In May 2016, the Horse River Wildfire devastated the City of Fort McMurray and surrounding areas of the Regional Municipality of Wood Buffalo (the Region) in Northern Alberta. The wildfire impacted over 500,000 hectares of land, and forced the evacuation of more than 88,000 people.
As part of the emergency response, firebreaks were created around urban areas to prevent the fire from spreading further to municipal infrastructure, public and private properties. The equipment used to create the firebreaks altered natural drainage patterns and compacted existing soils, reducing their ability to absorb water, instead, shedding runoff to erosion-prone areas.
Burned areas lost significant amounts of vegetation and soil function, resulting in increased runoff and significant erosion in wildfire-affected areas. The Region identified more than 300 sites that were subject to soil loss and poor slope stability, and retained Associated Engineering to help prioritize wildfire-related erosion sites, develop and implement design solutions to address erosion and drainage issues.
To evaluate the sites, Associated established a multi-disciplinary team including environmental scientists and engineers specializing in erosion and sediment control, civil infrastructure, geotechnical engineering, bioengineering, restoration ecology, and hydrology. We prioritized sites for rehabilitation by weighing a variety of factors to determine the level of risk, impact to public and private infrastructure, and environmentally sensitive areas. From these efforts, we identified fourteen sites as priorities for remediation.
Since most of the eroded sites were located in natural areas, the project team recommended bioengineering as the primary erosion repair strategy, augmented by conventional engineering techniques. Bioengineering is the use of plants to perform engineering functions. Native woody species develop deep root systems that increase shear strength in the soil and effectively reduce stormwater runoff by promoting infiltration and evapotranspiration.
Senior Environmental Scientist, Kristen Andersen, explains, “Bioengineering fosters natural ecological restoration processes. Planting pioneering species such as balsam poplar and willow at a high density promotes a dense root net during the first growing season. Poplar and willow are also fire resistant plants.”
The team also recommended soil decompaction techniques to promote re-forestation, reduce runoff, and improve infiltration in contributing drainage areas and affected areas. We were able to develop a low-cost soil roughening solution that uses the existing materials on site.
Project Manager, Jason Vanderzwaag, tells us, “The benefits of bioengineering include lower costs, minimized impacts from construction, carbon sequestration, and improved ecosystem functions related to watershed resiliency, water quality, habitat, and biodiversity.”
As the forest grows, natural successional processes will take effect, creating conditions for other forest species to establish. The added benefit for the community is the beautiful aesthetics of the forest as the trees grow.