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Bimodality in subaqueous dune height suggests flickering behavior at high flow
Sjoukje I de Lange1,2, Roeland C van de Vijsel3, Paul J J F Torfs4
1Hydrology and Environmental Hydraulics Group, Department of Environmental Sciences, Wageningen University & Research, Wageningen, Netherlands. delangesjoukje@gmail.com.
Nature Communications
|July 8, 2025
Summary
River bedforms exhibit flickering between low and high dune heights at high sediment transport stages. This dynamic behavior challenges traditional geomorphic equilibrium models and measurement techniques.
Area of Science:
- * Fluvial geomorphology
- * Sediment transport dynamics
- * Open-channel hydraulics
Background:
- * River bedforms significantly impact flow resistance and hydraulic processes.
- * Transitions between bed configurations (flat bed, ripples, dunes, upper stage plane bed) occur with increasing flow velocity.
- * Rapid shifts in bed configurations and bedform height variation are noted but understudied.
Purpose of the Study:
- * To investigate the understudied phenomenon of rapid bed configuration shifts in sandy rivers.
- * To reveal and characterize the flickering behavior of dune heights at high sediment transport stages.
- * To assess the implications of this dynamic behavior on geomorphic measurements and models.
Main Methods:
- * Analysis of existing experimental data on river bedforms.
- * Conducting a complementary experiment to gather new data.
- * Statistical analysis of dune height distributions to identify emergent modes.
Main Results:
- * Flickering between low and high dune heights was observed for transport stages exceeding 18.
- * A second mode in dune height distributions becomes increasingly distinct above this transport stage, indicating a critical transition.
- * Potential triggers include temporal changes in suspended sediment concentration affecting turbulence or dune kinematics.
Conclusions:
- * The observed flickering behavior challenges the assumption of static bed geometry in geomorphology.
- * Current field measurements and experimental designs may be inadequate due to this dynamic nature.
- * Further research is needed to quantify and understand flickering in sediment transport systems.
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