Preprints
https://doi.org/10.5194/esurf-2021-28
https://doi.org/10.5194/esurf-2021-28

  26 Apr 2021

26 Apr 2021

Review status: this preprint is currently under review for the journal ESurf.

Genesis and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring

Marco Piantini1,2, Florent Gimbert1, Hervé Bellot2, and Alain Recking2 Marco Piantini et al.
  • 1University Grenoble Alpes, CNRS, IRD, Institute for Geosciences and Environmental Research (IGE), Grenoble, France
  • 2University Grenoble Alpes, INRAE, ETNA, Grenoble, France

Abstract. In the upper part of mountain river catchments, large amounts of loose debris produced by mass wasting processes can accumulate at the base of slopes and cliffs. Sudden destabilizations of these deposits are thought to trigger energetic sediment pulses that may travel in downstream rivers with little exchange with the local bed. The dynamics of these exogenous sediment pulses remain poorly known because direct field observations are lacking, and the processes that control their formation and propagation have rarely been explored experimentally.

Here we carry out flume experiments with the aims of investigating (i) the role of sediment accumulation zones in the generation of sediment pulses, (ii) their propagation dynamics in low-order mountain channels, and (iii) the capability of seismic methods to unravel their physical properties. We use an original set-up where we supply with liquid and solid discharge a low slope storage zone acting like a natural sediment accumulation zone, and connected to a downstream 18 % steep channel equipped with geophones.

We show that the ability of the self-formed deposit to generate sediment pulses depends on the sand content of the mixture. In particular, when a high fraction of sand is present, the storage area experiences alternating phases of aggradation and erosion strongly impacted by grain sorting. The upstream processes also influence the composition of the sediment pulses, which are formed by a front made of the coarsest fraction of the sediment mixture, a body composed of a high concentration of sand corresponding to the peak of solid discharge, and a diluted tail that exhibits a wide grain size distribution. Seismic measurements reveal that the front dominates the overall seismic noise, but we observe a complex dependency between seismic power and sediment pulses’ transport characteristics, which questions the applicability of existing simplified theories in such context.

These findings challenge the classical approach for which the sediment budget of mountain catchments is merely reduced to an available volume, since not only hydrological but also granular conditions should be considered to predict the occurrence and propagation of such sediment pulses.

Marco Piantini et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-28', Anonymous Referee #1, 20 May 2021
  • RC2: 'Comment on esurf-2021-28', Anonymous Referee #2, 21 Jun 2021

Marco Piantini et al.

Data sets

Datasets for "Genesis and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring" Piantini Marco https://www.dropbox.com/sh/n3oqyl06csmnipg/AABnNuhwblRZIAhSRFt6EbEba?dl=0

Video supplement

Videos for "Genesis and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring" Piantini Marco https://www.dropbox.com/sh/ctyxz64hn0di41s/AAAgvoEkXihVE44norGPC-E8a?dl=0

Marco Piantini et al.

Viewed

Total article views: 591 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
479 102 10 591 24 2 4
  • HTML: 479
  • PDF: 102
  • XML: 10
  • Total: 591
  • Supplement: 24
  • BibTeX: 2
  • EndNote: 4
Views and downloads (calculated since 26 Apr 2021)
Cumulative views and downloads (calculated since 26 Apr 2021)

Viewed (geographical distribution)

Total article views: 519 (including HTML, PDF, and XML) Thereof 519 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 30 Jul 2021
Download
Short summary
We carry out laboratory experiments to investigate the formation and propagation dynamics of exogenous sediment pulses in mountain rivers. We show that the ability of a self-formed deposit to destabilize and generate sediment pulses depends on the sand content of the mixture, while each pulse turns out to be formed by a front, a body, and a tail. Seismic measurements reveal a complex and non-unique dependency between seismic power and sediment pulses’ transport characteristics.