While communities in the New South Wales’ (NSW) Manning Valley catchment are familiar with flood, last week the Manning River (Boolumbahtee in the local Biripi language) at Taree made history by exceeding the 1929 flood of record. Emergency services were faced with warning communities of an event for which no one had living memory. This resembled the Lismore community’s experiences in 2022, when the previous flood of record was exceeded by more than two metres.
Climate change means the greater chance emergency services will encounter more situations when they will need to warn communities of unprecedented natural hazards. The World Meteorological Organization’s State of the Global Climate 2024 report lists 152 unprecedented times of extreme weather throughout 2024. This highlights the critical need to understand how we can improve warnings to ensure community members act when they have no personal prior reference for such natural hazards.
Initial anecdotal evidence, including from emergency crews rescuing people from homes around Taree, suggests residents were caught off guard by the severity of the flood. Residents recounted their experiences in media reports that:
“This is next level. We didn’t expect this. There were no warnings...nobody knew how bad this was going to get. Its taken us completely by surprise.”
“The water came in really, really quickly, and it just started to flow into the house that quickly – I didn’t have a chance,”...“I went upstairs with my dog, and we stayed there last night and a little today, until we were able to get rescued.”
A NSW State Emergency Service representative said:
“What we are seeing is that some locations on the eastern seaboard had not seen this sort of flooding before...until you have seen it and witnessed it, you do not know how quicky those waters can rise and how dangerous it is.”
Natural Hazards Research Australia (the Centre) research in exploring the experiences of residents in the Northern Rivers and southeast Queensland 2022 floods found that residents experienced floods that were worse than expected and for some totally unexpected. Some had no idea that they were actually at-risk of flooding. The NSW Flood Inquiry concluded:
“Community flood plans were based on the highest recorded flood or the most severe flood in living memory. For many this was the 1974 flood which reached a height of 12.11m in Lismore. This assumption proved destructive and is indicative of a greater flaw in the flood warning system.”
When warning of extreme natural hazards, emergency services are often challenged by individuals’ decision-making process during stressful and uncertain circumstances. People use mental short-cuts or unwritten rules to inform their decisions, called heuristics. Heuristics predispose people to rely on comparison to similar past disasters to guide their behaviour. Optimism bias also means people tend to overestimate the probability of positive outcomes.
Deciding not to evacuate is not uncommon behaviour during floods. For example, in 2022 in the Northern Rivers and southeast Queensland 60% of residents did not evacuate despite receiving an evacuation warning from emergency services. Often, reliance on past experience results in people choosing to shelter in their homes as they have done successfully previously. However, during extreme events floodwaters rise faster and higher than expected, quickly overwhelming preparations and placing people in peril. Other reasons for staying can include caring for pets and worrying about property theft.
Without specific local flood knowledge of likely impacts, it is well established that communities struggle to correctly interpret warnings. Weather bureau forecasts provide technical information about predicted flood heights and timing, but this may not be easily accessible to or interpreted by everyone. And a decades old flood classification system of minor, moderate and major flooding only communicates broad possible consequences. Terminology such as ‘minor flooding’ may lead to the underestimation of risk, despite fatalities frequently occurring during minor floods, while ‘major flooding’ is open ended and may not fully communicate catastrophic or unprecedented events.
So how can the communication of flood warnings be improved to convince individuals to act in response to events they have never experienced? There is much to learn from exploring the experiences of those who have suffered the recent flood in NSW Manning Valley, however existing research and previous government inquires already give some suggestions.
Flood modelling provides the ability to estimate the extent and behaviour of floods beyond historical experience to appreciate potential flood consequences for local flood scenarios up to and including the largest floods possible. This is a valuable capability with the NSW Flood Inquiry and previous research suggesting that communicating such information in a visual form may aid community responses to and compliance with flood warnings. Flood mapping is not systematically used to communicate flood impacts in Australia, though has been used by some local governments, for example, Brisbane and Gold Coast in recent events. Recent US research found individuals preferred 3D street view visualisations of flood impacts over 2D maps. A national flood risk information portal would provide a useful resource for households to understand their flood risks well in advance of any flood threat.
Current Centre projects that could also help enhance warnings include:
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Developing an integrated predictive capability for extreme rainfall and inundation This project will develop a prototype predictive capability in collaboration with stakeholders and supported by social scientists, to improve forecasts of extreme rainfall and inundation and the communication of risk to emergency management.
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Communicating flood risk This research will improve the communication of flood risk to people in at-risk areas, including expected intensity and conditions, insurance information, improved flood-risk messaging (such as language, ratings, terminology), messaging suitability and social acceptance and implementation of changes into planning frameworks, community messaging and warning systems.
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Predictions in public: understanding the design, communication and dissemination of predictive maps to the public This project uses empirical and collaborative processes to contribute to and support a national approach to the future use of public-facing predictive fire spread products during an emergency.