Whitehorse’s stormwater system operates under a challenging mix of steep terrain, cold-climate hydrology, and limited monitoring data; conditions that demand a modelling approach beyond typical urban drainage assumptions. This work developed a city-wide stormwater modelling framework for the City of Whitehorse, including catchment delineation, construction of an integrated PCSWMM model, and advanced GIS workflows to evaluate drainage performance under historical conditions, climate change, and rain-on-snow scenarios. More than 850 catchments and 150 drainage networks were generated using high-resolution elevation and infrastructure datasets, revealing technical challenges related to snowmelt representation, parameter selection, connectivity assumptions, and large dataset management. Results identified capacity constraints, localized flooding mechanisms, culvert bottlenecks, and sediment-sensitive conveyance issues. Recommendations focus on improving GIS-based asset inventories, expanding long-term monitoring to support calibration, refining modelling methods for northern conditions, and strengthening defensible stormwater planning for cold-climate municipalities.
