Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuary
Tidal bars in estuaries are poorly understood compared to fluvial bars. There is limited theory that predicts tidal bar dimensions. Moreover, where fluvial channels bifurcate around bars, tidal channels around bars often develop either flood- or ebb-dominance which remains unexplained. Tidal experim...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2014-04-01
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| Series: | Advances in Geosciences |
| Online Access: | http://www.adv-geosci.net/39/21/2014/adgeo-39-21-2014.pdf |
| _version_ | 1811268130378350592 |
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| author | M. G. Kleinhans T. M. van Rosmalen C. Roosendaal M. van der Vegt |
| author_facet | M. G. Kleinhans T. M. van Rosmalen C. Roosendaal M. van der Vegt |
| author_sort | M. G. Kleinhans |
| collection | DOAJ |
| description | Tidal bars in estuaries are poorly understood compared to fluvial bars. There
is limited theory that predicts tidal bar dimensions. Moreover, where fluvial
channels bifurcate around bars, tidal channels around bars often develop
either flood- or ebb-dominance which remains unexplained. Tidal experiments
are rare and have not reproduced these phenomena to date because these are
usually highly ebb-dominated. Here we report preliminary experiments in a
novel setup that produce tidal bars from an initial situation with flat bed
and exactly symmetrical ebb- and flood-related sediment mobility. The bars
initially develop in a saw-tooth pattern with mutually evasive ebb- and flood
channels. The tips of the bars evolve further into lobate bars built up from
sediment from excavating channels. The bar tips form steep and high
obstructions for the opposing flow direction, which then diverges into
evasive channels. The bars develop into a diamond shape as channels bifurcate
and deepen around it. We further found that bar height correlates well to bar
width but not with bar length, whilst bar length correlates well to the tidal
excursion length. As the experiment progressed scour holes developed that
affected the channel and bar pattern and are considered artifacts of the
experiment. We conclude that the mutually evasive ebb- and flood-dominance of
channels emerges simultaneously with the onset of tidal bar formation, and
that these preliminary data confirm results from linear stability analyses.
The results are proof of principle for the novel experimental setup for tidal
systems. |
| first_indexed | 2024-04-12T21:16:13Z |
| format | Article |
| id | doaj.art-918120cab2e64329ae59d9b9e477c3fc |
| institution | Directory Open Access Journal |
| issn | 1680-7340 1680-7359 |
| language | English |
| last_indexed | 2024-04-12T21:16:13Z |
| publishDate | 2014-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Advances in Geosciences |
| spelling | doaj.art-918120cab2e64329ae59d9b9e477c3fc2022-12-22T03:16:26ZengCopernicus PublicationsAdvances in Geosciences1680-73401680-73592014-04-0139212610.5194/adgeo-39-21-2014Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuaryM. G. Kleinhans0T. M. van Rosmalen1C. Roosendaal2M. van der Vegt3Faculty of Geosciences, Universiteit Utrecht, Utrecht, the NetherlandsFaculty of Geosciences, Universiteit Utrecht, Utrecht, the NetherlandsFaculty of Geosciences, Universiteit Utrecht, Utrecht, the NetherlandsFaculty of Geosciences, Universiteit Utrecht, Utrecht, the NetherlandsTidal bars in estuaries are poorly understood compared to fluvial bars. There is limited theory that predicts tidal bar dimensions. Moreover, where fluvial channels bifurcate around bars, tidal channels around bars often develop either flood- or ebb-dominance which remains unexplained. Tidal experiments are rare and have not reproduced these phenomena to date because these are usually highly ebb-dominated. Here we report preliminary experiments in a novel setup that produce tidal bars from an initial situation with flat bed and exactly symmetrical ebb- and flood-related sediment mobility. The bars initially develop in a saw-tooth pattern with mutually evasive ebb- and flood channels. The tips of the bars evolve further into lobate bars built up from sediment from excavating channels. The bar tips form steep and high obstructions for the opposing flow direction, which then diverges into evasive channels. The bars develop into a diamond shape as channels bifurcate and deepen around it. We further found that bar height correlates well to bar width but not with bar length, whilst bar length correlates well to the tidal excursion length. As the experiment progressed scour holes developed that affected the channel and bar pattern and are considered artifacts of the experiment. We conclude that the mutually evasive ebb- and flood-dominance of channels emerges simultaneously with the onset of tidal bar formation, and that these preliminary data confirm results from linear stability analyses. The results are proof of principle for the novel experimental setup for tidal systems.http://www.adv-geosci.net/39/21/2014/adgeo-39-21-2014.pdf |
| spellingShingle | M. G. Kleinhans T. M. van Rosmalen C. Roosendaal M. van der Vegt Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuary Advances in Geosciences |
| title | Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuary |
| title_full | Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuary |
| title_fullStr | Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuary |
| title_full_unstemmed | Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuary |
| title_short | Turning the tide: mutually evasive ebb- and flood-dominant channels and bars in an experimental estuary |
| title_sort | turning the tide mutually evasive ebb and flood dominant channels and bars in an experimental estuary |
| url | http://www.adv-geosci.net/39/21/2014/adgeo-39-21-2014.pdf |
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