Hot in the city: planning for climate change impacts in urban Australia

Australia's climate is already changing as a result of human influence. Over the past 50 years, we have experienced increased average and maximum temperatures, decreases in daily minimum temperatures, a 10-40 per cent increase in fire weather, and drying trends across the south west and south east (Chapters 2 and 3, Hennessy et al., 2005; BoM and CSIRO 2007).

With four degrees of warming, the number of extreme heat days (days over 35°C) in Australian cities will increase dramatically, from 3.5 to 12 days in Sydney, 9 to 26 days in Melbourne, 28 to 67 days in Perth, 1 to 21 days in Brisbane and 11 to 308 days in Darwin (Braganza et al., 2013 [ch. 3, this volume] CSIRO and BoM, 2007). Rainfall and severe hail events are expected to intensify (CSIRO and BoM 2007; Rafter and Abbs 2009) and the number of extreme fire danger days for a projected 2.9°C wanning is expected to increase by between 100 and 300 per cent (CSIRO & BoM 2007; Braganza et al., 2013, ch. 3, this volume). The frequency of cyclone activity is projected to decrease, although the intensity of such events is likely to increase (Whetton et al., 201, ch. 2, this volume).

The IPCC projections of sea level rise for 2-5.4°C of global warming are conservatively in the range of 23-5lcm by 2100 (IPCC, 2007). Even small rises in sea level will greatly shorten the average recurrence interval (ARI) for coastal inundation events (Australian Government, 2009). For example, a sea level rise of 20cm would reduce the ARI for what is currently a l-in-100 year storm surge in south-east Queensland to 61 years. The interval drops to just 9 years with a rise of 1 metre (Wang et al., 2010).

It is trite but perhaps salutary to point out that, in Australia, these climate change impacts will take effect in conjunction with population growth and movement and other demographic change. A severe cyclone will cause less property damage in a sparsely developed area than in a densely populated city, although impacts on biodiversity and natural values or other economically valuable industries may be significant. The severity of impacts will also be mediated by what adaptation measures have been implemented: drought will be less disruptive to urban populations that have already reduced their water consumption or improved water storage and supply.

Over 90 per cent of Australia's population lives in a city or major regional centre. Nearly 70 per cent of Australians live in just six major cities and the population of these urban centres is increasing at a faster rate than the overall population (ABS, 2008). The preference for coastal living means that 83 per cent of the population lives within 50km of the coast and between 160,000 and 250,000 existing properties are at risk of coastal flooding with a sea level rise of 1.lm (Australian Government, 2009). With such high levels of urbanization and concentration of population into a handful of urban centres, the impacts of climate change on Australian cities is receiving closer attention.

The impacts on Australian cities will be both direct and indirect. As Chapter 9 has indicated, human health impacts from greater air pollution, heat stress, and an increase in heat-related violence will follow from heatwave events. There will also be major social and business disruption and economic loss as a result of the energy and transport infrastructure failures associated with extreme hot weather. Sea level rise will lead to an increase in the frequency of coastal erosion and inundation with attendant impacts on private and public infrastructure and assets. More intense rainfall and storm events will cause property damage from flooding, wind damage and hail, as well as risks to human life and health. Drying conditions will create profound water supply challenges for many urban centres, affecting the quality and quantity of water for domestic and industrial uses, as well as public sporting and recreational assets. These examples serve only to illustrate the numerous complex interactions between climate change effects and their manifestation in an urban context and to highlight the need for urban planners and managers to account for these events in their land use, building, public health, infrastructure and asset management and other strategies.

This chapter examines the way in which land use planning in Australia is accounting for the impacts of climate change and the implications of our urban populations, as at 2012. Section two examines the different planning responses to three types of climate change impact - sea level rise and coastal hazards, bushfire conditions and heatwave. It also discusses progress on adaptation planning in Australia's six largest cities. Section three recognizes the limitations of new planning measures for existing urban centres and the likelihood of future climate- or weather-related disasters. It outlines key features of recent responses to natural disasters. Section four considers some of the key barriers to enhanced adaptation planning in urban Australia and how they can be addressed.