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Effect of Sea‐Level Change on River Avulsions and Stratigraphy for an Experimental Lowland Delta

Chadwick, A. J. and Steele, S. and Silvestre, J. and Lamb, M. P. (2022) Effect of Sea‐Level Change on River Avulsions and Stratigraphy for an Experimental Lowland Delta. Journal of Geophysical Research. Earth Surface, 127 (7). Art. No. e2021JF006422. ISSN 2169-9003. doi:10.1029/2021jf006422.

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Lowland deltas experience natural diversions in river course known as avulsions. River avulsions pose catastrophic flood hazards and redistribute sediment that is vital for sustaining land in the face of sea-level rise. Avulsions also affect deltaic stratigraphic architecture and the preservation of sea-level cycles in the sedimentary record. Here, we present results from an experimental lowland delta with persistent backwater effects and systematic changes in the rates of sea-level rise and fall. River avulsions repeatedly occurred where and when the river aggraded to a height of nearly half the channel depth, giving rise to a preferential avulsion node within the backwater zone regardless of sea-level change. As sea-level rise accelerated, the river responded by avulsing more frequently until reaching a maximum frequency limited by the upstream sediment supply. Experimental results support recent models, field observations, and experiments, and suggest anthropogenic sea-level rise will introduce more frequent avulsion hazards farther inland than observed in recent history. The experiment also demonstrated that avulsions can occur during sea-level fall—even within the confines of an incised valley—provided the offshore basin is shallow enough to allow the shoreline to prograde and the river to aggrade. Avulsions create erosional surfaces within stratigraphy that bound beds reflecting the amount of deposition between avulsions. Avulsion-induced scours overprint erosional surfaces from sea-level fall, except when the cumulative drop in sea-level is greater than the channel depth and less than the basin depth. Results imply sea-level signals outside this range are removed or distorted in delta deposits.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemMATLAB
Chadwick, A. J.0000-0002-2552-0083
Steele, S.0000-0002-7149-2693
Silvestre, J.0000-0002-7747-893X
Lamb, M. P.0000-0002-5701-0504
Additional Information:© 2022. American Geophysical Union. Issue Online: 14 July 2022. Version of Record online: 14 July 2022. Accepted manuscript online: 02 July 2022. Manuscript accepted: 24 June 2022. Manuscript revised: 15 June 2022. Manuscript received: 07 September 2021. We thank Brian Fuller, Tom Ulizio, and Kirby Sikes for assistance in conducting the experiment, and thank Maarten G. Kleinhans, Wonsuck Kim, and Katherine Ratliff for constructive reviews. We acknowledge NSF Grant EAR 1427262 and the Resnick Sustainability Institute at the California Institute of Technology for support. Data Availability Statement. The data underlying this study are publicly available in the SEAD repository at (Chadwick, 2022). Analysis was performed and figures were made using MATLAB R2021b software available at (MATLAB, 2021). The authors declare no conflicts of interest relevant to this study.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:river deltas; sea-level rise; river avulsions; delta stratigraphy; geomorphology; sedimentology
Issue or Number:7
Record Number:CaltechAUTHORS:20220715-744506000
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Official Citation:Chadwick, A. J., Steele, S., Silvestre, J., & Lamb, M. P. (2022). Effect of sea-level change on river avulsions and stratigraphy for an experimental lowland delta. Journal of Geophysical Research: Earth Surface, 127, e2021JF006422.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115658
Deposited By: George Porter
Deposited On:18 Jul 2022 17:36
Last Modified:18 Jul 2022 17:36

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