There's a new paper published in The International Journal of Wildland Fire October about the importance of defensible space around houses. It has some good tips on preparing at the macro scale for bushfires. Unfortunately it costs $25 to get the full text. Let me know if you have a pdf copy you are willing to share.
Here's part of the abstract:
"Although state and local governments publish specific guidelines and
requirements, there is little empirical evidence to suggest how much
vegetation modification is needed to provide significant benefits. We
analysed the role of defensible space by mapping and measuring a suite
of variables on modern pre-fire aerial photography for 1000 destroyed
and 1000 surviving structures for all fires where homes burned from 2001
to 2010 in San Diego County, CA, USA. Structures were more likely to
survive a fire with defensible space immediately adjacent to them. The
most effective treatment distance varied between 5 and 20 m (16–58 ft)
from the structure, but distances larger than 30 m (100 ft) did not
provide additional protection, even for structures located on steep
slopes. The most effective actions were reducing woody cover up to 40%
immediately adjacent to structures and ensuring that vegetation does not
overhang or touch the structure."
This is the kind of science-based information that we need for making our bushfire preparations maximally effective. Interesting to note that distances larger than 30m did not provide additional protection, even for structures located on steep slopes, though I guess that could be interpreted to mean that if it was going to burn anyway because of the location on a steep slope, then creating a defensible space out beyond 30m wasn't going to change that.
The Abstract and pdf download can be found here: http://www.publish.csiro.au/nid/114/paper/WF13158.htm
The citation for the report is:
Syphard, A. D., Brennan, T. J., & Keeley, J. E. (2014). The role of defensible space for residential structure protection during wildfires. International Journal of Wildland Fire. Retrieved from http://dx.doi.org/10.1071/WF13158.
You can find more tips on bushfire preparation at Ignite Change.