1,- 1Newcastle University, School of Geography, Politics and Sociology, Newcastle, United Kingdom of Great Britain – England, Scotland, Wales (christopher.hackney@newcastle.ac.uk)
- 2Electric Power Unviersity, Hanoi, Vietnam
- 3Central Institute for Natural Resources and Environmental Studies (CRES), Vietnam National Unviersity
Bedforms exert a fundamental control upon water and sediment transport processes in alluvial systems, including the initiation of flow separation, the generation of shear layers and turbulence, flow resistance, bedload transport and sediment trapping. Dunes are common bedforms in alluvial river channels, having characteristic geometries (height, wavelength and lee-slope angles) and reflect the dominant hydraulic and sedimentological conditions in which they are formed. Yet, alluvial reaches are increasingly impacted by anthropogenic activities - including sand mining – which causes instantaneous changes to riverbed morphology, bedform geometries, and therefore water flow and sediment transport.
Here, we compare the anthropogenic morphological signatures of differing sand extraction methods at two reaches using high-resolution bathymetry surveys. Riverbed morphology was classified into five distinct bedform classes: dunes, scour patches, and three different extraction mechanisms: trawled, suction-mined and crane-mined.
Features associated with crane-mining exhibit the greatest roughness (maximum of 5.3) and mean lee-side angle (x̄ =13.04o, maximum 59o, where x̄ = the sample mean); however, trawled features have the largest average roughness (x̄ = 0.67). Dunes display the greatest mean wavelengths (x̄ 44.5 m), yet all mined bedforms display the greatest mean amplitudes (x̄ = 0.87 m, x̄ = 0.65 m, and x̄ = 0.98 m for crane-mined, suction-mined and trawled, respectively). Each sand mining mechanism causes geometrically distinct bedforms than those formed naturally in equilibrium with prevailing flow and sediment conditions, and therefore will have differing effects on flow conditions in which they occur. In particular, mined features with relatively higher roughness may impart greater flow depths beyond observed water levels and localised flood risk. Our work shows that human activitiy can fundamentally alter flows of water and sediment through river reaches, impacting flood risk.
How to cite: Hackney, C., Runeckles, H., Large, A., Do, N., and Le, H.: Differing sand mining mechanisms generate distinct bedform morphologies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18491, https://doi.org/10.5194/egusphere-egu26-18491, 2026.
