Collaborative Research: Predicting riverbank erosion in thawing permafrost

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Most Arctic floodplains have permanently frozen subsoil, or permafrost, that keeps the land intact and habitable along coasts and riverbanks. However, permafrost thaw can lead to widespread destabilization of the land and enhanced riverbank erosion. This erosion threatens critical infrastructure that is vital to national prosperity and security, and has led to the displacement of entire Alaskan communities. The main objective of this proposal is to develop and test a mathematical theory for riverbank erosion in permafrost. The theory will be tested using novel indoor permafrost-river experiments at the Caltech Earth Surface Dynamics Laboratory, and through measurements along the Koyukuk River, AK, in collaboration with the Native Alaskan community of Huslia. The work promises to fill a gap in our basic understanding of how river systems respond to global warming. In addition, it will contribute to climate-change adaptation planning for riverside communities in the Yukon River watershed. The next generation of scientists will be trained at the undergraduate and PhD levels in integrated hazard assessment by bringing together community engagement and basic and applied science to address an environmental crisis with both local and global implications. The main objective of this proposal is to develop and test a thermo-mechanical model for river-bank erosion in permafrost. In addition to seeking to understand the basic mechanics of bank erosion in cold environments, the model will be used to quantitatively assess how bank erosion rates will respond to climate change. The model will be tested against flume experiments specially designed to span the range of permafrost river characteristics and to test hypotheses related to river flow velocity, river water temperature, and bank sediment grain size. Measurements of hydraulic, mechanical and thermal properties of cutbanks along the Koyukuk River, Alaska, will be used to evaluate the model for entrainment- and ablation-limited regimes. This project was jointly funded by the Geomorphology and Land-use Dynamics and Arctic Natural Sciences Programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.