EGU21-4322
https://doi.org/10.5194/egusphere-egu21-4322
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Seismic quantification of river flow depth - from the flume to the field

Maarten Bakker1,2, Florent Gimbert1, Michael P. Lamb3, and Alain Recking2
Maarten Bakker et al.
  • 1University Grenoble Alpes, CNRS, Institute for Geosciences and Environmental research (IGE), Grenoble, France (maarten.bakker@univ-grenoble-alpes.fr)
  • 2INRAE, ETNA, University Grenoble Alpes, Grenoble, France
  • 3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA

Seismic measurements are used to study various processes that shape the Alpine landscape, including rock falls, debris flows, bedload transport and turbulent water flow. Here, we focus on the seismic quantification of turbulent flow conditions which is particularly useful for the remote monitoring of channels that are inaccessible (e.g. subglacial conduits) and/or highly dynamic (e.g. actively braiding river reaches). We test a physically-based model (Gimbert et al., 2014) to quantify force spectra generated by turbulent flow in flume experiments performed by Lamb et al. (2017) and subsequently apply the model to estimate river flow depth from continuous seismic measurements in the field.

In the flume, we assess near-bed flow velocity spectra and resulting drag and lift force spectra experienced by particles (D=0.075-0.20 m) on the cobble bed for a wide range of channel gradients (S=0.004-0.3) and submergence levels (h/D50=1-9.6). These measurements are used to test our model, and to quantify wake (interaction) effects and fluid-dynamic admittance on force spectral amplitude. Based on the conservation of turbulent energy in the Kolmogorov inertial subrange, we predict lift and drag force spectra to within ±5 dB rel. N2/Hz (frequency ~10-25 Hz) of the measured values.

We apply the calibrated model to bank-side geophone measurements from an Alpine stream (Séveraisse River, France). Using locally-derived seismic parameters, riverbed particle-size distribution and bed roughness, we can invert for water depth over a range of flow conditions, including flows with bedload transport (bedload transport dominates the seismic signal at higher frequencies). This allows us to monitor changes in flow depth during the course of a high-magnitude flood (October 2019). During the falling limb, the inferred flow depths progressively deviate from independently made water level measurements, indicating local riverbed aggradation of approximately 0.5 m, which is in agreement with post-flood observations. Through insights in near-bed turbulent flow conditions and their seismic signature, we can study flow-bedload transport interactions and the effects of extreme flow events on river morphodynamics.

References

Gimbert, F., Tsai, V. C. & Lamb, M. P. (2014). A physical model for seismic noise generation by turbulent flow in rivers. Journal of Geophysical Research: Earth Surface, 119(10), 2209-2238. http://dx.doi.org/10.1002/2014JF003201

Lamb, M. P., Brun, F. & Fuller, B. M. (2017). Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport. Water Resources Research, 53(9), 7607-7629. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017WR020883

How to cite: Bakker, M., Gimbert, F., Lamb, M. P., and Recking, A.: Seismic quantification of river flow depth - from the flume to the field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4322, https://doi.org/10.5194/egusphere-egu21-4322, 2021.

Displays

Display file