Published June 16, 2023 | Published + Supplemental Material
Journal Article Open

Sediment Entrainment and Slump Blocks Limit Permafrost Riverbank Erosion

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Abstract

Climatic warming and permafrost thaw are predicted to increase Arctic riverbank erosion, threatening communities and accelerating sediment, carbon and nutrient cycling between rivers and floodplains. Existing theory assumes that pore-ice thaw sets riverbank erosion rates, but overpredicts observed erosion rates by orders of magnitude. Here, we developed a simple model that predicts more modest rates due to a sediment-entrainment limitation and riverbank armoring by slump blocks. Results show that during times of thaw-limited erosion, the river rapidly erodes permafrost and undercuts its banks, consistent with previous work. However, overhanging banks generate slump blocks that must thaw and erode by sediment entrainment. Sediment entrainment can limit bank and slump block erosion rates, producing seasonally averaged rates more consistent with observations. Importantly, entrainment-limited riverbank erosion does not depend on water temperature, indicating that decadal erosion rates may be less sensitive to warming than predicted previously.

Additional Information

© 2023 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. The authors would like to thank the Tribal Council and residents of Beaver, AK for access to their land and logistical support during fieldwork, in particular Liz Blackbird, Kody Vanderpool, Clinton Wiehl, Richard J. Williams, and Paul Williams Jr. We thank Rain Blankenship, Hannah Dion-Kirshner, Emily Geyman, Yutian Ke, John Magyar, Edda Mutter, Justin Nghiem, Jocelyn Reahl, Emily Seelen, Isabel Smith, A. Joshua West, and Lisa Winter for their assistance during fieldwork and two anonymous reviewers, whose recommendations greatly improved the manuscript. The authors acknowledge funding from NSF Awards 2127442, 2031532, and 2053009, Caltech's Resnick Sustainability Institute, and the National Defense Science and Engineering Graduate Fellowship. Data Availability Statement. Soil bulk density and water content data were downloaded from https://doi.org/10.25675/10217/187212. Data for ground temperature were downloaded for site ID US O-82 from the Global Terrestrial Network for Permafrost (GTN-P) Database at http://gtnpdatabase.org/boreholes. Yukon River temperature and discharge data were downloaded from https://waterdata.usgs.gov/monitoring-location/15565447/ and https://waterdata.usgs.gov/monitoring-location/15453500/. Model code was written in Matlab R2022a under an academic license to the California Institute of Technology and code to run the model is available on Zenodo at https://doi.org/10.5281/zenodo.7958708. The authors declare no conflicts of interest relevant to this study.

Attached Files

Published - Geophysical_Research_Letters_-_2023_-_Douglas_-_Sediment_Entrainment_and_Slump_Blocks_Limit_Permafrost_Riverbank_Erosion.pdf

Supplemental Material - 2023gl102974-sup-0001-supporting_information_si-s01.pdf

Files

Geophysical_Research_Letters_-_2023_-_Douglas_-_Sediment_Entrainment_and_Slump_Blocks_Limit_Permafrost_Riverbank_Erosion.pdf

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023