The simulation of ice jam profiles in multi-channel systems using a one-dimensional network model

Abstract

This paper presents a new modelling method for simulating ice jam profiles in channel networks, implemented in the University of Alberta's public-domain hydrodynamic and river ice process model, River1D. The method includes provisions for handling junctions when solving the ice jam stability equation within a channel network. At junction elements, the solution of the ice jam stability equation is calculated as a function of the junction water discharge ratio. The model was first compared to a series of idealized test cases from a previous study that sought to investigation the impact of islands on ice jam profiles. Seventeen tests were performed in rectangular channels with islands of different length. The results from River1D agreed well with the results from the previous study, showing the same stage reduction along the length of the island and minimum depth at the upstream end of the island. The model was then applied to the Hay River Delta in the Northwest Territories of Canada. The model was first validated for open water scenarios (with surveyed data and 2D modelling results) and was then used to simulate a series of ice jam profiles and validated using data collected within the Hay River Delta during the 2009 breakup. Using just a single value of 0.055 for the under ice jam roughness, the modelled ice jam profiles agreed favourably with the surveyed levels. However, the model did have a tendency to under predict levels in the East Channel for the profile that was collected after an upstream ice jam release wave had passed through the delta. When jam consolidation was considered in the simulation, the model was able to more accurately simulate the surveyed levels. The model results suggest that ice jamming conditions during the 2009 breakup reduced the percentage of flow entering the East Channel compared to open water conditions.