River Dune Dynamics During Low Flows

Lokin, Lieke; Warmink, Jord Jurriaan; Bomers, Anouk; Hulscher, Suzanne J.M.H.

doi:10.1029/2021gl097127

Cited by 19 publications

(22 citation statements)

References 45 publications

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“…Regarding dune length, however, existing scaling laws suggest that dune length scales with water depth (Yalin, 1964;Julien and Klaassen, 1995;Van Rijn, 1984c), which is not confirmed in the area subject to study. Lokin et al (2022) observed the same, based on analysis of primary dune properties in the Waal River. They suggest that during low flows, the migration of primary dunes becomes more diffusive, due to a larger influence of gravity in the erosion-deposition processes for smaller forcing from the flow.…”

Section: Primary and Secondary Dune Morphodynamicsmentioning

confidence: 57%

“…The Waal River is the main branch of the River Rhine in the Netherlands (Figure 1), which carries a 30-year median discharge of approximately 1500 m 3 s −1 (Lokin et al, 2022). The Waal River connects the port of Rotterdam to the inland and Germany, and is subject to intensive shipping.…”

Section: Study Area and Description Of Datamentioning

confidence: 99%

“…The latter distinction was made because the bed sediments are finer in the south of the river compared to the north. Values for the discharge (Q), mean flow velocity (U ), and water depth (d) were adopted from Lokin et al (2022). They studied the primary dunes in the Waal river, over a reach of 16.5 km, between 2011 and 2020 and determined typical flow characteristics for the study area (Lokin et al, 2022, Table 1).…”

Section: Flow and Transport Conditionsmentioning

confidence: 99%

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Coexistence of two dune scales in a lowland river

Zomer

Vermeulen

Hoitink

2023

Preprint

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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.

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Section: Primary and Secondary Dune Morphodynamicsmentioning

confidence: 57%

Section: Study Area and Description Of Datamentioning

confidence: 99%

Section: Flow and Transport Conditionsmentioning

confidence: 99%

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Coexistence of two dune scales in a lowland river

Zomer

Vermeulen

Hoitink

2023

Preprint

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“…We acknowledge that large bedforms (Bradley & Venditti, 2019;Cisneros et al, 2020;Lokin et al, 2022) tend to exceed the roughness limit r/R ≃ H b /h > 1/7.5 explored by Gioia and Chakraborty (2006) to reproduce the pipe friction factor (assuming a preserved K41 (Frisch, 2001) inertial subrange). A range of more stringent conditions are discussed in the literature, from H b /h < 0.15 (Amir & Castro, 2011) to H b /h < 1/40 (Jiménez, 2004), for the establishment of rough wall similarity and the preservation of the canonical logarithmic region.…”

Section: Form Drag Contributionmentioning

confidence: 96%

On the Scaling and Growth Limit of Fluvial Dunes

2023

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Bedforms emerge in a variety of shapes and sizes when a granular erodible surface is subject to a strong enough shear flow, as observed in topographic data from submarine canyons, rivers, deserts, and planetary bodies. The two salient features of bedforms are the ability to collectively transport particles, and to generate form drag thus increasing flow resistance. These two mechanisms are in competition and contribute to force bedforms of increasing size migrating more slowly. In a dedicated large‐scale open channel flow facility, hierarchies of fluvial bedforms were generated and measured in equilibrium conditions. The corresponding scale‐dependent migration velocity and mass flux contributions were quantified in the wave number and frequency domains. Experimental results are paired with a validated set of theoretical models to demonstrate that ripples or dunes reach an equilibrium state when drag partitioning ensures high enough frictional drag to sustain the bedload transport of sediment, and low enough form drag to enable the migration of the largest bedform size. This mechanism is inferred to constrain the growth of bedforms when sediment supply is not the limiting factor.

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“…These dune height relations give a fair estimation of the dune height in shallow flows, but do not reflect the dynamics and the dune shape including slope angles and variability in lengths. Also, recent studies have shown that the dune shapes found in large rivers show different behavior than in flume experiments: dune height relative to the water depth is smaller in deep flows (Bradley & Venditti, 2017), lee slopes in deep rivers tend to have small slope angles (Cisneros et al., 2020), and dune length becomes longer during low flows (Lokin et al., 2022). Until now, dune models have mainly been applied on flume conditions (Paarlberg et al., 2009; Shimizu et al., 2009) and under normal to high flows (Paarlberg et al., 2010; Van Duin et al., 2021), while application and validation for low flows are not yet present in literature.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Sediment Transport Models on Simulating River Dune Dynamics

Lokin,

Warmink,

Hulscher

2023

Water Resources Research

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River dunes, dynamic bedforms in the river bed, limit navigable depths during low flows and increase bed roughness. To predict the navigable depth or where maintenance dredging is needed, a numerical dune development model can be a powerful tool. To study the effect of sediment transport on dune shape and propagation, four different sediment transport models were applied in an existing dune development model. Each sediment transport model was able to simulate dune propagation, while only sediment transport models based on the shear stress reshaped the river dunes. The tested sediment transport models can simulate dune celerity similar to observations and realistic, though different, dune shapes for low and median discharges. Implementation of a gravitational bed slope effect combined with a critical shear stress results in low angle dunes, which are representative for river dunes during low river flows. Sediment transport models with spatial relaxation, also result in low angle dunes. However, the relaxation parameters need to be redefined for low flow situation to prevent transition to upper stage plane bed at too low flow velocities. Further analysis of the resulting dune shapes shows that the sediment transport model determines the dune shape in terms of slope angles, while the dune height is related to the total transport capacity.

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River Dune Dynamics During Low Flows

Cited by 19 publications

References 45 publications

Coexistence of two dune scales in a lowland river

Coexistence of two dune scales in a lowland river

On the Scaling and Growth Limit of Fluvial Dunes

The Effect of Sediment Transport Models on Simulating River Dune Dynamics

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