The cooling and greening Melbourne map covers the city’s metropolitan areas and brings together 3 datasets captured in 2014 and 2018. The interactive map offers a visual capture of data at local government, suburb, ABS Statistical Area Level 1 (SA1) and Mesh Block levels.
Cooling and greening Melbourne map
Vegetation layers
Vegetation cover data layers show the percentage of each boundary area (local government area, suburb and Mesh Block) that is covered by vegetation – limited to urban areas only.
Vegetation cover is grouped into five height classes:
- grass (0-0.5m)
- shrub (0.5-3m)
- small tree (3-10m)
- medium tree (10-15m)
- large tree (15m+).
The 2 date vegetation change layer shows the increase and decrease in vegetation cover between 2014 and 2018, for all urban parts of the boundary areas. This change is depicted in percentage points which describes the actual amount of change.
Urban heat layers
The 2014 and 2018 urban heat data layers show how many degrees Celsius the average temperature within urban parts of each boundary area is above or below the non-urban baseline. Boundary areas for the urban heat data layers are local government area, suburb, and Mesh Block.
The urban heat island (UHI) is a measure of the deviation of urban temperatures relative to a non-urban baseline. Native vegetated sites were used to establish the baseline. The data provides a two-dimensional representation of UHI across Melbourne at 30-meter resolution landscape.
Heat vulnerability index
The heat vulnerability index (HVI) layers show the HVI rating assigned to the urban parts of each boundary area. This rating indicates how vulnerable specific populations are to extreme heat events.
The 2014 and 2018 HVI data layers show the HVI rating for each local government area, suburb, and Australian Bureau of Statistics (ABS) Statistical Area Level 1 (SA1).
The HVI rating is determined by 3 components:
- heat exposure
- sensitivity to heat due to land cover, population density, and age
- adaptive capacity, for example, socioeconomic advantage or disadvantage.
This data was integrated by:
- summing the scores from the 3 vulnerability components
- dividing the statistical areas into quintiles
- attributing the statistical areas with a heat vulnerability rating: 1 = low vulnerability, 5 = high vulnerability.
Equal weighting, one third each, is given to heat exposure, sensitivity to heat, and adaptive capability.
The 3 heat vulnerability components were determined as follows:
Heat exposure
In the absence of a dense network of meteorological stations to measure air temperature, satellite thermal infrared imagery has been used to estimate land surface temperatures (LST).
This is the indicator used to measure heat exposure within the HVI.
Sensitivity to heat
Heat sensitivity has been calculated using both demographic data and indicators that determine the extent to which heat is retained in urban environments:
- land cover – specifically, the presence of vegetation and roads
- demographic data, including:
- population density
- age – people younger than 4 and older than 65 are more sensitive to heat related health complications
- persons in need of care
Adaptive capacity
2 types of socio-economic indexes for areas (SEIFA) were used as the adaptive capacity indicators:
Less advantaged populations have fewer resources to respond and adapt to heat.
What areas are data available for?
This project has focused on analysing the relationship between vegetation, urban heat, and land use in Melbourne’s urban area. Temperatures in many urban areas are warmer than their rural surroundings. This is known as the urban heat island effect, which refers to temperature differences attributable to urbanisation. Urban heat islands can have multiple impacts on health, resource use, and air quality. Vegetation, in particular tall trees, can play an important role in reducing the urban heat island effect.
Urban Monitor vegetation data was available for most of Melbourne’s urban areas. Coverage was limited to State Government acquired aerial imagery, which is the primary data required for the Urban Monitor approach. Data covering approximately 674,000 ha was available for 2018, however a smaller area of coverage was available for 2014.
The Cooling and greening Melbourne interactive map data layers have been clipped to the urban area boundary which does not include agricultural and non-urban land. Data for both non-urban and urban areas is available for download.
Comparison of urban heat data
The 2014 and 2018 temperature readings are not directly compared in this project. Land surface temperature derived from Landsat thermal images is subject to the availability of satellite images. This causes significant annual variation between 2 different years due to climatic factors, which are difficult to control for.
Data collection
Vegetation cover data
The vegetation cover data was produced using CSIRO’s Urban Monitor. The Urban Monitor provides a three-dimensional spatial representation of vegetation at 20 cm resolution.
It uses stereo photogrammetry to compare the height of identified vegetation though a digital surface model, relative to a ground elevation model, and estimates vegetation height.
Images were captured in summer 2014 and summer 2018.
Urban heat data
The urban heat island (UHI) measure was derived from land surface temperature (LST) data based on Landsat 8 thermal infrared data collected by the United States Geological Survey (USGS).
The Landsat 8 thermal infrared data used for this study was collected by the USGS at approximately 9.50 AM Eastern Standard Time (EST); 10:50 AM Daylight Saving Time (DST). Data was captured through four satellite orbits over three summer periods (2013-2014, 2014-2015 and 2017-2018). The orbits captured temperature data in the morning, as this is the time at which land surface temperatures are most similar to near-ground air temperatures.
Only images in summer that were cloud free across metropolitan Melbourne were included in this project.
ABS Mesh Blocks
Mesh Blocks are the smallest geographic units for which statistical data is collected and processed by the ABS. Mesh Blocks vary in size from part of a city block to large areas of rural land. Each of these borders another to form a network covering the whole country including inlets and coasts.
Find out more about Mesh Blocks.
ABS Statistical Area Level 1
Statistical Areas Level 1 (SA1s) are larger geographical units that have a population of between 200 to 800 persons with an average population of approximately 400 persons. SA1s aim to separate out areas with different geographic characteristics within suburb and locality boundaries. SA1s are aggregations of Mesh Blocks.
The SA1 is the smallest geographical unit at which the HVI data could be processed, due to the integration of demographic and socio-economic data processed by the ABS at this level.
Find out more about Statistical Area Level 1.
