Black Saturday
February 2009 will be long remembered in Australia's bush fire history. On Feb. 7-8, a series of fires roared across Australia's southeastern state of Victoria, repeating their cyclical pattern once again. Only this time, the intensity and destructive path of these fires would be like nothing Australia and its firefighters had experienced before. The severity of these fires was such that more than 170 people living on the urban fringe perished, 500 more were seriously burned, more than 2,000 houses were consumed and Victoria's impressive firefighting system was vastly overwhelmed by unprecedented conditions. But what happened makes an interesting case study for fire managers worldwide due to the sheer scale and complexity of this enormous event.
To understand southeastern Australia's fire ecosystem, it's helpful to look at the region's history — going as far back as 40,000 years ago, when aboriginal culture dominated the vast continent. For generations, indigenous tribes used fire-farming techniques passed on through oral traditions to burn off the land in mosaic patterns. They modified their environment where possible to best suit their hunting-and-gathering lifestyle. The vegetation that survived and prospered evolved to become self-selecting, creating a collection of ecosystems that depend on fire as part of their natural life cycles.
Around 200 years ago European settlers began to reshape this landscape for their own needs. They cleared huge expanses of bushland for fields, timber industries and settlements, leaving behind some remnants of the earlier ecosystems as national parks. Throughout this expanding frontier, settlers used fire to clear land, but often not in the same patterns as the land's historic caretakers. As a result, forest fuel loadings built up in pockets. These remained in some cases up until the summer of 1939, when the first modern, massive fires roared across Victoria, incinerating entire timber industry towns and killing 71 people. This deadly fire event was named Black Friday. Years later, Ash Wednesday followed on Feb. 16, 1983, when another series of wind-driven bushfires washed across Victoria, causing 75 more fatalities.
Victoria's fertile fire environment is divided into four primary fuel types. Sclerophyll, one of the most significant, is made up largely from indigenous eucalyptus forests that cover the majority of the coastal and mountainous areas. The leaves of these trees contain highly flammable oils. When conditions are right, surface fires in these forests can climb easily into their crowns and be carried some distance. Another primary fuel in Victoria is a thick scrub brush that is less predictable when ignited than sclerophyll, and it will carry fire much more quickly. Modern pine plantations also are found across this region; they are defended from fire where possible due to their economic value. Finally, grass and crop fields are highly combustible when seasonally "cured."
The state's topography includes coastal regions, plateaus, hills and high mountain ranges. Each of the killer fire events here has been influenced by seasonal weather patterns that create the perfect recipe for massive fire movements when combined with the state's geography. Before each of these events, a high-pressure system moved in and stalled for days at a time, sinking super-dry air from the upper atmosphere, about 4 or 5 kilometers above the earth. This stagnant weather system increases ground air temperatures to over 40° Celsius and dries out the land.
Before this most recent event, three days of super-hot weather had baked Victoria in late January. That heatwave came after a month without any precipitation, marking the state's second-longest summer dry spell since Europeans settled in Australia. The conditions arrived on the back of a major drought, with 20 percent less rainfall than normal cycles in the past 12 years.
On Saturday, Feb. 7, this weather pattern and its unrelenting heat returned to Victoria, scorching the centrally located capital of Melbourne with temperatures up to 46.4° Celsius. This broiling, oppressive heat marked the city's highest temperature in 154 years of recordkeeping. The searing heat of the high-pressure weather mass built until the early evening of Saturday, when it was finally shoved eastward by an approaching cold front from the northwest. Dry, hot high-velocity winds — gusts were recorded at over 100 kilometers per hour — roared onward, leading this cold front across Victoria's preheated landscape.
In the path of these furnace winds, nine major fires ignited, with most beginning about mid-day. The hurricane-force winds soon drove these new conflagrations into huge monsters of flame. One fire was clocked moving from its origin location to a kilometer ahead in just six minutes. Other rapidly growing blazes, riding on the speed of the roaring winds, quickly fanned into a single solid wall of fire that was 100 kilometers wide at its peak. The fire consumed its way dangerously close to suburban Victoria before colliding and joining forces with still more fire fronts. By 5 p.m., the nine new fires were threatening at least 15 communities. There are a number of suspected causes for the various ignitions, but Australian law requires official investigations before determining cause.
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