Grant: Discovery Grants Program - Individual

There has been an increase in the number of extreme wildfires in Canada in recent years, with 2023 being the worst year on record. These wildfires have been devastating to watersheds in terms of loss of vegetation cover, increased runoff and erosion, and the delivery of sediments and chemicals to downstream rivers and lakes. The impacts on aquatic ecosystems are expected to be profound and include: (i) changes to the amount and timing of streamflows; (ii) the smothering by sediment of spawning gravels of key fish species such as salmonids and sturgeon; and (iii) the increased levels of fire-associated contaminants such as metals and polycyclic aromatic hydrocarbons (PAHs). Model-based projections indicate that extreme wildfires will increase in future decades in response to climate change, especially vegetation and soil moisture deficits, and increases in forest fuels due to a history of wildfire suppression and outbreaks of bark beetle infestations. Given these implications, there is an urgent need to understand how the hydrology and geomorphology of watersheds will respond to wildfires. Surprisingly, there is a dearth of information on this topic in Canada, and most watershed management and remediation following wildfires is based on studies undertaken in Australia, Portugal, Spain and, especially, the USA. While there are generic similarities in how watersheds respond to wildfires, there are also important differences which reflect regional variations in climate, vegetation and topography, as well as the age and severity of the wildfire. This project will determine the hydrological and geomorphological responses of several watersheds in British Columbia to wildfire by examining wildfire-affected watersheds with different characteristics (e.g., vegetation composition, slopes) and wildfires of different ages and severity. Specific objectives are: (i) to determine how wildfires modify rates of hillslope runoff and soil erosion; (ii) to determine the fluxes and storage of sediment and associated contaminants in receiving rivers after wildfires; and (iii) to advance the sediment fingerprinting technique to identify the sources of problematic sediment and contaminants in wildfire-impacted aquatic systems. The research aim is to establish a more wholistic understanding of how watersheds respond to wildfires in British Columbia, such that it should be possible to predict the hydrological and geomorphological responses of watersheds for future wildfires. This knowledge will enable targeted mitigation measures to be implemented following wildfires which will reduce detrimental impacts on aquatic ecosystems and water resources.