Constraining bedrock erosion during extreme flood events
The importance of high-magnitude, short-lived flood events in controlling the evolution of bedrock landscapes is not well understood. During such events, erosion processes can shift from one regime to another upon the passing of thresholds, resulting in abrupt landscape changes that can have a long...
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Language: | English |
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The University of Edinburgh
2016
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ftunivedinburgh:oai:era.ed.ac.uk:1842/15962 2023-07-30T04:04:28+02:00 Constraining bedrock erosion during extreme flood events Baynes, Edwin Richard Crews Attal, Mikael Kirstein, Linda Dugmore, Andrew Natural Environment Research Council (NERC) 27/06/2016 application/octet-stream application/pdf http://hdl.handle.net/1842/15962 en eng The University of Edinburgh The University of Edinburgh. College of Science and Engineering Baynes ERC, Attal M, Niedermann S, Kirstein LA, Dugmore AJ, Naylor M (2015) Erosion during extreme flood events dominates Holocene canyon evolution in North-East Iceland. Proceedings of the National Academy of Sciences 112 (8), 2355-2360 Baynes ERC, Attal M, Dugmore AJ, Kirstein LA, Whaler KA (2015) Catastrophic impact of extreme flood events on the morphology and evolution of the lower Jökulsá á Fjöllum (northeast Iceland) during the Holocene. Geomorphology, doi:10.1016/j.geomorph.2015.05.009 http://hdl.handle.net/1842/15962 erosion flooding geomorphology waterfalls knickpoints Thesis or Dissertation Doctoral PhD Doctor of Philosophy 2016 ftunivedinburgh https://doi.org/10.1016/j.geomorph.2015.05.009 2023-07-09T20:36:42Z The importance of high-magnitude, short-lived flood events in controlling the evolution of bedrock landscapes is not well understood. During such events, erosion processes can shift from one regime to another upon the passing of thresholds, resulting in abrupt landscape changes that can have a long lasting legacy on landscape morphology. Geomorphological mapping and topographic analysis document the evidence for, and impact of, extreme flood events within the Jökulsárgljúfur canyon (North-East Iceland). Surface exposure dating using cosmogenic 3He of fluvially sculpted bedrock surfaces determines the timing of the floods that eroded the canyon and helps constrain the mechanisms of bedrock erosion during these events. Once a threshold flow depth has been exceeded, the dominant erosion mechanism becomes the toppling and transportation of basalt lava columns and erosion occurs through the upstream migration of knickpoints. Surface exposure ages allow identification of three periods of rapid canyon cutting during erosive flood events about 9, 5 and 2 ka ago, when multiple active knickpoints retreated large distances (> 2 km), each leading to catastrophic landscape change within the canyon. A single flood event ~9 ka ago formed, and then abandoned, Ásbyrgi canyon, eroding 0.14 km3 of rock. Flood events ~5 and ~2 ka ago eroded the upper 5 km of the Jökulsárgljúfur canyon through the upstream migration of vertical knickpoints such as Selfoss, Dettifoss and Hafragilsfoss. Despite sustained high discharge of sediment-rich glacial meltwater (ranging from 100 to 500 m3 s-1); there is no evidence for a transition to an abrasion-dominated erosion regime since the last erosive flood: the vertical knickpoints have not diffused over time and there is no evidence of incision into the canyon floor. The erosive signature of the extreme events is maintained in this landscape due to the nature of the bedrock, the discharge of the river, large knickpoints and associated plunge pools. The influence of these controls on the dynamics ... Doctoral or Postdoctoral Thesis Iceland Selfoss Edinburgh Research Archive (ERA - University of Edinburgh) Dettifoss ENVELOPE(-16.385,-16.385,65.814,65.814) Ásbyrgi ENVELOPE(-16.498,-16.498,66.005,66.005) Jökulsárgljúfur ENVELOPE(-15.083,-15.083,64.517,64.517) Hafragilsfoss ENVELOPE(-16.391,-16.391,65.827,65.827) Geomorphology 250 422 436 |
institution |
Open Polar |
collection |
Edinburgh Research Archive (ERA - University of Edinburgh) |
op_collection_id |
ftunivedinburgh |
language |
English |
topic |
erosion flooding geomorphology waterfalls knickpoints |
spellingShingle |
erosion flooding geomorphology waterfalls knickpoints Baynes, Edwin Richard Crews Constraining bedrock erosion during extreme flood events |
topic_facet |
erosion flooding geomorphology waterfalls knickpoints |
description |
The importance of high-magnitude, short-lived flood events in controlling the evolution of bedrock landscapes is not well understood. During such events, erosion processes can shift from one regime to another upon the passing of thresholds, resulting in abrupt landscape changes that can have a long lasting legacy on landscape morphology. Geomorphological mapping and topographic analysis document the evidence for, and impact of, extreme flood events within the Jökulsárgljúfur canyon (North-East Iceland). Surface exposure dating using cosmogenic 3He of fluvially sculpted bedrock surfaces determines the timing of the floods that eroded the canyon and helps constrain the mechanisms of bedrock erosion during these events. Once a threshold flow depth has been exceeded, the dominant erosion mechanism becomes the toppling and transportation of basalt lava columns and erosion occurs through the upstream migration of knickpoints. Surface exposure ages allow identification of three periods of rapid canyon cutting during erosive flood events about 9, 5 and 2 ka ago, when multiple active knickpoints retreated large distances (> 2 km), each leading to catastrophic landscape change within the canyon. A single flood event ~9 ka ago formed, and then abandoned, Ásbyrgi canyon, eroding 0.14 km3 of rock. Flood events ~5 and ~2 ka ago eroded the upper 5 km of the Jökulsárgljúfur canyon through the upstream migration of vertical knickpoints such as Selfoss, Dettifoss and Hafragilsfoss. Despite sustained high discharge of sediment-rich glacial meltwater (ranging from 100 to 500 m3 s-1); there is no evidence for a transition to an abrasion-dominated erosion regime since the last erosive flood: the vertical knickpoints have not diffused over time and there is no evidence of incision into the canyon floor. The erosive signature of the extreme events is maintained in this landscape due to the nature of the bedrock, the discharge of the river, large knickpoints and associated plunge pools. The influence of these controls on the dynamics ... |
author2 |
Attal, Mikael Kirstein, Linda Dugmore, Andrew Natural Environment Research Council (NERC) |
format |
Doctoral or Postdoctoral Thesis |
author |
Baynes, Edwin Richard Crews |
author_facet |
Baynes, Edwin Richard Crews |
author_sort |
Baynes, Edwin Richard Crews |
title |
Constraining bedrock erosion during extreme flood events |
title_short |
Constraining bedrock erosion during extreme flood events |
title_full |
Constraining bedrock erosion during extreme flood events |
title_fullStr |
Constraining bedrock erosion during extreme flood events |
title_full_unstemmed |
Constraining bedrock erosion during extreme flood events |
title_sort |
constraining bedrock erosion during extreme flood events |
publisher |
The University of Edinburgh |
publishDate |
2016 |
url |
http://hdl.handle.net/1842/15962 |
long_lat |
ENVELOPE(-16.385,-16.385,65.814,65.814) ENVELOPE(-16.498,-16.498,66.005,66.005) ENVELOPE(-15.083,-15.083,64.517,64.517) ENVELOPE(-16.391,-16.391,65.827,65.827) |
geographic |
Dettifoss Ásbyrgi Jökulsárgljúfur Hafragilsfoss |
geographic_facet |
Dettifoss Ásbyrgi Jökulsárgljúfur Hafragilsfoss |
genre |
Iceland Selfoss |
genre_facet |
Iceland Selfoss |
op_relation |
The University of Edinburgh. College of Science and Engineering Baynes ERC, Attal M, Niedermann S, Kirstein LA, Dugmore AJ, Naylor M (2015) Erosion during extreme flood events dominates Holocene canyon evolution in North-East Iceland. Proceedings of the National Academy of Sciences 112 (8), 2355-2360 Baynes ERC, Attal M, Dugmore AJ, Kirstein LA, Whaler KA (2015) Catastrophic impact of extreme flood events on the morphology and evolution of the lower Jökulsá á Fjöllum (northeast Iceland) during the Holocene. Geomorphology, doi:10.1016/j.geomorph.2015.05.009 http://hdl.handle.net/1842/15962 |
op_doi |
https://doi.org/10.1016/j.geomorph.2015.05.009 |
container_title |
Geomorphology |
container_volume |
250 |
container_start_page |
422 |
op_container_end_page |
436 |
_version_ |
1772815928542625792 |