Fast fires

When wildfires move fast, the people in their path are left with little choice but to flee.

And wildfires are moving more aggressively than ever, forcing entire communities from their homes and leaving destruction in their wake.

Three memorable wildfires have recently made headlines around the world for how fast they spread, how intensely they burned and the lives they claimed.

The first was in June 2021, when a fast-moving fire destroyed the majority of the village of Lytton, B.C., killing two elderly people who became trapped by the advancing flames.

Earlier this summer on the Hawaiian island of Maui, a deadly fire ripped through the historic town of Lahaina so quickly that people fled into the ocean to escape the flames. So far, 115 people have been confirmed dead and 66 more are still missing.

Last month, what began as an unremarkable spot fire in West Kelowna grew more than a hundredfold from 64 hectares to 6,800 hectares (68 square kilometres) over a 24 hour period making it one of the fastest moving wildfires in B.C.s history. Over the course of several days, 170 structures were damaged or destroyed, and thousands were forced to evacuate.

Compared to when I was a wildland firefighter, it seems like fires are different, said Mathieu Bourbonnais, a former firefighter who is now an assistant professor of Earth, Environmental and Geographic Sciences at the University of British Columbias Okanagan campus.

These fires are faster and more aggressive, according to Bourbonnais.

That makes them more dangerous to fight, and more of a threat to the people who live in their path.

But by analyzing three factors weather conditions, topography and fuel, or whats known as a fire behaviour triangle those who fight and study fires say they can better understand and predict the conditions that lead to these fast-moving and destructive blazes and help prepare for a future where more fire is certain.

WATCH | Breaking down what causes some fires to move so fast:

In Lytton, Lahaina and West Kelowna, scorching hot weather conditions combined with powerful winds fuelled aggressive and life-threatening fire behaviour.

Wind is everything, said Jeffrey Nishima-Miller, a former B.C. wildfire fighter turned PhD candidate in Earth and Environmental Sciences at UBC Okanagan.

It fuels oxygen to the fire. Just the same way as if you had a campfire and youre blowing the embers to really start that fire. The wind acts as that really driving force.

In West Kelowna, wind gusts of 50 to 70 kilometres per hour were recorded the day the fire grew allowing it to spread about 20 kilometres in just 12 hours.

Heat mapping data from NASA shows the growth of the fire over several days as it moved east, over the crest of West Kelowna and down toward Lake Okanagan.

On Aug. 17, people across the lake in Kelowna watched in horror as the powerful winds pushed the flames toward them.

Soon, spot fires began appearing on the Kelowna side the fire had jumped across the body of water.

Bourbonnais said when fires become powerful enough, they can generate their own winds that fuel the fire, creating spot fires on the path ahead.

Those winds can also pick up embers and burning materials, allowing them to jump huge distances across highways, rivers, or, in the case of West Kelowna, a lake.

Those embers, you know, Ive seen them personally travel up to five kilometres, said Nishima-Miller.

Its not surprising with those extreme wind conditions that we were experiencing that those small embers picked up the two or so kilometres across the lake.

The day that Lytton burned, wind gusts of 71 km/h were recorded in the area.

In Lahaina, trade winds whipped into a frenzy by nearby Hurricane Dora fanned the flames, causing the fire to burn at a rate of what Hawaiis governor said was a mile a minute.

Thats 96 kilometres an hour, or about as fast as a car driving on a highway.

Topographical features like steep mountainsides, canyons and hill crests can exacerbate fire behaviour, because fires gain speed and power when they travel uphill.

Heat generated by fires rises, heating up material above it, drying it out and allowing it to catch fire faster as it moves up a slope.

On the flip side, fires will generally slow when they start to move downhill.

Nishima-Miller said thats why the fire behaviour in West Kelowna was so startling. Because rather than slow down, it only seemed to gain momentum as it travelled down the slope and toward homes.

I was watching from the other side of the lake and I have never seen fire activity like that, he said.

I did four seasons with the B.C. Wildfire Service based out of these areas. And to date, I have never seen fire go that fast downhill.

Because of its unique geography, Lytton is consistently one of the hottest places in the country. A sign on the side of the Trans-Canada Highway leading into town declares it Canadas hot spot.

The village is situated at the bottom of a canyon in B.C.s interior halfway between Vancouver and Kamloops.

The day before the fire, the temperature in Lytton spiked at 49.6 C, as western Canada sizzled under a record-shattering heat dome.

When that hot air rose, wind rushed down into the canyon toward Lytton, acting like a blowtorch on the dry landscape.

The fire was sparked at 4:48 p.m., on June 30 and quickly spread north through town, travelling at 20 km/h.

By the time Mayor Jan Polderman signed an evacuation order at 6 p.m. PT, fire was already burning through structures, sending people fleeing to the highway.

Its dire. The whole town is on fire, Polderman told CBC News that day.

It took, like, a whole 15 minutes from the first sign of smoke to, all of a sudden, there being fire everywhere.

Fire needs combustible material to spread.

In the weeks before the fires in Lytton, Lahaina and West Kelowna, all three regions had experienced sustained periods of drought.

Material like dry grasses, trees, shrubs and pinecones were abundant, quickly catching fire and fuelling the wildfires.

The spread of the fire in Lahaina was exacerbated by invasive species of plants like guinea grass and molasses grass that caught fire quickly and burned easily.

Bourbonnais said when an already aggressive fire cant be held off from structures and fuel sources, it can create conditions so severe that even firefighters have no choice but to get out of the way.

To be honest, sometimes it just becomes too dangerous to actually have personnel on that type of fire where youre seeing that kind of fire behaviour, he said.

As a wildland firefighter, those are the ones where we start talking about making sure you have an escape route, making sure you have a way to get out of the fire into a safety zone.

On Aug. 11 four days before the West Kelowna wildfire was sparked officials with the Canadian Forest Centre said 2023 was easily Canadas worst wildfire season ever recorded, with millions of hectares already burned.

Federal data revealed 13.4 million hectares had been burned across Canada significantly more than the 10-year average of 2.2 million hectares burned in any given year.

With climate change ushering in hotter, drier summers, the people who fight and study wildfires warn that aggressive fires are only going to become more severe and more common.

Robert Gray, a fire ecologist, said B.C. needs to ramp up its prescribed burns. Thats when controlled fires are intentionally used to burn dry parts of the landscape so it doesnt spark during fire weather and usher flames into populated areas.

Our treatments need to be on the scale of the fires that were seeing, Gray said.

So if were seeing 5,000 hectare fires, some of our treatments should be 5,000 hectares or more. Its that pattern that we need to create all across the landscape and we just need to do a lot more of it.

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He also says we have a limited amount of time to implement these treatments because climate change means hotter temperatures and likely more drought conditions, which will create more fuel for wildfires to consume.

Fire, Gray said, is in our future.