Episodes of vertical accretion and catastrophic stripping: A model of disequilibrium flood-plain development

Nanson, Gerald C.

doi:10.1130/0016-7606(1986)97<1467:eovaac>2.0.co;2

Cited by 284 publications

(216 citation statements)

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“…Unlike the eight other factors, valley confinement is not a process. It is an independent external variable that can have a profound impact on floodplain character by restricting channel migration; channel bends can become fixed in position by bedrock obstructions resulting in a dominance of overbank sedimentation and the construction of large levee banks (Nanson, 1986). In unconfined situations, and given sufficient power, channels are free to migrate and to build floodplains by a variety of processes.…”

Section: Floodplain Orders and Subordersmentioning

confidence: 99%

“…The main channel is laterally stable due to partial constriction in a confining bedrock valley which also acts to concentrate the erosional power of extreme flood events. Overbank deposition gradually builds a floodplain of sandy-silty alluvium over a period of hundreds or thousands of years, following which catastrophic erosion by a single large flood, or a series of more moderate floods, strips the floodplain to a basal lag deposit from which it slowly reforms (Nanson, 1986). This periodic destruction appears due to the progressive development of large sandy levee banks and floodplain surfaces of highly variable relief.…”

Section: Order A2 Confined Vertical-accretion Sandy Floodplainsmentioning

confidence: 99%

“…Stewart andLamarche, 1967 andBaker, 1977). (ii) Confined vertical-accretion sandy floodplain (after Nanson, 1986). (iii) Cut and fill floodplain (after Prosser, 1988).…”

Section: Order A2 Confined Vertical-accretion Sandy Floodplainsmentioning

confidence: 99%

“…It has been shown to be the dominant process along certain low-gradient single-thread channels (Beckinsale and Richardson, 1964;Schumm, 1968;Ritter et al, 1973;Rose et al, 1980;Nanson and Young, 1981;Burrin and Scaife, 1984;Burrin, 1985) and anastomosing channels (Smith, 1972(Smith, , 1974Smith and Smith, 1980) where there is insufficient stream power to permit channel migration. The most active vertical accretion environments occur along high-energy channels with sandy floodplains that can be destroyed catastrophically by large floods and subsequently reconstructed predominantly by overbank deposition (Schumm and Lichty, 1963;Burkham, 1972;Nanson, 1986). Levees, crevasse splays and backswamp deposits are very important styles of deposition and have been described in detail elsewhere (e.g.…”

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confidence: 99%

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A genetic classification of floodplains

1992

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Floodplains are formed by a complex interaction of fluvial processes but their character and evolution is essentially the product of stream power and sediment character. The relation between a stream's ability to entrain and transport sediment and the erosional resistance of floodplain alluvium that forms the channel boundary provides the basis for a genetic classification of floodplains. Three classes are recognised: (1) highenergy non-cohesive; (2) medium-energy non-cohesive; and (3) low-energy cohesive floodplains. Thirteen derivative orders and suborders, ranging from confined, coarse-grained, non-cohesive floodplains in highenergy environments to unconfined fine-grained cohesive floodplains in low-energy environments, are defined on the basis of nine factors (mostly floodplain forming processes). These factors result in distinctive geomorphological features (such as scroll bars or extensive backswamps) that distinguish each floodplain type in terms of genesis and resulting morphology. Finally, it is proposed that, because floodplains are derivatives of the parent stream system, substantial environmental change will result in the predictable transformation of one floodplain type to another over time. that distinguish each floodplain type in terms of genesis and resulting morphology. Finally, it is proposed that, because floodplains are derivatives of the parent stream system, substantial environmental change will result in the predictable transformation of one floodplain type to another over time.

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Section: Floodplain Orders and Subordersmentioning

confidence: 99%

Section: Order A2 Confined Vertical-accretion Sandy Floodplainsmentioning

confidence: 99%

“…Stewart andLamarche, 1967 andBaker, 1977). (ii) Confined vertical-accretion sandy floodplain (after Nanson, 1986). (iii) Cut and fill floodplain (after Prosser, 1988).…”

Section: Order A2 Confined Vertical-accretion Sandy Floodplainsmentioning

confidence: 99%

mentioning

confidence: 99%

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A genetic classification of floodplains

1992

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“…Part of the variability in geomorphic effects of extreme floods reflects climatological contrasts which affect vegetation cover and soil erodibility on valley bottoms and slopes [Wolman and Gerson, 1978;Schumm and Lichty, 1963]. Also important, however, are variations in local flood hydraulics and valley side sediment supply determined by the geomorphic setting [Nanson, 1986;Baker, 1977;Kochel, 1988;Miller, 1995]. Analyzing the evidence of flood impact variability, Miller [1990] and Magilligan [1992] found that the variable geomorphic effects of a particular flood are determined by the spatial distribution of unit flow power among individual reaches, a variable largely controlled by peak flood discharge as well as valley bottom width and slope.…”

Section: Introductionmentioning

confidence: 99%

Response of the Ha! Ha! River to the flood of July 1996 in the Saguenay region of Quebec: Large‐scale avulsion in a glaciated valley

Lapointe¹,

Secretan²,

Driscoll³

et al. 1998

Water Resources Research

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The character and age structure of valley fills in upper Wolumla Creek catchment, south coast, New South Wales, Australia

Fryirs

1998

Earth Surf. Process. Landforms

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Extensive valley fills at the base of the escarpment in upper Wolumla Creek, on the south coast of New South Wales, Australia, have formed from a combination of 'cut and fill' processes. The valley fills comprise series of alternating, horizontally bedded sand and mud units, reflecting reworking of detritus from deeply weathered granites of the Bega Batholith. Sand units are deposited as sand sheets or splays on floodplain surfaces or in floodouts that form atop intact valley fill surfaces downstream of discontinuous gullies. Alternatively, sands are deposited from bedload and form bars or part of the valley floor within channel fills. Organic-rich mud units are deposited from suspension in swamps or in seepage zones at the distal margin of floodouts. Within 5 km ofthe escarpment, valley deposits grade downstream from sand sheet and splay deposition in floodouts, to mud deposition in swamp and seepage zones. Radiocarbon dates indicate that virtually the entire valley fill of upper Wolumla Creek was excavated prior to 6000 years BP. Remnant terraces are evident at valley margins. The valley subsequently filled between 6000 years BP and 1000 years BP producing valley fills around 12 m deep, but no greater than 300 m wide. Reincision into the valley fill, on a scale smaller than the present incision phase, is indicated at around 1000 years BP, following which the channel refilled. Portion plans dated from 1865 refer to the study area as 'Wolumla Big Flat', and show large areas of swampy terrain, suggesting that the valley fill had re-established by this time. Within a few decades of European settlement the valley fill incised once more. Upper Wolumla Creek now has a channel over 10 m deep and 100 m wide in places, draining a catchment area of less than 20 km 2 .

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Episodes of vertical accretion and catastrophic stripping: A model of disequilibrium flood-plain development

Cited by 284 publications

References 0 publications

A genetic classification of floodplains

A genetic classification of floodplains

Response of the Ha! Ha! River to the flood of July 1996 in the Saguenay region of Quebec: Large‐scale avulsion in a glaciated valley

The character and age structure of valley fills in upper Wolumla Creek catchment, south coast, New South Wales, Australia

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