Riverbank erosion numerical modeling: groundwater and temperature dynamics in seasonally frozen rivers using a hypothetical bank geometry

Riverbank erosion is a significant contributor to sediment transport in rivers and a key factor shaping river ecosystems, which are affected by natural and human activities. Its dynamics depend on a variety of factors, including river flow, water levels, soil properties and composition, groundwater flow, topography, climate, soil moisture, temperature, and vegetation. The main drivers of riverbank erosion are particle detachment by water flow, gravity-induced mass failure, and seepage erosion. While these processes shape river channels and floodplain morphology and support ecological functions like habitat creation, they also pose risks such as land degradation and infrastructure damage.  In seasonally frozen rivers, bank erosion dynamics are further complicated by unique climatic and hydrogeomorphic conditions, including temperature fluctuations and variations in groundwater flow. These additional processes can cause erosion by themselves and can interact with the other processes. Especially, the interactions between these factors remain poorly understood, hindering accurate predictions of bank erosion events. This study examines how topography, river stage changes, groundwater flow, soil moisture, and temperature variations affect riverbank erosion in seasonally frozen rivers. The research focuses on three objectives: (i) assessing how topography influences riverbank erosion, (ii) examining the role of river stage fluctuations and soil types in erosion processes, and (iii) analyzing the impact of freeze-thaw cycles on groundwater movement and soil stability, bank erosion. A two dimensional (2D) vertical bank erosion model was developed that integrates temperature dynamics with groundwater flow, allowing realistic simulations of temperature-induced changes in soil permeability and groundwater behavior. The framework applied with dynamic boundary conditions, offering novel insights into riverbank erosion mechanisms. The simulations were at this first stage performed by using a hypothetical riverbank geometry. First findings show that the interactions of processes can lead to temporally varying rates of erosion which cannot be understood in isolation. Bank geometry is expected to play a significant role, with some profiles more prone to collapse than others. Additionally, river stage fluctuations and dynamic soil conditions are likely to exacerbate erosion risks. These insights will support the development of predictive tools for sediment management, climate-resilient riverbank protection, and sustainable ecosystem management in cold-region rivers.

Keywords: Riverbank erosion, groundwater modeling, temperature, seasonally frozen rivers, numerical modeling, freeze-thaw cycles.