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Climate-Change Controls on River Delta Avulsion Location and Frequency

Chadwick, A. J. and Lamb, M. P. (2021) Climate-Change Controls on River Delta Avulsion Location and Frequency. Journal of Geophysical Research. Earth Surface, 126 (6). Art. No. e2020JF005950. ISSN 2169-9003. doi:10.1029/2020JF005950.

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Coastal rivers that build deltas undergo repeated avulsion events—that is, abrupt changes in river course—which we need to understand to predict land building and flood hazards in coastal landscapes. Climate change can impact water discharge, flood frequency, sediment supply, and sea level, all of which could impact avulsion location and frequency. Here we present results from quasi-2D morphodynamic simulations of repeated delta-lobe construction and avulsion to explore how avulsion location and frequency are affected by changes in relative sea level, sediment supply, and flood regime. Model results indicate that relative sea-level rise drives more frequent avulsions that occur at a distance from the shoreline set by backwater hydrodynamics. Reducing the sediment supply relative to transport capacity has little impact on deltaic avulsions, because, despite incision in the upstream trunk channel, deltas can still aggrade as a result of progradation. However, increasing the sediment supply relative to transport capacity can shift avulsions upstream of the backwater zone because aggradation in the trunk channel outpaces progradation-induced delta aggradation. Increasing frequency of overbank floods causes less frequent avulsions because floods scour the riverbed within the backwater zone, slowing net aggradation rates. Results provide a framework to assess upstream and downstream controls on avulsion patterns over glacial-interglacial cycles, and the impact of land use and anthropogenic climate change on deltas.

Item Type:Article
Related URLs:
URLURL TypeDescription
Chadwick, A. J.0000-0002-2552-0083
Lamb, M. P.0000-0002-5701-0504
Additional Information:© 2021 American Geophysical Union. Issue Online: 23 June 2021; Version of Record online: 23 June 2021; Accepted manuscript online: 24 May 2021; Manuscript accepted: 18 May 2021; Manuscript revised: 14 May 2021; Manuscript received: 10 November 2020. The authors thank Vamsi Ganti, Andrew Moodie, Gary Parker, and Brad Murray for useful discussions. The authors acknowledge NSF Grant EAR 1427262 and the Resnick Sustainability Institute at the California Institute of Technology for support. The authors declare no conflict of interest. Data Availability Statement: The data and model code underlying this study are publicly available in the SEAD repository ( and Zenodo ( respectively.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:River deltas; River avulsions; Climate change; Sea-level rise; Sediment supply; Floods
Issue or Number:6
Record Number:CaltechAUTHORS:20210528-094925804
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Official Citation:Chadwick, A. J., & Lamb, M. P. (2021). Climate-change controls on river delta avulsion location and frequency. Journal of Geophysical Research: Earth Surface, 126, e2020JF005950.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109303
Deposited By: George Porter
Deposited On:28 May 2021 17:05
Last Modified:01 Dec 2021 08:05

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