A new framework for reducing vulnerable groups’ heat stress through green infrastructure is being used by the cities of Port Phillip and Greater Geelong to develop plans and prioritise projects.
University of Melbourne urban ecology and urban agriculture lecturer Dr Nick Williams along with colleagues Dr Andrew Coutts, an urban climatologist at Monash University, and Dr Stephen Livesley, a research fellow at the University off Melbourne’s School of Ecosystem and Forest Sciences, developed the methodology based on research carried out in 2012 and 2013 using Port Phillip as a case study.
The research used aerial thermal mapping to capture heat levels of the urban environment on a January day in 2012, identifying the city’s surface temperature hot spots.
This mapping was then overlaid with demographic mapping that identified where the members of the population most vulnerable to heat stress lived or were engaged in activities, such as retirement homes, primary schools, day care centres and social housing apartments.
A further overlay of the planning zones and known areas of activities that are high-risk on days of extreme heat, like shopping strips, the South Melbourne Market, popular pedestrian routes and public transport routes was added.
City of Port Phillip then considered a range of options to address heat in those critical priority areas where high heat and high vulnerability or high-risk activities coincide. The options included green walls, street trees, bio-retention basins for trees, irrigating urban open space, rain gardens and green roofs.
Dr Williams said the framework helped local government prioritise spending by identifying areas where the highest benefit could be gained in terms of risk and heat reduction.
“The City of Geelong is now in the process of using the framework to prioritise its green infrastructure policies and plans,” Dr Williams told The Fifth Estate.
He said a number of consultants were working with the city to map out the most effective areas for greening. These included prioritising east-west oriented streets over north-south oriented ones; looking at the height to width ratio of the streets, as “a narrow street will not give as much bang for the buck in terms of cooling as a wide street”.
“The research was driven by the fact that heatwaves are the biggest killer in Australia in terms of natural events,” Dr Williams said.
“Council and governments generally do realise this, but they seem to be encouraging people to stay inside in air conditioned environments [as a solution].”
He said a better approach was to change the fabric of how urban landscapes were designed and to mitigate the existing landscape, and this was the essence of the framework’s approach.
The framework addresses a range of other factors needing consideration in developing solutions, such as the amount of water available, methods of capturing water for irrigation, land use, cultural preferences, species choices, and whether the cool is to be provided at the street level for pedestrian-level benefits or at the roof level for a diffused cool that can benefit a wider area but to a lesser degree.
The research team are hoping the framework will be widely adopted by city and shire councils, as urban heat is increasingly becoming a major public health issue.
Dr Williams said there was ongoing research at the university’s Burnley campus into the degree of cooling effectiveness provided by different species, which species were most beneficial for human health, and also which species could absorb large amounts of water during rain events as part of a green roof system but also could cope with periods of extreme dry.
The relationship between transpiration rates and cooling effectiveness of plants in green facades and on green roofs is also the subject of current research, as is the integration of green infrastructure with water sensitive urban design.
“We are trying to really quantify the values of green infrastructure in terms of water, cooling, biodiversity and other benefits,” he said.
”There are a whole range of benefits it provides, and as cities get denser, we need to get smarter about to provide green infrastructure within ever-smaller spaces.”
Guidelines for implementing the framework can be found here.