The Role of Carparks As Urban Heat Islets in Western Sydney
Total Page：16
File Type：pdf, Size：1020Kb
The role of carparks as urban heat islets in western Sydney Chanda Prajapati June 2020 A thesis submitted in fulfillment of the requirements for the degree of Master of Research Western Sydney University Supervisor Dr. Sebastian Pfautsch i Statement of Authentication The work presented in this thesis is, to the best of my knowledge and belief, original except as acknowledged in the text. I hereby declare that I have not submitted this material, either in full or in part, for a degree at this or any other institution. …………………………………………………….. (Signature) i Acknowledgment I would like to express my sincere gratitude and thankfulness to my Supervisor, Dr. Sebastian Pfautsch, for his continuous support, guidance, patience, and invaluable assistance. I could not have imagined having a better advisor and mentor for the completion of my Master of Research. I am very much grateful for support and encouragement since tentative conversations about the possibility of undertaking a master’s research project, during my physical hard times to the end of the project. I would also like to thank Susanna Rouillard, GIS, and Data Visualisation Specialist for helping me in producing a GIS map. I am also thankful to Amrita Limbu, a Ph.D. scholar of Western Sydney University for constant support during the writing process. I owe a very special thanks to my parents (Krishna Bhakta and Churi Prajapati) and in-laws (Shyam and Laxmi Awale) for all their encouraging words throughout this journey. I would not have completed this road without their undeniable support of caring and nourishing my one-year-old son Kiaan. Finally, I appreciate the patience of my husband Kiran Awale, and his immense belief that I can complete this study. His endless care and support mentally and financially will always be remembered. Thank you for your unending love and support. I couldn’t have done this without you. ii Abstract Every summer, and at an increasing frequency and severity, residents of western Sydney experience extreme heat during the day and heat island effects during the night. The latter results in higher nighttime air temperatures in urban areas compared to nearby rural land. This phenomenon is linked to low vegetation cover and a large proportion of hard surfaces from buildings, roads, and carparks that dominate urban landscapes. Especially the dark, flat and unshaded surfaces of car parks store and re-radiate large amounts of solar energy and contribute substantially to local heat. The contribution of carparks to urban heat island effects and localised warming is well documented in the literature. Yet, the area taken up by these local heat islets in western Sydney remains unknown. This research quantified the current (2019) total area of carpark infrastructure across all suburbs that are contained in six local government areas (LGAs) in western Sydney. For the purpose of this study, carparks were defined as those exposed to solar radiation, thus excluding underground carparks and lower decks of multilevel carparks. Carparks with less than 10 parking bays were also excluded as their contribution to local warming was deemed insignificant. All carparks were remotely measured using high-resolution aerial images. In addition, changes in carparking space between 2010 and 2019, as well as the presence and extent of green infrastructure and tree shade provided in these carparks were determined. Lastly, the relationship between the dynamics of changes in carpark area and changes in the size of local populations were elucidated for each suburb in each LGA using Census data (only available for 2012 and 2018 during the time of this research). Image analyses resulted in the identification of 2250 carparks across a total area of 1300 km2 of urban and rural land covered by 143 suburb areas. Carpark surfaces were predominately (>90%) made from conventional black asphalt and far less from light-coloured concrete. The total area covered by car parks across this land increased by 21% from 4.8 km2 in 2010 to 5.8 km2 in 2019 while at the same time the total population increased 16%, from 1.12 million to 1.31 million people. The largest increase of carpark area was observed for the LGA of Blacktown, where 144 new carparks added 47 ha (+46%) of sealed black surface, nearly all of which was unshaded. At the same time, the population of Blacktown increased only by 15% (317,766 in 2012 to 366,379 in 2018). The largest increase in carpark area relative to the area of the LGA was in Camden where on average across all suburbs, carparking space grew by more than 50%. The area covered by carparks decreased only in the LGA of Parramatta City. In 2010, 3880 trees and other green infrastructure covered just 0.98% of the carparks in the six LGAs. By 2019, and as a result of the increasing total area of carparks, the proportion of green infrastructure remained just above 1%, even though the total number of trees counted in the carparks had risen to 4471. There was a highly significant (p <0.001) and positive relationship between the area covered by carparks in individual suburbs of the six LGAs and the number of trees growing in these carparks in 2010 and 2019. To document the capacity of tree shade to reduce local heat in carparks, additional empirical measurements of surface, air, and black globe temperatures (the latter as an approximation for a ‘feels like’ temperature) were collected in four carparks during sunny days in summer 2019/20. In all four carparks, measurements were collected in full sun and under tree shade on black asphalt. Tree shade reduced surface temperatures by 15-20℃, air temperature by 2-5℃, and black globe temperature by 5-10℃. iii The results of this study reveal the extent and dynamic changes of carparks in western Sydney. It is reasonable to expect that the increasing space used by carparks intensifies local heat in a part of the Sydney Basin that already experiences record temperatures in summer. This expectation is enforced by the finding that these carparks only contain 1% green infrastructure, and shade is provided by just 8 trees per 10,000 m2. Moreover, the overcapacity of current carparking space, where the relative expansion of this space markedly exceeds population growth in some LGAs is of great concern. Is capacity being built for anticipated growth in population, or is greenfield converted to unnecessary grey infrastructure? In any case, negative effects on summer heat remain. Rapid urban development in western Sydney is predicted to continue for the coming decades. Homes, work and transport infrastructure for an additional 800,000 residents must be provided by 2036. New insight offered through this research about the dynamic relationship between concurrent increases of local populations and carparks can now be used to develop more sustainable strategies to provide the required parking infrastructure. The data presented here make it obvious that regulators, urban planners, contractors, and land managers have failed to address the issue of increasing urban heat loads through carparks in the past decade of development in western Sydney. Hence, this research work can become a central point of reference to inform responsible infrastructure planning across the region. Heat in western Sydney is a regional issue that requires concerted solutions. As car dependency remains large in this region, carparks are a seemingly unavoidable source of radiant heat for some time to come. This situation demands that new and improved policies and regulations are developed that result in the construction of carparks that mitigate heat much better than today. In the meantime, local governments can ramp up their greening programs for carparks to improve the microclimate around these heat islets and increase the thermal comfort of their users. iv Contents 1 Introduction...................................................................................................................................... 1 1.1 Background .............................................................................................................................. 1 1.2 Heat in Western Sydney .......................................................................................................... 8 1.3 Car Dependency ....................................................................................................................... 9 1.4 Carparks as Sources of Urban Heat ....................................................................................... 10 1.5 Thesis Overview .................................................................................................................... 12 2 Materials and Methods ..................................................................................................................14 2.1 Study Areas ............................................................................................................................ 14 2.2 Carpark Assessments ............................................................................................................. 16 2.3 Demographic Data ................................................................................................................. 20 2.4 Carpark Heat .......................................................................................................................... 20 2.5 Statistical Analysis................................................................................................................. 21 3 Results............................................................................................................................................23