Dune morphology and hysteresis in alluvial channels during long-duration floods revealed using high temporal-resolution MBES bathymetry

Julia Cisneros, Jim Best, Thaiënne A G P van Dijk, Erik Mosselman

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Abstract

In natural rivers, flow discharge may fluctuate across a range of time scales – from diurnal to seasonal - but is often most pronounced during hydrographs that may encompass long-duration floods. Under these varying flows, bedforms can be created and modified by the flow without achieving any ‘equilibrium’ state. A lag between changes in flow and the morphological response of the bedforms, termed bedform hysteresis, is commonly present. Importantly for channel management and navigation, since dunes may grow larger during floods, but often experience a lagged decay in size during lowering water levels, critical water depths may be reached for inland shipping. There is also a consensus that dunes possess a more flattened shape, and lower leeside angle, than previously assumed in large rivers and that such dunes do not exhibit a region of permanent flow separation downstream of the dune. This different leeside shape thus questions traditional ideas of flow interactions with dunes, where flow separation in the steep dune lee side leads to energy loss (form drag) that increases flow resistance and energy expenditure within the flow. This paper quantifies dune hysteresis in the River Waal, Netherlands, by investigating how dune morphology changes through flood hydrographs, using high spatial- and temporal- resolution bathymetric data and robust computational analysis methods to produce probability density functions of dune morphology. This quantification aims to provide a better understanding of dune hysteresis in large rivers. The analysis examines several large data sets of river bathymetry from a 13 km reach of the River Waal, Netherlands, in a time series of bi-weekly multibeam echo sounder surveys over the last 12 years. Parameterization includes dune height, wavelength, leeside angle and leeside shape, to assess dune kinematics and hysteresis during different flood hydrographs.
Original languageEnglish
Title of host publicationProceedings of the International conference Marine and River Dune Dynamics 2019
Subtitle of host publication1-3 April 2019, Bremen Germany
EditorsAlice Lefebvre, Thierry Garlan, Christian Winter
PublisherSHOM
Pages51-56
Number of pages6
ISBN (Print)978-2-11-139488-9
Publication statusPublished - 2019
Event6th edi­ti­on of the International Conference on Ma­ri­ne and Ri­ver Dune Dy­na­mics - Bremen, Germany
Duration: 1 Apr 20193 Apr 2019
https://www.marum.de/Forschung/Page6449.html

Conference

Conference6th edi­ti­on of the International Conference on Ma­ri­ne and Ri­ver Dune Dy­na­mics
Abbreviated titleMA­RID VI
CountryGermany
CityBremen
Period1/04/193/04/19
Internet address

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    Cisneros, J., Best, J., van Dijk, T. A. G. P., & Mosselman, E. (2019). Dune morphology and hysteresis in alluvial channels during long-duration floods revealed using high temporal-resolution MBES bathymetry. In A. Lefebvre, T. Garlan, & C. Winter (Eds.), Proceedings of the International conference Marine and River Dune Dynamics 2019: 1-3 April 2019, Bremen Germany (pp. 51-56). SHOM.