Acceleration in snow and glacier melting increases outburst flooding risks for Quebec in the spring season. Computational models of river flow are useful for flood predictions and help improve quick decision-making actions in case of flood hazards. The integration of 1D with 2D models, referred to as a 1D-2D model, has proven to be more effective for simulating river flood inundations. The study assesses the accuracy and computational efficiency of the 1D-2D model, with and without an ice jam, and of a full 2D model without a jam. This study conducts comprehensive evaluations of the modelling techniques as applied to the adjacent areas of the Lake of Two Mountains, which is part of the widening delta of the Ottawa River at its confluence with the St. Lawrence River in Quebec. This study emphasises the impacts of an ice cover in the floods of the Ottawa River and the Lake of Two Mountains, and aims at providing essential insights for advancing flood prediction methods. It examines the impacts of glacial outbursts on flooding in cold regions. The results reveal that the 1D-2D model effectively mimics glacial outburst events, showcasing their influence on flooding in river and lake water bodies. Additionally, they demonstrate how ice outbursts escalate flood velocities and extents. The findings from this study hold substantial promise in enhancing flood management strategies and optimising the design of intervention structures in river systems. This study contributes to the ongoing efforts to mitigate the adverse effects of flood hazards in the future.