Australia must brace for clusters of natural disasters, not just isolated fires and floods
- Written by The Conversation
Around the world, communities are battling more extreme weather events. That includes residents in the path of Cyclone Narelle, which is threatening to form again over Western Australia.
But another concerning trend is that natural disasters are increasingly arriving in clusters, not in isolation.
Fires, storms, floods and heatwaves are are no longer neatly separated by season or geography. They are more often occurring together or are affecting different parts of the country at the same time.
Scientists describe these as compound or overlapping hazards. This is where two or more natural disasters happen simultaneously or in close succession. And they often affect the same places.
So how can we prepare for overlapping disasters? And what does it mean for our emergency services?
The danger of multiple disasters
International research suggests people are most at risk when a new disaster strikes and they haven’t yet recovered from an earlier event. To understand risk, it helps to understand these three terms:
- hazard, which is the dangerous event itself
- exposure, which refers to the people and things that could be affected
- vulnerability, which is a measure of how susceptible to harm people and things are.
When disasters overlap, all three components of risk will likely increase.
Overlapping hazards are different from so-called cascading hazards. Cascading hazards refer to when an initial event triggers a series of system failures. These failures often cause infrastructure breakdowns and social disruption, both of which can actually be worse than the original disaster event.
An example of this is the 2011 Tōhoku disaster in Japan. In this case, an earthquake triggered a tsunami which then inundated the Fukushima nuclear plant. These cascading hazards led to a nuclear crisis, mass evacuations, and long-term contamination. So it was the consequences of the earthquake, not the earthquake itself, that caused the most harm.
Overlapping hazards are often harder to manage. One reason is it’s hard to coordinate public warnings when multiple disasters strike. For example, a bushfire warning might instruct people to evacuate immediately, but a simultaneous flash flood may block the very roads needed to escape.
Overlapping hazards also stretch our emergency resources, often across multiple fronts at once. And recovery from one event is frequently interrupted by the next. This is why we can no longer rely on current disaster response frameworks, which tend to be built around isolated events.
A history of overlapping hazards
In Australia, we are fairly used to dealing with overlapping disasters.
In January this year, inland bushfires were burning in Victoria’s west under hot, dry conditions. Meanwhile, an intense coastal storm was brewing in that same region. This saw emergency operations move from fire suppression and evacuation to flood rescue, as flash flooding inundated sections of the Great Ocean Road and washed vehicles into the ocean.
In December 2025, Western Australia was hit by a tropical cyclone that caused flash flooding and widespread power outages. Within days, authorities were issuing fire danger warnings as a heatwave swept across the state’s southeast.
In late 2024, severe hail and flash flooding arrived in the aftermath of a bushfire in New South Wales’ Yass Valley. Residents barely had time to recover from the initial fire.
Research examining more than five decades of insurance losses shows Australia experiences the most overlapping hazards in December, January and February. This is when bushfire, tropical cyclone and severe storm seasons overlap. This makes summer the most high-risk period, particularly for disaster-prone regions.
When disasters converge
In Australia, natural disasters most often come in three combinations:
- heatwaves alongside drought
- heat followed by heavy rain
- strong winds combined with heavy rain.
Heatwaves and drought often occur together because dry soils reduce evaporation and push temperatures higher. This creates persistent hot and dry conditions, increasing the risk of bushfires. These hot conditions also put pressure on the agriculture and health care sectors. Recent Australian research suggests this combination of heatwaves and drought will only become more common and extreme.
In Australia, heavy rainfall is more likely to come after a heatwave. This is because extreme heat alters atmospheric conditions in a way that means subsequent rain often falls in shorter, heavier bursts.
Strong winds and heavy rainfall often occur together, most commonly when tropical cyclones develop. East coast lows, a type of intense weather system that usually forms off Australia’s eastern coast, may also create the right conditions for these overlapping hazards.
The role of climate change
Climate change acts as a “threat multiplier”, increasing the likelihood of extreme events occurring together or in rapid succession. Research shows extreme weather is becoming more frequent and intense.
In Australia, we have already recognised this trend, creating national frameworks to deal with a rising number of simultaneous, and often large-scale, disasters.
But sound policy does not guarantee effective emergency management. As the risk of overlapping hazards increases, we must actively involve communities in disaster planning. Through education programs and clear messaging, we can help them understand how disasters may combine. We can also give them strategies to make decisions when weather conditions change rapidly.
In our changing climate, overlapping hazards will only become more common. So there’s no better time to help our communities and first responders prepare.
