Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries
Analogue models or scale experiments of estuaries and short tidal basins are notoriously difficult to create in the laboratory because of the difficulty to obtain currents strong enough to transport sand. Our recently discovered method to drive tidal currents by periodically tilting the entire fl...
| Main Authors: | , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-11-01
|
| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/5/731/2017/esurf-5-731-2017.pdf |
| _version_ | 1818266984703328256 |
|---|---|
| author | M. G. Kleinhans M. van der Vegt J. Leuven L. Braat H. Markies A. Simmelink C. Roosendaal A. van Eijk P. Vrijbergen M. van Maarseveen |
| author_facet | M. G. Kleinhans M. van der Vegt J. Leuven L. Braat H. Markies A. Simmelink C. Roosendaal A. van Eijk P. Vrijbergen M. van Maarseveen |
| author_sort | M. G. Kleinhans |
| collection | DOAJ |
| description | Analogue models or scale experiments of estuaries and short tidal basins are
notoriously difficult to create in the laboratory because of the difficulty
to obtain currents strong enough to transport sand. Our recently discovered
method to drive tidal currents by periodically tilting the entire flume leads
to intense sediment transport in both the ebb and flood phase, causing dynamic
channel and shoal patterns. However, it remains unclear whether tilting
produces periodic flows with characteristic tidal properties that are
sufficiently similar to those in nature for the purpose of landscape
experiments. Moreover, it is not well understood why the flows driven by
periodic sea level fluctuation, as in nature, are not sufficient for
morphodynamic experiments. Here we compare for the first time the tidal
currents driven by sea level fluctuations and by tilting. Experiments were run
in a 20 × 3 m straight flume, the Metronome, for a range of tilting
periods and with one or two boundaries open at constant head with free inflow and
outflow. Also, experiments were run with flow driven by periodic sea level
fluctuations. We recorded surface flow velocity along the flume with particle
imaging velocimetry and measured water levels along the flume. We compared
the results to a one-dimensional model with shallow flow equations for a
rough bed, which was tested on the experiments and applied to a range of
length scales bridging small experiments and large estuaries. We found that
the Reynolds method results in negligible flows along the flume except for the
first few metres, whereas flume tilting results in nearly uniform reversing
flow velocities along the entire flume that are strong enough to move sand.
Furthermore, tidal excursion length relative to basin length and the
dominance of friction over inertia is similar in tidal experiments and
reality. The sediment mobility converges between the Reynolds method and tilting
for flumes hundreds of metres long, which is impractical. Smaller flumes
of a few metres in length, on the other hand, are much more dominated by friction
than natural systems, meaning that sediment suspension would be impossible in
the resulting laminar flow on tidal flats. Where the Reynolds method is limited
by small sediment mobility and high tidal range relative to water depth, the
tilting method allows for independent control over the variables flow depth,
velocity, sediment mobility, tidal period and excursion length, and tidal
asymmetry. A periodically tilting flume thus opens up the possibility of
systematic biogeomorphological experimentation with self-formed estuaries. |
| first_indexed | 2024-12-12T20:15:23Z |
| format | Article |
| id | doaj.art-b4021d47336445d3bf7b795be8a19c10 |
| institution | Directory Open Access Journal |
| issn | 2196-6311 2196-632X |
| language | English |
| last_indexed | 2024-12-12T20:15:23Z |
| publishDate | 2017-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Earth Surface Dynamics |
| spelling | doaj.art-b4021d47336445d3bf7b795be8a19c102022-12-22T00:13:23ZengCopernicus PublicationsEarth Surface Dynamics2196-63112196-632X2017-11-01573175610.5194/esurf-5-731-2017Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuariesM. G. Kleinhans0M. van der Vegt1J. Leuven2L. Braat3H. Markies4A. Simmelink5C. Roosendaal6A. van Eijk7P. Vrijbergen8M. van Maarseveen9Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the Netherlandsformerly at: Consmema Metalworking, Hattem, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsFaculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, the NetherlandsAnalogue models or scale experiments of estuaries and short tidal basins are notoriously difficult to create in the laboratory because of the difficulty to obtain currents strong enough to transport sand. Our recently discovered method to drive tidal currents by periodically tilting the entire flume leads to intense sediment transport in both the ebb and flood phase, causing dynamic channel and shoal patterns. However, it remains unclear whether tilting produces periodic flows with characteristic tidal properties that are sufficiently similar to those in nature for the purpose of landscape experiments. Moreover, it is not well understood why the flows driven by periodic sea level fluctuation, as in nature, are not sufficient for morphodynamic experiments. Here we compare for the first time the tidal currents driven by sea level fluctuations and by tilting. Experiments were run in a 20 × 3 m straight flume, the Metronome, for a range of tilting periods and with one or two boundaries open at constant head with free inflow and outflow. Also, experiments were run with flow driven by periodic sea level fluctuations. We recorded surface flow velocity along the flume with particle imaging velocimetry and measured water levels along the flume. We compared the results to a one-dimensional model with shallow flow equations for a rough bed, which was tested on the experiments and applied to a range of length scales bridging small experiments and large estuaries. We found that the Reynolds method results in negligible flows along the flume except for the first few metres, whereas flume tilting results in nearly uniform reversing flow velocities along the entire flume that are strong enough to move sand. Furthermore, tidal excursion length relative to basin length and the dominance of friction over inertia is similar in tidal experiments and reality. The sediment mobility converges between the Reynolds method and tilting for flumes hundreds of metres long, which is impractical. Smaller flumes of a few metres in length, on the other hand, are much more dominated by friction than natural systems, meaning that sediment suspension would be impossible in the resulting laminar flow on tidal flats. Where the Reynolds method is limited by small sediment mobility and high tidal range relative to water depth, the tilting method allows for independent control over the variables flow depth, velocity, sediment mobility, tidal period and excursion length, and tidal asymmetry. A periodically tilting flume thus opens up the possibility of systematic biogeomorphological experimentation with self-formed estuaries.https://www.earth-surf-dynam.net/5/731/2017/esurf-5-731-2017.pdf |
| spellingShingle | M. G. Kleinhans M. van der Vegt J. Leuven L. Braat H. Markies A. Simmelink C. Roosendaal A. van Eijk P. Vrijbergen M. van Maarseveen Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries Earth Surface Dynamics |
| title | Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries |
| title_full | Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries |
| title_fullStr | Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries |
| title_full_unstemmed | Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries |
| title_short | Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries |
| title_sort | turning the tide comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries |
| url | https://www.earth-surf-dynam.net/5/731/2017/esurf-5-731-2017.pdf |
| work_keys_str_mv | AT mgkleinhans turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT mvandervegt turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT jleuven turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT lbraat turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT hmarkies turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT asimmelink turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT croosendaal turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT avaneijk turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT pvrijbergen turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries AT mvanmaarseveen turningthetidecomparisonoftidalflowbyperiodicsealevelfluctuationandbyperiodicbedtiltinginscaledlandscapeexperimentsofestuaries |