynamics in rural streams : differences between geomorphologic units

Lefebvre

Marmonier

Peiry

2006

Ann. Limnol. - Int. J. Lim.

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Nitrogen dynamics were investigated in the top centimeters of bottom sediment in three different geomorphologic units (riffles, sand bars, pools) and along two contrasted reaches (nitrogen-rich, nitrogen-poor) of a rural stream. Some predictions of links between geomorphology and processes were verified: (i) hydrological exchanges and nitrification were lower in pools than in riffles and bars, whereas (ii) ammonification and denitrification were higher in pools. Studies of denitrification potential in six other reaches of three N-rich streams support these conclusions and demonstrate that pools are spots of high microbial activity in streams.

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Formation of riffle—pool sequences: field evidence for an autogenetic process

Cited by 75 publications

References 31 publications

Flow convergence routing hypothesis for pool‐riffle maintenance in alluvial rivers

Flow convergence routing hypothesis for pool‐riffle maintenance in alluvial rivers

Eskers in a complete, wet-based glacial system in the Phlegra Montes region, Mars

Nitrogen dynamics in rural streams : differences between geomorphologic units

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