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Urban Heat and Tree Mapping of Adelaide Metropolitan Area

Despite global efforts to reduce greenhouse gas emissions, impacts from climate change are inevitable. Adapting to climate change involves planning and action by individuals, communities and businesses to cope with the challenges and opportunities.  In an urban context, heat, tree canopy cover, water, biodiversity and urban design are particularly relevant for maintaining the wellbeing, liveability, resilience of local communities.

Urban Heat Mapping

  

The severity of heat experienced in cities during hot weather varies across the urban landscape. In particular, hard surfaces, like concrete or bitumen, result in higher surface temperatures compared to areas that allow the infiltration of water, such as parklands or vegetated areas.

The Urban Heat and Tree Mapping Viewer enables the exploration of high-resolution surface temperature data for the Adelaide metropolitan area.

This is the product of three separate mapping projects, commissioned by the four metropolitan Regional Climate Partnership groups: Resilient South, Adapt West, Resilient East and Adapting Northern Adelaide.   

The data presented can be used to:

• Evaluate how urban infrastructure choices affect the temperature characteristics and extents of urban heat islands,
• Help plan activities to mitigate high temperatures in the urban environment, and     
  
• Improve the resilience of communities and assets to extreme heat and prolonged heat events.

Periodic updating of the heat maps will enable evaluation of the effectiveness of climate change adaptation measures and investments in urban greening and climate-sensitive infrastructure.

The thermal, social vulnerability and vegetation greenness (Normalised Difference Vegetation Index (NDVI)) layers are provided through this map viewer with the permission of the local government authorities party to the Resilient South, Adapt West, Resilient East and Adapting Northern Adelaide Regional Climate Partnership groups.

Tree Canopy Mapping

LiDAR (Light Detection and Ranging) was acquired over the Adelaide Metropolitan area in 2018 (red in adjacent map) and 2019 (green) covering 18 local government areas.

The data was further analysed to create a number of layers that can be used to map canopy extent and height for all vegetation greater than 3m in height:

• Digital Canopy Model / Canopy Height Model that describes the horizontal extent and vertical height of tree canopies
• Tree Canopy Boundaries showing the precise horizontal extent of tree canopies
• Tree Canopy Coverage by unit area describing the percentage of tree canopy per 100m2
  

Layers

Heat Maps

The colour scale used in the heat maps represents surface temperatures recorded on the day of data capture, from coolest (blue) to hottest (red). The data was captured on three separate dates, each selected for being a day of above average summer temperature. It is not valid to compare the indicated surface temperatures across different capture zones (delineated by boundary lines in the mapping viewer), due to different ambient temperatures on each of the three days.

Tree Canopy

Tree canopy heights over the Adelaide Metropolitan area are mapped as dark blue for smaller trees to yellow for the tallest trees.  Tree canopy boundaries highlight tree canopy extents in bright green.

NDVI & Building Footprints

To support analysis, additional data layers have been added to the Urban Heat and Tree Mapping Viewer including:

• Building Footprints created from the LiDAR point cloud
• Vegetation greenness based on a Normalised Difference Vegetation Index (NDVI) from multispectral aerial imagery.
  

NDVI vegetation greenness is shown on a colour scale from brown representing low vegetation greenness to green representing high vegetation greenness. 

A number of spatial layers are also provided to provide context with the urban heat and tree mapping layers.  These include:-

• Administrative boundaries
• Cadastral information
• Land use
• Topographic overlays

Layers that can be explored through the Urban Heat and Tree Mapping Viewer include:

• _{elderly population (>75 years old);}
• _{people who need assistance due to disabilities;}
• _{people who speak English as a second language not well or not at all;}
• _{median rent paid by residents; and}
• _{Socio-Economic Indexes for Areas of Disadvantage (SEIFA Score).}

_{** The Normalised Difference Vegetation Index (NDVI) (Rouse Jr. et al. 1974) was developed as an index of plant “greenness” and attempts to track photosynthetic activity. It has since become one of the most widely applied indices. It is also based on the principle that well-nourished, living plants absorb red light and reflect near-infrared light. It also takes into account the fact that stressed or dead vegetation absorbs comparatively less red light than healthy vegetation.}