River-controlled permafrost dynamics are crucial for sediment transport, infrastructure stability, and carbon cycle, yet are not well understood under climate change. Leveraging remotely sensed datasets, in-situ hydrological observations, and physics-based models, we reveal overall warming and widening rivers across the Tibetan Plateau in recent decades, driving accelerated sub-river permafrost thaw. River temperature of a representative (Tuotuohe River) on the central Tibetan Plateau, has increased notably (0.39 degrees C/decade) from 1985 to 2017, facilitating heat transfer into the underlying permafrost via both convection and conduction. Consequently, the permafrost beneath rivers warms faster (0.37 degrees C-0.66 degrees C/decade) and has a similar to 0.5 m thicker active layer than non-inundated permafrost (0.17 degrees C-0.49 degrees C/decade). With increasing river discharge, the inundated area expands laterally along the riverbed (16.4 m/decade), further accelerating permafrost thaw for previously non-inundated bars. Under future warmer and wetter climate, the anticipated intensification of sub-river permafrost degradation will pose risks to riverine infrastructure and amplify permafrost carbon release.

River bank erosion supplies sediments to river systems, sustaining many river functions. To properly understand and ultimately model river bank erosion, we have to know the temporal and spatial distributions at which it occurs. This is especially challenging in cold-climate regions where a large variety of processes occur that contribute to river bank erosion. We therefore obtained a one-year dataset, using buried soil sensors, on bank erosion and its forcing parameters with a high temporal resolution to answer the question: what are the temporal and spatial distributions of river bank erosion in cold climate regions and what are the forcing conditions causing these distributions? We measured soil movements at multiple river bank sites throughout Finland and compared the movement times with soil moisture, soil and air temperature and discharge information. This analysis showed that there is no clear temporal distribution of bank movement in the Southernmost investigated site, while in the more Northern field sites soil movement was most frequent around the freezing and thawing periods. At one field site an additional period with an increased frequency of soil movement events is likely caused by reindeer during summer months. This research used a new type of dataset of soil temperature, moisture and movement. This unique dataset allowed us to identify individual soil movement events and helps to better understand river bank erosion and by extension fluvial systems in cold-climates.

Erosion of riverbanks is a natural phenomenon, which leads to the loss of important agricultural land areas. At the same time, riverbank erosion can be considered a natural risk that can cause major damage to road and railway infrastructure, flood management infrastructure, biodiversity and even the population located in flood risk areas. This phenomenon is generally more pronounced in the meanders of the rivers and in regions with higher flow rates, but it can be accentuated due to climate change which can lead to changes in watercourse flows. This study aimed to estimate the net annual soil loss due to riverbank erosion on the Siret River, Romania, using aerial photogrammetry and GIS analysis.

This review article deals with bank erosion from the perspective of rivers affected by seasonal ice formation. These rivers drain half of the terrestrial land surface globally, and are mainly located in both periglacial and cold, non-periglacial environments across the Northern Hemisphere. This review is based on a literature survey of 126 publications (articles, technical reports, conference papers and book chapters) documenting case studies in temperate and polar climates. The first details the global issues of bank erosion and pinpoints concerns specific to northern environments. The second describes the dominant erosion processes (fluvial vs. terrestrial), mechanisms (mechanical vs. thermal) and typical landforms encountered in the literature. The third reviews the environmental factors (hydraulic vs. non-hydraulic) controlling bank erosion, with a focus on the different forms of river ice. The fourth deals with the spatial and temporal variability in bank-erosion processes, discussing the distribution of process dominance occurring at the reach scale and the catchment scale, and describing the temporal window in which each process dominates. The fifth reviews the expected impacts on bank erosion resulting from climate-induced disturbances on hydrological cycles and from increasing anthropogenic pressures along riverbanks in northern countries. The relationships among erosion processes, environmental factors, climate change, and human impacts are summarized in a sixth that introduces a new synthetic conceptual diagram of bank erosion. Research needs that should be investigated in the future are highlighted in the seventh while the final synthesizes all the aspects presented in this review.