Modelling Waterfall Retreat in Heterogenous Bedrock
International audience Bedrock rivers are the mediators of environmental change through mountainous landscapes. In response to an increase in uplift rate for example, a “knickpoint” (often materialised as a waterfall) will propagate upstream, separating a domain downstream where the river and its ad...
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ftccsdartic:oai:HAL:insu-01445516v1 2023-05-15T16:52:34+02:00 Modelling Waterfall Retreat in Heterogenous Bedrock ATTAL, Mikaël Hodge, Rebecca, Williams, Richard Baynes, Edwin University of Edinburgh Durham University University of Glasgow Géosciences Rennes (GR) Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1) Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES) American Geophysical Union San Francisco, United States 2016-12-12 https://hal-insu.archives-ouvertes.fr/insu-01445516 en eng HAL CCSD insu-01445516 https://hal-insu.archives-ouvertes.fr/insu-01445516 American Geophysical Union Fall Meeting 2016 https://hal-insu.archives-ouvertes.fr/insu-01445516 American Geophysical Union Fall Meeting 2016, Dec 2016, San Francisco, United States. pp.EP33D-1029, 2016 [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology info:eu-repo/semantics/conferenceObject Poster communications 2016 ftccsdartic 2021-11-28T01:06:03Z International audience Bedrock rivers are the mediators of environmental change through mountainous landscapes. In response to an increase in uplift rate for example, a “knickpoint” (often materialised as a waterfall) will propagate upstream, separating a domain downstream where the river and its adjacent hillslopes have steepened in response to the change from a “relict” domain upstream which is adjusted to the conditions before the change (Crosby and Whipple 2006). Many studies assume that knickpoint propagation rate scales with drainage area, based on the stream power theory. However, recent studies in a range of locations have found no obvious relationship between knickpoint retreat rate and drainage area, potentially resulting from the stream power law neglecting (i) the influence of sediment on the processes associated with waterfall migration and (ii) thresholds for bedrock detachment (Cook et al. 2013; Mackey et al. 2014; DiBiase et al. 2015; Baynes et al. 2015; Brocard et al. 2016).In this study, we develop a 1D model of waterfall retreat in horizontally bedded bedrock with varying joint spacing. In the model, knickpoint migration is based on two rules: a waterfall will start migrating once the threshold flow depth (a function of knickpoint height and joint spacing) has been exceeded (Lamb and Dietrich 2009), and the migration rate will then be a function of the water-depth-to-waterfall-height ratio, based on experimental results by Baynes (2015). Using a hydrograph based on a Poisson rectangular pulse rainfall simulator (Tucker and Bras 2001), we demonstrate the importance of structure in controlling the speed at which waterfalls migrate but also their number and the length over which they are distributed (Fig. 1). The model is applied to the Jökulsá á Fjöllum, NE Iceland, where rapid migration of waterfalls as a result of discrete events has been identified (Baynes et al. 2015), using new constraints on joint spacing derived from high resolution lidar survey of the gorge walls. Conference Object Iceland Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Jökulsá á Fjöllum ENVELOPE(-16.707,-16.707,66.150,66.150) |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology |
spellingShingle |
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology ATTAL, Mikaël Hodge, Rebecca, Williams, Richard Baynes, Edwin Modelling Waterfall Retreat in Heterogenous Bedrock |
topic_facet |
[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology |
description |
International audience Bedrock rivers are the mediators of environmental change through mountainous landscapes. In response to an increase in uplift rate for example, a “knickpoint” (often materialised as a waterfall) will propagate upstream, separating a domain downstream where the river and its adjacent hillslopes have steepened in response to the change from a “relict” domain upstream which is adjusted to the conditions before the change (Crosby and Whipple 2006). Many studies assume that knickpoint propagation rate scales with drainage area, based on the stream power theory. However, recent studies in a range of locations have found no obvious relationship between knickpoint retreat rate and drainage area, potentially resulting from the stream power law neglecting (i) the influence of sediment on the processes associated with waterfall migration and (ii) thresholds for bedrock detachment (Cook et al. 2013; Mackey et al. 2014; DiBiase et al. 2015; Baynes et al. 2015; Brocard et al. 2016).In this study, we develop a 1D model of waterfall retreat in horizontally bedded bedrock with varying joint spacing. In the model, knickpoint migration is based on two rules: a waterfall will start migrating once the threshold flow depth (a function of knickpoint height and joint spacing) has been exceeded (Lamb and Dietrich 2009), and the migration rate will then be a function of the water-depth-to-waterfall-height ratio, based on experimental results by Baynes (2015). Using a hydrograph based on a Poisson rectangular pulse rainfall simulator (Tucker and Bras 2001), we demonstrate the importance of structure in controlling the speed at which waterfalls migrate but also their number and the length over which they are distributed (Fig. 1). The model is applied to the Jökulsá á Fjöllum, NE Iceland, where rapid migration of waterfalls as a result of discrete events has been identified (Baynes et al. 2015), using new constraints on joint spacing derived from high resolution lidar survey of the gorge walls. |
author2 |
University of Edinburgh Durham University University of Glasgow Géosciences Rennes (GR) Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1) Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES) American Geophysical Union |
format |
Conference Object |
author |
ATTAL, Mikaël Hodge, Rebecca, Williams, Richard Baynes, Edwin |
author_facet |
ATTAL, Mikaël Hodge, Rebecca, Williams, Richard Baynes, Edwin |
author_sort |
ATTAL, Mikaël |
title |
Modelling Waterfall Retreat in Heterogenous Bedrock |
title_short |
Modelling Waterfall Retreat in Heterogenous Bedrock |
title_full |
Modelling Waterfall Retreat in Heterogenous Bedrock |
title_fullStr |
Modelling Waterfall Retreat in Heterogenous Bedrock |
title_full_unstemmed |
Modelling Waterfall Retreat in Heterogenous Bedrock |
title_sort |
modelling waterfall retreat in heterogenous bedrock |
publisher |
HAL CCSD |
publishDate |
2016 |
url |
https://hal-insu.archives-ouvertes.fr/insu-01445516 |
op_coverage |
San Francisco, United States |
long_lat |
ENVELOPE(-16.707,-16.707,66.150,66.150) |
geographic |
Jökulsá á Fjöllum |
geographic_facet |
Jökulsá á Fjöllum |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
American Geophysical Union Fall Meeting 2016 https://hal-insu.archives-ouvertes.fr/insu-01445516 American Geophysical Union Fall Meeting 2016, Dec 2016, San Francisco, United States. pp.EP33D-1029, 2016 |
op_relation |
insu-01445516 https://hal-insu.archives-ouvertes.fr/insu-01445516 |
_version_ |
1766042906946174976 |