Modelling of Freeze-Up and Ice Cover Development in a Subarctic River Using a 2D Numerical Model

When the temperature of river water in a turbulent flow area drops below zero, supercooling occurs and various types of ice can develop over the surface and depth of the flow. The present study investigated, modelled, and predicted river ice formation using numerical models. The model parameters, such as Manning's coefficient and the surface heat flux coefficients, were calibrated, and the results were validated using measurement data from the subarctic, meandering Pulmankijoki River in northern Finland. A two-dimensional TELEMAC model was used for the hydrodynamic part, and a two-dimensional KHIONE model was used for the ice part of the numerical modelling. These models are open source and coupled river flow models that can determine ice parameters based on hydrodynamic and river channel geometry parameters. The modelling outcomes provided insights into the complex processes of ice formation and ice cover development. The findings identified favourable velocities for initial border ice development in different parts of a meandering river reach, including a straight reach and two meander bends. The final results also verified that the air temperature and heat flux parameter can serve as a key parameter for modelling river ice.