Natural Disasters and Their Planning Responses

Environmental attributes are key factors in determining land-use. Level topography is sought for industrial purposes, while ridgelines are desired for their vistas. Contrasting these incentives are the disincentives of low-lying lands periodically flooding and vegetation fuelling bushfire. In the same way as the aftermath of a road accident reminds us to drive more carefully, natural disasters remind us of these disincentives.



A Weeping Willow

This brief article discusses Australia’s natural disasters and how policy has sought to mitigate for future natural disasters. For example, did you realise that Weeping Willows were a policy response to flooding or that dams may be required of rural properties to fight bushfire? The two natural disasters of flooding and bushfire are discussed.


The majority of Australia’s established urban centres are situated on natural floodplains. This is the result of historical inertia relating to agricultural societies; waterways as a means transportation/trade and a continued preference to live in the coastal zone. Floodplains periodically flood after a combination of heavy rainfall and/or tidal flows. To plan for these flooding events the standard in NSW is to prohibit development in the Flood Planning Area, based on the ‘1 in 100 year flood level’. 

In the 1950’s after significant flooding, the Australian Government encouraged and subsided the planting of Salix caprea- the Weeping Willow. The rationale being that Willows absorbed significant amounts of water and in turn reduced the impact of flooding. Willows now characterise the majority of Australian riverbanks as a result of their ability to out-compete native species. In line with the majority of species introduced into foreign environments they have not achieved their desired objective. Today enormous private and public funds are being spent to remove these Willows. 

Prohibiting construction or only allowing the most appropriate development, such as pole structures below the ‘1 in 100 year flood’ level is considered the acceptable approach. Furthermore, provided urbanisation leads to increased run-off due to an increase in impermeable surfaces the most ideal precautionary approach would be to use the highest historical flood level instead of ‘1 in 100 year flood’. 

Recent devastating bushfires have included the Canberra bushfires of 2003 and the Victorian ‘black Saturday’ bushfires of 2011. Together they have resulted in the loss of over 4,000 structures and 180 lives. 

Bushfires have long been a key consideration in the development process with particular consideration given to road layouts, dwelling design and building setbacks in locations considered as vulnerable to bushfires. Key considerations in NSW are outlined by NSW Rural Fire Service, which include:

• A non-vegetated buffer between a dwelling and vegetation referred to as an Asset Protection Zone (APZ);
• Multiple exit and entry routes to and from a proposed subdivision;
• A road surrounding the sub-division that contributes to the APZ and allows fire-fighting forces easy access to defend assets.

Another policy that has indirect affiliations to bushfire protection is the construction of dams for rural residential properties. Provided that a dwelling is not connected to a reticulated water supply, water is captured in a dam for use by landowners for fire fighting, among other agricultural purposes. In times of bushfire or drought this water becomes a precious resource. The increasing demand for rural residential development driven by tree-changers has seen an exponential increase in the amount of dams. This is having a measurable impact on our river systems as the cumulative impact of taking water away from natural ecosystem processes is felt.

 

A recent study by Gibbons (2012) following the Victorian bushfires has identified the following six key variables to reduce the chances of dwellings being destroyed by bushfire:

• Tree and shrub cover within 40 metres of housing;
• The type of such cover (remnant or planted);
• Upwind distance from houses to groups of woody vegetation;
• Upwind distance from houses to public forest;
• The upwind distance to prescribed burning (within five years); and
• The number of buildings and houses within 40 metres of houses.

The 2009 Victorian Bushfires Royal Commission recommended that planning provisions relating to bushfire be amended and it can therefore be seen that in the same way that public opinion sways policies of Government, natural disasters have the power to dictate planning controls. After all, planning is a policy tool operating in a politically charged environment.

Australia is continually been reminded of the dynamic environment in which we live through natural disaster events. Recent disasters in the summer of 2012/13 have included flooding, heatwaves, bushfires and tropical cyclones. Planners are stewards of land-use and must enforce planning controls relating to environmental attributes to ensure that future natural disasters do not unnecessarily lead to the loss of life or property.

By Jeffrey Bretag (NSW)