Quantification of Bedform Characteristics Using Particle Image Velocimetry Technique and Bedform Tracking Method
Abstract
Fluvial Bedforms, as ripples and dunes, can be generally described as unsteady, non-homogeneous bathymetry features, which alter the bed roughness, contribute to sediment transport and affect river morphodynamic processes. With the expansion of eddy-resolving simulation to river reach scale, it is critical to define the correct boundary conditions at the river bed (bedform geometry) and their evolution in time (bedform migrating velocity). Bedforms of different type and size are known to co-exist, interact, and evolve exhibiting a scale-dependent migrating velocity (small scale bedforms advecting faster than large scale ones), which results in a complex multiscale, migration-deformation process (Nikora, 1997). Recent effort was devoted to the frequency-wavenumber spectral analysis of bed elevation data, to quantify the variability in bedform migration velocity (Guala et al., 2014), but a direct correspondence between spectral results and physical bedform evolution is still missing. To fill this gap we applied a cross correlation analysis, similar to Particle Image Velocimetry (PIV) algorithm, and a new bedform tracking method to two-dimensional spatio-temporal bed elevation data z=f(x,y,t) measured by high-resolution laser scanning device (Musa et al., 2018). The experiments were performed at the Saint Anthony Falls Laboratory (SAFL), in the 2.7m wide 85m long Main Channel, using a sediment recirculation system to ensure morphodynamic equilibrium in the channel test section and reproducing ripples and dunes. The experimental results confirm scale-dependent migration velocity in multi-scale bedforms and emphasize their interactions in the evolution of the channel bathymetry.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP51E2153L
- Keywords:
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- 1824 Geomorphology: general;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 1830 Groundwater/surface water interaction;
- HYDROLOGY;
- 1856 River channels;
- HYDROLOGY