Urban heat and tree canopy mapping
Understanding how we map Adelaide's urban environment
The Urban Heat and Tree Canopy Mapping Project gives us an indication of the current state of Adelaide’s urban forest.
‘Tree canopy’ refers to any horizontal vegetation that is 3m in height or greater. It’s at this point that trees are considered to begin to provide shading and cooling benefits.
Vegetation between 2 m and 3 m tall is considered as ‘mid-storey vegetation’ and is measured to show the extent of this emerging vegetation.
Mid-storey vegetation also contributes to cooling, amenity and biodiversity benefits but not to the same extent as trees over 3 m.
Urban Heat Islands are large areas of land (125m x 125m or greater) where heat has accumulated and is, on average, more than 2°C warmer than its surrounds.
Urban heat islands often occur in highly urbanised areas, with a high proportion of hard surfaces, such as buildings and roads, and a low proportion of green spaces or trees.
Artificial surfaces such as roads, footpaths and buildings are hotter than green spaces because they store and accumulate heat, and are less permeable to moisture, which help it to cool down.
Urban Heat Islands are problematic not just because they are hotter than surrounding areas, but also because the heat accumulated during the day radiates back into the environment into the night.
LiDAR technology was used in in this mapping project to map the urban forest and built environment.
It is a remote-sensing technology that uses a laser scanner installed in a light aircraft to ‘scan’ the Earth’s surface and features, such as trees and buildings.
LiDAR creates a highly accurate 3D point cloud which can be used to map the Earth’s surface in detail and create 3D models of features such as buildings and trees.
Permeable surfaces are ground surfaces where water can pass through to the soil underneath, such as bare soil and grass, and products like permeable pavers.
Impermeable surfaces are ground surfaces where water can’t pass through to the soil underneath, like regular pavements, concrete and roads.
Where there are impermeable surfaces, less water is available to trees and vegetation, and there is an increased risk of flash flooding because rain isn’t able to be absorbed into the ground.
Artificial surfaces such as roads, footpaths and buildings are hotter than green spaces because they store and accumulate heat, and are less permeable to moisture, which help it to cool down.