Wildifre papers Why some homes survived: Learning from the Fort McMurray wildfire disaster By Alan Westhaver, M.Sc. August 2016 ISBN: 978-1-927929-04-9
The wildland/urban interface disaster that struck Fort McMurray, Alberta in May 2016 destroyed more than 2,400 structures. It is the largest ever insured loss in Canada. It will alter the way that governments, communities and industry prepare for, respond to, and recover from future wildfires.
The Institute for Catastrophic Loss Reduction (ICLR) recognized the unprecedented opportunity this event held for firsthand learning towards the ultimate goal of lowering wildfire losses. With that in mind, ICLR dispatched an investigator for the purpose of examining, describing, and interpreting circumstances regarding the survival or destruction of Fort McMurray homes.
The vital question to be answered was: ‘Why did some homes survive this wildland/urban interface fire with little or no damage, while others were vulnerable to ignition and destroyed?’ Obtaining the answer to this question, and others arising from it, is urgent. Two similar catastrophes of escalating magnitude have occurred since 2003, and there is rising probability of more frequent infernos in the future given present trends in climate change, forest fuel accumulations, and expansion of people and development into wildlands. This unique study1 was carried out from May 19 to 28, 2016 in urban neighbourhoods at the forested ‘interface’ fringes of the city, and at forested acreages nearby.
After evaluating the fire environment and clearances between homes and the forest edge, the investigator discounted direct contact from flames or radiant heat of the forest fire as being significant sources of home ignition at Fort McMurray. Instead, it was concluded that wind-driven embers were the most probable cause for the majority of early home ignitions in the zone where the fire made its transition from forest into urban neighbourhoods. Once established, the fire would have spread from structure to structure as an urban conflagration, accounting for the majority of home losses.
The author has concluded that the Fort McMurray wildfire fits a pattern widely recognized as the ‘wildland/urban interface disaster sequence.’ That sequence can be broken, and catastrophic home losses can be prevented; however this depends on widespread adoption of risk mitigations within the home ignition zone. Therefore, it is speculated that if homeowners became more aware of how homes ignite and better understood how and why simple FireSmart measures work, they may be better motivated to correct weaknesses in wildfire defences. A communication tool for raising public understanding is suggested.