As climate change progresses, heatwaves are becoming more frequent, intense, and longer-lasting, posing significant risks to human health, infrastructure, and ecosystems. These risks are particularly pronounced in urban environments, where high population density and impervious surfaces can exacerbate temperature extremes.
Our project, led by Prof Jason Byrne of the University of Tasmania and funded by the National Disaster Risk Reduction Grant program (administered by the Tasmanian SES), provides insights for policymakers, urban planners, and the community, facilitating improved heatwave planning and mitigation strategies.
Objective
The objective of this study was to assess heatwave community risk in selected suburbs across five Local Government Associations (LGAs) in Tasmania: Clarence, Glenorchy, Hobart, Kingborough, and Launceston. By considering factors such as tree canopy cover, land surface temperature, and social vulnerability, we aimed to identify areas of higher vulnerability to heatwaves and provide valuable insights for future heatwave mitigation and adaptation planning.
Methodology
Our methodology involved developing a heatwave risk index by combining the Community Heat Exposure Index with vulnerable population data and IRSAD (Index of Relative Socio-economic Advantage and Disadvantage) data. The resulting index ranges from 1 to 10, with higher scores indicating higher risk. We also mapped outdoor refuges, areas where temperatures are expected to be lower during extreme heat days, which can provide respite during heatwaves.
Figure 1 Social Vulnerability Index - A map showcasing the distribution of social vulnerability in the study area, with purple colour indicating higher vulnerability due to socio-economic factors and population age.
Figure 2 Heat Susceptibility Index - A visual representation of the land surface temperature distribution in the study area, illustrating areas with higher and lower heat susceptibility.
Figure 3 Community Heat Exposure Index - A spatial representation of the potential heat exposure in residential, aged care, and health facility buildings within the study area.
Figure 4 Community Risk Index - A map showing the combined risk of heat exposure and social vulnerability in the study area, with red representing areas with a higher heat-related risks.
Results
The analysis revealed a strong and statistically significant negative correlation between tree canopy cover and land surface temperature based on more than 200,000 data points in the urban suburbs of the greater Hobart area. This relationship indicates that areas with higher tree canopy coverage have cooler surface temperatures, with a 1% increase in tree cover resulting in a ~0.06 degree decrease in temperature.
Figure 5 Scatterplot illustrating the correlation between tree canopy cover (%) and land surface temperature (°C) for each 30mx30m pixel in the study area. The linear regression line is overlaid on the scatterplot, showing the negative relationship between tree canopy cover and land surface temperature. This graph demonstrates that as tree canopy cover increases, the land surface temperature tends to decrease, highlighting the potential benefits of increasing green infrastructure in urban areas to mitigate heat-related risks.
Moreover, we identified areas with high vulnerability to heatwaves, providing insights for targeted interventions and investments to enhance community resilience and support vulnerable populations during extreme heat events.
The ten areas in Greater Hobart and Launceston with the highest community risk, identified by the percentage of residential buildings in zones with the maximum Community Heat Risk Index score of 10 (on a scale of 1 to 10, where 10 represents the highest risk), are:
- Dowsing Point – 52%
- Derwent Park – 43%
- Mayfield – 42%
- Goodwood – 38%
- Montrose – 30%
- Glenorchy – 28%
- Claremont – 23%
- Berriedale – 21%
- Chigwell – 19%
- Mowbray – 18%
- Rokeby –17%
The percentages reflect the proportion of residential buildings within each suburb that are categorised under the highest risk index.
Figure 6 Relative area of residential buildings as a percentage for each risk index class.
Conclusion
This study emphasises the importance of understanding and addressing the complex interplay of environmental and social factors that contribute to heatwave risk. By identifying areas with higher vulnerability, we can help inform targeted interventions and investments to enhance community resilience, such as increasing tree canopy cover, improving access to green spaces, and supporting vulnerable populations.
As heatwave risks continue to rise due to climate change and urbanisation, proactive planning and investment in heatwave mitigation and adaptation measures are essential. By working together to understand and address heatwave risks, we can build more resilient communities and protect the health and well-being of our most vulnerable populations.
