Predicting the unpredictable: how computer modelling now helps emergency services plan for disaster evacuation

Systems that simulate human behaviours can assist planning for when disaster rolls around, writes Matthew Agius at Cosmos Weekly.

Should I stay or should I go?

Whether to evacuate one’s home and leave a community is an incredibly difficult decision to make. Some delay the decision for as long as possible, and for those without practice or experience, evacuation often takes longer than anticipated.

In Australia, there’s no requirement to leave a property in the face of a hazardous event (in the USA, authorities take that decision out of individuals’ hands with compulsory evacuation orders).

While flooding hazards – like those experienced by the eastern states during recent La Niña seasons – kill many more people than bushfires, blazes are a regular fixture in the world’s driest inhabited continent.

The Black Saturday bushfires claimed 173 lives and razed two thousand homes in February 2009. This led to a royal commission and nationwide changes including a major overhaul of Australia’s bushfire danger rating system.

In Australia, there’s no requirement to leave a property in the face of a hazardous event.
A review found human readiness for those fires ranged from people having sophisticated plans, to no preparation at all. Over a third of those who initially stayed to defend their homes eventually evacuated because of higher perceived levels of danger, equipment failure or because their home caught fire.

A decade later, the Black Summer fires across Australia resulted in thirty-three deaths, the destruction of thousands of homes, and the death and displacement of almost three billion animals.

Of 80 recommendations made by the Royal Commission into National Natural Disaster Arrangements following the Black Summer fires, seven were related to evacuations. These included periodic review and updates of evacuation plans in relation to evacuation routes, educating communities including ‘seasonal’ populations, ensuring essential services and supplies, and the use of nationally consistent terminology.

Model behaviour: Predicting how people will respond to hazards

While educating, and potentially motivating, people to safeguard their lives by leaving a hazard area is important, the task of reviewing and updating evacuation plans – and predicting human behaviour that might transpire during a hazardous event – is far more complex.

Whether a person chooses to stay or leave, or how many community members may evacuate, is an important consideration for government planners and emergency services.

Will an access road be blocked because it’s full of cars driving the other way? Where are the places homeowners will remain to defend their property? How will behaviour change when there’s a fire burning 50 kilometres away, instead of five?

For midweek evacuations, they need to consider how parents will get their kids from schools, and how busy town centres will become when people start congregating.

So how do authorities predict the unpredictable?

Fortunately, there’s a model for that.

“Rarely when you tell a community of people to evacuate does every person leave.”

– Dhirendra Singh

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