Preliminary Assessment of the Flood Risk Potential Along the Hudson Bay Railway with Consideration of Climate Change Effects

ABSTRACT: The Hudson Bay Railway (HBR) in northern Manitoba is a vital land transportation route that provides access to the Port of Churchill. Extending for 810 km, the railway traverses various permafrost zones and passes through the Hudson Bay Lowlands, one of the largest peatlands in the world. Due to this ice-rich permafrost subgrade, wetland terrain, and the effects of climate change on the surrounding sensitive landscape, HBR has always required frequent maintenance. Climate change, with higher temperatures and changing precipitation patterns, has resulted in permafrost degradation, the recurrence of sinkholes, and alterations in surface and subsurface hydrologic flow pathways along the railway. In addition, there is a need to evaluate how flooding and washout induced embankment failure events, and potential derailments, may be affected. This highlights the need to assess the performance of the HBR drainage system under current and future climate conditions. This study quantified potential increases in runoff at Weir River bridge location along the HBR by developing a physically based, semi-distributed hydrological model within the Raven Hydrological Framework. The model was developed for the Weir River basin, a basin previously identified as highly prone to flooding. After the calibration and validation process, the model simulates peak flows under current conditions and future climate scenarios. The results showed flood magnitudes increased consistently across all return periods under future climate scenarios when compared to historical conditions. Although higher flows are projected, comparisons with existing channel geometry suggest a low likelihood of overtopping at the Weir River bridge under future conditions, though this assessment is subject to uncertainty due to the developed model's limitations.