Tree shade within urban parks and nature strips: standards and perspectives from measurement campaigns conducted in Queensland

Tree shade within urban parks and nature strips: standards and perspectives from measurement campaigns conducted in Queensland

Standardised tree shade assessments yield important information on canopy density, size and solar protection within the urban environment. Designing for shade by trees that are to be planted along narrow suburban nature strips, parks and playgrounds requires a detailed understanding of both the constraints and benefits based on location. Safety and the available space for maintaining a canopy, or intrusive root system growing within an urban setting, places practical limits on the species available to local governments and on shade designers. The results of three separate shade assessment campaigns conducted on trees growing within public parks and nature strips are presented with respect to a tree shade measurement standard utilising hemispherical canopy images photographed at over 1000 individual ground sites. The assessment technique, which utilises processed tree canopy images accessible from the public AtmoSEQ catalogue of site images, introduces solar path tracing with respect to site latitude and longitude to enable the development of a standard Shade Protection Index (SPI) for assessing the quality of shade by trees. Canopy assessments conducted using the SPI are compared against radiometer measurements of the site Ultraviolet Protection Factor (UPF). The utility of the SPI is examined on short sub-hourly time scales and extended to provide robust assessments of site shade quality on daily, seasonal and annual time frames. We report on the history of tree shade measurements conducted using the SPI within Brisbane and wider Queensland. Outcomes have contributed to Shade Tree Guidance and recent innovations including CanopyCast.

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