Scaling laws for sediment storage and turnover in river floodplains

Creators: Geyman, Emily C.¹; Ke, Yutian¹; Magyar, John S.¹; Reahl, Jocelyn N.²; Soldano, Vincent³; Brown, Nathan D.⁴; West, A. Joshua⁵; Fischer, Woodward¹; Lamb, Michael P.¹

1. California Institute of Technology
2. University of Colorado Boulder
3. University of Nevada Reno
4. The University of Texas at Arlington
5. University of Southern California

Abstract

Nearly 10% of Earth's continents are covered by river floodplains. These landscapes serve as weathering reactors whereby particles eroded from mountains undergo chemical and physical alteration before being exported to oceans. The time a particle spends in floodplain reservoirs regulates the style and extent of continental chemical weathering and the fate of terrestrial organic carbon. Despite its importance for the global carbon cycle, we still lack a quantitative understanding of floodplain storage timescales. Using a combination of geomorphic mapping, radiocarbon and luminescence dating, and numerical simulations of meander dynamics, we identify well-conserved scaling laws that describe floodplain storage times. Our results reveal that, to first order, floodplain storage durations are set by the ratio of river width to migration rate. The fact that most rivers erode about 1% of their width per year leads to a typical floodplain storage duration of ~5 thousand years.

Copyright and License

© 2025 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

Acknowledgement

We thank the Huslia, Beaver, and Alakanuk tribal and village councils for river and land access and the Yukon River Inter-Tribal Watershed Council for logistical support. We thank A. Attla, D. Dayton, S. Huffman, K. Vanderpool, R. Williams, C. Wiehl, J. Isidore, P. Phillips Jr., R. Stanislaus, and J. Stronghearts for river navigation and expertise. We thank M. Douglas for creating the initial version of the floodplain relative age map at Huslia (30). We also thank J. Anadu, R. Blankenship, M. Douglas, K. Dunne, H. Dion-Kirschner, E. Mutter, J. Nghiem, E. Seelen, and I. Smith for help in the field.

Funding

This work was supported by NSF award 2127442 and Caltech’s Resnick Sustainability Institute. E.C.G. thanks the NSF Graduate Research Fellowships Program and the Fannie and John Hertz Foundation.

Data Availability

All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. The ¹⁴C data, OSL data, and relative age maps are archived at https://doi.org/10.18739/A2NC5SF1K. The satellite-derived migration rates, based on the algorithm of Geyman et al. (27), are archived at https://doi.org/10.18739/A2WW7719J.

Supplemental Material

Supplementary Text; Figs. S1 to S22; Tables S1 to S14; References (PDF)

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