Preferred position model and subsurface symmetry of valleys

Palmquist, Robert C.

doi:10.1130/0016-7606(1975)86<1392:ppmass>2.0.co;2

Cited by 16 publications

(7 citation statements)

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“…Despite of internal meander migration, the meander belt as a whole is rather stable. This agrees with the findings of Coleman (1969), Palmquist (1975) and Brown (1997), who describe this phenomenon, especially from 'larger' river systems. As a result, at the edge of the Medjerda meander belt, well-stratified overbank deposits ( Figure 4) allow the interpretation of sediment series over long distances within the Ghardimaou Basin.…”

Section: Methodssupporting

confidence: 93%

Centennial-scale late-Pleistocene to mid-Holocene synthetic profile of the Medjerda Valley, northern Tunisia

Zielhofer

Faust

Escudero³

et al. 2004

The Holocene

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During the late Pleistocene to mid-Holocene, the Medjerda river system in Mediterranean Tunisia shows events of increased flooding and aggradation of relatively coarse overbank deposits. Geomorphic activity in river systems within this region correlate with aridification of the climate, but not with temperature. The late-Pleistocene to mid-Holocene synthetic profile of the Ghardimaou floodplain (mid-Medjerda river) indicates fluvial activity from 12.4 to 11.8, 6.6 to 6.0 and after 4.8 ka cal. BP. External correlations imply global and regional causes of the late-Pleistocene to mid-Holocene climatic development such as North Atlantic deep-water formation, fluctuations in Saharan humidity and impacts of local Mediterranean weather phenomena. Palaeomagnetic records offer additional opportunities to interpret fluvial activity in river systems, especially for detecting chronological hiatuses in apparently homogeneous sediment sequences.

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Section: Methodssupporting

confidence: 93%

Centennial-scale late-Pleistocene to mid-Holocene synthetic profile of the Medjerda Valley, northern Tunisia

Zielhofer

Faust

Escudero³

et al. 2004

The Holocene

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“…The maximum values of active bed thickness were approximately equal to one half of the mean depth of the highest flow recorded during the period when scour chains were in place. This maximum value equals those measured by Palmquist [1975].…”

Section: Scour and Fillmentioning

confidence: 71%

Sediment transport and resulting deposition in spawning gravels, north coastal California

Lisle¹

1989

Water Resources Research

288

257

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Incubating salmonid eggs in streambeds are often threatened by deposition of fine sediment within the gravel. To relate sedimentation of spawning gravel beds to sediment transport, infiltration of fine sediment (<2 mm in diameter) into clean gravel beds, bed material size distributions, scour-fill depths, and sediment transport during 10 storm flow events were measured in three streams of north coastal California. Although suspended sediment comprised most (75-94%) of the clastic load during storm flows, bed load material (0.25-2 mm) accounted for most (70-78%) of the fine sediment accumulated in experimental gravel implanted in the streambeds. Sand trapped in the interstices of the top several centimeters formed a seal that impeded deeper deposition of very fine sand and finer material. The seal was responsible at least in part for a decrease in the rate of fine-sediment accumulation with increasing cumulative bed load transport. Areas of the streambeds commonly scoured or filled 0.1 m or more during storm flows, and thus scour and fill commonly created a sandy layer at least as thick as the seal formed by sediment infiltration. Scour could erode eggs laid in the bed and expose deeper levels of the bed to infiltration by fine sediment, but at the same time could allow fine sediment to be winnowed away. Great temporal and spatial variation in sedimentation in these streams suggests that individual storms of moderate size pose a threat to eggs in many but not all areas selected by fish for spawning.

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“…The frequency and relative magnitude of such floods will determine the extent to which the deepest scour may rework the entire channel base. Although capable of increasing sandbody thickness in meandering channels by 100% (Palmquist 1975;Mlynarczyk & Rotnicki 1989) extreme scour is particularly common in ephemeral rivers (Foley 1978;Hassan 1990). This suggests that the degree to which scour is important may increase directly with discharge variability.…”

Section: Quantifying the Effects Of Scourmentioning

confidence: 99%

Fluvial scour and incision: models for their influence on the development of realistic reservoir geometries

Salter

1993

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The three-dimensional geometry of fluvial sandbodies may be very complicated. Factors influencing this complexity include the processes of fluvial scour and incision, both of which can promote local or widespread increases in sandbody thickness. Incision, as caused by downstream relative base-level fall, produces entrenched valleys that control the location of subsequent alluvial deposits. A simple model is presented that attempts to quantify the scale of this extrinsic incision and, in turn, highlights several sedimentary implications of base-level fall. In contrast, scour is an intrinsic process common to all fluvial systems, and is promoted by constriction, curvature or confluences within the major channels. Existing empirical relationships that predict fluvial sandbody width from thickness are oversimplistic, failing to consider the modification of sandbody dimensions by such intrinsic processes. At low aggradation rates sandbody thickness may exceed channel bankfull depth by 100%, due purely to the effects of scour. It is proposed that future fluvial width: thickness databases should stem from the classification of deposits according to the aggradational regime during their deposition. This will encourage the specific recognition of scour and incision, particularly in coastal plain alluvial deposits, and lead to an improved understanding of the controls upon sandbody deposition.

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Preferred position model and subsurface symmetry of valleys

Cited by 16 publications

References 0 publications

Centennial-scale late-Pleistocene to mid-Holocene synthetic profile of the Medjerda Valley, northern Tunisia

Centennial-scale late-Pleistocene to mid-Holocene synthetic profile of the Medjerda Valley, northern Tunisia

Sediment transport and resulting deposition in spawning gravels, north coastal California

Fluvial scour and incision: models for their influence on the development of realistic reservoir geometries

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