the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Coexistence of two dune scales in a lowland river
Bart Vermeulen
Antonius J. F. Hoitink
Abstract. A secondary scale of bedforms, superimposed on larger, primary dunes, has been observed in fluvial systems worldwide. This notwithstanding, very little is known about the morphological behaviour and characteristics of this secondary scale. This study aims to better characterize and understand how two dune scales coexist in fluvial systems, and how both scales adapt over time and space, considering their interdependence. The study is based on analysis of a biweekly multibeam echosounding dataset that spans a period of approximately three years and 34 kilometers in the Waal River, a lowland sand-bedded river. Results reveal that the secondary dune scale is ubiquitous across space and time, and not limited to specific flow or transport conditions. Whereas primary dunes lengthen during low flows, secondary dune height, lee slope angle and length correlate with discharge. Secondary dune size and migration strongly depend on the primary dune lee slope angle and height. Secondary dunes can migrate over the lee slope of low-angled primary dunes, and their height is inversely correlated to the upstream primary dune height and lee slope angle. In the Waal River, a lateral variation in bed grain size, attributed to shipping, largely affects dune morphology. Primary dunes are lower and less often present in the southern lane, where grain sizes are smaller. Here, secondary bedforms are more developed. At peak discharge, secondary bedforms even become the dominant scale, whereas primary dunes entirely disappear but reestablish during lower flows.
Judith Yttje Zomer et al.
Status: open (until 28 Jun 2023)
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RC1: 'Comment on esurf-2023-12', Anonymous Referee #1, 18 May 2023
reply
I have completed my review of the manuscript entitled "Coexistence of two dune scales in a lowland river" and I am pleased to recommend its publication with revisions. The paper represents a significant contribution to the field of bedform morphodynamics and carries implications for various related disciplines, including geomorphology, sediment transport, hydrology, river modeling, and sedimentology.
Please see my general comments and line-by-line comments attached.
Judith Yttje Zomer et al.
Judith Yttje Zomer et al.
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