Gale Zimmerman wrote:They advocate keeping a 10-15' perimeter around each building that has no flammable, or at least no easily flammable, material. ... We need your suggestions for managing this near-to-structures landscaping zone. ... If we decide to remove 20-50 huge old eucalyptus and cypress trees
Removing all
Eucalyptus spp. from your property is advisable — they turn into fuel-air bombs during bushfire conditions.
Embers will fly
kilometres, not just metres, and ember attack is the primary reason most houses are lost.
The role of buffers is to a) eliminate direct flame contact with walls, and b) reduce radiant heat levels. A 3-5m buffer will address the former, but is wholly inadequate for addressing the latter. We have a 20m buffer around our place. If your buffer isn't big enough, radiant heat will thermally stress and crack your windows, which will then fail and admit embers into the building. Radiant heat will also go through windows and set internal furnishings on fire. Even if radiant heat doesn't set anything inside on fire, it will cause petroleum-based products to start smoking and turn the inside of your house into a toxic gas chamber. This is, of course, not what you want if you need to retreat there when the flame front rolls over your property.
As far as landscaping goes, I'll go out on a limb and make a slightly odd suggestion: Since your property is so large, consider cordoning off a 20m buffer around all of your buildings, connecting it all to a goose pen, and seeding it with a mix of grasses that meet the dietary requirements of the birds.
The geese will mow the grass for you, you won't need to spend virtually anything on feed, weeds will be controlled, the land will be fertilised, root systems will penetrate deeper into the soil and help break up any clay, you'll have an excuse to inject water into the area which will find its way into the soil via goose excrement, if you have female geese you'll end up with eggs for breakfast, ultimately you'll have meat for dinner, and short, green grass is an excellent buffer against bushfires.
You can start off relatively cheaply with portable electric netting, see how it goes, and then migrate to more permanent fencing if it works out for you.
(Of course, geese are only one possibility. Certain ducks are also good lawn mowers. Muscovies are one breed that are very, very quiet (if noise is a concern). Alpacas would also work. If you are prepared to lay down some mesh and let the grass grow through, you could even do rabbits (and other critters that normally dig/burrow). Lots of options.)