Heatwave Risk Assessment

Person using Heatwave Risk Assessment Methodology pilot interface

 

A heatwave risk assessment to support local decision-making


Understanding the nature, scale and contributors to heat risk is essential for developing effective place-based mitigation, adaptation and response strategies, as well as targeting limited resources effectively.

 

This project sought to develop a risk assessment method tailored to the needs of local decision-makers. While the methodology is not publicly available, this page outlines some of the key features and considerations required to inform local risk assessment.

 

WSROC’s Heatwave Risk Assessment:

 

Provides high-resolution mapping for place-based decisions

Existing risk assessments did not provide the detail needed for the place-based decisions councils needed to make (e.g. On which streets should we prioritise tree-planting?). This risk assessment provides heatwave hazard mapping to 4m2, and risk mapping at Statistical Area 1 (SA1) in alignment with Census data.

 

Breaks down why risk is high in a local area

Is risk driven by urban design? Population age? Household income? Other factors? Or a combination of these? Understanding why risk is high in a particular location (SA1) is essential for informing effective, targeted investment.

 

Connects heatwave to human health impacts

Air temperature alone is a poor indicator of heat-health impacts. This risk assessment uses a hazard metric called Universal Thermal Climate Index (UTCI). UTCI is a ‘feels like’ temperature linked directly to human health. UTCI is generated by considering factors such as air temperature, humidity, windspeed, solar radiation and landcover. For more information on the benefits and drawbacks of different heat hazard data see Appendix 1.

(Data: Air temp, wind speed, humidity, landcover, canopy, building footprint and height, granularity to 2 metres).

 

Shows probability of different magnitude events

The risk assessment can tell us the likelihood of different heatwave magnitudes – from a low-intensity to extreme. This approach is commonly used for floods and storms to inform building codes, emergency plans, and is essential precursor for calculating financial impacts. This risk assessment shows three Annual Exceedance Probabilities; a 2-year, 10-year, and 100-year heatwave (i.e. those which have a 50%, 10%, 1% chance of occurring in any given year). To our knowledge this was the first probabilistic approach to heatwave in Australia. 

(Data: Air temperature, Bureau of Meteorology).

 

Shows changing risk with future climates

The risk assessment provides heatwave severity and frequency projections for four future climate years (2030, 2050, 2075 and 2090), and two emissions scenarios (RCP 4.5 and 8.5).

(Data: IPCC models, RCP4.5 and RCP8.5)  Note: 2025/26 update underway to integrate NarClim 2.0

 

Provides heat-specific vulnerability profile

The risk assessment includes a heatwave-specific vulnerability profile to assess the sensitivity and adaptive capacity of communities. This includes common indicators such as age, medical conditions, household income, education, and need for assistance. It also adds additional considerations specific to heatwave including: employment type (outdoor work), rental tenancy, access to transport, as well as proximity to medical facilities and cool spaces.

(Data: 2021 Census, Statistical Area 1, GIS queries based on local facility data).

 

Project findings:

During development and piloting of the risk assessment the project team found:

  • A strong need for this type of risk assessment at the local level for: emergency management, community engagement, urban and strategic planning, and environmental management.
  • Quality, accessible, regularly updated data is essential for producing quality risk assessments that can be updated over time. There are currently gaps in data that need to be filled.
  • The need to better understand the different elements of heatwave risk. Heatwave hazard impacts exposed elements in different ways. While the pilot focused on human impacts, other areas to explore include infrastructure, environments etc.


Next steps:

At present, the Heatwave Risk Assessment is being piloted in three local government areas with the potential to scale application across Greater Sydney, NSW or Australia.

Pending additional funding, next steps for the project include:

  • Refinement of the risk assessment interface to improve usability and accessibility for different parts of council and the community.
  • Testing the heatwave risk assessment methodology against empirical data.
  • Expanding the pilot to additional LGAs to better understand different use cases.
  • Developing additional risk profiles for elements at-risk, including infrastructure.

For further information contact WSROC: This email address is being protected from spambots. You need JavaScript enabled to view it., 0296714333.

 

The Heatwave Risk Assessment Methodology was funded through the joint Australian Government–NSW Government National Partnership Agreement on Disaster Risk Reduction.

Timing: Delivered 2022 – 2024

Project partners: Blacktown City Council, Hawkesbury City Council, Willoughby Council, NSW Reconstruction Authority.

Consulting partners: Water Technology 

 

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Further information: 

Other sources of heat risk assessment and advice

The Heatwave Risk Assessment is designed to inform long-term capital and operational planning. It does not provide advice on forecast weather, heatwave warnings, community messaging or risk treatment advice.

For further information on the above topics please visit the below information sources.

Heat-health risk linked to the Bureau of Meteorology’s weather forecast: University of Sydney’s Heatwatch

Heat-health community messaging and advice: NSW Beat the Heat

Heatwave warnings: NSW Ambulance's website

For risk treatment advice see WSROC’s other work.

 

Measuring heat hazard

There are many ways to measure heat and heat exposure. Measures of heat are typically based on temperature. This could include the temperature of surfaces or air measured at any number of locations and points in time. Measures of heat exposure may also include other factors such as humidity, wind speed, radiation, clothing and physiology.
When setting out to measure heat and assess heat exposure, it is important to understand the benefits and drawbacks of different types of data and select one that is fit for purpose. Consider:

  • What element of heat hazard are you measuring? Urban heat? Extreme heat? Heatwave? Average temperatures? For example, extreme heat often refers to peak daily temperature, while urban heat (stored and re-radiated solar energy) is best measured at night.

  • What kind of exposure needs to be assessed? Exposure of humans? Infrastructure? Vegetation? Infrastructure may best be assessed by surface temperature, while human exposure is strongly influenced by humidity.

  • Practical considerations of different measures? Cost, time, ties to legislation or policy.

 

Table 1. outlines five common measures of heat and summarises their applications, strengths and weaknesses.