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

<p>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 w...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	M. Piantini, F. Gimbert, H. Bellot, A. Recking
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Dynamic and structural geology QE500-639.5
Acceso en línea:	https://doaj.org/article/db64bfa4871f4898a819e04b69de14ed
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:db64bfa4871f4898a819e04b69de14ed
record_format	dspace
spelling	oai:doaj.org-article:db64bfa4871f4898a819e04b69de14ed2021-11-04T12:20:13ZTriggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring10.5194/esurf-9-1423-20212196-63112196-632Xhttps://doaj.org/article/db64bfa4871f4898a819e04b69de14ed2021-11-01T00:00:00Zhttps://esurf.copernicus.org/articles/9/1423/2021/esurf-9-1423-2021.pdfhttps://doaj.org/toc/2196-6311https://doaj.org/toc/2196-632X<p>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. 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 setup wherein we supply liquid and solid discharge to a low-slope storage zone acting like a natural sediment accumulation zone that is connected to a downstream 18 % steep channel equipped with geophones. We show that the ability of the self-formed deposit to generate sediment pulses is controlled by the fine fraction of the mixture. In particular, when coarse grains coexist with a high content of finer particles, 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 pulse transport characteristics, which questions the applicability of existing seismic theories in such a 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.</p>M. PiantiniM. PiantiniF. GimbertH. BellotA. ReckingCopernicus PublicationsarticleDynamic and structural geologyQE500-639.5ENEarth Surface Dynamics, Vol 9, Pp 1423-1439 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Dynamic and structural geology QE500-639.5
spellingShingle	Dynamic and structural geology QE500-639.5 M. Piantini M. Piantini F. Gimbert H. Bellot A. Recking Triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring
description	<p>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. 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 setup wherein we supply liquid and solid discharge to a low-slope storage zone acting like a natural sediment accumulation zone that is connected to a downstream 18 % steep channel equipped with geophones. We show that the ability of the self-formed deposit to generate sediment pulses is controlled by the fine fraction of the mixture. In particular, when coarse grains coexist with a high content of finer particles, 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 pulse transport characteristics, which questions the applicability of existing seismic theories in such a 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.</p>
format	article
author	M. Piantini M. Piantini F. Gimbert H. Bellot A. Recking
author_facet	M. Piantini M. Piantini F. Gimbert H. Bellot A. Recking
author_sort	M. Piantini
title	Triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring
title_short	Triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring
title_full	Triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring
title_fullStr	Triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring
title_full_unstemmed	Triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring
title_sort	triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/db64bfa4871f4898a819e04b69de14ed
work_keys_str_mv	AT mpiantini triggeringandpropagationofexogenoussedimentpulsesinmountainchannelsinsightsfromflumeexperimentswithseismicmonitoring AT mpiantini triggeringandpropagationofexogenoussedimentpulsesinmountainchannelsinsightsfromflumeexperimentswithseismicmonitoring AT fgimbert triggeringandpropagationofexogenoussedimentpulsesinmountainchannelsinsightsfromflumeexperimentswithseismicmonitoring AT hbellot triggeringandpropagationofexogenoussedimentpulsesinmountainchannelsinsightsfromflumeexperimentswithseismicmonitoring AT arecking triggeringandpropagationofexogenoussedimentpulsesinmountainchannelsinsightsfromflumeexperimentswithseismicmonitoring
_version_	1718444931604807680

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

Ejemplares similares