Fighting fire with fire: How controlled blazes are used to avert a greater catastrophe

As wildfires wreak havoc in California and leave 90 dead in Greece, Robert Matthews looks at why 'putting out the fire with gasoline' is often the only option

Firefighters battle the Ferguson Fire, the largest fire in the Sierra National Forest's history, in California on August 8. Courtesy US Forest Service

Searing heat, high winds, years of drought - the driving forces of the biggest wildfire ever to strike California seem obvious. But it’s equally clear that the standard ways of dealing with it are barely able to cope.

Around 14,000 fire-fighters have spent a fortnight battling fires that are expected to burn for the rest of the month.

Worse, there’s a growing belief that such fires will become – as one hard-pressed fire-fighter put it last week – “the new norm”.

But that, in turn, is sparking renewed interest in a radical approach to dealing with the threat.

And it involves literally fighting fire with fire.

For years, the key idea behind preventing conflagrations has been one of zero tolerance through measures like banning camping and setting up networks of lookout-towers that could stop small fires getting traction.

When the majority of fires had natural causes like lightning, this worked. But with increasing urbanisation it’s doomed to failure.

Since the early 2000s, California has tried to deal with the increasing threat through laws requiring homeowners to strip the land around their homes of vegetation that could turn into kindling.

But around the same time, researchers began taking an interest in a more radical approach, and switching from fire prevention to fire management.

Studies revealed that the zero-tolerance approach had an unintended consequence: a build-up of colossal amounts of dead wood in forests which themselves were becoming ever denser.

As a result, if a fire did break out there was a much higher risk of it turning into a conflagration.

In 2006, a four-year international research programme was set up by the European Union to investigate an idea already being used in parts of the US.

At its heart is the so-called fire triangle, which describes the three key requirements for a blaze: heat, oxygen and fuel. Remove any one, and fire becomes impossible.

And one of the best ways of removing fuel is to burn it – in a fire.

During the four years, the aptly-named Fire Paradox project showed that small, controlled fires set during the winter months consumed fuel that could otherwise feed a far bigger event.

The project also backed a strategy used by some fire-fighters in the US and Australia for dealing with major fires once they’ve begun.

This involves setting a controlled blaze ahead of the main one, and using it to clear vegetation that would otherwise feed the bigger fire. It’s a method now being used to contain some parts of California’s blaze.

But the project also uncovered the most paradoxical approach of all. This involves setting up a second line of fire close to the main blaze. The resulting inrush of air then drives the two fronts together so violently they put each other out.

While crazy-sounding, demonstrations of such “fire-fights” in Argentina showed they can work.

The sheer size of the California blaze means there’s no hope of surrounding it and attempting anything like this.

Even so, the lesson is clear:  the solution to some natural disasters lies in thinking well outside the box.

It’s an approach that’s now being used to deal with that  other existential threat to Californian life: earthquakes.

For decades, scientists looked for ways of predicting when the state’s notorious San Andreas fault would next give way, triggering a devastating earthquake.

Yet despite spending billions of dollars, they found no tell-tale signs they could rely on.

But now the US West Coast is going to benefit from a neat bit of lateral thinking. It exploits the fact that the most reliable indicator of any earthquake is the quake itself.

While no-one knows for certain when the San Andreas fault will next wreak destruction, one thing is for sure:  it will release waves of seismic energy through the ground.

Some of these waves are relatively harmless, while others cause the deadly up-and-down motion that wreaks most of the damage.

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And, crucially, the relatively harmless ones – known as P-waves - travel twice as fast as the deadly S-waves.

This means that a network of P-wave detectors can serve as an early warning system of impending disaster.

It’s an idea first used by Japanese engineers in the 1960s to protect the famous Bullet Train by automatically activating the brakes if P-waves were detected.

It’s since been rolled out across Japan, and a similar system has also been installed in Mexico.

Now the US Geological Survey is rolling out its own version, known as the ShakeAlert system.

Experiments suggest it can detect P-waves anything from a few seconds to tens of seconds ahead of the main quake.

That might not sound much, but it’s enough to issue warning to people to take cover, stop cars going onto bridges or into tunnels, and close down chemical plants and gas supplies.

That could save countless lives when the next Big One strikes. When the last one, a 7.9-Richter event, hit San Francisco in April 1906,  several thousand lost their lives – many in the fires fuelled by ruptured gas mains.

Experts estimate there’s a 1 in 5 chance of the next Big One striking San Francisco in the next 30 years. Combined with the threat from further conflagrations, Californians may soon find out if their reputation for embracing innovation will be their salvation.

Robert Matthews is Visiting Professor of Science at Aston University, Birmingham, UK