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Boulder concentration effects on sediment transport and deposition
Penghua Teng1, Dan A Nilsson2, Anders G Andersson1
1Division of Fluid and Experimental Mechanics, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, SE-971 87, Sweden.
Scientific Reports
|February 10, 2026
Summary
Riverbed boulder concentration significantly impacts sediment transport. Higher concentrations reduce flow resistance and shift deposition to sheltered areas, unlike isolated boulders causing localized sediment buildup.
Area of Science:
- Environmental Science
- Geomorphology
- Fluid Dynamics
Background:
- Riverbed boulders are critical geomorphic features influencing sediment dynamics.
- Understanding boulder-sediment interactions is key to predicting river morphology and sediment transport.
Purpose of the Study:
- To investigate the effects of varying boulder concentrations on riverbed sediment transport and deposition.
- To analyze how different boulder spacing regimes impact flow patterns and shear stress distribution.
Main Methods:
- Coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations were utilized.
- Large eddy simulation (LES) in a finite volume framework modeled fluid flow.
- Discrete Element Method (DEM) tracked individual sediment grains.
Main Results:
- Increased boulder concentration altered flow from isolated wakes to coherent recirculation zones.
- Near-bed shear stresses decreased between boulders at higher concentrations, reducing overall sediment transport.
- Sediment deposition shifted to sheltered inter-boulder corridors at high concentrations, forming stable belts.
Conclusions:
- Boulder concentration is a primary control on sediment transport and deposition patterns in rivers.
- The coupled CFD-DEM approach provides novel insights into boulder-sediment interactions in open-channel flow.
- This study establishes a foundation for analyzing sediment dynamics under diverse boulder arrangements.
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