Modeling long-term delta dynamics reveals persistent geometric river avulsion locations

dc.contributor.author

Ratliff, KM

dc.contributor.author

Hutton, EWH

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Murray, AB

dc.date.accessioned

2022-09-02T20:01:45Z

dc.date.available

2022-09-02T20:01:45Z

dc.date.issued

2021-04-01

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2022-09-02T20:01:44Z

dc.description.abstract

River deltas grow through repeated stacking of sedimentary lobes, the location and size of which are determined by channel avulsions (relatively sudden changes in river course). We use a model coupling fluvial and coastal processes to explore avulsion dynamics under a range of wave energies and sea-level-rise rates and find that the primary control on avulsion location and delta lobe size in our model is the critical superelevation ratio (SER), the amount of channel aggradation relative to the surrounding floodplain that is required to trigger an avulsion. The preferred avulsion location arises because of geometric constraints – a preferential avulsion node occurs at the break in floodplain slope that develops as the river progrades and/or sea level rises. This concavity develops in our model because the river profile aggrades and erodes via linear diffusion, whereas the diffusion of the floodplain topography is limited to episodic crevasse splays. These results are in contrast to recent modeling work, which was motivated by laboratory experiments and assumes a union between river channel and floodplain aggradation rates, and where avulsion nodes are driven by backwater hydrodynamics. The preferred avulsion length in our model scales well with laboratory, field, and model results without including hydrodynamic backwater effects. This work suggests an alternative mechanism to explain avulsion locations on deltas where floodplain topography aggrades and/or diffuses more slowly than the river channel profile, and it points to the need to elucidate river channel and floodplain connectivity over large space and time scales, and how the connectivity varies from one type of delta to another.

dc.identifier.issn

0012-821X

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1385-013X

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https://hdl.handle.net/10161/25677

dc.language

en

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Elsevier BV

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Earth and Planetary Science Letters

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10.1016/j.epsl.2021.116786

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river delta

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river avulsion

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avulsion node

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delta morphodynamics

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Modeling long-term delta dynamics reveals persistent geometric river avulsion locations

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Journal article

duke.contributor.orcid

Murray, AB|0000-0002-2484-9151

pubs.begin-page

116786

pubs.end-page

116786

pubs.organisational-group

Duke

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Nicholas School of the Environment

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Earth and Climate Sciences

pubs.publication-status

Published

pubs.volume

559

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