Flow structure and bedform dynamics around tidally-influenced bars
Keevil, C.E.; Parsons, D.R.; Ashworth, P.J.; Best, J.L.; Sandbach, S.D.; Smith, G.S.; Prokocki, E.W.; Nicholas, A.P.; Simpson, C.J. (2013). Flow structure and bedform dynamics around tidally-influenced bars, in: Van Lancker, V. et al. (Ed.) MARID 2013: Fourth International Conference on Marine and River Dune Dynamics. Bruges, Belgium, 15-17 April 2013. VLIZ Special Publication, 65: pp. 149-152 In: Van Lancker, V.; Garlan, T. (Ed.) (2013). MARID 2013: Fourth International Conference on Marine and River Dune Dynamics. Bruges, Belgium, 15-17 April 2013. VLIZ Special Publication, 65. Royal Belgian Institute of Natural Sciences/SHOM/Flanders Marine Institute (VLIZ): Oostende. ISBN 978-2-11-128352-7. 338 pp., more In: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950, more |  |
| Authors | | Top | - Keevil, C.E.
- Parsons, D.R.
- Ashworth, P.J.
| - Best, J.L.
- Sandbach, S.D.
- Smith, G.S.
| - Prokocki, E.W.
- Nicholas, A.P.
- Simpson, C.J.
|
| Abstract | Tidal bar complexes are common features of fluvio-tidal transition zones. Such features are generated by the complex interplay, across a broad range of spatio-temporal scales, between fluvial, tidal and wave hydrodynamics. This spatio-temporal variability is reflected in the generation and interactions of reach-scale flow structures around and over bar forms, which in turn drive bar-scale sediment transport and bedform scale morphodynamics. However, presently we do not possess adequate data or understanding to enable quantification of these relationships and how they change across the fluvio-tidal transition zone. This paper reports on the flow structure and morphodynamics around tidal bars through the fluvio-tidal transition in the Columbia River, WA, USA. Detailed flow mapping using an ADCP was conducted from a small launch highlighting the evolution of flow around km-scale tidally-influenced bars during the tidal cycle. These flow data were combined with targeted multibeam echo sounder (MBES) bathymetric surveys conducted from a second launch, thus allowing the link between flow forcing and bar- and bed- form geometries to be examined. Results show how the spatio-temporal variations in the hydraulics around bars are highly dynamic, which controls the likely transitions in bar morphologies as the tidal influence increases distally towards the river mouth and likely governs bar evolution and stability. |
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