Depositional processes along a very low-gradient, suspended-load stream: the Barwon River, New South Wales

Woodyer, K. D.; Taylor, Graham R.; Crook, Keith A. W.

doi:10.1016/0037-0738(79)90023-x

Cited by 100 publications

(95 citation statements)

References 13 publications

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“…1), although a detailed survey of the channel bed materials has not been undertaken. The absence or minimal occurrence of a coarse basal unit contrasts markedly with the deposits of other mud-dominated rivers reported in the literature where a well-defined basal sand unit is present (e.g., Jackson, 1978Jackson, , 1981Taylor and Woodyer, 1978;Woodyer et al, 1979;Page et al, 2003). The paucity of sand within the Red River deposits relates to sediment supply as the geomorphic setting of the river is within an extensive glaciolacustrine clay plain (the former bed of Lake Agassiz) in the Red River valley (Brooks, 2003a).…”

Section: Discussionmentioning

confidence: 69%

Deposits and Cutoff Ages of Horseshoe and Marion Oxbow Lakes, Red River, Manitoba*

Brooks

Medioli

2005

gpq

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Quatre échantillons de bois provenant des dépôts fluviatiles ont donné des âges au radiocarbone de 1600 ± 40, 1700 ± 40, 1660 ± 40 et 1620 ± 40 BP. On estime que les recoupements qui ont donné naissance aux deux lacs se sont produits il y a environ 1990 (Horseshoe) et 1520 cal. BP (Marion), ou peu après. Les dépôts alluvio-lacustres riches en limon des lacs ne comportent pas de structures et de textures assez nettes pour permettre d'identifier leur milieux de sédimentation. L'absence, dans les deux cas, de sédiments grossiers à la base de l'unité fluviatile laisse supposer que des quantités minimes, voire négligeables, de sable ont été transportées le long des thalwegs avant que les recoupements ne surviennent. La prédominance du limon dans les dépôts des lacs en croissant reflète la provenance des sédiments, le cadre géomorphologique de la rivière étant celui d'une vaste plaine d'argile glaciolacustre. Four wood samples from the fluvial deposits yielded radiocarbon ages of 1600 ± 40, 1700 ± 40, 1660 ± 40 and 1620 ± 40 BP. The cutoffs that led to the formation of Horseshoe and Marion lakes are interpreted to have occurred at ~1990 and ~1520 cal BP or shortly thereafter, respectively. The silt-rich, alluvial-lacustrine deposits in the lakes lack structural and textural characteristics that can be readily recognized in core to distinguish the depositional environments. The absence of coarse sediments at the base of the fluvial units at both sites implies that minor to negligible amounts of sand were transported along the thalwegs of the channels prior to the meanders being cutoff. The dominance of silt within the oxbow deposits reflects sediment supply as the geomorphic setting of the river is within an extensive glaciolacustrine clay plain. Los depósitos ricos en limo de origen lacustre-aluvial de los lagos carecen de las característi-cas estructurales y de textura que pueden ser reconocidos fácilmente en el núcleo testigo para distinguir los ambientes de depósito. La ausencia de sedimentos de tipo grueso en la base de la unidad fluvial en ambos sitios indica que un aporte pequeño o insignificante de arena fue transportado a lo largo de la vaguada de los canales antes de que ocurriera la formación de los meandros. La predominancia de limos entre los depósitos del brazo muerto refleja el origen de los sedimentos y concuerda con el cuadro geomorfológico de un rió situado dentro de una planicie arcillosa glaciolacustre muy extensa.

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Section: Discussionmentioning

confidence: 69%

Deposits and Cutoff Ages of Horseshoe and Marion Oxbow Lakes, Red River, Manitoba*

Brooks

Medioli

2005

gpq

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“…The earlier mentioned field observations, however, typically occurred at so-called outer-bank benches on sharply-curved bends where the channel widens upstream of the bend apex and has a shallow planar morphology. Their morphological structure typically consists of a basal layer of coarse sediment overlain by organic-rich, fine sediment (Woodyer et al, 1979;Nanson and Page, 1983;Hickin, 1986;Erskine and Livingstone, 1999;Cohen, 2003;Vietz et al, 2012). The basal layer is due to bar formation associated with high-energy flow environments whilst the overlying fine layer is due to sediment deposition in the low-energy flow environment associated with flow separation.…”

Section: Configuration Measured Physical Quantitiesmentioning

confidence: 99%

Flow separation at the inner (convex) and outer (concave) banks of constant‐width and widening open‐channel bends

Blanckaert

Kleinhans

McLelland

et al. 2012

Earth Surf Processes Landf

101

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There is a paucity of data and insight in the mechanisms of, and controls on flow separation and recirculation at natural sharply-curved river bends. Herein we report on successful laboratory experiments that elucidate flow structure in one constant-width bend and a second bend with an outer-bank widening. The experiments were performed with both a flat immobile gravel bed and mobile sand bed with dominant bedload sediment transport.In the constant-width bend with immobile bed, a zone of mainly horizontal flow separation (vertical rotational axis) formed at the inner bank that did not contain detectable flow recirculation, and an outer-bank cell of secondary flow with streamwise oriented rotational axis. Surprisingly, the bend with widening at the outer bank and immobile bed did not lead to a transverse expansion of the flow. Rather, flow in the outer-bank widening weakly recirculated around a vertical axis and hardly interacted with the inner part of the bend, which behaved as a constant-width bend.In the mobile bed experiment, downstream of the bend apex a pronounced depositional bar developed at the inside of the bend and pronounced scour occurred at the outside. Moreover the deformed bed promoted flow separation over the bar, including return currents. In the constant-width bend, the topographic steering impeded the generation of an outer-bank cell of secondary flow. In the bend with outer-bank widening, the topographic steering induced an outward expansion of the flow, whereby the major part of the discharge was conveyed in the central part of the widening section. Flow in the outer-bank widening was highly three dimensional and included return currents near the bottom.In conclusion, the experiments elucidated three distinct processes of flow separation common in sharp bends: flow separation at the inner bank, an outer-bank cell of secondary flow, and flow separation and recirculation in an outer-bank widening.

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“…Lateral channel activity (migration and avulsion) has been more pronounced, however, leading to the formation of many extensive low-gradient, 'fan-shaped' plains. In combination with unusually well-developed riparian vegetation assemblages and variations in sediment calibre, diverse river styles have developed across the Australian drylands, including numerous sandy, single-thread, planar-bed, straight rivers and sandy anabranching rivers (Figure 12.2(c) and see Box 12.3), muddy anastomosing rivers with extensive floodplains marked by waterholes, 'braided' channel and reticulate channel networks ( Figure 12.2(d)), distributary rivers (Figure 12.8(a)) and rivers that decrease in size downstream and disappear in floodouts on alluvial plains, in playas or among aeolian dunefields (Figure 12.8(a) and (b)) (Woodyer, Taylor and Crook, 1979;Nanson, Rust and Taylor, 1986;Nanson et al, 1988;Nanson, Tooth and Knighton, 2002;Dunkerley, 1992Dunkerley, , 2008aKnighton and Nanson, 1994a, 1997, 2000Bourke and Pickup, 1999;Tooth, 1999Tooth, , 2005Tooth and Nanson, 1999, 2000a, 2000bFagan and Nanson, 2004;Wakelin-King and Webb, 2007;Fisher et al, 2008). In some instances, 'reforming channels' occur farther downvalley and either join a larger river system or disappear in another floodout (Tooth, 1999).…”

Section: Lower Energy Dryland Rivers: Australiamentioning

confidence: 99%

Distinctiveness and Diversity of Arid Zone River Systems

Tooth

Nanson

2011

Arid Zone Geomorphology

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Depositional processes along a very low-gradient, suspended-load stream: the Barwon River, New South Wales

Cited by 100 publications

References 13 publications

Deposits and Cutoff Ages of Horseshoe and Marion Oxbow Lakes, Red River, Manitoba*

Deposits and Cutoff Ages of Horseshoe and Marion Oxbow Lakes, Red River, Manitoba*

Flow separation at the inner (convex) and outer (concave) banks of constant‐width and widening open‐channel bends

Distinctiveness and Diversity of Arid Zone River Systems

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