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More extensive land loss expected on coastal deltas due to rivers jumping course during sea-level rise

Chadwick, Austin J. and Steele, Sarah and Silvestre, Jose and Lamb, Michael P. (2022) More extensive land loss expected on coastal deltas due to rivers jumping course during sea-level rise. Proceedings of the National Academy of Sciences of the United States of America, 119 (31). Art. No. e2119333119. ISSN 0027-8424. PMCID PMC9351351. doi:10.1073/pnas.2119333119.

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River deltas are home to hundreds of millions of people worldwide and are in danger of sinking due to anthropogenic sea-level rise, land subsidence, and reduced sediment supply. Land loss is commonly forecast by averaging river sediment supply across the entire delta plain to assess whether deposition can keep pace with sea-level rise. However, land loss and deposition vary across the landscape because rivers periodically jump course, rerouting sediment to distinct subregions called delta lobes. Here, we developed a model to forecast land loss that resolves delta lobes and tested the model against a scaled laboratory experiment. Both the model and the experiment show that rivers build land on the active lobe, but the delta incurs gradual land loss on inactive lobes that are cut off from sediment after the river abandons course. The result is a band of terrain along the coast that is usually drowned but is nonetheless a sink for sediment when the lobe is active, leaving less of the total sediment supply available to maintain persistent dry land. Land loss is expected to be more extensive than predicted by classical delta-plain–averaged models. Estimates for eight large deltas worldwide suggest that roughly half of the riverine sediment supply is delivered to terrain that undergoes long periods of submergence. These results draw the sustainability of deltas further into question and provide a framework to plan engineered diversions at a pace that will mitigate land loss in the face of rising sea levels.

Item Type:Article
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URLURL TypeDescription and MATLAB codes
Chadwick, Austin J.0000-0002-2552-0083
Steele, Sarah0000-0002-7149-2693
Silvestre, Jose0000-0002-7747-893X
Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2022 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). Edited by Andrea Rinaldo, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland; received October 22, 2021; accepted June 9, 2022. We thank Vamsi Ganti for useful discussions and acknowledge NSF Grant EAR 1427262 and the Resnick Sustainability Institute at the California Institute of Technology for support. Author contributions: A.J.C. and M.P.L. designed research; A.J.C., S.S., J.S., and M.P.L. performed research; A.J.C., S.S., J.S., and M.P.L. analyzed data; and A.J.C., S.S., J.S., and M.P.L. wrote the paper. The authors declare no competing interest. This article is a PNAS Direct Submission. Data Availability Statement. The data and MATLAB codes underlying this study are publicly available and were deposited in the SEAD Internal Repository ( (59).
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:land loss; sea-level rise; river deltas; river avulsions; river diversions
Issue or Number:31
PubMed Central ID:PMC9351351
Record Number:CaltechAUTHORS:20220726-998173000
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115869
Deposited By: George Porter
Deposited On:27 Jul 2022 19:42
Last Modified:16 Aug 2022 23:34

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