10 Built environment | 6 Remaining risks to the built environment
State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
10 Built environment
At a glance
The most significant risks facing the built environment relate to an increased urban footprint, increased traffic congestion, increased sea levels and a range of weather-related incidents, especially mega-storms and mega-fires. Increasing infrastructure from population growth could lead to incidents that may affect the quality of urban drinking water.
The most significant risks to the built environment are shown in the assessment summary at the end of this section. The risks examined in this section are incidents occurring at one point in time, rather than the impacts of pressures that may occur over longer periods. The assessment was made using qualitative analysis based on expert opinion. In analysing risk, the effectiveness of management responses and the resilience of the system are taken into account. Only risks that are considered the most significant (in terms of the combination of likelihood and consequence) are shown in the assessment summary; risks that are assessed as falling within the shaded cells of the summary table are not shown.
Many of the risks to the built environment result from extreme natural events. Although the previous section concluded that the built environment is generally quite resilient to such events, the immediate consequences of these events in terms of property damage, human casualties and loss of amenity can be quite significant. Mega-storms, such as Cyclone Tracy, which devastated Darwin in 1974, or the hailstorm that hit Sydney in 2000, are considered to be the most significant risk to the built environment. Storms of this nature are rare events for any particular urban area at any particular time, but over a long period there is a strong likelihood that some major urban area will experience such a storm. Since climate change is expected to increase the frequency of such storms, this likelihood is expected to increase.
Mega-fires, of the type that struck Victoria in February 2009, are considered the next most significant risk. These are also likely to affect urban areas at some time in the future, although their consequences for the built environment are rated a little lower than the consequences of mega-storms.
Floods, localised storms and extreme heat events that impact on the built environment are considered almost certain to occur in the future, on the basis of historical evidence. Climate change is likely to increase their prevalence. The urban heat-island effect in cities (which causes a metropolitan area to be significantly warmer than its surrounding rural areas) means that increases in temperature from climate change are particularly problematic. However, the impacts of these are assessed as being moderate, rather than major or catastrophic.
The risk of weather-related events is difficult to manage, since they cannot be prevented (although measures that mitigate climate change would reduce their likelihood). Appropriate building codes can reduce the consequences, as can appropriate emergency responses; however, the 'power of nature' is such that, even if these things are done well, very significant impacts could still occur in extreme situations.
The increased urban footprint arising from population growth poses a significant risk to the built environment. Growth in the physical size of cities is almost certain to occur, with major implications for the livability of the built environment. Increased traffic congestion is another risk that could be expected to have major consequences for the built environment. This risk is considered likely rather than almost certain. Although congestion in Australian cities has been increasing over many years, there is some recent evidence that growth in motor vehicle use may be levelling off; if this continues, the likelihood of increased congestion will be reduced.
A rise in sea levels is considered almost certain. Based on projections of the extent of sea level rise in 2100, this would have a very significant impact on certain parts of coastal cities in Australia. However, since most parts of the built environment in Australia—even in coastal cities—would not be directly affected by a sea level rise, the overall impact of this risk is rated as only moderate.
Contamination of a major water supply is considered to pose a high degree of risk to the built environment. It could result from population growth placing pressure on critical infrastructure, leading to the breakdown of quality control. Such an incident is rated as possible; however, if it occurred in a major urban area, there would be major consequences, particularly for human health. Good management can minimise the likelihood of such incidents, and Australia generally has a very strong track record of managing the quality of urban water. However, increasing pressure on critical infrastructure means that there is a need to continually improve the quality of management of this infrastructure.
Aerial view of Carram Downs bushfire, 20 January 2009, Victoria
Photo by Winning Images
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