Scale‐Dependent Influence of Permafrost on Riverbank Erosion Rates

Abstract

At water level, the erosion of frozen bank materials by rivers leaves distinctive geomorphic features indicative of the presence of permafrost (ground that remains below 0°C for two or more consecutive years). These features include thermal-erosion niching (bank undercutting), massive cantilever failures in non-cohesive sediments, and exposed ground ice (Figure 1). From above and at larger spatial scales, however, no clear geomorphic signature of permafrost has been documented in river planform (McNamara & Kane, 2009). Due to this lack of a planform signature of permafrost on rivers, an examination of riverbank erosion rates is required to answer the fundamental

A Model for Thaw and Erosion of Permafrost Riverbanks

“…Importantly, bank erosion rates in the buffered regime are sensitive to water temperature because warmer water temperatures cause the thawed layer to thicken and fail more rapidly, while entrainment‐limited banks are insensitive to water temperature. Therefore, our mathematical description of the buffered regime can reconcile theoretical predictions that permafrost bank thaw rates should exceed sediment entrainment rates for much of the summer with field observations of riverbanks with exposed or thinly covered permafrost in late summer (Fuchs et al., 2020; Kanevskiy et al., 2016) and remote sensing observations of slow migration for permafrost rivers (Rowland et al., 2019; Rowland, Crosby, et al., 2023; Rowland, Schwenk, et al., 2023).…”

“…Developing a 2D or 3D model requires considering the heterogeneities in bank ice distribution and their potential as failure planes (Barnhart et al., 2014; Kanevskiy et al., 2016), allowing for variable locations bank failure (Zhang et al., 2021; Zhao et al., 2021, 2022), and tracking the erosion of sediment following mass failure (e.g., Asahi et al., 2013; Parker et al., 2011). This includes constraining forces resulting from hydrologic connectivity between the river and its banks (Kurylyk et al., 2016; Zhao et al., 2020) as well as a more detailed investigation of interactions between riverbank pore water flow and heat transfer (Rowland, Crosby, et al., 2023; Rowland, Schwenk, et al., 2023). Extending our model to riverbanks that are exposed subaerially or experience periodic inundation will also require considering heat fluxes due to insolation and air temperature (Walker et al., 1987; Walvoord & Kurylyk, 2016).…”

Space‐Time Inconsistencies in the Dynamics of Water Coverage: Tracking Walking Floods

“…Remarkably, the lowest displacement ( d ext and d tot < 0.3) was characteristic of most of the boreal belt, especially across northern North America, Europe, and the vast majority of Russia. Local inundation dynamics were well captured at the landscape level with an approximate concentric expansion and retraction dynamic, possibly explained by the temperature‐dominated (as opposed to precipitation‐dominated) timing of floods (Kireeva et al., 2020; Papa et al., 2008; Torre Zaffaroni, Baldi, et al., 2023), the glacial processes that have shaped the topography of these landscapes in the past (i.e., a currently inactive geomorphological agent), and the role of permafrost in channeling water (Blöschl et al., 2020; Buttle et al., 2016; Rowland et al., 2023). It is crucial to note that these regions, due to the observed and potential effects of climate change on permafrost stocks (Holgerson & Raymond, 2016; Schuur et al., 2015; Smith et al., 2022), may face increased rates of displacement and geomorphological alterations, putting at risk local and downstream communities and ecosystems (Lafrenière & Lamoureux, 2019).…”

Remote Sensing of Multitemporal Functional Lake‐To‐Channel Connectivity and Implications for Water Movement Through the Mackenzie River Delta, Canada

“…The sensitivity of connectivity to water level indicates that predicted future changes to the northern Mackenzie River hydrologic cycle, such as increasing winter and spring streamflow at the expense of summer streamflow (Scheepers et al., 2018) and increasingly frequent and intense future precipitation events (Kuo et al., 2020), are cause for future monitoring. Additionally, permafrost thaw (Lantz & Kokelj, 2008) and resulting increased erosion rates (Rowland et al., 2023), and subsidence (Forbes et al., 2022) are predicted to influence the Mackenzie River Delta region going forward. Each of these projected changes may influence functional and structural lake‐to‐channel connectivity in different ways; with changes to streamflow resulting in higher and earlier springtime connectivity but decreased summertime connectivity, increased erosion leading to higher TSS and therefore higher functional connectivity, and increased subsidence leading to shifting lake sill elevations and functional connectivity elevation thresholds.…”