The spatiotemporal distribution of river bank erosion events and their drivers in seasonally frozen regions

Abstract

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.